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প্রাকজন্ম বিকাশৰ জীবন-বিজ্ঞান

The Biology of Prenatal Development
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Chapter 1   Introduction

The dynamic process by which the single-cell human zygote(zī΄gōt)[1] becomes a 100 trillion (1014) cell adult[2] is perhaps the most remarkable phenomenon in all of nature.

Researchers now know that many of the routine functions performed by the adult body become established during pregnancy – often long before birth.[3]

The developmental period before birth is increasingly understood as a time of preparation during which the developing human acquires the many structures, and practices the many skills, needed for survival after birth.

Chapter 1   Introduction

যি সক্রিয় প্রণালীৰ দ্বাৰা এক-কোষী মানব জনন-খোক (জাইগোট) বিকাশ হৈ ১০০-ট্রিলিয়ন সংখ্যাৰ প্রাপ্তবয়স্ক কোষত পৰিণত হয়, বোধহয় ই প্রকৃতিৰ আটাইতকৈ লক্ষ্য কৰিব লগীয়া ঘটনা।

বর্তমান গবেষক সকলে জানে যে প্রাপ্তবয়স্ক শৰীৰে সচাৰচৰ সমাপন কৰা অনেক কার্য্য গর্ভধাৰণৰ সময়ত প্রতিষ্ঠিত হয়- প্রায়ে জন্মৰ বহু দিনৰ আগতেই।

জন্মৰ আগৰ বিকশিত কাল বেচিকৈ সাজু হোৱাৰ সময় ৰূপে জনা যায় যি কালচোৱাৰ ভিতৰত মানুহে অনেক আবয়ব অর্জন কৰে, আৰু অনেক কৌশল আয়ত্ব কৰে যি জন্মৰ পিচত জীয়াই থাকিবলৈ আৱশ্যক হয়।

Chapter 2   Terminology

Pregnancy in humans normally lasts approximately 38 weeks[4] as measured from the time of fertilization,[5] or conception,[6] until birth.

During the first 8 weeks following fertilization, the developing human is called an embryo,[7] which means "growing within."[8] This time, called the embryonic period,[9] is characterized by the formation of most major body systems.[10]

From the completion of 8 weeks until the end of pregnancy, "the developing human is called a fetus," which means "unborn offspring." During this time, called the fetal period, the body grows larger and its systems begin to function.[11]

All embryonic and fetal ages in this program refer to the time since fertilization.[12]

Chapter 2   Terminology

গর্ভাৱস্থা সাধাৰণতে ৩৮ সপ্তাহমান থাকে আৰু এই সময় গর্ভসঞ্চাৰ হোৱাৰ পৰা জন্মক্ষণলৈ গণনা কৰা হয়।

গর্ভধাৰণৰ পিচৰ প্রথম ৮ সপ্তাহত বিকশিত মানবক এক ভ্রূণ বুলি কোৱা হয়, যাৰ অর্থ "অভ্যন্তৰত বিকাশ"। এই সময়চোৱাক, যাক ভ্রূণাৱস্থা বুলি অভিহিত কৰা হয়, শৰীৰ প্রণালীৰ প্রধান অঙ্গসমুহ গঠন হোৱা অৱস্থাৰূপে বর্ণনা কৰা হয়।

৮-তম সপ্তাহ অন্ত হোৱাৰ পৰা গর্ভাৱস্থা অন্ত হোৱালৈকে "বিকশিত মানবক ভ্রূণ বুলি অভিহিত কৰা হয়", যাৰ অর্থ হৈছে "অজাত সন্তান"। এই সময়চোৱাত, যাক ভ্রূণাৱস্থা বুলি কোৱা হয়, শৰীৰৰ আকাৰ বৃদ্ধি হয় আৰু তাৰ সকলোবোৰ প্রণালীয়ে কাম কৰিবলৈ আৰম্ভ কৰে।

এই প্রক্রিয়াৰসকলো ভ্রূণাৱস্থাৰ কালছোৱাক গর্ভধাৰণৰ সময়ৰ পৰা গণনা কৰা হয়।

 

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[1] Gasser, 1975, 1.
[2] Guyton and Hall, 2000, 2; Lodish et al., 2000, 12.
[3] Vindla and James, 1995, 598.
[4] Cunningham et al., 2001, 226; O’Rahilly and Müller, 2001, 92.
[5] O’Rahilly and Müller, 1987, 9.
[6] Spraycar, 1995, 377 & 637.
[7] O’Rahilly and Müller, 2001, 87.
[8] Quote from Ayto, 1990, 199.
[9] Human development during the 8-week embryonic period has been divided into a series of 23 stages called Carnegie Stages. These stages are well described in O’Rahilly and Müller, 1987. Because human growth is unique and dependent on multiple factors, different embryos may reach a certain developmental milestone or a certain size at slightly different ages. This internationally-accepted staging system provides a way to describe development independent of age and size. Each of the 23 Carnegie Stages has specific structural features. As we describe various milestones of development, the Carnegie Stage at which they occur will be noted by a designation such as: [Carnegie Stage 2]. See Appendix B for additional information relating embryonic staging and age assignments.
[10] Moore and Persaud, 2003, 3.
[11] Quotes from Moore and Persaud, 2003, 3: “After the embryonic period (eight weeks), the developing human is called a fetus.“ Also see O’Rahilly and Müller, 2001, 87.
[12] This convention, termed “postfertilization age“ by O’Rahilly, has been long preferred by embryologists. [see Mall, 1918, 400; O’Rahilly and Müller, 1999b, 39; O’Rahilly and Müller, 2001, 88 & 91.] Obstetricians and radiologists typically assign age based on the time elapsed since the first day of the last menstrual period prior to fertilization. This is correctly termed “postmenstrual age“ and begins 2 weeks before fertilization occurs. To summarize: postmenstrual age = postfertilization age + 2 weeks. Therefore, postmenstrual age equals approximately 2 weeks at the time of fertilization. The commonly used term “gestational age“ has been used with both age conventions and is best either avoided or carefully defined with each use.

Page 3


The Embryonic Period (The First 8 Weeks)

Embryonic Development: The First 4 Weeks

Chapter 3   Fertilization

Biologically speaking, "human development begins at fertilization,"[13] when a woman and a man each combine 23 of their own chromosomes through the union of their reproductive cells.

A woman's reproductive cell is commonly called an "egg" but the correct term is oocyte (ō´ō-sīt).[14]

Likewise, a man's reproductive cell is widely known as a "sperm," but the preferred term is spermatozoon (sper´mă-tō-zō´on).[15]

Following the release of an oocyte from a woman's ovary in a process called ovulation (ov´yū-lā´shŭn),[16] the oocyte and spermatozoon join within one of the uterine tubes,[17] which are often referred to as Fallopian tubes.

The uterine tubes link a woman's ovaries to her uterus or womb.

The resulting single-celled embryo is called a zygote,[18] meaning "yoked or joined together."[19]

The Embryonic Period (The First 8 Weeks)

Embryonic Development: The First 4 Weeks

Chapter 3   Fertilization

জীৱ বিজ্ঞানৰ ফালৰ পৰা কবলৈ গলে "মানৱৰ বিকাশ গর্ভধাৰণৰ পৰা আৰম্ভ হয়," যেতিয়া এগৰাকী নাৰী আৰু এজন পুৰুষে পুনৰুত্‍পাদী কোষৰ সম্বন্ধৰ দ্বাৰা প্রত্যেকে নিজৰ ২৩ তাকৈ ক্রমোজমৰ মিলন সংঘটিত কৰে।

সাধাৰণতে এগৰাকী নাৰীৰ পুনৰুত্‍পাদী কোষক এক "ডিম্ব" বুলি কোৱা হয় কিন্তু শুদ্ধ শব্দ হৈছে ওকাইট।

তেনেদৰে, এজন পুৰুষৰ পুনৰুত্‍পাদীকোষক সর্বসাধাৰণতে 'বীর্য্য" বুলি জনা যায় কিন্তু শুক্রাণু(স্পার্মাটোজুন) বেচি অর্থবহ।

ওভুলেশ্বন নামৰ প্রক্রিয়াৰ দ্বাৰা নাৰীৰ ডিম্বাশয়ৰ পৰা এটা ওকাইট নির্গত হোৱাৰ পিচত জৰায়ু মধ্যস্থ এক নলীত, যাক প্রায়েফোলোপিয়ান টিউব নামেৰে জনা যায়, ওকাইট আৰু শুক্রাণুৰ এমাহৰ ভিতৰত মিলন হয়।

এগৰাকী নাৰীৰ ডিম্বাশয় জৰায়ু মধ্যস্থ নলীয়ে জৰায়ু বা গর্ভৰ লগত সংযোগ কৰে।

তাৰ ফলস্বৰূপে গঠন হোৱা এক কোষী ভ্রূণক জাইগোট বুলি কোৱা হয়, যাৰ অর্থ হৈছে "যুঁৱলি লগোৱা বা সংযোগ কৰা।"

Chapter 4   DNA, Cell Division, and Early Pregnancy Factor (EPF)

DNA

The zygote's 46 chromosomes[20] represent the unique first edition of a new individual's complete genetic blueprint. This master plan resides in tightly coiled molecules called DNA. They contain the instructions for the development of the entire body.

DNA molecules resemble a twisted ladder known as a double helix.[21] The rungs of the ladder are made up of paired molecules, or bases, called guanine, cytosine, adenine, and thymine.

Guanine pairs only with cytosine, and adenine with thymine.[22] Each human cell contains approximately 3 billion (3×109) base pairs.[23]

The DNA of a single cell contains so much information that if it were represented in printed words, simply listing the first letter of each base would require over 1.5 million (1.5×106) pages of text![24]

If laid end-to-end, the DNA in a single human cell measures 3⅓ feet or 1 meter.[25]

If we could uncoil all of the DNA within an adult's 100 trillion (1014) cells, it would extend over 63 billion (6.3×1010) miles. This distance reaches from the earth to the sun and back 340 times.[26]

Cell Division

Approximately 24 to 30 hours after fertilization, the zygote completes its first cell division.[27] Through the process of mitosis, one cell splits into two, two into four, and so on.[28]

Early Pregnancy Factor (EPF)

As early as 24 to 48 hours after fertilization begins, pregnancy can be confirmed by detecting a hormone called "early pregnancy factor" in the mother's blood.[29]

Chapter 4   DNA, Cell Division, and Early Pregnancy Factor (EPF)

DNA

জাইগোটৰ ৪৬ টা ক্রোমোজমে এক সম্পূর্ণ জেনেটিক চানেকিৰে সৈতে এক নতুন ব্যক্তিত্বৰ এটি অভিনব প্রথম সংস্কৰণ ৰূপে অঙ্কিতকৰে। এই মুখ্য আচনিখন ডি এন এ নামৰ কুণ্ডলী বান্ধি থকা অণুৰ মাজত থাকে। ইয়াত সম্পূর্ণ শৰীৰৰ বিকাশৰ বাবে আবশ্যক আদেশবোৰ অন্তর্ভুক্তথাকে।

ডি এন এ অণুবোৰ দেখিবলৈ এখন পাঁকখোৱা জখলাৰ দৰে যাক ডাবল হেলিক্স নামেৰে জনা যায়। জখলাৰ ধাপবোৰ গোৱানিন, চাইটোচিন এডেনিন আৰু থাইমিন নামৰ একোযোৰ যুৰীয়া অণু বা আধাৰৰ দ্বাৰা গঠিত।

গোৱানিন কেবল চাইটোচিনৰ লগতহে যোৰ খায়, আৰু এডেনিনৰ লগত থাইমিনৰ। প্রত্যেক মানৱ কোষত প্রায় ৩০০ কোটি মান আধাৰৰ এনেকুৱা যোৰা থাকে।

এটা কোষৰ ডি এন এ-ত ইমানেই তথ্য অন্তর্ভুক্ত হৈ আছে যে যদি প্রত্যেক আধাৰৰ প্রথম আখৰৰে আৰম্ভ কৰি চপা কৰিবলৈ লোৱা হয় তেন্তে ১৫ লাখতকৈ বেচি পৃষ্ঠাৰ তথ্য চপা হৈ ওলাব!

যদি এটা মুৰৰ লগত আনটো মুৰ লগ লগাই জোখা হয়, এটা মানব কোষৰ ডি এন এ-ৰ দৈর্ঘ্য৩ ৩/৩ ফুটৰ বা ১ মিটাৰ হয়।

যদি আমি এজন প্রাপ্তবয়স্কৰ ১০০X১০,০০০৩ লাখ কোষৰ ডি এন এ-ৰ আটাইবোৰ কুণ্ডলি খুলি দিব পাৰো তেন্তে এইবোৰ ৬৩০০ কোটি মাইলতকৈও বেচি প্রসাৰিত হব। এই দুৰত্ব পৃথিবীৰ পৰা সুর্য্যৰ দুৰত্বৰ ৩৪০ গূণ।

Cell Division

গর্ভসঞ্চাৰৰ প্রায় ২৪-ৰ পৰা ৩০ ঘণ্টাৰ পিচত, জাইগোটৰ প্রথম বিভাজন সম্পূর্ণ হয়। মাইটোচিচ(কোষ-বিভাজন) প্রক্রিয়াৰ দ্বাৰা এটা কোষ দুটাত বিভক্ত হয়, দুটা চাৰিটাত, আৰু এনেদৰে চলি থাকে।

Early Pregnancy Factor (EPF)

গর্ভসঞ্চাৰ আৰম্ভ হোৱাৰ ২৪-ৰ পৰা ৪৮ ঘণ্টা নৌহওতেই, মাতৃৰ তেজত "আগতীয়া গর্ভাৱস্থা গূণক" নামৰ হৰমোন বিচাৰি উলিয়াই গর্ভাৱস্থা নিশ্চিত কৰিব পাৰি।

 

 


[13] Quote from Moore and Persaud, 2003, 16; From O’Rahilly and Müller, 1987, 9: “Fertilization is the procession of events that begins when a spermatozoon makes contact with an oocyte or its investments and ends with the intermingling of maternal and paternal chromosomes at metaphase of the first mitotic division of the zygote.“ See Carlson, 2004, 3; O’Rahilly and Müller, 2001, 8. [Carnegie Stage 1]
[14] O’Rahilly and Müller, 2001, 25: “The term ‘egg’ should be discarded from human embryology.“ From O’Rahilly and Müller, 1987, 9: “The term ‘egg’ is best reserved for a nutritive object frequently seen on the breakfast table.“
[15] O’Rahilly and Müller, 2001, 23-24.
[16] O’Rahilly and Müller, 2001, 30.
[17] Dorland and Bartelmez, 1922, 372; Gasser, 1975, 1; Mall, 1918, 421; O’Rahilly and Müller, 2001, 31.
[18] Gasser, 1975, 1; O’Rahilly and Müller, 2001, 33.
[19] Quote from Saunders, 1970, 1; Spraycar, 1995, 1976.
[20] Guyton and Hall, 2000, 34.
[21] Guyton and Hall, 2000, 24; Watson and Crick, 1953, 737.
[22] Guyton and Hall, 2000, 24; Lodish et al., 2000, 103; Watson and Crick, 1953, 737.
[23] Lodish et al., 2000, 456.
[24] See Appendix A.
[25] See Appendix A; Alberts et al., 1998, 189.
[26] See Appendix A.
[27] Hertig, 1968, 26; Hertig and Rock, 1973, 130; (cited by O’Rahilly and Müller, 1987, 12); Shettles, 1958, 400.
[28] Guyton and Hall, 2000, 34.
[29] Moore and Persaud, 2003, 33 & 60; Morton et al., 1992, 72; Nahhas and Barnea, 1990, 105.

