Timeline human development: Difference between revisions

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== Week -2 ==
({{GA}} Week 1)
{| class="prettytable" width=100%
|-bgcolor="FAF5FF"
| <center>'''Day'''</center>
| width="100px"|<center>'''Menstrual cycle'''</center>
| '''Event'''
|-
| <center>1</center>
| Menstrual Phase
| [[File:Menstrual cycle.png|90px|left|link=Menstrual Cycle]]
[[Menstrual Cycle]] changes: Uterine endometrium (loss), Ovary (Follicle Development)
|-bgcolor="F5FAFF"
| <center>2</center>
| &nbsp;
| [[File:Human-_menstrual_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]]
|-
| <center>3</center>
| &nbsp;
|
|-bgcolor="F5FAFF"
| <center>4</center>
| &nbsp;
| &nbsp;
|-
| <center>5</center>
| Proliferative Phase
| [[File:Smear- early proliferative.jpg|90px|link=Menstrual_Cycle_-_Histology]][[File:Ova41he.jpg|90px|link=Menstrual Cycle]] [[Menstrual Cycle]] changes: Uterine endometrium (proliferation), Ovary (Follicle Development)
|-bgcolor="F5FAFF"
| <center>6</center>
|
|
|-
| <center>7</center>
| &nbsp;
| &nbsp;
|}
== Week -1 ==
({{GA}} Week 2)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| width="100px"|'''Menstrual cycle'''
| '''Event'''
|-
| <center>8</center>
| Proliferative Phase
|
|-bgcolor="F5FAFF"
| <center>9</center>
| &nbsp;
| [[File:Smear-_mid-proliferative.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Human-_mid-proliferative_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Ovary10x.jpg|90px]] [[File:Ova20he.jpg|90px]] [[Menstrual Cycle]] - Mid proliferative
|-
| <center>10</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>11</center>
| &nbsp;
| &nbsp;
|-
| <center>12</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>13</center>
| &nbsp;
| [[File:Smear-_late-proliferative.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Human-_late_proliferative_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Menstrual cycle.png|90px|link=Menstrual Cycle]] [[Menstrual Cycle]] - Late Proliferative
|-
| <center>14</center>
| Ovulation
Capacitation
| [[File:Human_ovulation_06.jpg|90px]] [[Image:Human oocyte.jpg|90px]] [[File:Follicle 001 icon.jpg|90px|link=Ovulation Movie]]
|}
== Week 1 ==
[[Week 1]] ({{GA}} Clinical Week 3)
[[File:Week1_summary.jpg|thumb|Week 1 summary]]
{| class="prettytable" width=75%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| width="100px"|<center>'''Stage'''</center>
| '''Event'''
|-
| <center>1</center>
| Secretory Phase
[[Carnegie stage 1|'''Stage 1''']]
| [[Image:Early_zygote.jpg|90px]] [[File:Stage1 size with ruler.jpg|90px]][[File:Smear-_secretory.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Human-_secretory_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[Fertilization]], Secretory Phase
|-bgcolor="F5FAFF"
| <center>2</center>
| [[Carnegie stage 2|'''Stage 2''']]
| [[Image:Stage2.jpg|90px]] [[File:Week1 001 icon.jpg|90px|link=Week 1 Movie]] [[Morula]], Blastula
|-
| <center>3</center>
| &nbsp;
| [[File:Human-blastocyst-day-3-6-icon.jpg|90px|link=Blastocyst Day 3-6 Movie]] [[Blastocyst Development]]
|-bgcolor="F5FAFF"
| <center>4</center>
| [[Carnegie stage 3|'''Stage 3''']]
| [[Image:CSt3.jpg|90px]] Blastocyst Hatching (zona pellucida lost)
|-
| <center>5</center>
| &nbsp;
| [[File:Smear-_late_secretory.jpg|90px]] [[File:Human-_late_secretory_uterine_endometrium.jpg|90px]] Late Secretory, Blastocyst (free floating)
|-bgcolor="F5FAFF"
| <center>6</center>
| [[Carnegie stage 4|'''Stage 4''']]
| [[Implantation|Adplantation]]
|-
| <center>7</center>
| [[Carnegie stage 5|'''Stage 5''']]
| [[File:Week2_001 icon.jpg|90px|link=Implantation_Movie]][[File:Stage5_bf11L.jpg|90px|link=Carnegie stage 5]]
|}
== Week 2 ==
[[Week 2]] ({{GA}} Week 4)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>8</center>
|
|  [[File:Week2_001 icon.jpg|90px|link=Implantation_Movie]] [[Implantation]]
|-bgcolor="F5FAFF"
| <center>9</center>
| &nbsp;
| &nbsp;
|-
| <center>10</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>11</center>
| &nbsp;
| &nbsp;
|-
| <center>12</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>13</center>
| [[Carnegie stage 6|'''Stage 6''']]
| [[File:Stage6_bf03.jpg|90px|link=Carnegie stage 6]][[File:Chorion 001 icon.jpg|90px|link=Development Animation - Chorionic Cavity]] Chorionic Cavity
|-
| <center>14</center>
| &nbsp;
| &nbsp;
|}
== Week 3 ==
[[Week 3]] ({{GA}} Week 5)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>15</center>
|
|
|-bgcolor="F5FAFF"
| <center>16</center>
| [[Carnegie stage 7|'''Stage 7''']]
| [[File:Stage7-bf1.jpg|90px|link=Carnegie_stage_7]] [[File:Stage7-sem2.jpg|90px|link=Carnegie_stage_7]] [[Image:Stage7.jpg|90px|link=Carnegie_stage_7]]
|-
| <center>17</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>18</center>
| [[Carnegie stage 8|'''Stage 8''']]
| [[Image:Stage8_human.jpg|90px|link=Carnegie_stage_8]] [[File:Neuralplate_001 icon.jpg|90px|link=Development Animation - Neural Plate]] {{neural}}  neurogenesis, neural groove and folds are first seen
|-
| <center>19</center>
| &nbsp;
| [[Image:Stage8_SEM1.jpg|90px|left]]
|-bgcolor="F5FAFF"
| <center>20</center>
| [[Carnegie stage 9|'''Stage 9''']]
| [[File:Stage9_bf2c.jpg|90px|link=Carnegie_stage_9]] [[File:Stage9_sem1b.jpg|90px|link=Carnegie_stage_9]] [[Musculoskeletal_System_Development|Musculoskeletal]]  somitogenesis, first somites form and continue to be added in sequence caudally (1 - 3 somite pairs).
{{neural}} the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open
[[Neural Crest Development|Neural Crest]]  mesencephalic neural crest is visible{{#pmid:17848161|PMID17848161}}
|-
| <center>21</center>
| &nbsp;
| [[Cardiovascular System Development|Heart]]  cardiogenesis, week 3 begins as paired heart tubes.
|}
== Week 4 ==
[[Week 4]] ({{GA}} Week 6)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>22</center>
| [[Carnegie stage 10|'''Stage 10''']]
| [[File:Stage10_bf2c.jpg|90px|link=Carnegie_stage_10]] [[File:Stage10_sem10c.jpg|90px|link=Carnegie_stage_10]] [[File:Neuraltube_001 icon.jpg|90px|link=Development Animation - Neural Tube]]
[[Neural Crest Development|Neural Crest]] differentiation at spinal cord level from day 22 until day 26
{{neural}} folds begin to fuse near the junction between brain and spinal cord, when [[Neural Crest Development|Neural Crest]] cells are arising mainly from the neural ectoderm
[[Neural Crest Development|Neural Crest]] trigeminal, facial, and postotic ganglia components visible{{#pmid:17848161|PMID17848161}}
[[Neural Crest Development|Neural Crest]]  migration of vagal level neural crest cells begins (7-10 somite stage)
{{neural}} rostral neural tube forms 3 primary brain vesicles (week 4)
[[Respiratory_System_Development|Respiratory]]  Week 4 - laryngotracheal groove forms on floor foregut.
|-bgcolor="F5FAFF"
| <center>23</center>
| &nbsp;
| [[Cardiovascular System Development|Heart]] begins to beat in Humans by day 22-23, first functioning embryonic organ formed.
|-
| <center>24</center>
| [[Carnegie stage 11|Stage 11]]
| [[File:Stage11_bf2c.jpg|90px|link=Carnegie_stage_11]]
[[Endocrine_-_Thyroid_Development|Thyroid]] thyroid median endodermal thickening in the floor of pharynx
{{neural}} rostral (or cephalic) neuropore closes within a few hours; closure is bidirectional, it takes place from the dorsal and terminal lips and may occur in two areas simultaneously. The two lips, however, behave differently.
[[Neural_-_Ventricular_System_Development|Ventricular System]] Optic ventricle appears and the neural groove/tube space is initially filled with amniotic fluid.{{#pmid:2285038|PMID2285038}}
|-bgcolor="F5FAFF"
| <center>25</center>
| [[Carnegie stage 12|Stage 12]]
| [[File:Stage12_bf2b.jpg|90px|link=Carnegie_stage_12]] [[File:Stage12 sem1.jpg|90px|link=Carnegie_stage_12]]
{{pituitary}} Week 4  hypophysial pouch, Rathke's pouch, diverticulum from roof
{{liver}} septum transversum forming liver stroma and hepatic diverticulum forming hepatic trabeculae{{#pmid:9407542|PMID9407542}}
