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7 1/2 week embryo, 7.5 week embryo, seven and a half week embryo

Interactive Prenatal Development Timeline

[All ages refer to time since fertilization] [Features] [Help] [Tutorial]   [Print preview] [PDF]

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Intermediate


BODY SYSTEMS SELECTION MENU
Nervous System Cardiovascular Muscular Early Events
Special Senses Respiratory Skeletal General
Blood & Immune Gastrointestinal Endocrine Growth Parameters
Skin Renal/Urinary Reproductive Movement
 




Go to Weeks:
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-16 16-20 20-24 24-28 28-32 32-36 36-38

Unit 1:   The First Week
     
   
Unit 3:   2 to 3 Weeks
     
  • (2 weeks, 1 day):
  • Early Events3 germ layers
  • Early EventsRostral-caudal orientation
  • (2 weeks, 2 days):
  • Blood & ImmuneErythroblasts in yolk sac
  • Blood & ImmuneThree types of blood-forming cells in
  •          yolk sac
  • Early EventsAmnion with two cell layers
  • Early EventsSecondary villi
  • (2 weeks, 4 days):
  • GastrointestinalForegut, midgut, and hindgut
  • Nervous SystemBrain is first organ to appear
  • Early EventsConnecting stalk
  • (2 weeks, 5 days):
  • Nervous SystemNeural plate induced by notochordal
  •          process
  • (2 weeks, 6 days):
  • Blood & ImmuneNumerous blood islands in umbilical
  •          vesicle
  • GastrointestinalForegut
  • GastrointestinalStomodeum forming
  • CardiovascularBeginnings of the heart can be seen
  • CardiovascularBlood vessels emerge simultaneously in
  •          umbilical vesicle, embryo proper, amnion,
  •          and connecting stalk
  • CardiovascularDorsal aortae (paired)
  • CardiovascularPaired tubular heart
  • Nervous SystemForebrain, midbrain, and hindbrain
  • Nervous SystemNeural groove deepens substantially
  • Nervous SystemThree main divisions of brain
  • Early EventsNeural crest: Rostral and facial
  • (3 weeks):
  • CardiovascularBlood and blood vessels
   
Unit 5:   4 to 5 Weeks
     
   
Unit 7:   6 to 7 Weeks
     
   
Unit 9:   8 to 9 Weeks
     
   
Unit 11:   10 to 11 Weeks
     
   
Unit 13:   3 to 4 Months
     
   
Unit 15:   5 to 6 Months
     
   
Unit 17:   7 to 8 Months
     
   
Unit 19:   9 Months to Birth
     
  • (37 weeks):
  • GastrointestinalFetus drinks an estimated 15 oz (or
  •          450cc) of amniotic fluid/day
  •  
  • (38 weeks):
  • RespiratoryAir breathing begins
  • CardiovascularBy term, the typical umbilical cord
  •          measures 20 to 24 inches (50 to 60 cm)
  • CardiovascularHeart beats 54 million times before
  •          birth
  • CardiovascularMajor circulatory changes
  • Nervous SystemSpinal cord ends at third lumbar
  •          vertebrae
  • GeneralBrain weight 350 grams
  • GeneralCrown-heel length 50 cm
  • GeneralFetus initiates labor
  • GeneralHead circumference 35 cm
  • GeneralTime to be born!
   
Fertilization
Play Movie - Cell Division
Week 1 ends
Play Movie - 1 to 2 weeks, implantation and HCG
Week 2 ends
Play Movie - 2 to 3 week embryo, amnion, germ layer
Week 3 ends
Play Movie - 3 to 4 week embryo, folding of the embryo
Week 4 ends
Play Movie - 4 to 5 week embryo, The Heart in Action
Week 5 ends
Play Movie - 5 to 6 week embryo, hand plates develop
Week 6 ends
Play Movie - 6 to 7 week embryo, hand movement
Week 7 ends
Play Movie - 7 to 8 week embryo, fingers, toes
Week 8 ends
Play Movie - 8 to 9 week fetus, reflexive movement
Week 9 ends
Play Movie - 9 to 10 week fetus, sucking, swallowing
Week 10 ends
Play Movie - 10 to 11 week fetus, eyes roll, yawns
Week 11 ends
Play Movie - 11 to 12 week fetus, nails, fingerprints
Month 3 ends
Play Movie - 3 to 4 month fetus, the rooting reflex
Month 4 ends
Play Movie - 4 to 5 month fetus, bronchial tree
Month 5 ends
Play Movie - 5 to 6 months fetus, responds to sound
Month 6 ends
Play Movie - 6 to 7 month fetus, response to light
Month 7 ends
Play Movie - 7 to 8 month fetus, behavioral states
Month 8 ends
Play Movie - 8 to 9 month fetus, firm hand grasp
Month 9 ends
Play Movie - 9 months to Birth, ready for Birth
Birth
380 events on this timeline
Click any picture to see more!
Unit 2:   1 to 2 Weeks
     