Page 4


Chapter 5   Early Stages (Morula and Blastocyst) and Stem Cells

By 3 to 4 days after fertilization, the dividing cells of the embryo assume a spherical shape and the embryo is called a morula (mōr´ū-lă).[30]

By 4 to 5 days, a cavity forms within this ball of cells and the embryo is then called a blastocyst.[31]

The cells inside the blastocyst are called the inner cell mass and give rise to the head, body, and other structures vital to the developing human.[32]

Cells within the inner cell mass are called embryonic stem cells because they have the ability to form each of the more than 200 cell types contained in the human body.[33]

Chapter 5   Early Stages (Morula and Blastocyst) and Stem Cells

গর্ভসঞ্চাৰৰ ৩-ৰ পৰা ৪ দিনৰ পিচত ভ্রূণৰ বিভক্ত হোৱা কোষবোৰে গোলাকাৰ আকৃতি গ্রহণ কৰে আৰু ভ্রূণক তেতিয়া মোৰুলা(morula) বোলা হয়।

৪-ৰ পৰা ৫ দিনৰ ভিতৰত, কোষৰ এই গোলাৰ মাজত এটি ফাটল সৃষ্টি হয় আৰু ভ্রূণক তেতিয়া ব্লাস্টোচিষ্ট (blastocyst_ বুলি কোৱা হয়।

ব্লাস্টোচিষ্টৰ ভিতৰত থকা কোষবোৰক অন্তৰস্থ কোষ ভৰ বুলি কোৱা হয় আৰু ই মূৰ, শৰীৰ আৰু বিকশিত মানবৰ বাবে অত্যাৱশকীয় অঙ্গসমুহ সৃষ্টি কৰে।

মানুহৰ শৰীৰত থকা ২০০-ৰো অধিক প্রকাৰৰকোষ সৃষ্টি কৰাৰ ক্ষমতা থকাৰ বাবে অন্তৰস্থ কোষ বোৰৰ ভিতৰত থকা কোষক ভ্রূণসংক্রান্তঠাৰি কোষ বোলা হয়।

Chapter 6   1 to 1½ Weeks: Implantation and Human Chorionic Gonadotropin (hCG)

After traveling down the uterine tube, the early embryo embeds itself into the inner wall of the mother's uterus. This process, called implantation, begins 6 days and ends 10 to 12 days after fertilization.[34]

Cells from the growing embryo begin to produce a hormone called human chorionic gonadotropin (human kō-rē-on'ik gō'nad-ō-trō'pin), or hCG, the substance detected by most pregnancy tests.[35]

HCG directs maternal hormones to interrupt the normal menstrual cycle, allowing pregnancy to continue.[36]

Chapter 6   1 to 1½ Weeks: Implantation and Human Chorionic Gonadotropin (hCG)

জৰায়ুমধ্যস্থ নলীয়েদি গতি কৰাৰ পিচত ভ্রূণৰ আগতীয়া ৰূপে মাতৃ জৰায়ুৰ ভিতৰৰ দেৱালত পোত খায় ধৰে। অধিৰোপন(implantation) নামৰ এই প্রক্রিয়া গর্ভসঞ্চাৰৰ ৬ দিনৰ পিচত আৰম্ভ হয় আৰু ১০-ৰ পৰা ১২ দিনৰ পিচত অন্ত হয়।

বৃদ্ধি হোৱা ভ্রূণৰ কোষবোৰে মানব কৰিওনিক গোনাদোট্রপিন বা hCG নামৰ হৰমোন সৃষ্টি কৰিবলৈ আৰম্ভ কৰে, যিটো পদার্থ প্রায়বোৰ গর্ভধাৰণ পৰীক্ষাত ধৰা পৰে।

HCG-এ মাটেমেল হৰমোনক সাধাৰণ মাহেকীয়া চক্রত ব্যঘাত জন্মাবলৈ নির্দেশ দি গর্ভধাৰণ আগবঢাবলৈ অনুমতি দিয়ে।

Chapter 7   The Placenta and Umbilical Cord

Following implantation, cells on the periphery of the blastocyst give rise to part of a structure called the placenta (plă-sen'tă), which serves as an interface between the maternal and embryonic circulatory systems.

The placenta delivers maternal oxygen, nutrients, hormones, and medications to the developing human; removes all waste products; and prevents maternal blood from mixing with the blood of the embryo and fetus.[37]

The placenta also produces hormones and maintains embryonic and fetal body temperature slightly above that of the mother's.[38]

The placenta communicates with the developing human through the vessels of the umbilical (ŭm-bil'i-kăl) cord.[39]

The life support capabilities of the placenta rival those of intensive care units found in modern hospitals.

Chapter 7   The Placenta and Umbilical Cord

অধিৰোপণৰ পিচত, ব্লাস্টোচিষ্টৰ ওচৰে পাঁজৰে থকা কোষবোৰে প্লাচেন্টা(গর্ভৰ ফুল) নামৰ এক গাঁথনিৰ সৃষ্টি কৰে যিয়ে মাতৃ আৰু ভ্রূণসংক্রান্ত সঞ্চালন প্রণালীৰ মাজৰ এক অন্তবর্তী পৃষ্ঠ ৰূপে কাম কৰে।

গর্ভফুলে মাকৰ পৰা অক্সিজেন, খাদ্য হৰমোন, ঔষধ বাঢ়ি অহা মানৱলৈ যোগান ধৰে; সকলোবোৰ মল আতৰায় দিয়ে; আৰু মাকৰ তেজ ভ্রূণ আৰু গর্ভৰ তেজৰ লগত মিলিত হোৱাত বাধা দিয়ে।

গর্ভফুলে হৰমোনউত্‍পাদন কৰে আৰু মাকৰ তাপমানতকৈ ভ্রূণ আৰু গর্ভৰ তাপমান অলপমান বেচিকৈ ৰাখে।

বাঢ়ি অহা মানবৰ লগত নাভী সংলগ্ন নাড়ীৰ মাধ্যমেৰে গর্ভফুলে সংযোগ স্থাপন কৰে।

গর্ভফুলৰ জীবন প্রতিপালন কৰাৰ ক্ষমতা আধুনিক চিকিত্সালয়ত দেখিবলৈ পোৱা অবিশ্রান্ত যত্ন একক(intensive care unit)-ৰ লগত তুলনা কৰিব পাৰি।

 

 


[30] Gasser, 1975, 1; O’Rahilly and Müller, 2001, 37; Spraycar, 1995, 1130: “Morula“ is derived from the Latin word morus meaning “mulberry.“ [Carnegie Stage 2]
[31] O’Rahilly and Müller, 2001, 39. [Carnegie Stage 3]
[32] Gasser, 1975, 1; O’Rahilly and Müller, 2001, 39; Sadler, 2005, 6.
[33] Alberts et al., 1998, 32. For a discussion and definition of embryonic stem cells see the website of the National Institutes of Health: http://stemcells.nih.gov/infoCenter/stemCellBasics.asp#3
[34] O’Rahilly and Müller, 2001, 40; Implantation begins with attachment of the blastocyst at about 6 days after fertilization. [Attachment of the blastocyst to the inner wall of the uterus is a transient event and is the hallmark of Carnegie Stage 4.] See also Adams, 1960, 13-14; Cunningham et al., 2001, 20; Hamilton, 1949, 285-286; Hertig, 1968, 41; Hertig and Rock, 1944, 182; Hertig and Rock, 1945, 81 & 83; Hertig and Rock, 1949, 183; Hertig et al., 1956, 444. [Carnegie Stage 5]
[35] Chartier et al., 1979, 134; Cunningham et al., 2001, 27; O’Rahilly and Müller, 2001, 43.
[36] Cunningham et al., 2001, 20 & 26-27; O’Rahilly and Müller, 2001, 31.
[37] Hertig, 1968, 16; Cunningham et al., 2001, 86 & 136; For a detailed description of the placenta see Hamilton and Boyd, 1960. For a detailed description of the placenta vasculature see Harris and Ramsey, 1966. This separation of maternal and fetal blood is almost but not quite perfect as a small number of fetal cells may be found in the maternal circulation and vice-versa. See Cunningham et al., 2001, 96 & 136.
[38] Liley, 1972, 101; O’Rahilly and Müller, 2001, 78-79.
[39] For a detailed description of umbilical cord formation see Florian, 1930.

Page 5


Chapter 8   Nutrition and Protection

By 1 week, cells of the inner cell mass form two layers called the hypoblast and epiblast.[40]

The hypoblast gives rise to the yolk sac,[41] which is one of the structures through which the mother supplies nutrients to the early embryo.[42]

Cells from the epiblast form a membrane called the amnion (am-nē-on),[43] within which the embryo and later the fetus develop until birth.

Chapter 8   Nutrition and Protection

১ সপ্তাহৰ ভিতৰতে অভ্যন্তৰ কোষ ভৰৰ কোষবোৰে হাইপোব্লাস্ট আৰু এপিব্লাস্ট নামৰ দুটা স্তৰ সৃষ্টি কৰে।

হাইপোব্লাস্টে কুহুমৰ মোনাৰ সৃষ্টি কৰে যাৰ মাজেৰে মাতৃয়ে ভ্রূণৰ আগতীয়া অৱস্থাত খাদ্য যোগান ধৰে।

এপিব্লাস্টৰ কোষবোৰে এমনিয়ন নামৰ এক পাতল পর্দাৰ সৃষ্টি কৰে যাৰ ভিতৰত জন্ম নোহোৱালৈকে ভ্রূণ আৰু পাচত গর্ভৰ বিকাশ হয়।

Chapter 9   2 to 4 Weeks: Germ Layers and Organ Formation

By approximately 2½ weeks, the epiblast has formed 3 specialized tissues, or germ layers, called ectoderm, endoderm, and mesoderm.[44]

Ectoderm gives rise to numerous structures including the brain, spinal cord, nerves, skin, nails, and hair.

Endoderm produces the lining of the respiratory system and digestive tract and generates portions of major organs such as the liver and pancreas.

Mesoderm forms the heart, kidneys, bones, cartilage, muscles, blood cells, and other structures.[45]

By 3 weeks the brain is dividing into 3 primary sections called the forebrain, midbrain, and hindbrain.[46]

Development of the respiratory and digestive systems is also underway.[47]

As the first blood cells appear in the yolk sac,[48] blood vessels form throughout the embryo, and the tubular heart emerges.[49]

Almost immediately, the rapidly growing heart folds in upon itself as separate chambers begin to develop.[50]

The heart begins beating 3 weeks and 1 day following fertilization.[51]

The circulatory system is the first body system, or group of related organs, to achieve a functional state.[52]

Chapter 9   2 to 4 Weeks: Germ Layers and Organ Formation

প্রায় ২ ১/২ সপ্তাহমানৰ পাচত এপিব্লাস্টে ৩টা বিশেষ ধৰণৰ পাতল কোষ-ছাল বা এক্টোডার্ম, এন্ডোডার্ম আৰু মেচোডার্ম নামৰ পাতল কোষ-ছাল গঠন কৰে।

এক্টোডার্মে অসংখ্য অঙ্গ-প্রত্যঙ্গ যেনেদৰে মস্তিষ্ক মেৰুদণ্ড স্নায়ু ছাল নখ আৰু চুলি ইত্যাদি সৃষ্টি কৰে।

এক্টোডার্মে শ্বাস-নিশ্বাস প্রণালী আৰু হজমী নলীৰ বাহিৰৰ আবৰণ গঠণ কৰে আৰু প্রধান অঙ্গবোৰ যেনেদৰে কলিজা আৰু গঠন কৰে।

মেচোডার্মে হৃদয়, মূত্রাশয়, হাড়, কোমলাস্থি, মাংসপেশী, তেজৰ কণিকা, আৰু অন্য গাঁথনিবোৰ গঠন কৰে।

৩ সপ্তাহ হওতে মস্তিষ্ক ৩টা প্রাথমিক ভাগত বিভক্ত হয় যিবোৰৰ নাম পূর্বমস্তিষ্ক, মধ্যমস্তিষ্ক, আৰু পশ্চাদ্স্তিষ্ক।

শ্বাস-নিশ্বাস প্রণালী আৰু পাচনতন্ত্রৰ বিকাশো লগতে চলি থাকে।

যেতিয়া তেজৰ প্রথম কণিকাবোৰ কুহুম মোনাত দেখা দিয়ে, সম্পূর্ণ ভ্রূণত তেজৰ নলাবোৰ গঠন হয়, আৰু নলাকৃতিৰ হৃদয়খন প্রকাশ পায়।

প্রায় লগেলগে, দ্রুতভাবে বৃদ্ধি পোৱাহৃদয়খন নিজৰ ওপৰতে বেলেগ বেলেগ কোঠালীত ভাঁজ খাই বিকাশ হবলৈ ধৰে।

গর্ভসঞ্চাৰৰ ৩ সপ্তাহ আৰু এদিনৰ পাচত হৃদয়খন ধপধপাবলৈ আৰম্ভ কৰে।

ৰক্ত সঞ্চালন প্রণালীয়েই শৰীৰৰ প্রণালী বা সম্পর্কীয় অঙ্গবোৰৰ সমষ্টি যি প্রথমে কাম কৰিব পৰা স্থিতি লাভ কৰে।

Chapter 10   3 to 4 Weeks: The Folding of the Embryo

Between 3 and 4 weeks, the body plan emerges as the brain, spinal cord, and heart of the embryo are easily identified alongside the yolk sac.

