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]

Choose level of difficulty:
Advanced

BODY SYSTEMS/REGIONS SELECTION MENU

Select/Clear All


Show Footnotes	Show Bibliography	Page Language:	Additional Language:

	Unit 1: The First Week
	Play Movie		See Snapshots

(Day 0): Embryonic Period Begins Fertilization Zygote formation Otic invagination Opening between gut and umbilical vesicle decreases Pharynx (Day 0 - Day 1): Carnegie Stage 1 Metabolic activation of the oocyte (Day 1 - Day 2): Cleavage Early pregnancy factor (EPF) (Day 1 - Day 3): Activation of the genome (Day 2): Carnegie Stage 2 (Day 3 - Day 4): Compaction Morula (meaning mulberry) (Day 4): Carnegie Stage 3 Embryonic disc (Day 4 - Day 5): Blastocyst Dorsal & ventral surfaces (Day 5): Inner cell mass (Day 5 - Day 6): Hatching (Day 6): Carnegie Stage 4 (Day 6 - 1 week, 5 days): Blastocyst attaches to endometrium (1 week): Carnegie Stage 5a Amniotic cavity formation begins Extra-embryonic mesoblast Hypoblast & epiblast Solid trophoblast Synctiotrophoblast & cytotrophoblast Less Events...

		Take a quiz

	Unit 3: 2 to 3 Weeks
	Play Movie		See Snapshots

(2 weeks, 1 day): 3 germ layers Bilateral symmetry Cloacal membrane Prechordal plate Primitive groove Rostral-caudal orientation (2 weeks, 2 days): Carnegie Stage 7 Allantoic diverticulum Amnion with two cell layers Notochordal process Secondary villi Allantoic diverticulum Primordial germ cells Erythroblasts in umbilical vesicle Three types of hemopoietic cells in umbilical vesicle (2 weeks, 3 days): Anlage of the thyroid (2 weeks, 4 days): Carnegie Stage 8 Connecting stalk Primitive pit Neural ectoderm Neural groove and folds Notochordal and neurenteric canals Notochordal plate Prechordal plate with 1 retinal field Uteroplacental circulation well established Foregut, midgut, and hindgut Brain is first organ to appear (2 weeks, 5 days): Prechordal plate with 2 retinal fields (2 weeks, 6 days): Carnegie Stage 9 Somites 1 - 3 pairs of somites Cephalic and caudal folds Primitve streak reaches neurenteric canal Caudal eminence Forebrain, midbrain, and hindbrain Hindbrain with four rhombomeres Isthmus rhomencephali demarcates midbrain and hindbrain Neural crest Neural groove deepens substantially Primary neuromeres Otic disc First pharyngeal pouch Stomodeum forming Blood vessels emerge independently in umbilical vesicle, embryo proper, amnion, and connecting stalk Cardiogenic plate, cardiac jelly, myocardial mantle, and endocardial plexus Dorsal aortae (paired) First pair of aortic arches Paired pericardial cavities Paired tubular heart Septum transversum Foregut First somites Numerous blood islands in umbilical vesicle Less Events...