{{neural}} caudal neuropore takes a day to close (closure is approximately at future somitic pair 31/sacral vertebra 2)
{{neural}} secondary neurulation begins
[[Neural_-_Ventricular_System_Development|Ventricular System]] onset of the ventricular system and separates the ependymal from the amniotic fluid.{{#pmid:2285038|PMID2285038}}
{{neural crest}} cardiac crest, neural crest from rhombomeres 6 and 7 that migrates to pharyngeal arch 3 and from there the truncus arteriosus{{#pmid:17848161|PMID17848161}}
[[Neural Crest Development|Neural Crest]] vagal neural crest enter the foregut (20-25 somite stage)
|-
| <center>26</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>27</center>
| &nbsp;
| &nbsp;
|-
| <center>28</center>
| [[Carnegie stage 13|Stage 13]]
| [[File:Stage13_bf1c.jpg|90px|link=Carnegie_stage_13]] [[File:Stage13_sem1c.jpg|90px|link=Carnegie_stage_13]] {{neural}} the neural tube is normally completely closed, ventricular system now separated from amniotic fluid. Neural crest at spinal level is segregating, and spinal ganglia are in series with the somites. Spinal cord ventral roots beginning to develop.{{#pmid:3354839|PMID3354839}}
telencephalon cavity appears
[[Neural - Vascular Development]] - hindbrain is supplied by two parallel neural arteries (or channels) that obtain their blood supply from carotid-vertebrobasilar anastomoses given by the pharyngeal arch arteries; trigeminal artery, the otic artery, hypoglossal artery, and the proatlantal artery.{{#pmid:26060802|PMID26060802}}
[[Gastrointestinal_Tract_-_Liver_Development|Liver]] epithelial cord proliferation enmeshing stromal capillaries{{#pmid:9407542|PMID9407542}}
[[Sensory_-_Smell_Development|Smell]]  Crest comes from the nasal plates{{#pmid:15604533|PMID15604533}}
[[Integumentary_System_Development|Skin]] 4 weeks - simple ectoderm epithelium over mesenchyme
[[Integumentary_System_Development|Skin]] 1-3 months ectoderm- germinative (basal) cell repeated division of generates stratified epithelium; mesoderm- differentiates into connective tissue and blood vessels
{{vision}} Optic vesicle lies close to the surface ectoderm. The surface ectoderm overlying the optic vesicle, in response to this contact, has thickened to form the lens placode.{{#pmid:7364662|PMID7364662}}
[[Respiratory_System_-_Diaphragm|Diaphragm]] - pleuroperitoneal fold (PPF) first discernible in human embryos (CRL 6mm).{{#pmid:19711422|PMID19711422}}
|}
== Week 5 ==
[[Week 5]] ({{GA}} Clinical Week 7)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>29</center>
|
| {{pituitary}} Week 5  elongation, contacts infundibulum, diverticulum of diencephalon
{{heart}}  Week 5 septation starts, atrial and ventricular
{{respiratory}}  Week 5 left and right lung buds push into the pericardioperitoneal canals (primordia of pleural cavity)
[[Respiratory_System_Development|Respiratory]]  Week 5 to 17 lung histology - pseudoglandular
{{hearing}}  Week 5 cochlear part of otic vesicle elongates (humans 2.5 turns)
|-bgcolor="F5FAFF"
| <center>30</center>
| &nbsp;
| &nbsp;
|-
| <center>31</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>32</center>
| [[Carnegie stage 14|Stage 14]]
| [[File:Stage14_bf2l.jpg|90px|link=Carnegie_stage_14]] [[File:Stage14_sem1c.jpg|90px|link=Carnegie_stage_14]] [[Placodes]] sensory placodes, lens pit, otocyst, nasal placode, primary/secondary vesicles, fourth ventricle of brain
[[Mesoderm]] continued segmentation of paraxial mesoderm (somite pairs), heart prominence
[[Head_Development|Head]] 1st, 2nd and 3rd pharyngeal arch, forebrain, site of lens placode, site of otic placode, stomodeum
'''Body - '''heart, [[Gastrointestinal_Tract_-_Liver_Development|liver]], umbilical cord, mesonephric ridge visible externally as bulges.
[[Musculoskeletal_System_-_Limb_Development|Limb]] upper and lower limb buds growing.
[[Musculoskeletal_System_-_Muscle_Development_Timeline#Abdominal_Wall|Abdominal Wall]] mesoderm of the primary body wall coalesced in the ventral midline to create the abdominal cavity.{{#pmid:22976993|PMID22976993}}
{{neural}} first appearance of the future cerebral hemispheres. Cerebellar plate differentiated to an intermediate layer, and future rhombic lip identifiable{{#pmid:3377191|PMID3377191}}
[[Neural - Vascular Development]] - basilar artery forms from the consolidation of the neural arteries.{{#pmid:26060802|PMID26060802}}
[[Neural_-_Ventricular_System_Development|Ventricular System]] Subarachnoid space initially as irregular spaces on the ventral surface of the spinal cord.{{#pmid:16228957|PMID16228957}}
[[Gastrointestinal_Tract_-_Liver_Development|Liver]] hepatic gland and its vascular channels enlarge, hematopoietic function appears{{#pmid:9407542|PMID9407542}}
[[Vision_-_Lens_Development|Eye - Lens]] the lens placode is indented by the lens pit.{{#pmid:7364662|PMID7364662}}
|-
| <center>33</center>
| [[Carnegie stage 15|Stage 15]]
| [[File:Stage15_bf1c.jpg|90px|link=Carnegie_stage_15]]
{{neural}} cranial nerves (except olfactory and optic) are identifiable in more advanced embryos{{#pmid:3213956|PMID3213956}}
[[Neural - Vascular Development]] - vertebral arteries form from transverse anastomoses between cervical intersegmental arteries, beginning with the proatlantal artery and proceeding downward to the 6th intersegmental artery,{{#pmid:26060802|PMID26060802}}
[[Vision_-_Lens_Development|Eye - Lens]] the lens pit is closed. The lens vesicle and optic cup lie close to the surface ectoderm and appear to press against the surface.{{#pmid:7364662|PMID7364662}}
|-bgcolor="F5FAFF"
| <center>34</center>
|
| &nbsp;
|-
| <center>35</center>
| &nbsp;
| [[Sensory_-_Vision_Development|Vision]] 35 to 37 days retinal pigment present
|}
== Week 6 ==
[[Week 6]] ({{GA}} Clinical Week 8)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>36</center>
|
| [[Endocrine_-_Pituitary_Development|Pituitary]] Week 6 - connecting stalk between pouch and oral cavity degenerates
[[Endocrine_-_Parathyroid_Development|Parathyroid]] Week 6 - diverticulum elongate, hollow then solid, dorsal cell proliferation
[[Endocrine_-_Thymus_Development|Thymus]] Week 6 - diverticulum elongate, hollow then solid, ventral cell proliferation
[[Endocrine_-_Adrenal_Development|Adrenal]] Week 6  - fetal cortex forms from mesothelium adjacent to dorsal mesentery, medulla neural crest cells from adjacent sympathetic ganglia
[[Respiratory_System_Development|Respire]] Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes
[[Tongue_Development|Tongue]]  Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes gustatory papilla, caudal midline near the foramen caecum (week 6 to 7 - nerve fibers approach the lingual epithelium)
|-bgcolor="F5FAFF"
| <center>37</center>
| [[Carnegie stage 16|Stage 16]]
| [[File:Stage16_bf1c.jpg|90px|link=Carnegie_stage_16]] [[Neural System Development|Neural]] first parasympathetic ganglia, submandibular and ciliary, are identifiable{{#pmid:2751117|PMID2751117}}
[[Neural - Vascular Development]] -  development of the middle cerebral artery is first identified as small buds originating proximal to the anterior cerebral artery on the anterior division of the primitive internal carotid artery.{{#pmid:26060802|PMID26060802}}
[[Musculoskeletal_System_-_Limb_Development|Limb]] upper limb bud '''nerves''' median nerve, radial nerve and ulnar nerve entered into hand plate, '''myoblasts''' spindle shaped and oriented parallel to limb bud axis.
[[Musculoskeletal_System_-_Muscle_Development_Timeline#Abdominal_Wall|Abdominal Wall]] muscle cell migration about 25% of the hemicircumference of the abdominal cavity, the lateral plate mesoderm has become more condensed and thicker in the area around the myoblasts.{{#pmid:22976993|PMID22976993}}
[[Cardiovascular System Development|Heart]]  outflow tract elliptical configuration with four cushions, the two larger fusing at this stage. Semilunar valve leaflets form at the downstream end of the cushions