Rapid growth causes folding of the relatively flat embryo.[53] This process incorporates part of the yolk sac into the lining of the digestive system and forms the chest and abdominal cavities of the developing human.[54]

Chapter 10   3 to 4 Weeks: The Folding of the Embryo

৩ আৰু ৪ সপ্তাহৰ ভিতৰত শৰীৰৰ নক্সা প্রকাশ হয় যেতিয়া ভ্রূণৰ মস্তিষ্ক, মেৰুদণ্ড, আৰু হৃদয়খন কুহুম মোনাৰ কাষত সহজতে চিনাক্ত কৰিব পাৰি।

খৰতকীয়া বিকাশৰ ফলত আপেক্ষিক ভাবে সমতল ভ্রূণত ভাজ লাগি যায়। এই প্রক্রিয়ায় পাচনতন্ত্রৰ চামনিখনৰ ভিতৰত কুহুমৰ মোনাখন সংলগ্ন কৰে আৰু বিকাশিত মানবৰ বুকু আৰু পেটৰ গর্ত গঠন কৰে।

 

 


[40] O’Rahilly and Müller, 2001, 39.
[41] Moore and Persaud, 2003, 50; O’Rahilly and Müller, 2001, 82. [Carnegie Stages 5 & 6]; In humans, the term “yolk sac“ has fallen out of favor among some embryologists (including O’Rahilly and Müller) because it is not a nutrient reservoir and does not contain yolk. The technically preferred term is umbilical vesicle. This structure plays a vital role in the transfer of nutrients from mother to embryo before placental circulation becomes fully functional.
[42] Campbell et al., 1993, 756; Kurjak et al., 1994, 437; O’Rahilly and Müller, 2001, 82.
[43] O’Rahilly and Müller, 1987, 29; O’Rahilly and Müller, 2001, 43. [Carnegie Stages 4-5]
[44] O’Rahilly and Müller, 2001, 14 & 135. [Carnegie Stage 7]; It should be noted there are many examples of organs derived from multiple germ layers. For instance, the liver is largely derived from endoderm but contains blood vessels and blood cells derived from mesoderm and nerves of ectodermal origin.
[45] Moore and Persaud, 2003, 80 & 83; Sadler, 2005, 9.
[46] Bartelmez, 1923, 236; Müller and O’Rahilly, 1983, 419-420 & 429; O’Rahilly and Gardner, 1979, 123 & 129; O’Rahilly and Müller, 1984, 422; O’Rahilly and Müller, 1987, 90; O’Rahilly and Müller, 1999a, 47 & 52. [Carnegie Stage 9]
[47] DiFiore and Wilson, 1994, 221; Fowler et al., 1988, 793; Grand et al., 1976, 793-794 & 796 & 798; O’Rahilly, 1978, 125; O’Rahilly and Boyden, 1973, 238-239; O’Rahilly and Müller, 1984, 421; O’Rahilly and Tucker, 1973, 6 & 8 & 23; Streeter, 1942, 232 & 235.
[48] Carlson, 2004, 117.
[49] Gilmour, 1941, 28; O’Rahilly and Müller, 1987, 86. [Carnegie Stage 9]
[50] Campbell, 2004, 14; Carlson, 2004, 116 & 446; Navaratnam, 1991, 147-148; O’Rahilly and Müller, 1987, 99. [Carnegie Stage 10]
[51] Campbell, 2004, 14; Carlson, 2004, 430; De Vries and Saunders, 1962, 96; Gardner and O’Rahilly, 1976, 583; Gilbert-Barness and Debich-Spicer, 1997, 650; Gittenger-de Groot et al., 2000, 17; van Heeswijk et al., 1990, 151; Kurjak and Chervenak, 1994, 439; Navaratnam, 1991, 147-148; O’Rahilly and Müller, 1987, 99; Wisser and Dirschedl, 1994, 108. [Carnegie Stage 10, possibly late Stage 9]
[52] Moore and Persaud, 2003, 70: “The cardiovascular system is the first organ system to reach a functional state.“
[53] Moore and Persaud, 2003, 78.
[54] Gasser, 1975, 26; Moore and Persaud, 2003, 78.

Page 6


Embryonic Development: 4 to 6 Weeks

Chapter 11   4 Weeks: Amniotic Fluid

By 4 weeks the clear amnion surrounds the embryo in a fluid-filled sac.[55] This sterile liquid, called amniotic (am-nē-ot'ik) fluid, provides the embryo with protection from injury.[56]

Embryonic Development: 4 to 6 Weeks

Chapter 11   4 Weeks: Amniotic Fluid

৪ সম্তাহ হওতে পৰিষ্কাৰ এম্নিঅনে তৰল পদার্থৰে পূর্ণ মোনাৰ ভিতৰত ভ্রূন আবৰি ধৰে। এই এননিওটিক ফ্লুইড নামৰ জীবাণুমুক্ত জুলীয়া পদার্থই ভ্রূণক আঘাতৰ পৰা ৰক্ষা কৰাৰ ব্যবস্থা কৰে।

Chapter 12   The Heart in Action

The heart typically beats about 113 times per minute.[57]

Note how the heart changes color as blood enters and leaves its chambers with each beat.

The heart will beat approximately 54 million (5.4×107) times before birth and over 3.2 billion (3.2×109) times over the course of an 80-year lifespan.[58]

Chapter 12   The Heart in Action

বৈশিষ্ট্য অনুযায়ী হৃদয় মিনিটত ১১৩ বাৰ স্পন্দণ কৰে।

লক্ষ্য কৰিবলগীয়া কথা হৈছে তেজ প্রতি কোঠালীত প্রবেশ কৰাৰ ফলত হৃদয়ৰ ৰঙ কেনেকৈ সলনি হয়।

জন্মৰ আগতে হৃদয় প্রায় ৫৪০ লক্ষ্য বাৰ আৰু এক ৮০ বছৰীয়া জীবন কালত প্রায় ৩২০ কোটি বাৰ স্পন্দণ কৰে।

Chapter 13   Brain Growth

Rapid brain growth is evidenced by the changing appearance of the forebrain, midbrain, and hindbrain.

Chapter 13   Brain Growth

পূর্বমস্তিষ্ক, মধ্যমস্তিষ্ক আৰু পশ্চাদমস্তিষ্কৰ সলনি হৈ থকা আকৃতিৰ দ্বাৰা মস্তিষ্কৰ দ্রুত বিকাশ প্রমানিত হয়।

Chapter 14   Limb Buds

Upper and lower limb development begins with the appearance of the limb buds by 4 weeks.[59]

The skin is transparent at this point because it is only one cell thick.

As the skin thickens, it will lose this transparency, which means that we will only be able to watch internal organs develop for about another month.[60]

Chapter 14   Limb Buds

৪ সপ্তাহৰ পাচত অঙ্গ-প্রত্যঙ্গৰ কলি হেন আবির্ভাবৰ লগতে উর্ধ্ব আৰু নিম্ন অঙ্গ-প্রত্যঙ্গৰ বিকাশ আৰম্ভ হয়।

কেবল এক কোষপৰিমান ডাঠ হোৱাৰবাবে এই সময়ত ছালখন দেখিবলৈ স্বচ্ছ।

ছালখন ডাঠ হৈ অহাৰ লগে-লগে, ইয়াৰ স্বচ্ছতা লোপ পাবলৈ ধৰে, যাৰ দ্বাৰা আমি ইয়াকে বুজিব পাৰো য়ে এতিয়াৰ পৰা আমি শৰীৰৰ ভিতৰৰ অঙ্গ-প্রত্যঙ্গৰ বিকাশ প্রায় এমাহলৈহে মাথো দেখা পাম।

Chapter 15   5 Weeks: Cerebral Hemispheres

Between 4 and 5 weeks, the brain continues its rapid growth and divides into five distinct sections.[61]

The head comprises about one-third of the embryo's total size.[62]

The cerebral (ser'ĕ-brăl) hemispheres appear,[63] gradually becoming the largest parts of the brain.[64]

Functions eventually controlled by the cerebral hemispheres include thought, learning, memory, speech, vision, hearing, voluntary movement, and problem-solving.[65]

Chapter 15   5 Weeks: Cerebral Hemispheres

৪ আৰু ৫ সপ্তাহৰ ভিতৰত, মস্তিষ্কৰ বিকাশ দ্রুত গতিৰে হৈ থাকে আৰু ৫ টা স্বতন্ত্র ভাগত বিভক্ত হয়।

ভ্রণৰ প্রায় ১/৩ অংশৰ দ্বাৰা মূৰৰ গঠন হয়।

ক্রমান্বয়ে গুৰুমস্তিষ্কৰ গোলার্ধ প্রকট হৈ উঠে, আৰু মস্তিষ্কৰ বৃহত্তম অঙ্গ ৰূপে পৰিগণিত হয়।

অৱশেষত গুৰুমস্তিষ্কৰ দ্বাৰা নিয়ন্ত্রিত হোৱাবিভিন্ন কার্য্যবোৰ হল বিচাৰবুদ্ধি, শিক্ষা, স্মৃতি, বাকশক্তি, দৃষ্টি, শ্রবণ, স্বেচ্ছাকৃত চলন, আৰু সমস্য-সমাধান।

 

 


[55] Gasser, 1975, 30; O’Rahilly and Müller, 2001, 80.
[56] O’Rahilly and Müller, 2001, 81.
[57] van Heeswijk et al., 1990, 153.
[58] See Appendix A.
[59] Gasser, 1975, 49 & 59; O’Rahilly and Gardner, 1975, 11; O’Rahilly and Müller, 1985, 148 & 151; O’Rahilly and Müller, 1987, 143; Streeter, 1945, 30; Uhthoff, 1990, 7 & 141. [upper and lower limb buds: Carnegie Stages 12 & 13]
[60] Moore and Persaud, 2003, 486; O’Rahilly, 1957, 459; O’Rahilly and Müller, 2001, 165. For information about the first-trimester, direct-imaging technique used in this program (called embryoscopy), see Cullen et al., 1990.
[61] O’Rahilly and Müller, 1999a, 134; Sadler, 2005, 106. [Carnegie Stage 15]
[62] Laffont, 1982, 5.
[63] Bartelmez and Dekaban, 1962, 25; Campbell, 2004, 17; O’Rahilly and Gardner, 1979, 130; O’Rahilly et al., 1984, 249; O’Rahilly and Müller, 1999a, 115; van Dongen and Goudie, 1980, 193. [Carnegie Stage 14]
[64] Moore, 1980, 938.
[65] Guyton and Hall, 2000, 663-677.

Page 7


Chapter 16   Major Airways

In the respiratory system, the right and left main stem bronchi (brong'kī) are present[66] and will eventually connect the trachea (trā´kē-ă), or windpipe, with the lungs.

Chapter 16   Major Airways

শ্বাস-নিশ্বাস প্রণালীতে, সৌঁ আৰু বাও হাতৰ প্রধান দণ্ডকায়শ্বাস-নলীদ্বয়থাকে আৰু কালক্রমে ই ট্রেচিয়া অথবা শ্বাসনলী, হাঁওফাঁওৰ লগত সংযুক্ত কৰিব।

Chapter 17   Liver and Kidneys

Note the massive liver filling the abdomen adjacent to the beating heart.

The permanent kidneys appear by 5 weeks.[67]

Chapter 17   Liver and Kidneys

বিৰাট যকৃতে পেটক পৰিপূর্ণ কৰাটা লক্ষ্য কৰক বৃহত্‍ যকৃত্‍খন লক্ষ্য কৰক।

৫ সপ্তাহৰ ভিতৰত স্থায়ী মূত্রাধাৰ প্রকট হয়।

Chapter 18   Yolk Sac and Germ Cells

The yolk sac contains early reproductive cells called germ cells. By 5 weeks these germ cells migrate to the reproductive organs adjacent to the kidneys.[68]

Chapter 18   Yolk Sac and Germ Cells

জীবাণু কোষ নামৰ আগতীয়া পুনৰূত্‍পাদী কোষবোৰ কুহুম মোনাত অন্তর্ভুক্ত হয়। ৫ সপ্তাহৰ ভিতৰত এই জীবাণু কোষবোৰ মূত্রাশয়ৰ কাষত থকা পুনৰুত্‍পাদী অঙ্গবোৰলৈ প্রব্রজন কৰে।

Chapter 19   Hand Plates and Cartilage

Also by 5 weeks, the embryo develops hand plates,[69] and cartilage formation begins by 5½ weeks.[70]

Here we see the left hand plate and wrist at 5 weeks and 6 days.

Chapter 19   Hand Plates and Cartilage

৫ সপ্তাহৰ ভিতৰতে, ভ্রূণে হাতৰ ফলিবোৰ বিকাশ কৰে আৰু ৫ ১/২ সপ্তাহৰ ভিতৰত কোমলাস্থিবোৰৰো গঠন আৰম্ভ হয়।

ইয়াত আমি ৫ আৰু ৬ সপ্তাহৰ পাচৰ বাঁও হাতৰ ফলি আৰু হাতৰ সৰু গাঁঠি দেখিবলৈ পাইছোঁ।

 

 


[66] Moore and Persaud, 2003, 245; O’Rahilly and Boyden, 1973, 239; O’Rahilly and Müller, 2001, 291; Sparrow et al., 1999, 550.
[67] Angtuaco et al., 1999, 13; Lipschutz, 1998, 384; Moore and Persaud, 2003, 288; O’Rahilly and Müller, 1987, 167 & 182; O’Rahilly and Müller, 2001, 301; Sadler, 2005, 72. [Carnegie Stage 14]
[68] O’Rahilly and Müller, 2001, 23; Waters and Trainer, 1996, 16; Witschi, 1948, 70, 77 & 79.
[69] O’Rahilly and Müller, 1987, 175; Streeter, 1948, 139. [Carnegie Stage 15 ]
[70] O’Rahilly and Gardner, 1975, 4. [Carnegie Stages 16 and 17 ]

Page 8


Embryonic Development: 6 to 8 Weeks

Chapter 20   6 Weeks: Motion and Sensation

By 6 weeks the cerebral hemispheres are growing disproportionately faster than other sections of the brain.

The embryo begins to make spontaneous and reflexive movements.[71] Such movement is necessary to promote normal neuromuscular development.

A touch to the mouth area causes the embryo to reflexively withdraw its head.[72]

Embryonic Development: 6 to 8 Weeks

Chapter 20   6 Weeks: Motion and Sensation

৬ সপ্তাহৰ ভিতৰত গুৰুমস্তিষ্কৰ গোলার্ধ মস্তিষ্কৰ আন অঙ্গৰ তুলনাত অসমানুপাতিক ভাবে বৃদ্ধি হবলৈ ধৰে।

ভ্রূণে স্বত:ফূর্ত আৰু অনৈচ্ছিক ভাবে চলাচল কৰিবলৈ আৰম্ভ কৰে। এনে ধৰণৰ চলাচল স্নায়ু-পেশীৰ স্বাভাবিক বিকাশৰ বাবে আবশ্যক।

মুখমণ্ডলত স্পর্শ কৰিলে ভ্রূণে আপোনাআপুনি মূৰটো কোঁচ খুৱাই দিয়ে।

Chapter 21   The External Ear and Blood Cell Formation

The external ear is beginning to take shape.[73]

By 6 weeks, blood cell formation is underway in the liver where lymphocytes are now present.[74] This type of white blood cell is a key part of the developing immune system.