		Take a quiz

	Unit 5: 4 to 5 Weeks
	Play Movie		See Snapshots

(4 weeks, 4 days): Carnegie Stage 14 Adenohypophysis All 16 secondary neuromeres Cerebellum with intermediate layer Cerebral hemispheres Di-telencephalic sulcus Dorsal and ventral thalami Dorsal funiculus Mamillary region Medial and lateral longitudinal fasciculi Median ventricular eminence Pontine flexure Preoptico-hypothalamo-tegmental tract Rhombic lip Sulcus medius Synencephalon Tegmentum Tentorium cerebelli, medial portion Torus hemisphericus (TH) Velum transversum Ventral longitudinal fasciculus Eyes located on sides of head Lens pit Optic cups Epicardium Sinu-atrial (SA) node Right and left main stem bronchi Ureteric buds (4 weeks, 5 days): Carnegie Stage 15 Adult lamina terminalis Amygdaloid area Cerebellar plate First axodendritic synapses in cervical spinal cord First nerve fibers Habenular nucleus Habenulo-interpeduncular tract Hypothalamic sulcus Hypothalamus Lateral ventricle Lateral ventricular eminence Locus caeruleus Longitudinal zones in diencephalon Mesencephalic tract of CN 5 Most cranial nerves seen Postoptic recess Sclerotomic material around notochord (rhombomere D level) Subthalamus Superior colliculi Superior medullary velum Supramamillary commissure Synapses among motor neurons in spinal cord Tectobulbar tract Tentorium Third ventricle Trigemino-cerebellar tract Lens vesicles beneath surface Nasal pits Optic chiasma Optic stalk Lateral and medial nasal processes bilaterally Blood vessels penetrate diencephalon Coronary arteries (terminal end) Posterior communicating arteries Vertebrae well defined (4 weeks, 5 days - 5 weeks, 3 days): Aortic and pulmonary valves (5 weeks): Pacemaker cells in sinus venosus Arytenoid and epiglottal swellings Lobar pattern mimics adult pattern T-shaped laryngeal inlet Circular muscles in esophagus Less Events...

		Take a quiz

	Unit 7: 6 to 7 Weeks
	Play Movie		See Snapshots

(6 weeks, 2 days): Carnegie Stage 18 Embryo with dorsal concavity Archistriatum Cerebrospinal fluid production begins Choroid folds in fourth ventricle Choroid plexuses in fourth and lateral ventricles Dentate nucleus in internal cerebellar swellings External cerebellar swellings contain flocculi Four amygdaloid nuclei Hippocampus reaches olfactory region Nucleus ambiguus of the vagus (CN10) Prosencephalic septum Red nucleus Substantia nigra Supraoptic commissure Two or more semicurcular ducts Vomeronasal organ. nerve, and ganglion Nasolacrimal duct Nerve fibers in retina Optic fibers Primordium of stapes surrounds stapedial artery Bucconasal membrane Origin of left coronary artery Septum secundum and foramen ovale Submandibular glands (6½ weeks): Ossification in mandible & maxilla Volar pads on palms (6 weeks, 5 days): Carnegie Stage 19 Choana Ganglion of nervus terminalis Globus pallidus externus in the diencephalon Intermediate layer in dorsal thalamus Lateral recesses in fourth ventricle Lemniscal decussation Medial accessory olivary nucleus Nuclei of forebrain septum Nucleus accumbens Nucleus accumbens Occipital pole of cerebral hemispheres Subcommissural organ Cartilaginous styloid process Cochlear nuclei Optic fibers enter chiasmatic plate Circulus arteriosus (Circle of Willis) complete Origin of right coronary artery Beginnings of occipital and sphenoid bones Three semicircular ducts (6 weeks, 6 days): Membrane blocking rectum ruptures (7 weeks): Head rotates Heart rate peaks (165 to 170 beats/minute) Bronchopulmonary segments complete Ovaries Crown-heel length 2.2 cm Less Events...

		Take a quiz

	Unit 9: 8 to 9 Weeks
	Play Movie		See Snapshots

(8 weeks, 1 day): Fetal Period Begins (8 weeks, 1 day - 9 weeks): Anal canal patent (8½ weeks): Neurons synapse in cerebral cortex (marginal zone) Plantar pads toes (9 weeks): External capsule Olivary nucleus with five components Drinking fluid is becoming routine Sucking the thumb (9 weeks - 10 weeks): Larynx recanalizes

		Take a quiz

	Unit 11: 10 to 11 Weeks
	Play Movie		See Snapshots

(10½ weeks): Volar and plantar pads regress (11 weeks): Intestines absorb water & glucose Small intestine lined with villi Intermediate layer Crown-heel length

		Take a quiz

	Unit 13: 3 to 4 Months
	Play Movie		See Snapshots

(13 weeks): Tooth development (dentine) Crown-heel length 15 cm (14 weeks): Cerebellum resembles adult structure Gender-dependent jaw movement Crown-heel length 17 cm (15 weeks): Crown-heel length 19.5 cm (16 weeks): Quickening Canalicular stage begins Colon lined with villi Crown-heel length 21 cm