[[Head_Development|Head]] lip and palate components of the upper lip, medial nasal prominence and maxillary process present, median palatine process appears.
[[Integumentary_System_-_Eyelid_Development|Eyelid]] prior to the development of the eyelids, one small sulcus or groove forms above the eye (eyelid groove) and another below it.{{#pmid:7364662|PMID7364662}}
|-
| <center>38</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>39</center>
| &nbsp;
| &nbsp;
|-
| <center>40</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>41</center>
| [[Carnegie stage 17|Stage 17]]
|  [[File:Stage17_bf1c.jpg|90px|link=Carnegie_stage_17]]
* {{neural}}
** telencephalon areas of the future archicortex, paleocortex, and neocortex, visible. Beginning of future choroid plexus{{#pmid:2802187|PMID2802187}}
** primordium of the epidural space appears first on the ventral part of the vertebral canal and develops rostro-caudally{{#pmid:15478101|PMID15478101}}
* [[Sensory_-_Smell_Development|Smell]] olfactory nerve fibres enter the brain{{#pmid:15604533|PMID15604533}}
* [[Integumentary_System_-_Eyelid_Development|Eyelid]] sulcus (groove) above and below eye deepen and eyelid folds develop (below first and then above){{#pmid:7364662|PMID7364662}}
* [[Respiratory_System_-_Diaphragm|Diaphragm]] - pleuroperitoneal fold (PPF) no longer separated from the diaphragm (CRL 14mm){{#pmid:19711422|PMID19711422}}
* [[Musculoskeletal_System_-_Muscle_Development_Timeline#Abdominal_Wall|Abdominal Wall]] muscle cells now migrated approximately 50% of the distance to the ventral midline, inner and outer layers were not discernible yet.<ref name="PMID22976993" />
|-
| <center>42</center>
| &nbsp;
| [[Cardiovascular System Development|Heart]]  separation of common cardiac outflow (aortic arch and pulmonary aorta)
|}
== Week 7 ==
[[Week 7]] ({{GA}} Clinical Week 9)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>43</center>
|
| [[Endocrine_-_Pancreas_Development|Pancreas]] Week 7 to 20  pancreatic hormones secretion increases, small amount maternal insulin
[[Respiratory_System_Development|Respiratory]]  Week 7 - enlargement of liver stops descent of heart and lungs
|-bgcolor="F5FAFF"
| <center>44</center>
| [[Carnegie stage 18|Stage 18]]
| [[File:Stage18_bf1c.jpg|90px|link=Carnegie_stage_18]]
[[Musculoskeletal_System_-_Limb_Development|Limb]] [[Musculoskeletal_System_-_Bone_Development|Bone]] forms by endochondrial ossification and throughout embryo replacement of cartilage with bone (week 5-12).
{{neural}} [[Sensory_-_Smell_Development|Smell]] vomeronasal fibres and nervus terminalis{{#pmid:15604533|PMID15604533}}
[[Gastrointestinal_Tract_-_Liver_Development|Liver]] obturation due to epithelial proliferation, bile ducts became reorganized, continuity between liver cells and gut{{#pmid:9407542|PMID9407542}}
[[Neural_-_Ventricular_System_Development|Ventricular System]] duramater appears and spaces surround the circumference of the spinal cord, which coalesce and contain many blood vessels.{{#pmid:15478101|PMID15478101}}
[[Genital - Female Development]] opening of the paramesonephric (Müllerian) duct to the coelomic cavity formed as an invagination of the coelomic epithelium{{#pmid:12740945|PMID12740945}}
[[Musculoskeletal_System_-_Muscle_Development_Timeline#Abdominal_Wall|Abdominal Wall]] separation of the myoblasts into distinct inner and outer layers, with unidirectional orientation. Abdominal wall thicker in the region where secondary structures were forming compared with the primary body wall region, dorsally outermost layer of connective tissue approximately half of this thickness.{{#pmid:22976993|PMID22976993}}
|-
| <center>45</center>
| &nbsp;
| &nbsp;
[[Gastrointestinal_Tract_-_Liver_Development|Liver]] (stage 18 to 23)  biliary ductules developed in periportal connective tissue
produces ductal plates that receive biliary capillaries{{#pmid:9407542|PMID9407542}}
|-bgcolor="F5FAFF"
| <center>46</center>
| &nbsp;
| &nbsp;
|-
| <center>47</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>48</center>
| [[Carnegie stage 19|Stage 19]]
|  [[File:Stage19_bf1c.jpg|90px|link=Carnegie_stage_19]]
* [[Sensory_-_Vision_Development|Vision]] - (stage 19 -22) [[Integumentary_System_-_Eyelid_Development|eyelid]] folds develop into the eyelids and cover more of the eye as the palpebral fissure takes shape. The upper and the lower eyelids meet at the outer canthus in Stage 19.{{#pmid:7364662|PMID7364662}}
* [[Cardiovascular System Development|Cardiovascular]]
** arterial system<ref name=KeibelMall1912>{{Ref-KeibelMall1912}}</ref> [[Book - Manual of Human Embryology 18-6|Chapter 18]] [[:File:Keibel Mall 2 390.jpg|fig. 447]]).
** aortic arches <ref name=Congdon1922>{{Ref-Congdon1922}}</ref> stages 11–19 (figs. 29–40).
** [[Cardiovascular System Development|Heart]] fusion of aortic and mitral endocardial cushion material</ref>{{Ref-Teal1986}}</ref>
* [[Respiratory System Development|Respiratory]] - first generation of subsegmental bronchi now complete, see bronchial tree reconstruction<ref name=Wells1954>{{Ref-Wells1954}}</ref> (plates 3 and 4).
* [[Gastrointestinal Tract Development|Gastrointestinal]] - anal membrane defined.
* [[Renal System Development|Renal]] - Cloacal membrane ruptures from urinary pressure at [[Carnegie stage 18|stage 18]] or [[Carnegie stage 19|stage 19]],
* {{genital}}
** {{testis}} - Rete testis develops from the seminiferous cords at stages 19–23, and tunica albuginea forms.<ref name=Jirasek1971>{{Ref-Jirasek1971}}</ref>.
** {{ovary}} - Rete ovarii cords are developing.<ref>{{Ref-Wilson1926a}}</ref>
** [[Uterus Development|Uterus]] Müllerian duct grows independently from the invagination of the coelomic epithelium during stages 19-23{{#pmid:12740945|PMID12740945}}
* [[Musculoskeletal System Development|Musculoskeletal]]
** Sternum right and left sternal bars are present.<ref>{{Ref-Gasser1975}}</ref> (figs. 7-17 and 7-22)
** [[Musculoskeletal_System_-_Muscle_Development_Timeline#Abdominal_Wall|Abdominal Wall]] segregation of the myoblasts into four distinct muscle groups with unidirectional orientation of myoblasts. Myoblast migrated over half of the distance to the ventral midline, abdominal wall thickest where the muscles migrated and the outermost layer of connective tissue comprises approximately half of the total thickness of the abdominal wall. Rectus muscle completely separated after migrating over half the distance to the midline.{{#pmid:22976993|PMID22976993}}
* {{neural}}
** rhombencephalon migration for olivary and arcuate nuclei begins.
** choroid plexus of the fourth ventricle present.
** stria medullaris thalami reaches the habenular nuclei.
** habenular commissure  begins to develop.
** accessory olivary nucleus appears{{#pmid:2268071|PMID2268071}}
** [[Neural - Vascular Development]] - middle cerebral artery becomes more prominent, the plexi fuse into a single artery and further branches pierce the cerebral hemisphere.{{#pmid:26060802|PMID26060802}}
|-
| <center>49</center>
| &nbsp;
| &nbsp;
|}
== Week 8 ==
[[Week 8]] ({{GA}} Clinical Week 10)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>50</center>
| [[Carnegie stage 20|Stage 20]]
|  [[File:Stage20_bf1c.jpg|90px|link=Carnegie_stage_20]]
[[Head_Development|Head]] scalp vascular plexus visible
[[Musculoskeletal_System_-_Limb_Development|Limb]]  upper limbs begin to rotate ventrally
[[Neural System Development|Neural]] amygdaloid body has at least four individual nuclei{{#pmid:2268071|PMID2268071}}
oculomotor nerve shows a dorsolateral and a ventromedial portion
rhombic lip (rhombencephalon) formation of the cerebellum (intermediate layer) and of the cochlear nuclei
cerebellum cell layer (future Purkinje cells) develops
choroid plexuses of the fourth and lateral ventricles
[[Integumentary_System_-_Eyelid_Development|Eyelid]]  the inner canthus is established.{{#pmid:7364662|PMID7364662}}
|-bgcolor="F5FAFF"
| <center>51</center>
| &nbsp;