Chapter 21   The External Ear and Blood Cell Formation

বাহ্যিক কানে আকাৰ লাভ কৰিবলৈ আৰম্ভ কৰে।

৬ সপ্তাহৰ ভিতৰত, যকৃত্‍ৰ ভিতৰত তেজৰ কণিকাবোৰ গঠন হবলৈ ধৰে যত এতিয়া লিম্ফোচাইটবোৰে স্থান লাভ কৰে। এনে ধৰণৰ শুভ্র ৰক্ত কণিকা অসংক্রাম্য পদ্ধতি বিকাশ হোৱাৰ এক মূল উপাদান।

Chapter 22   The Diaphragm and Intestines

The diaphragm (dī'ă-fram), the primary muscle used in breathing, is largely formed by 6 weeks.[75]

A portion of the intestine now protrudes temporarily into the umbilical cord. This normal process, called physiologic herniation (fiz-ē-ō-loj'ik her-nē-ā'shŭn), makes room for other developing organs in the abdomen.[76]

Chapter 22   The Diaphragm and Intestines

সাধাৰণতে ৬ সপ্তাহৰ ভিতৰতে উশাহ লওতে ব্যবহাৰ হোৱা মুখ্য মাংসপেশী, মধ্যচ্ছদাৰ গঠন হয়।

অন্ত্রৰ এক অংশ সাময়িক ভাবে নাভী সংলগ্ন নাড়ীয়েদি বাহিৰলৈ ওলাই আহে। ফিজিওলজিক হেমিয়েশ্বন নামৰ প্রক্রিয়ায় তলপেটৰ ভিতৰত অন্য বিকাশমুখী অঙ্গসমুহৰ বাবে ঠাই উলিয়ায় দিয়ে।

Chapter 23   Hand Plates and Brainwaves

At 6 weeks the hand plates develop a subtle flattening.[77]

Primitive brainwaves have been recorded as early as 6 weeks and 2 days.[78]

Chapter 23   Hand Plates and Brainwaves

৬ সপ্তাহৰ অন্তত হাতৰ ফলিবোৰে এক অস্পষ্ট চেপেটা অঙ্গ বিকাশ কৰে।

৬ সপ্তাহ আৰু ২ দিনৰ পাচতেই মস্তিষ্ক তৰঙ্গ ৰেকর্ড কৰিব পৰা গৈছে।

 

 


[71] Birnholz et al., 1978, 539; de Vries et al., 1982, 301 & 304: “The first movements were observed at 7.5 weeks postmenstrual age.“ [or 5½ weeks postfertilization age]; Humphrey, 1964, 99: earliest reflex 5½ weeks; Humphrey, 1970, 12; Humphrey and Hooker, 1959, 76; Humphrey and Hooker, 1961, 147; Kurjak and Chervenak, 1994, 48; Visser et al., 1992, 175-176: “Endogenously generated fetal movements can first be observed after 7 weeks postmenstrual age (i.e. 5 weeks after conception);“ Natsuyama, 1991, 13; O’Rahilly and Müller, 1999a, 336: 5½ weeks postfertilization; Sorokin and Dierker, 1982, 723 & 726; Visser et al., 1992, 175-176; Natsuyama, 1991, 13: Spontaneous movement observed by “Carnegie stage 15“ (about 33 days postfertilization); Hogg, 1941, 373: Reflex activity begins at 6½ weeks [adjusted to postfertilization age].
[72] Goodlin, 1979, D-128.
[73] Karmody and Annino, 1995, 251; O’Rahilly and Müller, 2001, 480; Streeter, 1948, 190.
[74] Kurjak and Chervenak, 1994, 19.
[75] de Vries et al., 1982, 320.
[76] Gilbert-Barness and Debich-Spicer, 1997, 774; Grand et al., 1976, 798; O’Rahilly and Müller, 1987, 213; Sadler, 2005, 66; Spencer, 1960, 9; Timor-Tritsch et al., 1990, 287.
[77] O’Rahilly and Müller, 1987, 202-203.
[78] Borkowski and Bernstine, 1955, 363 (cited by Bernstine, 1961, 63 & 66; O’Rahilly and Müller, 1999a, 195; van Dongen and Goudie, 1980, 193.); Hamlin, 1964, 113. For a summary of in utero fetal encephalography (measuring brainwaves) in the near- term fetus using abdominal and vaginal electrodes see Bernstine et al., 1955.

Page 9


Chapter 24   Nipple Formation

Nipples appear along the sides of the trunk shortly before reaching their final location on the front of the chest.[79]

Chapter 24   Nipple Formation

বুকুৰ সন্মুখত অবস্থান গ্রহণ কৰাৰ আগতেই শৰীৰৰ কাষত স্তনবৃন্ত প্রকট হৈ ওলায় আহে।

Chapter 25   Limb Development

By 6½ weeks, the elbows are distinct, the fingers are beginning to separate,[80] and hand movement can be seen.

Bone formation, called ossification (os'i-fi-kā'shŭn), begins within the clavicle, or collar bone, and the bones of the upper and lower jaw.[81]

Chapter 25   Limb Development

৬ ১/২ সপ্তাহতেই কিলাকুটী পৰিষ্কাৰকৈ দেখা পোৱা যায়, আঙুলিবোৰ পৃথক হয়, আৰু হাতৰ চলাচল দেখা যায়।

ডিঙিৰ হাড় বা ক্লাভিকল আৰু ওপৰৰ আৰু তলৰ হনুৰ হাড়ৰ ভিতৰত হাড়ৰ গঠন বা অচ্চিফিকেশ্বন আৰম্ভ হয়।

Chapter 26   7 Weeks: Hiccups and Startle Response

Hiccups have been observed by 7 weeks.[82]

Leg movements can now be seen, along with a startle response.[83]

Chapter 26   7 Weeks: Hiccups and Startle Response

৭ সপ্তাহৰ পাচতে হিঁকতি অহা দেখা গৈছে।

আকস্মিক সঁহাৰিৰে সৈতে ভৰিৰ চলাচল এতিয়া দেখিব লৈ পোৱা যায়।

Chapter 27   The Maturing Heart

The four-chambered heart is largely complete.[84] On average, the heart now beats 167 times per minute.[85]

Electrical activity of the heart recorded at 7½ weeks reveals a wave pattern similar to the adult's.[86]

Chapter 27   The Maturing Heart

৪-কোঠালিৰ হৃদয়খন প্রায় সম্পূর্ণকৈ গঠন হৈছে। এতিয়া হৃদয়ে প্রতি মিনিটত গড়ে ১৬৭ বাৰ স্পন্দন কৰে।

৭ ১/২ সপ্তাহত ৰেকর্ড হোৱা হৃদয়ৰ বৈদ্যুতিক কার্য্যকলাপে প্রাপ্তবয়স্কৰ দৰে তৰঙ্গৰ আর্হি দেখুৱায়।

Chapter 28   Ovaries and Eyes

In females, the ovaries are identifiable by 7 weeks.[87]

By 7½ weeks, the pigmented retina of the eye is easily seen and the eyelids are beginning a period of rapid growth.[88]

Chapter 28   Ovaries and Eyes

স্ত্রীলিঙ্গৰ ক্ষেত্রত, ডিম্বাশয় 7 সপ্তাহতে চিনাক্ত কৰিব পাৰি।

৭ ১/২ সপ্তাহত, ৰঙ বোলোৱা চকুৰ অক্ষিপট সহজতে দেখা পোৱা যায় আৰু চকুৰ পতাৰ দ্রুত বিকাশ হবলৈ আৰম্ভ কৰে।

Chapter 29   Fingers and Toes

Fingers are separate and toes are joined only at the bases.

The hands can now come together, as can the feet.[89]

Knee joints are also present.[90]

Chapter 29   Fingers and Toes

আঙুলিবোৰ পৃথক আৰু ভৰিৰ আঙুলিবোৰ গুজিতহে লগ লাগি থাকে।

এতিয়া ভৰি দুটাৰ দৰে হাত দুটাও একেলগ হব পাৰে।

আঁঠুৰ গাঁঠিও গঠন হয়।

 

 


[79] O’Rahilly and Müller, 1985, 155: “The nipple appears at stages 17 and 18.“ [41-44 days postfertilization]; Wells, 1954, 126.
[80] O’Rahilly and Müller, 2001, 221; Streeter, 1948, 187.
[81] Carlson, 2004, 189; O’Rahilly and Gardner, 1972, 293; O’Rahilly and Gardner, 1975, 19; O’Rahilly and Müller, 2001, 385; Sperber, 1989, 122 & 147. [Carnegie Stage 19]
[82] de Vries et al., 1982, 305 & 311; Visser et al., 1992, 176.
[83] de Vries et al., 1988, 96; Visser et al., 1992, 176.
[84] Cooper and O’Rahilly, 1971, 292; James, 1970, 214; Jordaan, 1979, 214; Streeter, 1948, 192; Vernall, 1962, 23: “The four chambers of the heart and the associated major vessels are externally apparent in a close approximation to their adult positions.“ [Carnegie Stage 18]
[85] van Heeswijk et al., 1990, 153.
[86] Straus et al., 1961, 446 (cited by Gardner and O’Rahilly, 1976, 571.):  “…an electrocardiogram with the classical P, QRS, and T configuration has been obtained from a 23mm human embryo (Straus, Walker, and Cohen, 1961).“
[87] O’Rahilly and Müller, 2001, 320. [Carnegie Stage 20]
[88] Andersen et al., 1965, 646; O’Rahilly, 1966, 35; O’Rahilly and Müller, 1987, 259; Pearson, 1980, 39; Streeter, 1951, 193. [Carnegie Stage 22] Pigment within the retina is present from about 37 days postfertilization per O’Rahilly, 1966, 25. [Carnegie Stage 16]
[89] Streeter, 1951, 191; reiterated by O’Rahilly and Müller, 1987, 257.
[90] O’Rahilly and Gardner, 1975, 11; O’Rahilly and Müller, 1987, 262.

Page 10


The 8-Week Embryo

Chapter 30   8 Weeks: Brain Development

At 8 weeks the brain is highly complex[91] and constitutes almost half of the embryo's total body weight.[92]

Growth continues at an extraordinary rate.

The 8-Week Embryo

Chapter 30   8 Weeks: Brain Development

৮ সপ্তাহৰ অন্তত মস্তিষ্কই অতিকৈ বিকাশ লাভ কৰে ইয়াৰ ওজন ভ্রূণৰ সম্পূর্ণ ওজনৰ প্রায় আধা মানেই হয়গৈ।

বিকাশৰ হাৰ অসাধাৰণ ভাবে বৃদ্ধি হয়।

Chapter 31   Right- and Left-Handedness

By 8 weeks, 75 percent of embryos exhibit right-hand dominance. The remainder is equally divided between left-handed dominance and no preference. This is the earliest evidence of right- or left-handed behavior.[93]

Chapter 31   Right- and Left-Handedness

৮ সপ্তাহত ভ্রূণৰ ৭৫% অংশই সোঁ-হাতৰ প্রাধান্য প্রদর্শন কৰে। বাকী অংশ সমান ভাবে বাও-হাতৰ প্রাধান্য আৰু কোনো অগ্রাধিকাৰ নথকাৰ মাজত বিভক্ত হয়। এয়ে হৈছে সোঁ হাত আৰু বাও হাতৰ আচৰণৰ আটাইতকৈ আগতীয়াকৈ পোৱা প্রমাণ।

Chapter 32   Rolling Over

Pediatric textbooks describe the ability to "roll over" as appearing 10 to 20 weeks after birth.[94] However, this impressive coordination is displayed much earlier in the low-gravity environment of the fluid-filled amniotic sac.[95] Only the lack of strength required to overcome the higher gravitational force outside the uterus prevents newborns from rolling over.[96]

The embryo is becoming more physically active during this time.

Motions may be slow or rapid, single or repetitive, spontaneous or reflexive.

Head rotation, neck extension, and hand-to-face contact occur more often.[97]

Touching the embryo elicits squinting, jaw movement, grasping motions, and toe pointing.[98]

Chapter 32   Rolling Over

শিশুৰোগ চিকিত্সাসংক্রান্ত পাঠ্যপুথিবোৰত জন্ম হোৱাৰ ১০-ৰ পৰা ২০ সপ্তাহৰ পাচত "বাগৰ মৰা" ক্ষমতা দেখা যায় বুলি বর্ণনা কৰা হৈছে। কিন্তু, এই আকর্ষনীয় সমন্বয় এমনিওটিক মোনাৰ তৰল পদার্থ পূর্ণ নিম্ন মাধ্যাকর্ষণ শক্তিৰ পৰিবেশত বহু আগতেই দেখা যায়। কেবল জৰায়ুৰ বাহিৰত থকা উচ্চ মাধ্যাকর্ষণ শক্তিক অতিক্রম কৰিবলৈ আৱশ্যক হোৱা শক্তি নথকা বাবেহে নবজাতকে চকাচুৱাই বাগৰ মাৰিব নোৱাৰে।

এই সময়চোৱাত ভ্রূণ শাৰীৰিক ভাবে আগতকৈ বেচি সক্রিয় হৈ উঠে।

চলাচলবোৰ ধীৰ বা দ্রুত, এক বা বাৰংবাৰ, স্বত:স্ফূর্ত বা আত্মপ্রত্যাবর্ত্তনশীল হব পাৰে।

মূৰৰ আবর্তন, ডিঙিৰ বৃদ্ধি, আৰু হাতৰ লগত মুখৰ সম্পর্ক বেচি সঘনাই হবলৈ ধৰে।

ভ্রূণক চুলে চকু ‌‌‌‌‌কেঁৰা কৰা, থুতৰি লৰাচৰা হোৱা, থপিউৱা ভঙ্গি কৰা আৰু ভৰিৰ আঙুলিৰে ইঙ্গিত কৰা আদি ঘটে।

Chapter 33   Eyelid Fusion

Between 7 and 8 weeks, the upper and lower eyelids rapidly grow over the eyes and partially fuse together.[99]

Chapter 33   Eyelid Fusion

৭ আৰু ৮ সপ্তাহৰ ভিতৰত ওপৰৰ আৰু তলৰ চকুৰ পতা চকুৰ ওপৰত বিকাশ হবলৈ ধৰে আৰু আংশিক ভাবে লগ লাগি যায়।

Chapter 34   "Breathing" Motion and Urination

Although there is no air in the uterus, the embryo displays intermittent breathing motions by 8 weeks.[100]

By this time, kidneys produce urine which is released into the amniotic fluid.[101]

In male embryos, the developing testes begin to produce and release testosterone (tes-tos´tĕ-rōn).[102]

Chapter 34   "Breathing" Motion and Urination

যদিও জড়ায়ুৰ ভিতৰত বায়ু নাই, ৮ সপ্তাহত ভ্রূণে মাজে মাজে উশাহ লোৱাৰ ভঙ্গি প্রদর্শনকৰে।

এই সময়তে, মুত্রাশয়ে পেচাব উত্পাদন কৰিবলৈ লয় যি এমনাওটিক তৰললৈ নির্গত হয়।

পুৰুষ ভ্রণত বিকশিত পতীক্ষাবোৰে টেষ্ট'ষ্টাৰোন উত্পাদন আৰু বন্ধ মুক্ত কৰিবলৈ আৰম্ভ কৰে৷

Chapter 35   The Limbs and Skin

The bones, joints, muscles, nerves, and blood vessels of the limbs closely resemble those in adults.[103]

By 8 weeks the epidermis, or outer skin, becomes a multi-layered membrane,[104] losing much of its transparency.

Eyebrows grow as hair appears around the mouth.[105]

Chapter 35   The Limbs and Skin

অঙ্গপ্রত্যঙ্গৰ হাড়, গাঁঠি, আঁহপাহ আৰু ৰক্ত বাহিকাবোৰ প্রাপ্ত বয়স্কলোকৰ ওচৰত নিবিড়ভাবে একে যেন লাগে৷

8 সপ্তাহমানৰ ভিতৰত মাখিছাল বা বাহিৰৰ ছাল তাৰ স্বচ্ছতা হেৰুৱাই বহু-তৰপীয়া চর্মপ্রদ হৈ পৰে৷

মুখমণ্ডলৰ চাৰিওপিনে চুলি গজিলে চকুচেলাউৰি বৃদ্ধি হয়৷

Chapter 36   Summary of the First 8 Weeks

Eight weeks marks the end of the embryonic period.

During this time, the human embryo has grown from a single cell into the nearly 1 billion (109) cells[106] which form over 4,000 (4×103) distinct anatomic structures.