		Take a quiz

	Unit 15: 5 to 6 Months
	Play Movie		See Snapshots

(21 weeks): Periderm disappears Sratum corneum (22 weeks): Behavioral states Cornea structure (23 weeks): Brain weight 100 grams (24 weeks): Crown-heel length 34.5 cm

		Take a quiz

	Unit 17: 7 to 8 Months
	Play Movie		See Snapshots

(30 weeks): Head circumference 30 cm (32 weeks): Lower esophagus muscles functional Crown-heel length 45 cm

		Take a quiz

	Unit 19: 9 Months to Birth
	Play Movie		See Snapshots

(37 weeks): Fetus drinks an estimated 15 oz (or 450cc) of amniotic fluid/day (38 weeks): Birth Spinal cord ends at third lumbar vertebrae Brain weight 350 grams Crown-heel length 50 cm Head circumference 35 cm Heart beats 54 million times before birth This timeline has more than 3.1 million configurations

		Take a quiz

Fertilization

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

Birth

Click any fact to learn more!

Click any picture to see more!

	Unit 2: 1 to 2 Weeks
	Play Movie		See Snapshots

(1 week, 1 day): Bilaminar embryonic disc HCG (human chorionic gonadotropin) (1 week, 2 days): Carnegie Stage 5b Chorion Early decidual reaction Exocoelomic membrane Isolated trophoblastic lacunae Primary umbilical vesicle Embryonic disc 0.1 mm diameter (1 week, 2 days - 20 weeks): Corpus luteum of pregnancy (1 week, 4 days): Carnegie Stage 5c Longitudinal axis Trophoblastic vascular circle (1 week, 5 days): Implantation complete Embryonic disc diameter: 0.15 to 0.20 mm (1 week, 6 days): Carnegie Stage 6 Amnion with single cell layer Chorionic villi Primitive streak and node Secondary umbilical vesicle Angiogenesis in chorionic mesoblast Blood islands in umbilical vesicle Blood vessels in villi Less Events...