| [[Gastrointestinal Tract Development|Gastrointestinal Tract]]  anal membrane perforates
|-
| <center>52</center>
| [[Carnegie stage 21|Stage 21]]
|  [[File:Stage21_bf1c.jpg|90px|link=Carnegie_stage_21]]
{{neural}}  cortical plate appears in the area of future insula{{#pmid:2252222|PMID2252222}}
[[Neural - Vascular Development]] - formation of the anterior communicating artery.{{#pmid:26060802|PMID26060802}}
[[Musculoskeletal_System_-_Limb_Development|Limb]] upper and lower limbs rotate
[[Coelomic Cavity Development|Intraembryonic Coelom]]  pericardioperitoneal canals close
[[Musculoskeletal_System_-_Muscle_Development_Timeline#Abdominal_Wall|Abdominal Wall]] Myoblasts have reached the ventral midline and myotubes were present and oriented uniformly within all muscle groups. The rectus abdominis formed distinct bundles of muscle. Connective tissue layers comprised the majority of the thickness of the abdominal wall, outermost layer of connective tissue accounted for the majority of this thickness.{{#pmid:22976993|PMID22976993}}
|-bgcolor="F5FAFF"
| <center>53</center>
| &nbsp;
| &nbsp;
|-
| <center>54</center>
| [[Carnegie stage 22|Stage 22]]
|  [[File:Stage22_bf1c.jpg|90px|link=Carnegie_stage_22]] {{neural}}  neocortical fibres project to epithalamus, to dorsal thalamus, and to mesencephalon{{#pmid:2252222|PMID2252222}}
[[Musculoskeletal_System_-_Limb_Development|Limb]] fingers and toes lengthen
[[Sensory_-_Smell_Development|Smell]] Stage 22 to early fetal period - migratory streams of neurons from the subventricular zone of the olfactory bulb towards the future claustrum{{#pmid:15604533|PMID15604533}}
[[Uterus Development|Uterus]]  [[Vagina Development|Vagina]] fused duct (uterovaginal canal) bifurcated at the caudal portion at Carnegie stages 22 and 23{{#pmid:12740945|PMID12740945}}
|-
|-bgcolor="F5FAFF"
| <center>55</center>
|
| [[Genital_System_Development|Genital]] 8 Weeks  Testis - mesenchyme, interstitial cells (of Leydig) secrete testosterone, androstenedione
[[Genital_System_Development|Genital]] 8 to 12 Weeks - hCG stimulates testosterone production
[[Tongue_Development|Tongue]] Week 8 - nerves penetrate epitheilai basal lamina and synapse with undifferentiated, elongated, epithelial cells (taste bud progenitor cell){{#pmid:8955790|PMID8955790}}
|-
| <center>56</center>
| [[Carnegie stage 23|Stage 23]]
|  [[File:Stage23_bf1c.jpg|90px|link=Carnegie_stage_23]] Stage 23 defines the end of the embryonic (organogenesis) period
[[Mesoderm]] heart prominence, ossification continues
[[Head_Development|Head]]  nose, eye, external acoustic meatus, eyelids, external ears, rounded head
'''Body '''- straightening of trunk, umbilical cord, intestines herniated at umbilicus
[[Musculoskeletal_System_-_Limb_Development|Limb]] upper limbs longer and bent at elbow, hands and feet turned inward, foot with separated digits, wrist, hand with separated digits
[[Coelomic_Cavity_Development|Extraembryonic Coelom]]  chorionic cavity is now lost by fusion with the expanding amniotic cavity
{{neural}} rhombencephalon, pyramidal decussation present, nuclei and tracts similar to those present in the newborn cerebellum present as only a plate connected to midbrain and hindbrain through fibre bundles{{#pmid:2244584|PMID2244584}}
[[Musculoskeletal_System_-_Axial_Skeleton_Development|Axial Skeleton]] vertebral column 33 or 34 cartilaginous vertebrae (20-33 mm in total length), vertebral pedicles, articular and transverse processes identifiable (no spinous processes){{#pmid:7216919|PMID7216919}}
[[Musculoskeletal_System_-_Muscle_Development_Timeline#Abdominal_Wall|Abdominal Wall]] Rectus muscle forms 2 or 3 distinct layers with myotube orientation uniform in all muscles. The external oblique and internal oblique started to expand in thickness, transversus a thin layer of muscle.{{#pmid:22976993|PMID22976993}}
|-
| <center>&nbsp;</center>
| [[Week 8]]
| [[Gastrointestinal_Tract_-_Stomach_Development| Stomach]] Week 8 - Gastrin containing cells in stomach antrum. Somatostatin cells in both the antrum and the fundus.
[[Genital - Female Development]] paired paramesonephric (Müllerian) ducts contact each other and are fused into a single tube that separates again and returns to the mesonephric (Wolffian) ducts. The paramesonephric ducts have not yet reached the urogenital sinus.{{#pmid:12740945|PMID12740945}}
|}
== Week 9  ==
({{GA}} Clinical Week 11)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>57</center>
| Fetal Period
| [[File:Size comparison embryo-fetus actual.jpg|90px|link=Fetal Development]]
{{hearing}} Week 9 - mesenchyme surrounding membranous labrynth (otic capsule) chondrifies
{{smell}} Embryonic/Fetal transition - localized incomplete lamination of the olfactory bulb{{#pmid:15604533|PMID15604533}}
|-bgcolor="F5FAFF"
| <center>58</center>
| &nbsp;
| &nbsp;
|-
| <center>59</center>
|
| &nbsp;
|-bgcolor="F5FAFF"
| <center>60</center>
| &nbsp;
| &nbsp;
|-
| <center>61</center>
|
| &nbsp;
|-bgcolor="F5FAFF"
| <center>62</center>
| &nbsp;
| &nbsp;
|-
| <center>63</center>
|
| Week 9 - CRL 43 mm, femur length 6 mm
9 weeks CRL 50 mm - {{genital}} genitalia in both sexes look identical{{#pmid:17875485|PMID17875485}}
uterus - paramesonephric ducts come into apposition with the urorectal septum and begin to fuse
|}
== Week 10  ==
({{GA}} Clinical Week 12)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
| <center>64</center>
|
|  [[File:Size comparison embryo-fetus actual.jpg|90px|link=Fetal Development]]
[[Gastrointestinal Tract Development|Gastrointestinal Tract]]  Week 10 intestines in abdomen
[[Endocrine_-_Pituitary_Development|Pituitary]] growth hormone and ACTH detectable
[[Endocrine_-_Pancreas_Development|Pancreas]]  Week 10 glucagon (alpha) differentiate first, somatostatin (delta), insulin (beta) cells differentiate, insulin secretion begins
[[Tongue_Development|Tongue]] Week 10 shallow grooves above the taste bud primordium
[[Gastrointestinal_Tract_-_Stomach_Development| Stomach]]  Week 10 - Glucagon containing cells in stomach fundus.
[[Integumentary_System_-_Nail_Development|Nail Development]] fingernails appear
{{outer ear}} Week 10 - Meatal plug extends in a disc-like fashion, the meatus is boot-shaped with a narrow neck and the sole of the meatal plug spreading widely to form the future tympanic membrane medially. Proximal portion of the neck starts to be resorbed.
{{inner ear}} Week 10 - neural-crest-derived melanocytes migrate into the cochlea. They penetrate the basement membrane of the lateral wall epithelium and develop into the intermediate cells of the stria vascularis.{{#pmid:25663387|PMID25663387}}
|-bgcolor="F5FAFF"
| <center>65</center>
| &nbsp;
| &nbsp;
|-
| <center>66</center>
|
| &nbsp;
|-bgcolor="F5FAFF"
| <center>67</center>
| &nbsp;
| &nbsp;
|-
| <center>68</center>
|
| &nbsp;
|-bgcolor="F5FAFF"
| <center>69</center>
| &nbsp;
| &nbsp;
|-
| <center>70</center>
|
| Week 10 - CRL 55 mm, femur length 9 mm, biparietal diameter 17 mm
|}
== Week 11 ==
({{GA}} Clinical Week 13)
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Day'''</center>
| <center>'''Stage'''</center>
| '''Event'''
{{neural}} - [[Neural - Cerebrum Development|Cerebrum]] appearance of the first sulcus (week 11-15, {{GA}} 13-17 weeks){{#pmid:17962979|PMID17962979}}
|-
| <center>71</center>
|
| [[File:Size comparison embryo-fetus actual.jpg|90px|link=Fetal Development]]
[[Endocrine_-_Thyroid_Development|Thyroid]] colloid appearance in thyroid follicles, iodine and thyroid hormone (TH) synthesis
[[Gastrointestinal_Tract_-_Stomach_Development| Stomach]] Week 11 - Serotonin containing cells in both the antrum and the fundus.
|-bgcolor="F5FAFF"
| <center>72</center>
| &nbsp;
| &nbsp;
|-
| <center>73</center>
|
| &nbsp;
|-bgcolor="F5FAFF"
| <center>74</center>
| &nbsp;
| &nbsp;
|-
| <center>75</center>
|
| &nbsp;
|-bgcolor="F5FAFF"
| <center>76</center>
| &nbsp;
| &nbsp;
|-
| <center>77</center>
|
| Week 11 - CRL 68 mm, femur length 12 mm, biparietal diameter 20 mm
|}