The embryo now possesses more than 90 percent of the structures found in adults.[107]

Chapter 36   Summary of the First 8 Weeks

আঁঠ সপ্তাহত ভ্রুণ সম্বন্ধীয় কাল সমাপ্ত হয়৷

এই সময়ত মানুহৰ ভ্রুণ এটা একক জীৱকোষ প্রায় ১ কোটি জীৱকোষলৈ বৃদ্ধি হয় যি ৪,০০০ দেহতাত্ত্বিক আকাৰ গঠন কৰে৷

এতিয়া ভ্রুণটোৱে প্রাপ্ত বয়স্কমানুহৰ গাত থকা আকাৰৰ ৯০% তকৈ অধিক দখল কৰে৷

 

 


[91] O’Rahilly and Müller, 1999a, 288: “The brain at [Carnegie] Stage 23 is far more advanced morphologically than is generally appreciated, to such an extent that functional considerations are imperative.“
[92] Jordaan, 1979, 149.
[93] Hepper et al., 1998, 531; McCartney and Hepper, 1999, 86.
[94] Bates, 1987, 534.
[95] de Vries et al., 1982, 320; Goodlin and Lowe, 1974, 348; Humphrey, 1970, 8.
[96] Liley, 1972, 101.
[97] de Vries et al., 1982, 311.
[98] Humphrey, 1964, 102; Humphrey, 1970, 19.
[99] Process described by Andersen et al., 1965, 648-649; O’Rahilly, 1966, 36-37; O’Rahilly and Müller, 1987, 261. [Carnegie Stage 23]
[100] Connors et al., 1989, 932; de Vries et al., 1982, 311; McCray, 1993, 579; Visser et al.,1992, 177.
[101] O’Rahilly and Müller, 2001, 304; Windle, 1940, 118; (Windle reports urine formation begins at nine weeks.)
[102] Moore and Persaud, 2003, 307; Waters and Trainer, 1996, 16-17.
[103] O’Rahilly and Gardner, 1975, 15: ”By the end of the embryonic proper (Stage 23, 8 postovulatory weeks), all of the major skeletal, articular, muscular, neural, and vascular elements of the limbs are present in a form and arrangement closely resembling those of the adult.“ See O’Rahilly, 1957, for a summary of joint types and a description of limb joint development during the embryonic period. See Gray et al., 1957, for a detailed examination of the bones and joints of the hand throughout the embryonic and fetal periods.
[104] Hogg, 1941, 407; Pringle, 1988, 178.
[105] Hogg, 1941, 387; O’Rahilly and Müller, 2001, 169.
[106] Pringle, 1988, 176.
[107] O’Rahilly and Müller, 2001, 87: “It has been estimated that more than 90% of the more than 4500 named structures of the adult body become apparent during the embryonic period (O’Rahilly).“

Page 11


The Fetal Period (8 Weeks through Birth)

Chapter 37   9 Weeks: Swallows, Sighs, and Stretches

The fetal period continues until birth.

By 9 weeks, thumb sucking begins[108] and the fetus can swallow amniotic fluid.[109]

The fetus can also grasp an object,[110] move the head forward and back, open and close the jaw, move the tongue, sigh,[111] and stretch.[112]

Nerve receptors in the face, the palms of the hands, and the soles of the feet can sense light touch.[113]

"In response to a light touch on the sole of the foot," the fetus will bend the hip and knee and may curl the toes.[114]

The eyelids are now completely closed.[115]

In the larynx, the appearance of vocal ligaments signals the onset of vocal cord development.[116]

In female fetuses, the uterus is identifiable[117] and immature reproductive cells called oogonia (ō-ō-gō′nē-ă) are replicating within the ovary.[118]

External genitalia begin to distinguish themselves as either male or female.[119]

The Fetal Period (8 Weeks through Birth)

Chapter 37   9 Weeks: Swallows, Sighs, and Stretches

জন্ম নোহোৱা পর্য্যন্ত ভ্রুন সম্বন্ধীয় পর্যায় অবিৰামভাৱে চলি থাকে৷

৯ সপ্তাহমানৰ ভিতৰতে বুঢ়া আঙুলি চোহা আৰম্ভ হয় আৰু ভ্রুণে গর্ভঝিলিক তৰল পদার্থ গিলিব পাৰে৷

ভ্রুণে এটা বস্তুক খামুচি ধৰিব আৰু মূৰটো আগলৈ আৰু পিচলৈ লৰাবও পাৰে, চুয়াল খুলিব আৰু বন্ধ কৰিব, জিভাখন লৰাব, দীঘল উশাহ লব আৰু বঢ়াব পাৰে৷

মুখমণ্ডলত স্নায়ু অনুভূতিগ্রাহী ইন্দ্রিয়, হাতদুটাৰ তলুৱা আৰু ভৰিৰ তলুৱাই অলপ চুলেই গম পাব পাৰে৷

"ভৰিব তলুৱাত অলপ স্পর্শ কৰিলেই" ভ্রুণে তপিনা আৰু আঠু ঘূৰাব আৰু ভৰিৰ তলুৱা বেঁকা কৰিব পাৰে৷

এতিয়া চকুৰপতা দুটা সম্পূর্ণ বন্ধ৷

শ্বাসনলীৰ উর্দ্ধভাগত মৌখিক সন্ধি বন্ধৰ আৱির্ভাবে মৌখিক ৰজ্জুসদৃশ বিকাশৰ সংকেত দিয়ে৷

স্ত্রীৰ ভ্রুণবোৰত জৰায়ু চিনিব পৰা হয় আৰু অণ্ড সৃষ্টি পৰিপক্ক নামৰ অপৰিপক্ক প্রজনন সম্বন্ধীয় জীৱকোষে ডিম্বাশয়ৰ ভিতৰত প্রতিৰুপ সৃষ্টি কৰে৷

বাহিৰৰ জননেন্দ্রিয়ই পুৰুষ বা স্ত্রী হিচাপে নিজকে প্রভেদ কৰিবলৈ আৰম্ভ কৰে৷

Chapter 38   10 Weeks: Rolls Eyes and Yawns, Fingernails & Fingerprints

A burst of growth between 9 and 10 weeks increases body weight by over 75 percent.[120]

By 10 weeks, stimulation of the upper eyelid causes a downward rolling of the eye.[121]

The fetus yawns and often opens and closes the mouth.[122]

Most fetuses suck the right thumb.[123]

Sections of intestine within the umbilical cord are returning to the abdominal cavity.[124]

Ossification is underway in most bones.[125]

Fingernails and toenails begin to develop.[126]

Unique fingerprints appear 10 weeks after fertilization. These patterns can be used for identification throughout life.[127]

Chapter 38   10 Weeks: Rolls Eyes and Yawns, Fingernails & Fingerprints

আৰু ৯ আৰু 10 সপ্তাহৰ ভিতৰত শৰীৰৰ ৭৫ % ওজন বৃদ্ধি হয়৷

১০ সপ্তাহমানৰ পিচত, ওপৰৰ চকুৰ পতাৰ সজীৱতাই চকুৰ আবর্ত্তন নিন্মাভিমুখী কৰে৷

ভ্রুণে হামিয়ায় আৰু মুখখন মেলে আৰু বন্ধ কৰে৷

অধিকাংশ ভ্রুণে সোহাতৰ বুঢ়া আঙুলিটো চোহে৷

নাড়ী সম্বন্ধীয় ৰজ্জুৰ ভিতৰত পেটৰ নাড়ীৰ খণ্ডবোৰ উদৰ সম্বন্ধীয় ৰন্ধ্রলৈ ঘুৰি আহে৷

অধিকাংশ হাঁড়ত অস্থিৰ উত্পত্তি আৰম্ভ হয়৷

হাত আৰু ভৰি আঙুলি নখৰ বিকাশ হয়৷

উর্ব্বৰতা বৃদ্ধি-কৰণৰ কেই ১০ সপ্তাহমানৰ পিচত একক আঙুলি চাপে দেখা দিয়ে৷ এই আর্হিবোৰক চিনাক্তিৰ কাৰণে গেটেই জীৱনটোত ব্যৱহাৰ কৰিব পাৰি৷

Chapter 39   11 Weeks: Absorbs Glucose and Water

By 11 weeks the nose and lips are completely formed.[128] As with every other body part, their appearance will change at each stage of the human life cycle.

The intestine starts to absorb glucose and water swallowed by the fetus.[129]

Though sex is determined at fertilization, external genitalia can now be distinguished as male or female.[130]

Chapter 39   11 Weeks: Absorbs Glucose and Water

১১ সপ্তাহমানৰ ভিতৰত নাক আৰু ওঠ সম্পূর্ণৰুপে গঠন হয়৷ শৰীৰৰ অন্যান্য অংশৰ সৈতে মানৱজীৱণ চক্রৰ প্রত্যেকটো স্তৰতে সেইবোৰৰ আকৃতিৰ পৰিবর্ত্তন হয়৷

পাকস্থলীয়ে ভ্রুণে গিলা গ্লুকোচ আৰু পানী সুহিবলৈ আৰম্ভ কৰে৷

যদি উর্ব্বৰতা কৰণত লিঙ্গক স্থিৰ কৰা হয়, বাহিৰৰ জননেন্দ্রিৰ এতিয়া পুৰুষ বা স্ত্রীৰ প্রভেদ স্খিৰ কৰা হয়৷

 

 


[108] Liley, 1972, 103.
[109] Campbell, 2004, 24; de Vries, 1982, 311; Petrikovsky et al., 1995, 605.
[110] Robinson and Tizard, 1966, 52; Valman and Pearson, 1980, 234.
[111] de Vries et al., 1982, 305-307.
[112] de Vries et al., 1982, 311.
[113] Humphrey, 1964, 96; Humphrey, 1970, 16-17 (cited by Reinis and Goldman, 1980, 232); Humphrey and Hooker, 1959, 77-78.
[114] Robinson and Tizard, 1966, 52; Quote from Valman and Pearson, 1980, 234.
[115] Andersen et al., 1965, 648-649; O’Rahilly and Müller, 2001, 465; Pearson, 1980, 39-41.
[116] O’Rahilly and Müller, 1984, 425. See also Campbell, 2004, 29.
[117] O’Rahilly, 1977a, 128; O’Rahilly, 1977b, 53; O’Rahilly and Müller, 2001, 327.
[118] O’Rahilly and Müller, 2001, 25 & 322.
[119] Campbell, 2004, 28 & 35; O’Rahilly and Müller, 2001, 336.
[120] Brenner et al., 1976, 561.
[121] Goodlin, 1979, D-128; Humphrey, 1964, 102.
[122] de Vries et al., 1982, 309.
[123] Hepper et al., 1991, 1109.
[124] Grand et al., 1976, 798; Pringle, 1988, 178; Sadler, 2005, 66; Spencer, 1960, 9. [Pringle reports the bowel returns into the abdomen during the ninth or tenth week.]
[125] Cunningham et al., 2001, 133.
[126] O’Rahilly and Müller, 2001, 170-171.
[127] Babler, 1991, 95; Penrose and Ohara, 1973, 201; For an overview of ridge formation in the skin of the hands see Cummins, 1929.
[128] Timor-Tritsch et al., 1990, 291.
[129] Koldovský et al., 1965, 186.
[130] O’Rahilly and Müller, 2001, 336; Wilson, 1926, 29.

Page 12


Chapter 40   3 to 4 Months (12 to 16 Weeks): Taste Buds, Jaw Motion, Rooting Reflex, Quickening

Between 11 and 12 weeks, fetal weight increases nearly 60 percent.[131]

Twelve weeks marks the end of the first third, or trimester, of pregnancy.

Distinct taste buds now cover the inside of the mouth. By birth, taste buds will remain only on the tongue and roof of the mouth.[132]

Bowel movements begin as early as 12 weeks and continue for about 6 weeks.[133]

The material first expelled from the fetal and newborn colon is called meconium (mĭ-kō'nē-ŭm).[134] It is composed of digestive enzymes, proteins, and dead cells shed by the digestive tract.[135]

By 12 weeks, upper limb length has nearly reached its final proportion to body size. The lower limbs take longer to attain their ultimate proportions.[136]

With the exception of the back and the top of the head, the body of the entire fetus now responds to light touch.[137]

Sex-dependent developmental differences appear for the first time. For instance, female fetuses exhibit jaw movement more frequently than males.[138]

In contrast to the withdrawal response seen earlier, stimulation near the mouth now evokes a turning toward the stimulus and an opening of the mouth.[139] This response is called the "rooting reflex" and it persists after birth, helping the newborn find his or her mother's nipple during breastfeeding.[140]

The face continues to mature as fat deposits begin to fill out the cheeks[141] and tooth development begins.[142]

By 15 weeks, blood-forming stem cells arrive and multiply in the bone marrow. Most blood cell formation will occur here.[143]

Although movement begins in the 6-week embryo, a pregnant woman first senses fetal movement between 14 and 18 weeks.[144] Traditionally, this event has been called quickening.[145]

Chapter 40   3 to 4 Months (12 to 16 Weeks): Taste Buds, Jaw Motion, Rooting Reflex, Quickening

১১ আৰু ১২ সপ্তাহৰ মাজত, ভ্রুণৰ ওজন ৬০% বৃদ্ধি হয়৷

বাৰ সপ্তাহে গর্ভাৱস্থাৰ প্রথম তৃতীয় বা ত্রৈমাসিকৰ সমাপ্তিক চিহ্নিত কৰে৷

এতিয়া স্বাদ আৰম্ভনিয়ে মুখৰ ভিতৰত নির্দিষ্টভাবে আবৰি ধৰে৷ জন্মৰ পিচত স্বাদ আৰম্ভণি মাত্র জিভা আৰু মুখৰ ভিতৰত ওপৰ অংশ অর্থাত্ তালুত থাকি যাব৷

নাড়ী-ভুৰুৰ গতি ১২ সপ্তাহৰ আগতেই আৰম্ভ হয় আৰু ৬ সপ্তাহো একেৰাহে চলি থাকে৷

ভ্রুণ আৰু নতুন কোষ্ঠৰ পৰা বাহিৰ কৰা বস্তুবোৰক ভ্রুণ বিষ্ঠা কোৱা হয়৷ ই হজম সম্বন্ধীয় পাচক ৰস, প্রোটিন আৰু একক কার্যকৰা কার্য সমূহ আৰু মৃতকোষবোৰৰ সমষ্টি৷

১২ সপ্তাহমানৰ ভিতৰত, ওপৰৰ অঙ্গ প্রত্যঙ্গৰ দৈর্ঘ্যই শৰীৰ আকাৰৰ প্রায় অন্তিম অনুপাতৰ ওচৰ পায়৷ তলৰ অঙ্গ প্রত্যঙ্গই শেষ অনুপাত পাবলৈ বেচি সময় লয়৷

মূৰৰ পিচফালে আৰু ওপৰ ভাগৰ বাহিৰে এতিয়া গোটেই ভ্রুণে ছুলেই গম পায়৷

লিঙ্গ-নির্ভৰশীলতা বিকাশ সম্বন্ধীয় পার্থক্যবোৰক প্রথমবাৰ দেখা যায়৷ উদাহৰণ স্বৰুপে, স্ত্রী ভ্রুণে দাঁতৰ মাৰিৰ গতিক পুৰুষ ভ্রুণ গতিতকৈ বেচি ঘনেঘনে প্রদর্শন কৰে৷

আগতে দেখা অপসৰন সহাঁৰিৰ বিপৰীতে, এতিয়া মুখৰ ওচৰত উদ্দীপনাই উত্তেজনা আৰু মুখৰ মুকলি অংশত এটা আৱর্ত্তন সৃষ্টি কৰে৷ সেই সহাঁৰিটোক "শিপা ওলোৱা প্রতিবিম্ভ" কোৱা হয় যি জন্মৰ পিচত টিকি থাকে আৰু মাকৰ পিয়াহৰ গাখীৰ খোৱাৰ সময়ত নৱজাত শিশুটোৱে মাকৰ স্তনবৃন্তটো বিচাৰি পায়৷

মুখমণ্ডলে একেৰাহে পৰিপক্ক কৰি থাকে যিহেতু চর্বীয়ে গাল দুখনক পূৰঠ কৰে আৰু দাঁতৰ বিকাশ আৰম্ভ হয়৷

১৫ সপ্তাহমাণৰ পিচত তেজ গঠন কৰা ঠাৰি সদৃশ জীৱকোষে দেখা দিয়ে আৰু অস্থিসজ্জাত পূৰণ কৰে৷ অধিকাংশ ৰক্তকোষ গঠন ইয়াত হয়৷

যদিও দুর্ব্বল ভ্রুনত ৬ সপ্তাহমানৰ গতি আৰম্ভ হয়, এগৰাকী গর্ভৱতী স্ত্রীয়ে ভ্রুণ সম্বন্ধীয় গতিৰমাজত ১৪ আৰু ১৮ সপ্তাহৰ ভিতৰত অনুভৱ কৰে৷ পৰম্পৰাগত ভাৱে, এই ঘটনাটোক পুনর্জীৱনদান কোৱা হয়৷

 

 


[131] Brenner, 1976, 561.
[132] Lecanuet and Schaal, 1996, 3; Miller, 1982, 169; Mistretta and Bradley, 1975, 80.
[133] Abramovich and Gray, 1982, 296; Ramón y Cajal and Martinez, 2003, 154-155, report visualizing defecation (bowel movements) with ultrasound in utero in all 240 fetuses studied between 15 and 41 weeks [postmenstrual age].
[134] O’Rahilly and Müller, 2001, 257; For a description of meconium by Aristotle see Grand et al., 1976, 791.
[135] Grand et al., 1976, 806.
[136] Moore and Persaud, 2003, 105.
[137] Lecanuet and Schaal, 1996, 2; Reinis and Goldman, 1980, 232.
[138] Hepper et al., 1997, 1820.
[139] Mancia, 1981, 351.
[140] Bates, 1979, 419.
[141] Poissonnet et al., 1983, 7; Poissonnet et al., 1984, 3: In a study of 488 fetuses, Poissonnet’s group found that adipose tissue (fat) appears in the face from 14 weeks postfertilization. By 15 weeks, fat appears in the abdominal wall, back, kidneys, and shoulders. By 16 weeks, fat is also present throughout the upper and lower limbs.
[142] Pringle, 1988, 178. [Thirteenth week postfertilization]
[143] Pringle, 1988, 179.
[144] Sorokin and Dierker, 1982, 720; Leader, 1995, 595: “Some pregnant women reported fetal flutters as early as 12 weeks (quickening).“ Women also tend to accurately recognize fetal movement at earlier fetal ages during second and subsequent pregnancies as compared to first pregnancies.
[145] Spraycar, 1995, 1479; Timor-Tritsch et al., 1976, 70.