		Take a quiz

	Unit 4: 3 to 4 Weeks
	Play Movie		See Snapshots

(3 weeks, 1 day): Carnegie Stage 10 4 to 12 pairs of somites Chiasmatic plate Forebrain with neuromeres D1 and D2 Mesencephalic flexure Neural tube Segment D in rhombencephalon Some secondary neuromeres Telencephalon Optic primordia Optic primordia fill neuromere D2 Optic sulcus in forebrain Otic pits Otic plates Hyoid arch Mandibular arch and maxillary process Oropharyngeal membrane Pharyngeal arches 1 and 2 Pharyngeal cleft 1 Second pharyngeal cleft and pouch Atria (right and left) far apart Endocardial tubes fuse forming tubular heart Heart begins beating Left ventricle, right ventricle, conotruncus Pericardium Sinus venosus Tubular heart begins folding Umbilical arteries Umbilical veins (right and left) Pharyngeal groove and ridge with laryngotracheal sulcus Respiratory primordium Hepatic plate Midgut emerging Thyroid primordium emerges from floor of pharynx (3 weeks, 1 day - 4 weeks): Body cavities Folding of the embryo (3 weeks, 2 days): Nephrogenic cord emerges (at 10 somites) (3 weeks, 3 days): Carnegie Stage 11 13 to 20 pairs of somites Segmentation of mesoblast alongside neural tube bilaterally Adenohypophysial primordia Facio-vestibulocochlear ganglia Glossopharyngeal and vagal ganglia Lamina terminalis Mesencephalon contains tectum and tegmentum Neural crest production and migration continue Neurohypophysial primordia Notochord Rostral neuropore closes Trigeminal ganglia Nasal plate Optic evagination (starting at 14 somites) Optic neural crest Optic sulcus Optic vesicle (17 to 19 somites) Optic vesicles form Otic vesicle Maxillary and mandibular processes (bilaterally) Membrane between future mouth and throat may begin to rupture Angiogenesis along surface of central nervous system Aortic sac Atrioventricular canal Capillary plexus begins forming around brain and spinal cord Conotruncus Conus cordis emerging from right ventricle Endocardium Heart contractions produce peristaltic blood flow Interventricular septum Primordium of myocardium Sinus venosus separating from left atria Trigeminal and otic arteries Cystic primordium Hepatic diverticulum Liver Cloacal membrane Mesonephric duct emerges from nephrogenic cord Nephric vesicles Primordial germ cells begin moving from umbilical vesicle to hindgut (3 weeks, 3 days - 5 weeks, 6 days): All eight rhombomeres (3 weeks, 5 days): Carnegie Stage 12 21 - 29 pairs of somites Ectodermal ring complete Progressively C-shaped embryo Brain involves 40% of neural tube Caudal neuropore closes Caudal neuropore closes Embryonic commissural plate Hypoglossal cord enters pharyngeal arch 4 Hypoglossal nucleus Mamillary recess Marginal layer in rhombencephalon Mesencephalic flexure at 90 degrees Mesencephalon with two neuromeres: M1 and M2 Motor neurons in basal plate of rhomencephalon Neural cord within caudal eminence Neurofibrils form in rhombencephalon Primordia of ventral thalamus and subthalamus in diencephalon Sulcus limitans Sulcus limitans in midbrain Telencephalon medium Nasal discs form part of ectodermal ring Optic vesicles covered by sheath Otocyst nearly closed Oropharyngeal membrane is ruptured Pharyngeal arches 1, 2, and 3 Pharyngeal arches with dorsal and ventral parts Atrioventricular canal Common cardinal veins (right and left) Heart circulates blood to and from central nervous system, umbilical vesicle, and chorion Hepatic primordium with abundant vascular plexus Hepatocardiac channels (right and left) Internal carotid arteries Right and left dorsal aorta fuse forming descending aorta Rostral and caudal cardinal veins along brain and spinal cord feeding common cardinal veins Septum primum and foramen primum sometimes present Sinu-atrial foramen prevents backflow into sinus venosus Sinus venosus collects veinous blood from entire embryo Unidirectional circulation Vitelline arteries and veins Cervical sinus Lung bud Tracheo-esophageal septum Alimentary epithelium invades stroma of liver Alimentary epthelium proliferates in primordia of stomach, liver, and dorsal pancreas First part of pancreas Gastric portion of foregut elongates (25 to 28 somites) Omental bursa Umbilical vesicle elongates Upper limb primordium at level of somites 8 to 10 Telopharyngeal bodies (3 weeks, 5 days - 4 weeks): Laryngotracheal groove (3 weeks, 5 days - 7 weeks, 1 day): Sacrocaudal spinal cord formation (secondary neurulation) (4 weeks): Carnegie Stage 13 Amnion surrounds connecting stalk and vitelline stalk Umbilical cord Adenohypophysial pouch Cerebellum Commissural plate Common afferent tract Fourth ventricle Interstitial nucleus (part of medial longitudinal fasciculus) Isthmus rhombencephali (a new neuromere) Most cranial nerve ganglia Oculomotor and trochlear nuclei Terminal-vomeronasal neural crest Basement membrane of otic disc surrounds otic vesicle Endolymphatic appendage Otic vesicle closed Retinal and lens discs Lower lip forms from merging of mandibular processes Aortic arches 4 and 6 Atrioventricular bundle Atrioventricular cushions (rostroventral and caudodorsal) Basilar and vertebral arteries Cardiac contractions still under myogenic control Celiac artery, superior and inferior mesenteric arteries Circulatory system "well established" Contractions well coordinated and sequential from sinus venosus to atria to ventricles Ductus venosus Gas exchange through placenta begins Gelatinous reticulum (or cardiac mesenchyme) Heart chambers bulging with fluid Heart now functions as two parallel pumps Heart with right and left ventricles Hepatocardiac vein Myocardium wall 3 to 4 cells thick Septum primum, foramen primum Small arteries emerging throughout mesoderm Ventricle walls trabeculated Vitelline veins empty exclusively into hepatic plexus Bronchial buds Embryonic stage begins Right and left lung buds Trachea Diverticulum ilei marks division between foregut and hindgut Intestines growing in length Pleuroperitoneal canals Stalk of umbilical vesicle lengthens and narrows Stomach assumes shape of a spindle Umbilical vesicle at height of development Ventral pancreas Vitelline duct Glomeruli emerge in mesonephros Mesonephric duct attached to cloaca Nephric tubules now S-shaped Primordial germ cells migrate to mesonephric ridges Primordial germ cells number several hundred Urorectal cleavage line Diaphragm primordia Upper & lower limb buds Upper and lower limb buds Melanoblasts in epidermis Periderm Thyroid bilobed and attached to pharynx by thryoglossal duct Spleen primordia Thymic primordia Less Events...

