Template talk:Week 4 Embryo Stages and Events table

From Embryology

Template:Week 1 Embryo Stages and Events table

Week 2 - Human Embryo Stages and Events (GA week 4) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
8
Stage 5 Stage5 bf11b.jpg Week2 001 icon.jpg Implantation
9
  Macaque Xi at interphase 02.jpg X inactivation
10
   
11
   
12
   
13
Stage 6 Chorion 001 icon.jpg Chorionic Cavity
14
   
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References


Week 3 - Human Embryo Stages and Events (GA week 5) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
15
16
Stage 7
Stage7.jpg
Gastrulation primitive node (Hensen's node, primitive knot) The small circular region located at the cranial end of the primitive streak, where gastrulation occurs, and is a controller of this process. The process establishes the 3 germ cell layers: Endoderm, Mesoderm and Ectoderm. The second role is to act as an initial generator of the left-right (L-R) body axis.
17
   
18
Stage 8
Stage8 human.jpg
Neural - neurogenesis, neural groove and folds are first seen
19
 
Stage8 SEM1.jpg
20
Stage 9
Stage9 bf1c.jpg
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 - mesencephalic neural crest is visible[1]

21
  Heart - cardiogenesis, week 3 begins as paired heart tubes.
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. <pubmed>17848161</pubmed>
Week 4 - Human Embryo Stages and Events (GA week 6) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
22
Stage 10 Stage10 dorsal1.jpg Stage10-dorsal2.jpg

neural crest - differentiation at spinal cord level from day 22 until day 26

neural - neural folds begin to fuse near the junction between brain and spinal cord, when neural crest - cells are arising mainly from the neural ectoderm

neural crest - trigeminal, facial, and postotic ganglia components visible[1]

neural crest - migration of vagal level neural crest cells begins (7-10 somite stage)

neural - Brain rostral neural tube forms 3 primary brain vesicles (week 4)

respiratory - Week 4 laryngotracheal groove forms on floor foregut.

23
  heart - begins to beat in Humans by day 22-23, first functioning embryonic organ formed.
24
Stage 11 Stage11 bf1c.jpg

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.

Optic ventricle appears

25
Stage 12 Stage12 bf1c.jpg

pituitary - Week 4 hypophysial pouch, Rathke's pouch, diverticulum from roof

liver septum transversum forming liver stroma and hepatic diverticulum forming hepatic trabeculae[2]

neural - caudal neuropore takes a day to close (closure is approximately at future somitic pair 31/sacral vertebra 2)

neural - secondary neurulation begins

neural crest - cardiac crest, neural crest from rhombomeres 6 and 7 that migrates to pharyngeal arch 3 and from there the truncus arteriosus[1]

neural crest - vagal neural crest enter the foregut (20-25 somite stage)

26
   
27
   
28
Stage 13 Stage13 bf1c.jpg 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.[3]

telencephalon cavity appears

liver epithelial cord proliferation enmeshing stromal capillaries[2]

smell Crest comes from the nasal placodes[4]

integumentary - 4 weeks simple ectoderm epithelium over mesenchyme

integumentary - 1 to 3 months ectoderm - germinative (basal) cell repeated division of generates stratified epithelium; mesoderm - differentiates into connective tissue and blood vessels

Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. 1.0 1.1 O'Rahilly R & Müller F. (2007). The development of the neural crest in the human. J. Anat. , 211, 335-51. PMID: 17848161 DOI.
  2. 2.0 2.1 Godlewski G, Gaubert-Cristol R, Rouy S & Prudhomme M. (1997). Liver development in the rat and in man during the embryonic period (Carnegie stages 11-23). Microsc. Res. Tech. , 39, 314-27. PMID: 9407542 <314::AID-JEMT2>3.0.CO;2-H DOI.
  3. Müller F & O'Rahilly R. (1988). The development of the human brain from a closed neural tube at stage 13. Anat. Embryol. , 177, 203-24. PMID: 3354839
  4. Müller F & O'Rahilly R. (2004). Olfactory structures in staged human embryos. Cells Tissues Organs (Print) , 178, 93-116. PMID: 15604533 DOI.
Week 5 - Human Embryo Stages and Events (GA week 7) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
29
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 - Week 5 to 17 lung histology - pseudoglandular

hearing - Week 5 cochlear part of otic vesicle elongates (humans 2.5 turns)

30
   
31
   
32
Stage 14
Stage14 bf1c.jpg
ectoderm - 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 - 1st, 2nd and 3rd pharyngeal arch, forebrain, site of lens placode, site of otic placode, stomodeum

Body - heart, liver, umbilical cord, mesonephric ridge visible externally as bulges.