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Chapter 41   4 to 5 Months (16 to 20 Weeks): Stress Response, Vernix Caseosa, Circadian Rhythms

By 16 weeks, procedures involving the insertion of a needle into the abdomen of the fetus trigger a hormonal stress response releasing noradrenalin, or norepinephrin (nor-ep'i-nef'rin), into the bloodstream.[146]

In the respiratory system, the bronchial tree is now nearly complete.[147]

A protective white substance, called vernix caseosa (ver'niks caseo'sa), now covers the fetus. Vernix protects the skin from the irritating effects of amniotic fluid.[148]

From 19 weeks fetal movement, breathing activity, and heart rate begin to follow daily cycles called circadian (ser-kā'dē-ăn) rhythms.[149]

Chapter 41   4 to 5 Months (16 to 20 Weeks): Stress Response, Vernix Caseosa, Circadian Rhythms

১৬ সপ্তাহমানৰ ভিতৰত ভ্রুণৰ তপিনাত এটা বেজী দিলে তেজৰ সোঁতালৈ এটা ই নোৰাড্রেনেলাইন বা বা নোৰেপিনেট্রাইন মুকলি কৰি এটা হৰমোন সম্বন্ধীয় চাপৰ সহাঁৰি দিয়ে৷ নৱজাত আৰু বয়সস্থলোকে বিয়পি পৰা কার্য-পদ্ধতিলৈ এটা একেধৰনৰ সাহাঁৰি প্রদর্শন কৰে৷

নিশ্বাস - প্রশ্বাস পদ্ধতিত শ্বসনীয় গছ জোপা এতিয়া প্রায় সম্পূর্ণ হ'ল৷

ভার্মিক্স কাচিওচা নামৰ এটা সংৰক্ষক বস্তৱে এতিয়া গর্ভস্থ ভ্রুণক ৰক্ষা কৰে৷ ভার্মিক্সে গর্ভঝিল্লি সম্বন্ধীয় তৰল পদার্থৰ প্রদাহযুক্ত ফলৰ পৰা ছালক ৰক্ষা কৰে৷

১৯ সপ্তাহৰ পৰা উশাহ লোৱা কার্য-কলাপ আৰু হৃদয়ৰ স্পন্দন হাৰে চার্কাডিয়ান অনুক্রম নামৰ দৈনিক আবর্তন অনুসৰণ কৰিবলৈ আৰম্ভ কৰে৷

Chapter 42   5 to 6 Months (20 to 24 Weeks): Responds to Sound; Hair and Skin; Age of Viability

By 20 weeks the cochlea, which is the organ of hearing, has reached adult size[150] within the fully developed inner ear. From now on, the fetus will respond to a growing range of sounds.[151]

Hair begins to grow on the scalp.

All skin layers and structures are present, including hair follicles and glands.[152]

By 21 to 22 weeks after fertilization, the lungs gain some ability to breathe air.[153] This is considered the age of viability because survival outside the womb becomes possible for some fetuses.[154]

Chapter 42   5 to 6 Months (20 to 24 Weeks): Responds to Sound; Hair and Skin; Age of Viability

২০ সপ্তাহৰ ভিতৰত শ্রৱণ শক্তিৰ ইন্দ্রিয় কর্ণকম্বুয়ে কাণৰ ভিতৰত সম্পূর্ণৰুপে বিকশিত বয়স্ক আকাৰ ধাৰণ কৰে৷ এতিয়াৰ পৰা ভ্রুণে ধ্বনিৰ এটা বৃদ্ধি হোৱা পৰিসৰক উত্তৰ দিব৷

মূৰৰ ছালত চুলি গজিবলৈ আৰম্ভ কৰে৷

চুলিৰোম কূপ আৰু ৰস গ্রন্থিকে লৈ সকলো ছাল তৰপ আৰু আকাৰ বিদ্যমান৷

গর্ভৱতীকৰণৰ ২১-২২ দুসপ্তাহৰ ভিতৰত, ফুচফুচে উশাহ লবলৈ কিছুমান ক্ষমতা পায়৷ ইয়াক বাচি থকাৰ সাধ্যতাৰ বয়স বিবেচনা কৰা হয় কাৰণ কিছুমান ভ্রুণৰ কাৰণে গর্ভৰ বাহিৰত জীয়াই থকাটো সম্ভৱ হয়৷ মেডিকেল উন্নতিৰ এটা সুদীর্ঘ উত্তৰাধিকাৰ সূত্রই নির্দিষ্ট সময়ৰ আগতে জন্মহোৱা কেচুৱাৰ জীৱনৰ বচাই ৰখা সম্ভৱ কৰিছে৷

 

 


[146] Giannakoulopoulos et al., 1999, 494 & 498-499; Glover and Fisk, 1999, 883; Smith et al., 2000, 161. Cortisol levels also rise after invasive procedures following 21 weeks postfertilization - see Giannakoulopoulos et al., 1994, 80.
[147] DiFiore and Wilson, 1994, 221-222; Pringle, 1988, 178. [There is some disagreement among experts regarding when the bronchial tree is complete. Some say completion occurs as early as 16 weeks postfertilization while others say it occurs after birth.]
[148] Campbell, 2004, 48; Moore and Persaud, 2003, 107; O’Rahilly and Müller, 2001, 168.
[149] de Vries et al., 1987, 333; Goodlin and Lowe, 1974, 349; Okai et al., 1992, 391 & 396; Romanini and Rizzo, 1995, 121; For a description of the circadian system, see Rosenwasser, 2001, 127; From Vitaterna et al., 2001, 92: Glossary: “Circadian: A term derived from the Latin phrase “circa diem,“ meaning “about a day;“ refers to biological variations or rhythms with a cycle of approximately 24 hours.“
[150] Lecanuet and Schaal, 1996, 5-6; Querleu et al., 1989, 410.
[151] Glover and Fisk, 1999, 882; Hepper and Shahidullah, 1994, F81; Querleu et al., 1989, 410; Sorokin and Dierker, 1982, 725 & 730; Valman and Pearson, 1980, 233-234.
[152] Pringle, 1988, 180.
[153] Hansen and Corbet, 1998, 542.
[154] O’Rahilly and Müller, 2001, 92, report the age of viability as 20 weeks postfertilization; Draper et al., 1999, 1094, report a survival rate of 2% at 20 weeks postfertilization, 6% at 21 weeks, and 16% at 22 weeks. Moore and Persaud, 2003, 103, report viability at 22 weeks; Wood et al., 2000, 379, report survival rates of 11% at 21 weeks, 26% at 22 weeks and 44% at 23 weeks (postfertilization weeks) based on premature birth data from the United Kingdom during 1995. Cooper et al. 1998, 976, (Figure 2) report infants with a birth weight over 500 grams experienced survival rates (all approximate) of 28% at 21 weeks postfertilization, 50% at 22 weeks, 67% at 23 weeks, and  77% at 24 weeks. Draper et al., 2003, updated their previously published survival tables for premature infants and now report an overall survival rate of 7% at 20 weeks, 15% at 21 weeks, 29% at 22 weeks, 47% at 23 weeks and 65% at 24 weeks. [All ages corrected to reflect postfertilization age.] These survival tables are available online at http://bmj.bmjjournals.com/cgi/content/full/319/7217/1093/DC1. Their methodology is described in their earlier paper (Draper et al., 1999, 1093-1094.) Note: These published survival tables reflect postmenstrual ages. Hoekstra et al., 2004, e3, report a survival rate of 66% at 23 weeks and 81% at 24 weeks “gestational age“ [not specifically defined] for premature births from 1996 to 2000 at their center in Minneapolis, Minnesota.

Page 14


Chapter 43   6 to 7 Months (24 to 28 Weeks): Blink-Startle; Pupils Respond to Light; Smell and Taste

By 24 weeks the eyelids reopen[155] and the fetus exhibits a blink-startle response.[156] This reaction to sudden, loud noises typically develops earlier in the female fetus.[157]

Several investigators report exposure to loud noise may adversely affect fetal health. Immediate consequences include prolonged increased heart rate, excessive fetal swallowing, and abrupt behavioral changes.[158] Possible long-term consequences include hearing loss.[159]

The fetal respiratory rate can rise as high as 44 inhalation-exhalation cycles per minute.[160]

During the third trimester of pregnancy, rapid brain growth consumes more than 50 percent of the energy used by the fetus. Brain weight increases between 400 and 500 percent.[161]

By 26 weeks the eyes produce tears.[162]

The pupils respond to light as early as 27 weeks.[163] This response regulates the amount of light reaching the retina[164] throughout life.

All components required for a functioning sense of smell are operational. Studies of premature babies reveal the ability to detect odors as early as 26 weeks after fertilization.[165]

Placing a sweet substance in the amniotic fluid increases the rate of fetal swallowing. In contrast, decreased fetal swallowing follows the introduction of a bitter substance. Altered facial expressions often follow.[166]

Through a series of step-like leg motions similar to walking, the fetus performs somersaults.[167]

The fetus appears less wrinkled as additional fat deposits form beneath the skin.[168] Fat plays a vital role in maintaining body temperature and storing energy after birth.

Chapter 43   6 to 7 Months (24 to 28 Weeks): Blink-Startle; Pupils Respond to Light; Smell and Taste

২৪ সপ্তাহমানৰ ভিতৰত চকুৰ পতা খোলে আৰু ভ্রুণে এটা চকুৰ টিপ জিকাৰ প্রদর্শন কৰে৷ ডাঙৰ শব্দৰ প্রতি এই প্রতিক্রিয়াটো গতানুগতিকভাবে স্ত্রী ভ্রুণত আগতে বিকাশ ঘটে৷

অনেক গৱেষকে ডাঙৰ শব্দৰ প্রতি উন্মোচনে ভ্রুণৰ স্বাস্থ্যৰ ওপৰত বিৰুপ প্রভাৱ বিস্তাৰ কৰিব পাৰে বুলি কয়৷ তত্ক্ষনাত পৰিণাম হল সুদীর্ঘ বর্দ্ধিত হৃদপিন্ড স্পন্দন হাৰ, অত্যন্ত ভ্রুণ সম্বন্ধীয় গলাধঃ কৰণ আৰু আকস্মিক আচৰণ সম্বন্ধীয় পৰিবর্ত্তন৷ দীর্ঘকাল পৰিণাম সম্ভবনীয় শ্রবণ শক্তি হানি৷

ভ্রুণ সম্বন্ধীয় উশাহলোৱা হাৰ প্রতি মিনিটত নাক আৰু মুখেৰে উশাহ ৪৪ টানিলোৱা - উশাহ বাহিৰ কৰাৰ দৰে বেচি হব পাৰে৷

গর্ভাৱস্থাৰ তিনিমাহৰ ভিতৰত দ্রুত মগজু বৃদ্ধিয়ে ভ্রুণে ব্যৱহাৰ কৰা শক্তিৰ ৫০ % তকৈ অধিক ক্ষয় কৰে৷ মস্তিষ্ক ওজন বৃদ্ধি হয় ৪০০ আৰু ৫০০ শতাংশত ভিতৰত হয়৷

২৬ সপ্তাহমানৰ ভিতৰত চকুৰ পৰা চকু-লো ওলায়৷

চকুৰমনিয়ে পোহৰৰ প্রতি সোনকালেই ২৭ সপ্তাহমানৰ প্রতিক্রিয়া প্রদর্শন কৰে৷ এই প্রতিক্রিয়াই গোটেই জীৱনটোত অক্ষিপটলৈ যোৱা পোহৰক নিয়মিত কৰে৷

ঘ্রান শক্তিয়ে কাম কৰিবৰ কাৰণে আৱশ্যক সকলো উপাদান কার্যকৰণ সম্বন্ধীয়৷ জন্মহোৱা কেচুৱাৰ অধ্যয়নে গর্ভৱতী কৰণৰ পিচত কেৱা সপ্তাহৰ আগতে কেছুৱাই ঘ্রাণ শক্তি আহৰণৰ কৰা ক্ষমতাক বিদিত কৰে৷

এটা সোৱাদ বস্তুক গর্ভঝিলি সম্বন্ধীয় জলীয় পদার্থত ৰাখিলে ভ্রুন সম্বন্ধীয় গিলাব হাৰ বৃদ্ধি হয়৷ তাৰ বিপৰীতে হ্রাস হোৱা ভ্রুণ সম্বন্ধীয় গিলাব হাৰ বৃদ্ধি হয় ৷ পৰিবর্ত্তন কৰা মুখমণ্ডল সম্বন্ধীয় প্রকাশে ঘনে ঘনে অনুসৰণ কৰে৷

খোজ কঢ়া ধৰণৰ পদক্ষেপৰ নিচিনা ভৰিৰ গতিৰ এটা অনুভূতিৰ যোগেদি ভ্রুণে খৰ বাগৰ মাৰে৷

ভ্রুণক কম সংকুচিত দেখা যায় যিহেতু ওপৰঞ্চি চর্বী ছালৰ তলত জমা হয়৷ জন্মৰ পিচত শৰীৰ তাপমান আৰু শক্তিক ৰক্ষনাবেক্ষণ কৰাত চর্বীয়ে এটা গুৰুত্বপূর্ণ ভূমিকা গ্রহণ কৰে৷

 

 


[155] Open eyes are visualized by 4D ultrasound following 22 weeks postfertilization per Campbell 2002, 3; De Lia, 2002, personal communication; O’Rahilly and Müller, 2001, 465. For a detailed ultrastructural study of the union between the upper and lower eyelids see Andersen et al., 1967, 293.
[156] Birnholz and Benacerraf, 1983, 517 (cited by Drife, 1985, 778); See also Campbell, 2002, 3: Professor Stuart Campbell correctly points out that the eyes of the fetus are closed most of the time and a true blink requires the eyes to be open. Perhaps the “blink-startle“ response would be more accurately termed “squint-startle.“
[157] Lecanuet and Schaal, 1996, 9.
[158] Visser et al., 1989, 285.
[159] Gerhardt, 1990, 299; Petrikovsky et al., 1993, 548-549; Pierson, 1996, 21 & 26.
[160] Natale et al., 1988, 317.
[161] Growth of the human brain, 1975, 6; Mancuso and Palla, 1996, 290.
[162] Isenberg et al., 1998, 773-774.
[163] Robinson and Tizard, 1966, 52.
[164] Noback et al., 1996, 263.
[165] Lecanuet and Schaal, 1996, 3.
[166] Lecanuet and Schaal, 1996, 3; Liley, 1972, 102; Moore and Persaud, 2003, 219; Reinis and Goldman, 1980, 227.
[167] Liley, 1972, 100.
[168] England, 1983, 29.