		Take a quiz

	Unit 6: 5 to 6 Weeks
	Play Movie		See Snapshots

(5 weeks, 2 days): Carnegie Stage 16 All cranial nerves identifiable Archipallium, paleopallium, and neopallium Cochlear nerve present Commissure of the trochlear nerve Diencephalic subthalamic nucleus Epiphysis cerebri Glial cells identifiable adjacent to neurons Hypoglossal nerve reaches tongue Infundibular recess and infundibulum Marginal ridge Neurohypophysial outgrowth Olfactory tubercle Pontine flexure deepens Primordial plexiform layer in area of future temporal lobe Retinal fissure closes Olfactory fibers enter brain Olfactory tubercle present Frontonasal prominence Atrioventricular (AV) node Circle of Willis almost complete Epiglottis Thyroid detaches from pharynx Thyroid with right and left lobes connected by an isthmus (5½ weeks): Dental lamina (5½ weeks - 6 weeks): Subtle movement begins (5 weeks, 4 days - 6 weeks): Mitral and tricuspid valves (5 weeks, 5 days - 7 weeks, 1 day): Melanocytes in epidermis (5 weeks, 6 days): Carnegie Stage 17 All 39 somite pairs present All spinal nerves present Capillaries between adenohypophysis and hypothalamus Commissure of the oculomotor nerves Cortical nucleus in amygdaloid body Dentate and isthmic nuclei in cerebellum Dura begins forming in basal area First hint of septal nucleus Frontal and tempororal poles of cerebral hemispheres Gustatory fibers separate from common afferent tract Hemispheric stalk Intermediate layer in tectum mesencephali Interventricular foramen Spinal cord reaches caudal tip of body Subarachnoid space Synapses in spinal cord between interneurons and primary afferent neurons Blind nasal sac Cell islands in olfactory tubercle Crescentic lens cavity Nostril becomes continuous with nasal sac Primary lens fiber Primordia of orbital muscles Globular process emerges from each medial nasal process Anterior choroid artery Appendix Cartilage in occipital sclerotomes (1-4) Hypoglossal foramen through sclerotome 4 (6 weeks): Tooth buds (Deciduous) Inferior vena cava Internal and external jugular veins Portal vein Intestines fill base of umbilical cord Handplates develop subtle flattening Milk lines Blood formation & lymphocytes in liver Crown-heel length 1.6 cm Less Events...