== Second Trimester ==
== Second Trimester ==
({{GA}} Clinical Week 14) [[Second Trimester]]
({{GA}} Clinical Week 14) [[Second Trimester]]


{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Week'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-bgcolor="F5FAFF"
| <center>12</center>
| Clinical second trimester
| [[File:Fetal_head_lateral.jpg|90px|link=Fetal Development]] Week 12 - CRL 85 mm, femur length 15 mm, biparietal diameter 25 mm
[[Sensory_-_Hearing_and_Balance_Development|Hearing]] Week 12-16 - Capsule adjacent to membranous labrynth undegoes vacuolization to form a cavity (perilymphatic space) around membranous labrynth and fills with perilymph
[[Genital_System_Development|Genital]] male and female external genital differences observable
[[Respiratory_System_Development|Respiratory]]  Month 3-6 - lungs appear glandular, end month 6 alveolar cells type 2 appear and begin to secrete surfactant
[[Tongue_Development|Tongue]] Week 12 - first differentiated epithelial cells (Type II and III)
[[Genital_System_Development|Genital]] female genital canal (80 days) formed with absorption of the median septum
|-
| <center>13</center>
| &nbsp;
| [[Tongue_Development|Tongue]]  Week 12 to 13 - maximum synapses between cells and afferent nerve fibers
[[Hearing_-_Outer_Ear_Development|Hearing - Outer Ear Development]] Week 13 - Meatal plug disc-like, innermost surface in contact with the primordial malleus, contributes to the formation of the tympanic membrane.
&nbsp;
|-bgcolor="F5FAFF"
| <center>14</center>
|
| [[Tongue_Development|Tongue]] Week 14 to 15 - taste pores develop, mucous
[[Ovary Development]] 100 days - primary follicles present
[[Integumentary_System_-_Nail_Development|Nail Development]] toenails appear
[[Head Development]] facial skeleton remodelling begins
[[Hearing - Inner Ear Development|Hearing - Inner Ear Development]] Week 14  {{GA}} 16 - neural-crest-derived melanocytes, now intermediate cells of the stria vascularis, tightly integrate with Na+ /K+ -ATPase-positive marginal cells, which started to express KCNQ1 in their apical membrane.{{#pmid:25663387|PMID25663387}}
|-
| <center>15</center>
| &nbsp;
| [[Endocrine_-_Pancreas_Development|Pancreas]] glucagon detectable in fetal plasma.
{{spleen}} Week 15 -alpha-smooth muscle actin (alpha-SMA)-positive reticulum cells scattered around the arterioles.{{#pmid:19255788|PMID19255788}}
===Fetal Timeline===
|-bgcolor="F5FAFF"
| <center>16</center>
| 14 cm
| [[File:Fetal_size_change.jpg|90px|link=Fetal Development]] [[Sensory_-_Hearing_and_Balance_Development|Hearing]]  Week 16-24 - Centres of ossification appear in remaining cartilage of otic capsule form petrous portion of temporal bone. Continues to ossify to form mastoid process of temporal bone.
[[Endocrine_-_Pituitary_Development|Pituitary]] adenohypophysis fully differentiated
[[Respiratory_System_Development|Respiratory]]  Week 16 to 25 lung histology - canalicular
[[Hearing_-_Outer_Ear_Development|Hearing - Outer Ear Development]] Week 16.5 - External auditory meatus is fully patent throughout its length, lumen is still narrow and curved.
[[Hearing - Inner Ear Development|Hearing - Inner Ear Development]] Week 16  {{GA}} 18 -  cells in the outer sulcus express KCNJ10 and gap junction proteins GJB2/CX26 and GJB6/CX30, but these are not expressed in the spiral ligament.{{#pmid:25663387|PMID25663387}} [[:File:Gap junction 01.jpg|gap junction cartoon]]
{{neural}} - [[Neural - Cerebrum Development|Cerebrum]] development of the periinsular sulci (week 16-17, {{GA}} 18-19 weeks){{#pmid:17962979|PMID17962979}}
[[Integumentary_System_Development|Skin]] 4 months - basal cell- proliferation generates folds in basement membrane; neural crest cells- (melanocytes) migrate into epithelium; embryonic connective tissue- differentiates into dermis, a loose ct layer over a dense ct layer. Beneath the dense ct layer is another loose ct layer that will form the subcutaneous layer. Ectoderm contributes to nails, hair follictles and glands. Nails form as thickening of ectoderm epidermis at the tips of fingers and toes. These form germinative cells of nail field. Cords of these cells extend into mesoderm forming epithelial columns. These form hair follocles, sebaceous and sweat glands.
primary follicles begin to form in the ovary and are characterized by an oocyte
glandular urethra forms and skin folds present
|-
| <center>17</center>
|
| [[File:Brain_week_17_histology.jpg|90px]] [[Neural System Development|Neural]] - Brain development histology week 17
[[Neural - Cerebellum Development|Cerebellum]] [[Magnetic Resonance Imaging]] (MRI) can study the developing cerebellum from 17 to 18 weeks ({{GA}} 19 to 20 weeks).
[[Integumentary System - Tooth Development|Tooth Development]] Week 17 - First papilla of the permanent dentition appear (first molar) immediately behind the second milk molar, milk teeth are well advanced (Fetus 180 mm).
|-bgcolor="F5FAFF"
| <center>18</center>
|
| [[File:Bailey095.jpg|90px]]{{tongue}}  Week 18 - substance P detected in dermal papillae, not in taste bud primordia
{{integumentary}}  vernix caseosa covers skin
[[Cardiovascular_System_-_Spleen_Development|Spleen]] Week 18 - alpha-SMA-positive reticulum cells increase in number and began to form a reticular framework. An accumulation of T and B lymphocytes occurred within the framework, and a primitive white pulp was observed around the arterioles.{{#pmid:19255788|PMID19255788}}
[[Hearing_-_Outer_Ear_Development|Hearing - Outer Ear Development]] week 18 - External auditory meatus is already fully expanded to its complete form.
{{neural}} - [[Neural - Cerebrum Development|Cerebrum]] central sulci and opercularization of the insula (week 18-20, {{GA}} 20-22 weeks){{#pmid:17962979|PMID17962979}}
|-
| <center>19</center>
| &nbsp;
| {{neural}} week 19 neuronal migration ends and the [[Neural_System_-_Glial_Development#Radial_Glia|radial glial cells]] that aided the migration now become transformed into astrocytes and astrocytic precursors.{{#pmid:3339373|PMID3339373}}
|-bgcolor="F5FAFF"
| <center>20</center>
| &nbsp;
| {{pituitary}} week 20 to 24  growth hormone levels peak, then decline
{{integumentary}} lanugo, skin hair
[[Integumentary_System_Development|Skin]] 5 months - Hair growth initiated at base of cord, lateral outgrowths form associated sebaceous glands; Other cords elongate and coil to form sweat glands; Cords in mammary region branch as they elongate to form mammary glands.
|-
| <center>21</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>22</center>
| &nbsp;
| [[File:Gray0038.jpg|90px|link=Fetal Development]] [[Neural System Development|Neural]] brain cortical sulcation - sylvian fissure, interhemispheric fissure, callosal sulcus, parietooccipital fissure, and hippocampic fissures present{{#pmid:11158907|PMID11158907}}
[[Cardiovascular_System_-_Spleen_Development|Spleen]] - Week 22 - antigenic diversity of the reticular framework was observed, and T and B lymphocytes were segregated in the framework. T lymphocytes were sorted into the alpha-smooth muscle actin-positive reticular framework, and the periarteriolar lymphoid sheath (PALS) was formed around the arteriole. B lymphocytes aggregated in eccentric portions to the PALS and formed the lymph follicle (LF). The reticular framework of the LF was alpha-SMA-negative. {{#pmid:19255788|PMID19255788}}
{{neural}} - [[Neural - Cerebrum Development|Cerebrum]]  covering of the posterior insula (week 22-24, {{GA}} 24-26 weeks){{#pmid:17962979|PMID17962979}}
|-
| <center>23</center>
| &nbsp;
| &nbsp;
|-bgcolor="F5FAFF"
| <center>24</center>
| &nbsp;
| [[Respiratory_System_Development|Respiratory]]  Week 24 to 40 lung histology - terminal sac
[[Cardiovascular_System_-_Spleen_Development|Spleen]] Week 24 - marginal zone appeared in the alpha-smooth muscle actin-positive reticular framework around the white pulp.{{#pmid:19255788|PMID19255788}}
{{tooth}} Week 24 - Permanent incisors and canines appear.
Earliest potential survival expected if born
ovarian follicles can consist of growing oocytes surrounded by several layers of granulosa cells
|-
| <center>25</center>
| &nbsp;
| [[Respiratory_System_Development|Respiratory]]  end month 6 alveolar cells type 2 appear and begin to secrete surfactant
{{neural}} - [[Neural - Cerebrum Development|Cerebrum]]  closure of the laeteral sulcus (Sylvian fissure or lateral fissure) (week 25-26, {{GA}} 27-28 weeks){{#pmid:17962979|PMID17962979}}
|}