Page 15


Chapter 44   7 to 8 Months (28 to 32 Weeks): Sound Discrimination, Behavioral States

By 28 weeks the fetus can distinguish between high- and low-pitched sounds.[169]

By 30 weeks, breathing movements are more common and occur 30 to 40 percent of the time in an average fetus.[170]

During the last 4 months of pregnancy, the fetus displays periods of coordinated activity punctuated by periods of rest. These behavioral states reflect the ever-increasing complexity of the central nervous system.[171]

Chapter 44   7 to 8 Months (28 to 32 Weeks): Sound Discrimination, Behavioral States

২৮ সপ্তাহ মানত ভ্রুণে উচ্চ আৰু নিম্ন শব্দৰ মাজত থকা পার্থক্যটো বুজিব পাৰে৷

৩০ সপ্তাহমানত উশাহলোৱা গতি অধিক স্বাভাবিক হয় আৰু এটা সাধাৰণ ভ্রুণত সময়ৰ ৩০ -৪০% হয়৷

গর্ভাৱস্থাৰ শেষ ৪ মাহত ভ্রুণে মাজেমাজে জিৰণিৰ সৈতে সমন্বয়যুক্ত কার্যকলাপৰ সময় প্রদর্শন কৰে৷ এই আচৰণ সম্বন্ধীয় অৱস্থাই কেন্দ্রীয় স্নায়ু প্রণালী সম্বন্ধীয় পদ্ধতিৰ জটিলতা সদায় বৃদ্ধি কৰে৷

Chapter 45   8 to 9 Months (32 to 36 Weeks): Alveoli Formation, Firm Grasp, Taste Preferences

By approximately 32 weeks, true alveoli (al-vē'ō-lī), or air "pocket" cells, begin developing in the lungs. They will continue to form until 8 years after birth.[172]

At 35 weeks the fetus has a firm hand grasp.[173]

Fetal exposure to various substances appears to affect flavor preferences after birth. For instance, fetuses whose mothers consumed anise, a substance which gives licorice its taste, showed a preference for anise after birth. Newborns without fetal exposure disliked anise.[174]

Chapter 45   8 to 9 Months (32 to 36 Weeks): Alveoli Formation, Firm Grasp, Taste Preferences

৩২ সপ্তাহমানৰ ভিতৰত ফুচফুচত আচল সৰু ছিদ্র বা বায়ু "জালিমোনা" বিকাশ হবলৈ আৰম্ভ কৰে৷ সেইবোৰ জন্মৰ পিচত ৮ বছৰ মানলৈকে একেৰাহে চলি থাকিব৷

৩৫ সপ্তাহমানত ভ্রুণৰ হাতৰ খামোচ টো টান হয়৷

জন্মৰ পিচত বিভিন্ন বস্তুৰ প্রতি ভ্রুন সম্বন্ধীয় উন্মোচনে সুগন্ধ অগ্রাধিকাৰক প্রভাৱিত কৰে৷ উদাহৰণ স্বৰুপে, যিবোৰ ভ্রুণৰ মাক বিলাকে চফ খায় জন্মৰ পিচত কেচুৱাইও চফ খাবলৈ ভাল পায়৷ নৱজাত কেচুৱাই বিনা ভ্রুণসম্বন্ধীয় উন্মোচনত চফ খাবলৈ ভাল নাপায়৷

Chapter 46   9 Months to Birth (36 Weeks through Birth)

The fetus initiates labor[175] by releasing large amounts of a hormone called estrogen (es´trō-jen)[176] and thus begins the transition from fetus to newborn.

Labor is marked by powerful contractions of the uterus, resulting in childbirth.[177]

From fertilization to birth and beyond, human development is dynamic, continuous, and complex. New discoveries about this fascinating process increasingly show the vital impact of fetal development on lifelong health.

As our understanding of early human development advances, so too will our ability to enhance health––both before and after birth.

Chapter 46   9 Months to Birth (36 Weeks through Birth)

ভ্রুণে এস্ট্রজেন নামৰ বহু পৰিমানৰ হৰমোন মুকলি কৰি শ্রম আৰম্ভ কৰে আৰু এনেকৈ ভ্রুণৰ পৰা নতুন জন্ম হোৱা কেচুৱাটোলৈ পৰিবর্তন কৰে৷

জৰায়ুৰ দ্বাৰা শক্তিশালী সংকোচনৰ ফলত শ্রমৰ দ্বাৰা শিশুৰ জন্ম হয়

গর্ভৱতীকৰণৰ পৰা জন্মলৈকে আৰু তাৰ পিচতো মানুহৰ বিকাশ পৰিবর্তনশীল নিৰবচ্ছিন্ন আৰু জটিল এই চিত্তাকর্ষক নতুন আৱিস্কাৰে গোটেই জীবন স্বাস্থ্যৰ দেখুবায় গুৰুত্বপূর্ণ বিকাশৰ প্রভাব প্রদর্শন কৰে৷

যিহেতু আমাৰ মানুহৰ স্বাস্থ্য সম্বন্ধীয় আমাৰ বুজাবুজি উন্নতি হৈছে৷ তেনেকৈয়ে স্বাস্থ্যৰ বৃদ্ধি কৰিবলে আমাৰ ক্ষমতাও জন্ম আৰু তাৰ আগতে বৃদ্ধিক৷

 

 


[169] Glover and Fisk, 1999, 882; Hepper and Shahidullah, 1994, F81.
[170] Connors et al., 1989, 932; de Vries et al., 1985, 117; Patrick et al., 1980, 26 & 28; Visser et al., 1992, 178.
[171] DiPietro et al., 2002, 2: “One of the hallmarks of development before birth is the coalescence of patterns of fetal and behavioral and cardiac function into behavioral states, which is widely viewed as reflective of the developing integration of the central nervous system.“
[172] Lauria et al., 1995, 467.
[173] Moore and Persaud, 2003, 108.
[174] Schaal et al., 2000, 729.
[175] Liley, 1972, 100.
[176] Moore and Persaud, 2003, 131.
[177] Cunningham et al., 2001, 252.

Page 16


Appendix A − Calculations

To the Sun and Back: Determining the Length of DNA in an Adult

Given:

1.      The DNA molecule measures 3.4×10-9 meters per 10 base pairs.[178]

2.      There are 3 billion (3×109) base pairs per cell.

3.      There are an estimated 100 trillion (1014) cells per adult.

4.      The distance from the earth to the sun is approximately 93 million miles.

5.      There are 2.54 centimeters (cm) per inch.

Step 1   Compute the length of DNA in a single cell:

3.4×10-9 meters/10 base pairs ×  3×109 base pairs/cell = 1.02 meters of DNA per cell

Step 2   Compute the total length of DNA in an adult’s 100 trillion cells:

1.02 meters of DNA/cell × 1014 cells  =  1.02×1014 meters of DNA per adult*

Step 3   Convert 1.02×1014 meters to miles:

1.02×1014 meters × 100 cm/meter × 1inch/2.54 cm × 1 foot/12 inches × 1 mile/5,280 feet
 = 6.3379×1010miles of DNA

Step 4   Compute how many round trips from the earth to the sun:

6.3379×1010 miles of DNA ÷ (93,000,000 miles/trip × 2 trips/round trip) =

340 round trips between earth and sun

Therefore, the DNA in a single adult, if oriented in linear fashion, would exceed 63 billion miles in length. This is long enough to extend from the earth to the sun and back––340 times.

* Approximately 25 trillion red blood cells are present in the adult.[179] It should be noted that red blood cells contain DNA early in their maturation phase but this DNA degenerates and is not present in the mature form. This calculation includes the DNA from red blood cells.

 

 


[178] Lodish et al., 2000, 104.
[179] Guyton and Hall, 2000, 2.

Page 17


A Tight Squeeze: Appreciating the Number of Bases Contained in the DNA of a Single Cell

The following page contains a list of 3,808 capital letters each of which represents a single base.

Given:

1.      A, G, T, and C each represent a base within the DNA of a single cell.

2.      Each line contains 68 letters without spaces representing 68 bases.

3.      Each page contains 56 lines. (Page size: 8½ × 11 inches, font: Times New Roman, font size: 10, spaces between letters: none, lines: single spaced, margins: as shown)

4.      Each cell contains 3 billion base pairs equaling 6 billion bases.

The calculation of the number of pages required to list all DNA bases in a single cell is as follows:

68 bases/line × 56 lines/page  =  3,808 bases/page

6,000,000,000 bases/cell ÷ 3,808 bases/page  =  1,575,630 pages/cell



ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG
ATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCGATCG

Page 18


Climate Control: Approximating the Normal Range of Embryonic and Fetal Body Temperature

Given:

1.      The placenta maintains embryonic and fetal temperature between 0.5 ºC and 1.5 ºC above maternal core temperature.[180]

2.      Maternal core temperature is approximately 99.6º Fahrenheit.

3.      The formula to convert temperature from Fahrenheit (ºF) to Celsius (ºC) is:

ºC = 5/9 (ºF - 32)

The calculation to compute the range of embryonic and fetal body temperature is as follows:

Step 1             Convert maternal core temperature to Celsius:

Maternal core temperature in ºC: ºC = 5/9 (99.6 - 32) = 37.56 ºC

Step 2             Compute lower and upper ranges of fetal body temperature in Celsius:

Lower range (Celsius) = maternal core temperature + 0.5 ºC = 37.56 + 0.5 = 38.2 ºC

Upper range (Celsius) = maternal core temperature + 1.5 ºC = 37.56 + 1.5 = 39.2 ºC

Step 3             Convert results to Fahrenheit:

ºC = 5/9 (ºF - 32)                     9/5 ºC = (ºF - 32)                     ºF = 9/5 ºC + 32

Substituting to find the lower limit of fetal body temperature

ºF = 9/5 ºC + 32                      ºF = 9/5 (38.16) + 32   ºF = 100.7º

Substituting to find the upper limit of fetal body temperature

ºF = 9/5 ºC + 32 ºF = 9/5 (39.16) + 32   ºF = 102.5º

Summary of Normal Embryonic and Fetal Body Temperature Range

  ºF ºC
Lower Limit 100.7 38.2
Upper Limit 102.5 39.2

 

 


[180] Liley, 1972, 101.

Page 19


The Beat Goes On: Estimating the Total Number of Heartbeats Before Birth and Beyond

The Embryonic Period

Week # Average Heart Rate
(Beats per Minute)
Beats per Week Running Total
4 113.00 1,139,040 1,139,040
5 132.00 1,330,560 2,469,600
6 151.00 1,522,080 3,991,680
7 170.00 1,713,600 5,705,280
8 169.03 1,703,845 7,409,125
(Approximately 7.41 million beats during the embryonic period)

Various authors agree the heart rate peaks at 7 weeks. Reported heart rates vary however. Van Heeswijk et al. report a peak heart rate of 167 ± 8 beats per minute (bpm)[181] while Leeuwen et al. report a peak rate of 175 bpm.[182] Van Lith et al. report the median fetal heart rate peaks at 177 bpm at 7 weeks.[183] One hundred seventy (170) bpm has been chosen as the peak heart rate for illustration purposes in this calculation. The heart rate for the various weeks from 7 through 38 have been calculated via linear interpolations[184] assuming heart rates of 170 bpm at 7 weeks and 140 bpm at term or 38 weeks.[185]

(Note: Heart rates are estimated. Living conditions and individual experience can and will vary.)

The Fetal Period

Week # Average Heart Rate
(Beats per Minute)
Beats per Week Running Total
9 168.06 1,694,090 9,103,216
10 167.10 1,684,336 10,787,551
11 166.13 1,674,581 12,462,132
12 165.16 1,664,826 14,126,958
13 164.19 1,655,071 15,782,029
14 163.23 1,645,316 17,427,346
15 162.26 1,635,562 19,062,907
16 161.29 1,625,807 20,688,714
17 160.32 1,616,052 22,304,766
18 159.35 1,606,297 23,911,063
19 158.39 1,596,542 25,507,605
20 157.42 1,586,787 27,094,393
21 156.45 1,577,033 28,671,425
22 155.48 1,567,278 30,238,703
23 154.52 1,557,523 31,796,226
24 153.55 1,547,768 33,343,994
25 152.58 1,538,013 34,882,008
26 151.61 1,528,259 36,410,266
27 150.65 1,518,504 37,928,770
28 149.68 1,508,749 39,437,519
29 148.71 1,498,994 40,936,513
30 147.74 1,489,239 42,425,752
31 146.77 1,479,484 43,905,237
32 145.81 1,469,730 45,374,966
33 144.84 1,459,975 46,834,941
34 143.87 1,450,220 48,285,161
35 142.90 1,440,465 49,725,626
36 141.94 1,430,710 51,156,337
37 140.97 1,420,956 52,577,292
38 140.00 1,411,201 53,988,493
(Approximately 54 million beats before birth)

Counting the Beats of a Lifetime

The Postnatal Period from Birth to 80 Years

Year # Average Heart Rate
(Beats per Minute)*[186]
Beats per Year Running Total
1 120 63,115,200 63,115,200
2 110 57,855,600 120,970,800
3 103 54,173,880 175,144,680
4 103 54,173,880 229,318,560
5 103 54,173,880 283,492,440
6 103 54,173,880 337,666,320
7 95 49,966,200 387,632,520
8 95 49,966,200 437,598,720
9 95 49,966,200 487,564,920
10 95 49,966,200 537,531,120
11 85 44,706,600 582,237,720
12 85 44,706,600 626,944,320
13 85 44,706,600 671,650,920
14 85 44,706,600 716,357,520
15 80 42,076,800 758,434,320
16 80 42,076,800 800,511,120
17 75 39,447,000 839,958,120
18 75 39,447,000 879,405,120
19 70 36,817,200 916,222,320
20 70 36,817,200 953,039,520
21-80 70 2,209,032,000 3,162,071,520
(Approximately 3.16 billion beats from birth to age 80 years)
Estimated Total Heart Beats From the
3-Week Embryo to Age 80 Years
3,216,060,000
(Approximately 3.2 Billion Beats Per Lifetime)

 

 


[181] van Heeswijk et al., 1990, 153.
[182] Leeuwen et al., 1999, 265.
[183] van Lith et al., 1992, 741.
[184] See Appendix A.
[185] DiPietro et al., 1996, 2559.
[186] Age appropriate pediatric heart rates adapted from Bates, 1987, 541.