   
Unit 4:   3 to 4 Weeks
     
  • (3 weeks, 1 day):
  • GastrointestinalMidgut emerging
  • RespiratoryRespiratory outgrowth
  • CardiovascularAtria (right and left) far apart
  • CardiovascularCirculatory system function begins
  • CardiovascularEndocardial tubes fuse forming tubular
  •          heart
  • CardiovascularHeart begins beating
  • CardiovascularPericardium
  • CardiovascularPrimary head vein
  • CardiovascularSinus venosus
  • CardiovascularTubular heart begins folding
  • CardiovascularUmbilical arteries
  • CardiovascularUmbilical veins (right and left)
  • Nervous SystemNeural tube
  • Early EventsBody cavities
  • Early EventsHyoid arch
  • (3 weeks, 3 days):
  • EndocrineThyroid complete
  • GastrointestinalCystic primordium
  • GastrointestinalLiver
  • GastrointestinalMembrane between future mouth and throat
  •          may begin to rupture
  • Nervous SystemNeuropore (near brain) closes
  • Nervous SystemNotochord
  • (3 weeks, 5 days):
  • GastrointestinalFirst part of pancreas
  • GastrointestinalPharyngeal arch 3
  • RespiratoryLung bud
  • CardiovascularDescending aorta
  • CardiovascularInternal carotid arteries
  • CardiovascularUnidirectional circulation
  • Nervous SystemBrain involves 40% of neural tube
  • Nervous SystemLowermost spinal cord formation begins
  • Nervous SystemNeural tube closes (lower back)
  • Early EventsSomites: Pairs 21 through 29
  • Early EventsUpper limb primordium at level of
  •          somites 8 to 10
  • GeneralProgressively C-shaped embryo
  • (4 weeks):
  • SkinSkin is so thin, you can see through it!
  • GastrointestinalEsophagus primordia
  • GastrointestinalIntestines growing in length
  • GastrointestinalPancreas: Ventral pancreas
  • GastrointestinalPharynx
  • GastrointestinalSmall & large intestines
  • RespiratoryBronchial buds
  • RespiratoryLungs begin filling chest cavity
  • RespiratoryTrachea
  • CardiovascularCirculatory system "well established"
  • CardiovascularFunctioning two-chamber heart
  • CardiovascularHeart chambers bulging with fluid
  • CardiovascularHeart now functions as two parallel
  •          pumps
  • CardiovascularHeart rate (about) 113 beats/min
  • Special SensesMost cranial nerve ganglia
  • Nervous SystemCerebellum
  • Nervous SystemFourth ventricle
  • Early EventsAmnion surrounds embryo
  • Early EventsLimb buds - the first sign of arms and
  •          legs
  • Early EventsLower limb buds
  • Early EventsUmbilical cord emerging
  • Early EventsUpper and lower limb buds
   
Unit 6:   5 to 6 Weeks
     
   
Unit 8:   7 to 8 Weeks
     
   
Unit 10:   9 to 10 Weeks
     
   
Unit 12:   11 to 12 Weeks
     
   
Unit 14:   4 to 5 Months
     
   
Unit 16:   6 to 7 Months
     
   
Unit 18:   8 to 9 Months
     
  • (34 weeks):
  • GeneralRapid weight gain
  •  
  • (35 weeks):
  • MuscularFirm grip
  • GeneralAmniotic fluid volume peaks
  •  
  • (36 weeks):
  • RespiratorySurfactant production accelerates
  • GeneralBrain weight 300 grams
  • GeneralCrown-heel length 48.5 cm
   


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