== Third Trimester ==
== Third Trimester ==
({{GA}} Clinical Week 28) [[Third Trimester]]
{| class="prettytable" width=100%
|-bgcolor="F5FAFF"
| <center>'''Week'''</center>
| <center>'''Stage'''</center>
| '''Event'''
|-
|
| Clinical third trimester
| [[File:Fetal_size_change.jpg|90px|link=Fetal Development]] {{hearing}} 3rd Trimester - vibration acoustically of maternal abdominal wall induces startle respone in fetus.
|-bgcolor="F5FAFF"
| <center>27</center>
|
| &nbsp;
|-
| <center>28</center>
| &nbsp;
| {{respiratory}} Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs
|-bgcolor="F5FAFF"
| <center>29</center>
|
| &nbsp;
{{tooth}} Week 29 - Permanent premolars (correspond to the milk molars) appear.
|-
| <center>30</center>
| &nbsp;
| &nbsp;
[[Genital_System_Development|Genital]] male gonad (testes) descending
|-bgcolor="F5FAFF"
| <center>31</center>
|
| &nbsp;
|-
| <center>32</center>
| &nbsp;
| {{nail}} fingernails reach digit tip
|-bgcolor="F5FAFF"
| <center>33</center>
| &nbsp;
| {{neural}}  brain cortical sulcation - primary sulci present{{#pmid:11158907|PMID11158907}}
|-
| <center>34</center>
| &nbsp;
| {{neural}}  brain cortical sulcation - insular, cingular, and occipital secondary sulci present{{#pmid:11158907|PMID11158907}}
|-bgcolor="F5FAFF"
| <center>35</center>
| &nbsp;
| &nbsp;
|-
| <center>36</center>
| &nbsp;
|  [[File:Frazer006_bw600.jpg|90px|link=Fetal Development]] [[Integumentary_System_-_Nail_Development|Nail Development]] toenails reach digit tip
[[Vision_-_Lens_Development|Lens Development]] - lens growth and interocular distance plateaus after 36 weeks of gestation{{#pmid:19541779|PMID19541779}}
|-bgcolor="F5FAFF"
| <center>37</center>
| &nbsp;
| &nbsp;
|-
| <center>38</center>
| Birth
| [[File:Newborn.jpg|90px|link=Birth]] Clinical Week 40
[[Cardiovascular System Development|Heart]] pressure difference closes foramen ovale leaving a fossa ovalis
{{thyroid}} TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels
{{adrenal}} - zona glomerulosa, zona fasiculata present