Page 20


Appendix B − Relating Embryonic Age & Stage

O'Rahilly and Müller's Age Assignments vs. Carnegie Stages, 1987 to 2001

Carnegie
Stage
Number
of Somites
Greatest
Length (mm)
1987 Age [187]
Convention
(in PF Days*)
1999 Age [188]
Convention
(in PF Days*)
2001 Age [189]
Convention
(in PF Days*)
1   0.1 - 0.15 1 - 1
2   0.1 - 0.2 1½ - 3 2 - 3 2 - 3
3   0.1 - 0.2 4 4 - 5 4 - 5
4   0.1 - 0.2 5 - 6 6 6
5   0.1 - 0.2 7 - 12 7 - 12 -
5a   0.1 7 - 8 - 7 - 8
5b   0.1 9 - 9
5c   0.15 - 0.2 11 - 12 - 11 - 12
6   0.2 13 17 17
6a   - - - -
6b   - - - -
7   0.4 16 19 19
8   1.0 - 1.5 18 23 -
8a   - - - 23
8b   - - - 23
9 1-3 1.5 - 2.5 20 26 25
10 4-12 2 - 3.5 22 29 28
11 13-20 2.5 - 4.5 24 30 29
12 21-29 3 - 5 26 31 30
13 30+ 4 - 6 28 32 32
14   5 - 7 32 33 33
15   7 - 9 33 35 36
16   8 - 11 37 37 38
17   11 - 14 41 40 41
18   13 - 17 44 42 44
19   16 - 18 47½ 44 46
20   18 - 22 50½ 47 49
21   22 - 24 52 50 51
22   23 - 28 54 52 53
23   27 - 31 56½ 56 56

* PF Days = Postfertilization Days

 

There is international agreement among embryologists that human development during the embryonic period be divided into 23 stages (which were initially proposed by Mall, described by Streeter, and amended by O'Rahilly and Müller in 1987).[190] These have come to be known as Carnegie Stages. Particular internal and external features are required for inclusion in any given embryonic stage. These stages are independent of age and length and the use of the term 'stage' should be reserved for reference to this system per O'Rahilly and Müller in multiple publications.

Along with nearly-universal acceptance of the human embryonic staging system, a variety of age assignments have been proposed for each embryonic stage. Streeter believed the embryonic period spanned a 47- to 48-day period instead of the 56-day period accepted today. The Endowment for Human Development adopts the convention set forth by O'Rahilly and Müller in 1987 which has received widespread, but not universal, acceptance. O'Rahilly and Müller have since proposed amending this convention in light of transvaginal ultrasound data through a personal communication with Dr. Josef Wisser in 1992.[191] These alternate proposals are provided for the interested reader.

For instance, the onset of embryonic cardiac contraction (onset of the heartbeat) has long been described as a Carnegie Stage 10 or possibly a late Stage 9 event.[192] We report this event occurring at an age of 3 weeks, 1 day (22 days) postfertilization using the 1987 convention. Others may report this occurrence at 28 or 29 days as shown above. Of interest is a paper by Wisser and Dirschedl who reported using transvaginal ultrasound to visualize the embryonic heartbeat 23 days postfertilization in two embryos fertilized in vitro “with exactly known … age” and “in embryos from 2 mm of greatest length onwards.”[193] This finding most closely coincides with the 1987 age convention. Schats et al. reported the earliest cardiac activity at 25 days after follicle aspiration in embryos conceived in vitro.[194] Tezuka et al. reported the earliest cardiac activity at 23 days postfertilization in embryos conceived naturally.[195]

There is considerable variation in normal human development during the postnatal period. The prenatal period is no different with variations in the size, rate of growth, and order of appearance of some structures or functions. No one knows the exact age range for each stage with absolute certainty. These approximations may change in the future as additional knowledge is gained through careful, published research.

 

 


[187] O'Rahilly and Müller, 1987, 3. Greatest length data is essentially uniform throughout the various texts.
[188] O'Rahilly and Müller, 1999a. Various pages.
[189] O'Rahilly and Müller, 2001, 490. Table A-1 – essentially unchanged from the 1996 edition. The 2001 convention differs only slightly from the 1999 convention as shown.
[190] O'Rahilly and Müller, 2001, 3.
[191] O'Rahilly and Müller, 1999a, 13.
[192] See footnote #51.
[193] Quotes from Wisser and Dirschedl, 1994, 108.
[194] Schats et al., 1990, 989.
[195] Tezuka, 1991, 211.

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Page 27


Full Names of Journals Cited

Journal Abbreviation Journal Name
Acta Anat Acta Anatomica
Acta Opthalmol Acta Ophthalmologica
Adv Contracept Advances in Contraception
Alcohol Res Health Alcohol Research & Health
Am J Anat The American Journal of Anatomy
Am J Cardiol The American Journal of Cardiology
Am J Kidney Dis American Journal of Kidney Diseases
Am J Obstet Gynecol American Journal of Obstetrics and Gynecology
Am J Reprod Immunol American Journal of Reproductive Immunology and Microbiology
Am J Respir Cell Mol Biol American Journal of Respiratory Cell and Molecular Biology
Am J Roentgenol American Journal of Roentgenology
Anat Embryol Anatomy and Embryology
Ann Otol Rhinol Laryngol The Annals of Otology, Rhinology, and Laryngology
Ann R Coll Surg Eng Annals of the Royal College of Surgeons of England
Arch Dis Child Archives of Disease in Childhood
Arch Ophthalmol Archives of Ophthalmology
Aust N Z J Psychiatry The Australian and New Zealand Journal of Psychiatry
Biol Neonate Biology of the Neonate
Birth Defects Orig Artic Ser Birth Defects Original Article Series
Br J Obstet Gynaecol British Journal of Obstetrics and Gynaecology
Br Med Bull British Medical Bulletin
Br Med J British Medical Journal
Chem Senses Chemical Senses
Child Dev Child Development
Clin Obstet Gynecol Clinical Obstetrics and Gynecology
Contrib Embryol Contributions to Embryology
Dev Med Child Neurol Developmental Medicine and Child Neurology
Dev Pharmacol Ther Developmental Pharmacology and Therapeutics
Early Hum Dev Early Human Development
Eur J Obstet Gynecol Reprod Biol European Journal of Obstetrics, Gynecology, and Reproductive Biology
Eye Eye
Facial Plast Surg Facial Plastic Surgery
Fertil Steril Fertility and Sterility
Fetal Ther Fetal Therapy
Gastroenterology Gastroenterology
Gynecol Invest Gynecologic Investigation
Gynecol Obstet Invest Gynecologic and Obstetric Investigation
Int J Psychoanal The International Journal of Psycho-Analysis
Ir J Med Sci Irish Journal of Medical Science
J Clin Ultrasound Journal of Clinical Ultrasound
J Comp Neurol The Journal of Comparative Neurology
J Med Genet Journal of Medical Genetics
J Comp Neurol Journal of Neuroradiology
J Pathol Bacteriol The Journal of Pathology and Bacteriology
J Pediatr Surg Journal of Pediatric Surgery
J Perinat Med Journal of Perinatal Medicine
J Anat Journal of Anatomy
JAMA JAMA : The Journal of the American Medical Association
Lancet Lancet
N Engl J Med The New England Journal of Medicine
N Z Med J New Zealand Medical Journal
Nature Nature
Neurology Neurology
Neuropsychologia Neuropsychologia
Nutr Rev Nutrition Reviews
Obstet Gynecol Obstetrics & Gynecology
Pediatr Pathol Lab Med Pediatric Pathology & Laboratory Medicine
Pediatr Res Pediatric Research
Pediatrics Pediatrics
Physiol Rev Physiological Reviews
Science Science
Semin Pediatr Surg Seminars in Pediatric Surgery
Semin Perinatol Seminars in Perinatology
Semin Reprod Endocrinol Seminars in Reproductive Endocrinology
Semin Roentgenol Seminars in Roentgenology
Teratology Teratology
Trans Am Neurol Assoc Transactions of the American Neurological Association
Ultrasound Obstet Gynecol Ultrasound in Obstetrics & Gynecology
Z Anat Entwicklungsgesch Zeitschrift fur Anatomie und Entwicklungsgeschichte

Page 28


Program Index

A

Page Links

abdomen 8, 9, 14
abdominal 6, 12
activity 10, 14, 16
adenine 4
adult(s) 3, 4, 10, 11, 14
age 14
age of viability 14
air 11, 14, 16
alveoli 16
amnion 6, 7
amniotic fluid 7, 11, 12, 14, 15
anise 16
articular 11

B

base pairs 17
base(s) 4, 18
behavior(al) 11, 15, 16
billion 4, 7, 11
birth 3, 6, 7, 11, 12, 13, 15, 16
blastocyst 5
blink-startle 15
blood 4, 5, 6, 7, 9, 11, 13
blood cells 6
blood vessels 6, 11
blueprint 4
body 3, 4, 5, 6, 11, 12, 13, 15
body plan 6
bone(s) 6, 10, 11, 12, 13
bowel 13
brain 6, 7, 9, 11, 15
breastfeeding 13
breathing 9, 11, 16
bronchi 8
bronchial tree 14
buds 7, 13

C

cardiac 16, 21
cardiovascular 6
Carnegie Stage(s) 3, 4, 5, 6, 7, 8, 9, 10, 21
cartilage 6, 8
cell(s) 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 16
central nervous system 16
cerebral hemispheres 7, 9
chambers 6, 7
cheeks 13
chest 6, 10
childbirth 16
chromosomes 4
circulatory 5, 6
clavicle 10
close 12
cochlea 14
collar bone 10
conception 3
contraction 16
cytosine 4

D

day(s) 5, 6, 8, 10
development(al) 3, 4, 6, 7, 9, 12, 13, 16
diaphragm 9
digestive 6, 13
distinguish(ed) 12, 16
DNA 4, 17, 18

E

ear 9, 14
early pregnancy factor (EPF) 4
earth 4, 17
ectoderm 6
egg 4
elbows 10
electrocardiogram 10
electrodes 9
embryo 3, 4, 5, 6, 7, 8, 9, 11, 13
embryology 4
embryonic 3, 4, 5, 7, 9, 11, 19, 20
embryonic period 11, 20
encephalography 9
endoderm 6
energy 15
enzymes 13
epiblast 6
epidermis 11
estrogen 16
extension 11
eye(s) 10, 11, 12, 15
eyelids 10, 11, 12, 15

Page 29


F

Page Links

face 11, 12, 13
Fallopian tubes 4
fat 13, 15
female 10, 12, 13, 15
fertilization 3, 4, 5, 6, 12, 14, 15, 16
fetal 3, 5, 12, 13, 14, 15, 16
fetal period 3, 12, 17
fetus 3, 5, 6, 12, 13, 14, 15, 16
fingerprints 12
fingers 10
flattening 9
fluid 7, 11, 12, 14, 15
folding 6
follicles 14
forebrain 6, 7
formation 3, 8, 11, 12
function(s) 3, 7, 21
fuse 11

G

genitalia 12
germ cells 8
germ layers 6
gestational age 3, 14
glands 14
glucose 12
grasp 12, 16
grasping 11
gravity 11
grow(ing)(s) 3, 5, 6, 9, 11, 14
growth 6, 7, 10, 11, 12, 15
guanine 4

H

hair 6, 11, 14
hand(s) 8, 9, 10, 11, 12, 16
head 5, 7, 9, 11, 12, 13
health 15, 16
hearing 7, 14, 15
hearing loss 15
heart 6, 7, 8, 10, 14, 15
heart rate 14, 15, 20
heartbeat(s) 20
helix 4
hindbrain 6, 7
hormone(s) 5
hours 4, 14
human 3, 4, 5, 6, 11, 12, 16
human chorionic gonadotropin (hCG) 5
hypoblast 6

I

implantation 5
inner cell mass 5, 6
intestine 9, 12

J

jaw 10, 11, 12, 13
jaw movement 11, 13
joints 10, 11

Page 30


K

Page Links

kidneys 6, 8, 11
knee 10

L

labor 16
larynx 12
learning 7
left-handed 11
leg 15
licorice 16
life cycle 12
lifespan 7
light 12, 13, 15
limb(s) 7, 11, 13
lips 12
liver 6, 8, 9
lungs 8, 14, 16
lymphocytes 9

M

male 11, 12, 13
man 4
marrow 13
maternal 4, 5, 19
meconium 13
medications 5
memory 7
menstrual cycle 5
mesoderm 6
metaphase 4
meters 17
midbrain 6, 7
miles 4, 17
million 4, 7, 17
mitosis 4
molecule(s) 4, 17
morula 5
mouth 9, 11, 12, 13
move 12
movement(s) 7, 9, 10, 11, 13, 14, 16
mulberry 5
muscle(s) 6, 11
muscular 11

N

nails 6
nerve(s) 6, 11
neural 11
neuromuscular 9
newborn(s) 11, 13, 14, 16
nipple(s) 10, 13
noise 15
noradrenaline 14
norepinephrine 14
nose 12

O

odors 15
oocyte 4
oogonia 12
open(s) 12, 13, 15
ossification 10
ovaries 4, 10
ovary 4, 12
ovulation 4
oxygen 5

Page 31


P

Page Links

palms 12
pancreas 6
percent 11, 12, 13, 15, 16
physiologic herniation 9
placenta 5, 19
postfertilization age 9, 10, 13, 14, 15, 20
postmenstrual age 3, 9, 13, 14
postnatal 20
preference(s) 11, 16
pregnancy 3, 4, 5, 13, 15, 16
premature(ly) 14, 15
prenatal 21
problem-solving 7
proportion 13
protection 7
pupils 15

Q

quickening 13

R

reflex 13
reflexive(ly) 9, 11
reopen 15
reproductive 4, 8, 12
respiratory 6, 8, 14, 15
respond(s) 13, 14, 15
response 10, 12, 13, 14, 15
retina 10, 15
right-hand 11
rolling over 11
roof 13
rooting reflex 13
rotation 11

S

sac 6, 7
scalp 14
sense(s) 12, 13, 15
sex 12
sigh 12
skeletal 11
skin 6, 7, 11, 14, 15
skin layers 14
sole(s) 12
somersaults 15
sounds 14, 16
speech 7
sperm 4
spermatozoon 4
spinal cord 6
spontaneous 9, 11
squinting 11
startle 10, 15
stem cells 5, 13
stimulation 12, 13
stress response 14
stretch 12
structure(s) 3, 5, 6, 11, 14, 21
survival 3, 14
swallow(ed)(ing) 12, 15
system(s) 3, 5, 6, 8, 9, 14, 16, 21

T

taste 13, 16
taste buds 13
tears 15
temperature 5, 15, 19
testes 11
testosterone 11
thought 7
thumb sucking 12
thymine 4
toes 10, 12
tongue 12, 13
tooth 13
touch(ing) 9, 11, 12, 13
trachea 8
transparency 7, 11
trillion 3, 4, 17
trimester 13, 15
trunk 10

U

umbilical cord 5, 9, 12
umbilical vesicle 6
urine 11
uterine tube(s) 4, 5
uterus 4, 5, 11, 12, 16

V

vascular 11
vernix caseosa 14
viability 14
vocal cord development 12
vocal ligaments 12

W

walking 15
water 12
weight 11, 12, 13, 15
white blood cell 9
windpipe 8
woman 4, 13
womb 4, 14
wrinkled 15
wrist 8

Y

yawns 12
yolk sac 6, 8

Z

zygote 3, 4