		Take a quiz

	Unit 8: 7 to 8 Weeks
	Play Movie		See Snapshots

(7 weeks, 1 day): Carnegie Stage 20 Cerebral hemispheres expand beyond lamina terminalis Cerebral peduncles Cuneate and gracile decussating fibers Interpeduncular groove Medial septal nucleus Nigrostriatal fibers Nucleus of diagonal band Septum verum Optic commissure Facial processes no longer distinguishable (7 weeks, 1 day - 8 weeks): Folds in stomach wall (7 weeks, 2 days): Coronary arteries and veins complete (7 weeks, 3 days): Carnegie Stage 21 Anterior and inferior horns of lateral ventricle C-shaped lateral ventricle Cerebral hemispheres cover more than half of diencephalon Cortical plate within primordial plexiform layer Glial and neurilemmal (Schwann) cells within cranial nerves Global pallidus internus Hippocampus Internal fiber layer of cerebellum Lateral olfactory tract Pineal recess Primordium of dentate nucleus Pyrimadal cells in hippocampus Subthalamic nucleus proper, entopeduncular nucleus, and globus pallidus externus within subthalamus Sulcus transversus rhombencephali Ventral part of lateral geniculate body Cartilaginous nasal septum Anterior and middle cerebral arteries Anterior and posterior choroid arteries Chondrocranium with dorsum sellae and hypophysial fossa Dens (of second cervical vertebrae) (7½ weeks): EKG pattern similar to adult Plantar pads toes Volar pads on fingertips (7 weeks, 5 days): Carnegie Stage 22 Cerebral hemispheres cover 75% of diencephalon Claustrum Commissural plate thickens Cortical plate expanding rapidly Folds in roof of third ventricle Internal capsule with connections to epithalamus, dorsal thalamus, and mesencephalon Nerve fibers between neopallial subplate and internal capsule Putamen Spinothalamic tract Thalamocortical fibers Intradural veins (sinuses) Endolymphatic, jugular, and hypoglossal foramina Optic foramen, foramen rotundum, internal acoustic foramen (8 weeks): Carnegie Stage 23, Embryonic Period Ends Brain highly complex Brain represents 43% of embryo Caudate nucleus and putamen within corpus striatum Cerebellar commissures Cerebellum with external germinal layer Choroid plexus now lobular Cortical plate covers nearly all of neopallial surface Cranial nerve distribution resembles adult pattern Dura lines entire vertebral canal Fasciculus cuneatus and fasciculus gracilis form the decussation of the medial lemnisci Handedness Hippocampus reaches temporal pole Inferior and superior cerebellar peduncles Insula Most cisterns present Pons Principal nucleus of inferior olivary nuclei Pyramidal decussations Subarachnoid space Suprapineal recess Optic tract reaches ventral portion of lateral geniculate body Retina with 4 of the10 layers found in adult Blood supply to the brain closely resembles adult pattern Superior sagittal sinus Superior vena cava Pseudoglandular stage begins Longitudinal muscles in esophagus Foramen magnum (wide) Leydig cells (testes) produce testosterone Crown-heel length 4.3 cm Less Events...

		Take a quiz

	Unit 10: 9 to 10 Weeks
	Play Movie		See Snapshots

(10 weeks): Commissure of the fornix Palatine tonsils Tooth buds (secondary teeth) Left brachiocephalic vein Physiologic herniation ends Ossification underway in most bones Epidermis with periderm, intermediate, and basal layers Crown-heel length 7.5 cm (10 weeks - 12 weeks): Langerhans cells enter epidermis

		Take a quiz

	Unit 12: 11 to 12 Weeks
	Play Movie		See Snapshots

(12 weeks): Corpus callosum Crura cerebri Myelination in spinal cord All facial muscles in final positions Bile production begins in liver Bowel movements Sebaceous glands Crown-heel length 12 cm Head circumference 10 cm

		Take a quiz

	Unit 14: 4 to 5 Months
	Play Movie		See Snapshots

(18 weeks): Apocrine sweat glands Eccrine sweat glands (19 weeks): Sulci on surface of cerebral hemispheres Melanin production (20 weeks): Surfactant production (low levels) Peyer's patches Crown-heel length 28 cm Head circumference 20 cm

		Take a quiz

	Unit 16: 6 to 7 Months
	Play Movie		See Snapshots

(25 weeks): Intestinal lining contains all adult cell types (26 weeks): Terminal sac stage begins (28 weeks): Crown-heel length 39.5 cm

		Take a quiz

	Unit 18: 8 to 9 Months
	Play Movie		See Snapshots

(36 weeks): Surfactant production accelerates Brain weight 300 grams Crown-heel length 48.5 cm

		Take a quiz

Nervous	Cardiovascular	Musculoskeletal	Early Events
Special Senses	Respiratory	Skin	Growth Parameters
Movement	Gastrointestinal	Endocrine	General
Facial	Genitourinary	Blood & Immune	"Gee Whiz" Facts