|}


== Postnatal ==
== Postnatal ==

Revision as of 12:03, 12 May 2018

Embryology - 20 Apr 2024    Facebook link Pinterest link Twitter link  Expand to Translate  
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Introduction

From a single cell to a newborn infant in 9 months.
Early zygote.jpg Newborn.jpg Human development timeline graph 01.jpg

This page is organised to show week by week human development features and approximate timing of key events with more detailed information about specific events in different systems. For a less detailed timeline see week by week.

Embryonic Development
  • "Weeks" refer to embryonic development from fertilization.
    • Clinical weeks (shown in brackets) or Gestational Age GA) is from the first day of the Last Menstrual Period (LMP).
  • "Stages" refer to the Carnegie stages of development.
  • "Timing" refers to days from fertilization or post conception age (PC), not the clinical or gestational age (GA) calculated from LMP (add 2 weeks).
  • Dates and staging are also "ideal", and there is significant biological variability in the general timing of events.
  • Week 1 to Week 8 (GA 10)are considered the embryonic period of development.
  • Week 9 to week 37 (GA 11-39) or birth are considered the fetal period of development.
  • First month (4 weeks) after birth is the neonatal period of development.


Each developmental feature is linked to online content with more detailed information and resources such as images and movies. The superscript numbers are the original source references. There are similar "timelines" for other species shown below.


Timeline Links: human timeline | mouse timeline | mouse detailed timeline | chicken timeline | rat timeline | zebrafish timeline | Medaka | comparative | Category:Timeline
Human Trimesters - Systems  
Period: first trimester timeline | second trimester timeline | third trimester timeline

Systems: bone timeline | eye neural crest timeline | heart abnormality timeline | hearing timeline | hearing EAM timeline | muscle timeline | ovary timeline | pelvis timeline | placental villi timeline | shoulder timeline | smell timeline | spleen timeline | ventricular timeline

Historic  
upper limb ossification timeline | lower limb ossification timeline | 1932 Guinea pig day 11-21 | 1933 Guinea pig day 21-35
Embryology History: 1600-1699 | 1700-1799 | 1800-1899 | 1900-1909 | 1910-1919 | 1920-1929 | 1930-1939 | 1940-1949 | 1950-1959 | 1960-1969 | 1970-1979 | 1980-1989 | 1990-1999 | Historic Papers | Embryologists

Human Systems

Alphabetical: bone timeline | eye neural crest timeline | heart abnormality timeline | hearing EAM timeline | muscle timeline | ovary timeline | placental villi timeline | shoulder timeline | smell timeline | spleen timeline | ventricular timeline


Second Trimester

(GA Clinical Week 14) Second Trimester


Third Trimester

Postnatal

Week
Stage
 Event
+1
Normal Newborn Neural Exam Movies  
Normal Newborn Neural Exam Movies

The newborn neuromuscular system can be initially assessed by 6 quick tests (posture, square window, arm recoil, popliteal angle, scarf sign and heel to ear). The following short videos show clinical examination of these assessments and a number of neonatal reflexes.

Later developmental assessment includes behaviour, reflexes (primitive and postural), muscular tone, and motor (gross, fine, co-ordination).

Normal Newborn Neural Exam Movies

Newborn Behaviour
Newborn-normal-behaviour.jpg
 ‎‎Behaviour
Page | Play
Newborn n 02.jpg
 ‎‎Cranial Nerves
Page | Play
Newborn Tone
Newborn n 03.jpg
 ‎‎Resting Posture
Page | Play
Newborn n 04.jpg
‎‎ Tone Upper Limb
Page | Play
Newborn n 05.jpg
‎‎ Arm Traction
Page | Play
Newborn n 06.jpg
 ‎‎Arm Recoil
Page | Play
Newborn n 07.jpg
 ‎‎Scarf Sign
Page | Play
Newborn n 08.jpg
 ‎‎Hand Position
Page | Play
Newborn n 09.jpg
 ‎‎Lower Limb
Page | Play
Newborn n 10.jpg
 ‎‎Leg Traction
Page | Play
Newborn n 11.jpg
 ‎‎Leg Recoil
Page | Play
Newborn n 12.jpg
 ‎‎Popliteal Angle
Page | Play
Newborn n 13.jpg
 ‎‎Heel to Ear
Page | Play
Newborn n 14.jpg
 ‎‎Neck Tone
Page | Play
Newborn n 15.jpg
 ‎‎Head Lag
Page | Play
Newborn n 16.jpg
 ‎‎Head Control
Page | Play
Newborn Positions
Newborn n 17.jpg
 ‎‎Prone Position
Page | Play
Newborn n 18.jpg
 ‎‎Ventral Suspend
Page | Play
Newborn n 19.jpg
 ‎‎Vertical Suspend
Page | Play
Newborn Reflexes
Newborn n 20.jpg
 ‎‎Tendon Reflexes
Page | Play
Newborn n 21.jpg
 ‎‎Plantar Reflex
Page | Play
Newborn n 22.jpg
 ‎‎Reflex Suck,Root
Page | Play
Newborn n 23.jpg
 ‎‎Moro Reflex
Page | Play
Newborn n 24.jpg
 ‎‎Galant Reflex
Page | Play
Newborn n 25.jpg
 ‎‎Stepping Reflex
Page | Play
Newborn n 26.jpg
 ‎‎Grasp Reflex
Page | Play
Newborn Head
Newborn n 27.jpg
‎‎ Head Shape
Page | Play
Newborn n 28.jpg
‎‎Head Circumference
Page | Play
Neural Exam Movies: normal behaviour | cranial nerves | Newborn Tone - resting posture | upper extremity‎ | arm traction | arm recoil | scarf sign | hand position | lower extremity | leg traction‎ | leg recoil‎‎ | popliteal angle‎ | heel to ear | neck tone | head lag‎ | head control | Newborn Positions - prone | ventral suspension | vertical suspension | Newborn Reflexes - deep tendon reflexes | plantar reflex‎ | suck, root | Moro | Galant | stepping‎ | grasp | Newborn Head - head shape and sutures‎ | head circumference‎ | Neonatal Diagnosis


+2
  
+3
  
+4
   vision - eye globe growth plateaus after 42 weeks of gestation[1]  
+5
    
Month
   testis | spermatozoa - about 2 months of age, primordial germ cells (gonocytes) are replaced by adult dark (Ad) and pale (Ap) spermatogonia forming the spermatogonial stem cell (SSC) population that at puberty will commence differentiation into spermatozoa.
Year
  
Year 1
   neural Hearing (6 months to 5 years) thalamocortical afferents to the deeper cortical layers mature and are the first source of input to the auditory cortex[2]


Normal 12 Month Neural Exam Movies  
Normal 12 Month Neural Exam Movies

The following short videos show clinical examination of neural development assessments and a number of reflexes.


12 Months Neural Exam Movies: Shy | Social and Language | Cranial Nerves | Tone - Tone | Reflexes - deep tendon reflexes | plantar reflex‎ | Parachute | Pincer Grasp | Beads in the Cup | Play Ball | Transition in and out of Sitting | Creeping | Stoop and Recover | Motor/Gait - Stand, Walks with Support | Toddler’s Gait | Head Circumference | Neural Exam Movies
Year 2
    
Year 3
   Adrenal - Year 3 zona reticularis present.


Normal 30 Month Neural Exam Movies  
Normal 30 Month Neural Exam Movies

The following short videos show clinical examination of neural development assessments and a number of reflexes.


Neural Exam Movies: Establishing Relationship | Follows Commands | Points to Pictures | Names Pictures | Response to Questions | Pointing to and Naming Body Parts | Motor/Coordination - Using Puppets | Using Measuring Tape | Block Tower | Drawing | Tone | Deep Tendon Reflex | Kicking and Throwing a Ball | Walking, Running
4
    
5
   neural hearing - (5 to 12 years) commissural and association axons in the superficial cortical layers allows communication between subdivisions of the auditory cortex[2]
7-13
   puberty - Female
9-15
 puberty - Male

References

  1. ↑ Paquette LB, Jackson HA, Tavaré CJ, Miller DA & Panigrahy A. (2009). In utero eye development documented by fetal MR imaging. AJNR Am J Neuroradiol , 30, 1787-91. PMID: 19541779 DOI.
  2. ↑ 2.0 2.1 Moore JK. (2002). Maturation of human auditory cortex: implications for speech perception. Ann Otol Rhinol Laryngol Suppl , 189, 7-10. PMID: 12018354


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Cite this page: Hill, M.A. (2024, April 20) Embryology Timeline human development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Timeline_human_development

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