Limb - upper and lower limb buds growing

neural - first appearance of the future cerebral hemispheres. Cerebellar plate differentiated to an intermediate layer, and future rhombic lip identifiable[1]

liver hepatic gland and its vascular channels enlarge, hematopoietic function appears[2]

33
Stage 15
Stage15 bf1.jpg

neural - cranial nerves (except olfactory and optic) are identifiable in more advanced embryos[3]

34
 
35
  vision - 35 to 37 days retinal pigment present
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. Müller F & O'Rahilly R. (1988). The first appearance of the future cerebral hemispheres in the human embryo at stage 14. Anat. Embryol. , 177, 495-511. PMID: 3377191
  2. Godlewski G, Gaubert-Cristol R, Rouy S & Prudhomme M. (1997). Liver development in the rat and in man during the embryonic period (Carnegie stages 11-23). Microsc. Res. Tech. , 39, 314-27. PMID: 9407542 <314::AID-JEMT2>3.0.CO;2-H DOI.
  3. Müller F & O'Rahilly R. (1988). The development of the human brain, including the longitudinal zoning in the diencephalon at stage 15. Anat. Embryol. , 179, 55-71. PMID: 3213956
Week 6 - Human Embryo Stages and Events (GA week 8) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
36
Pituitary - Week 6 connecting stalk between pouch and oral cavity degenerates

Parathyroid - Week 6 diverticulum elongate, hollow then solid, dorsal cell proliferation

Thymus - Week 6 diverticulum elongate, hollow then solid, ventral cell proliferation

Adrenal - Week 6 fetal cortex forms from mesothelium adjacent to dorsal mesentery, medulla neural crest cells from adjacent sympathetic ganglia

Respire - Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes

Tongue Week 6 - gustatory papilla, caudal midline near the foramen caecum (week 6 to 7 - nerve fibers approach the lingual epithelium)

37
Stage 16
Stage16 bf1c.jpg
Neural - first parasympathetic ganglia, submandibular and ciliary, are identifiable[1]

Limbs 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.

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 lip and palate components of the upper lip, medial nasal prominence and maxillary process present, median palatine process appears.

38
   
39
   
40
   
41
Stage 17
Stage17 bf1c.jpg

Neural - telencephalon areas of the future archicortex, paleocortex, and neocortex, visible. Beginning of future choroid plexus[2]

Sense - Smell olfactory nerve fibres enter the brain[3] Neural - primordium of the epidural space appears first on the ventral part of the vertebral canal and develops rostro-caudally[4]

Pancreas - rotation of the developing stomach moves ventral bud dorsally and fuses with the dorsal bud.

42
  Heart - separation of common cardiac outflow (aortic arch and pulmonary aorta)
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. <pubmed>2751117</pubmed>
  2. <pubmed>2802187</pubmed>
  3. <pubmed>15604533</pubmed>
  4. <pubmed>15478101</pubmed>
Week 7 - Human Embryo Stages and Events (GA week 9) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
43
{{Pancreas{{ Week 7 to 20 pancreatic hormones secretion increases, small amount maternal insulin

respiratory Week 7 - enlargement of liver stops descent of heart and lungs

44
Stage 18 Stage18 bf1c.jpg

limb bone form by endochondrial ossification and throughout embryo replacement of cartilage with bone (week 5-12).

smell vomeronasal fibres and nervus terminalis[1]

liver obturation due to epithelial proliferation, bile ducts became reorganized, continuity between liver cells and gut[2]

neural duramater appears[3]

45
   

liver (stage 18 to 23) biliary ductules developed in periportal connective tissue produces ductal plates that receive biliary capillaries[2]

46
   
47
   
48
Stage 19 Stage19 bf1c.jpg Neural System Development accessory olivary nucleus appears[4]
49
   
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. Müller F & O'Rahilly R. (2004). Olfactory structures in staged human embryos. Cells Tissues Organs (Print) , 178, 93-116. PMID: 15604533 DOI.
  2. 2.0 2.1 Godlewski G, Gaubert-Cristol R, Rouy S & Prudhomme M. (1997). Liver development in the rat and in man during the embryonic period (Carnegie stages 11-23). Microsc. Res. Tech. , 39, 314-27. PMID: 9407542 <314::AID-JEMT2>3.0.CO;2-H DOI.
  3. Patelska-Banaszewska M & Woźniak W. (2004). The development of the epidural space in human embryos. Folia Morphol. (Warsz) , 63, 273-9. PMID: 15478101
  4. Müller F & O'Rahilly R. (1990). The human brain at stages 18-20, including the choroid plexuses and the amygdaloid and septal nuclei. Anat. Embryol. , 182, 285-306. PMID: 2268071
Week 8 - Human Embryo Stages and Events (GA week 10) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
50
Stage 20 Stage20 bf1c.jpg

Head scalp vascular plexus visible

limb upper limbs begin to rotate ventrally

neural - amygdaloid body has at least four individual nuclei[1]

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

51
  Gastrointestinal Tract anal (cloacal) membrane perforates
52
Stage 21 Stage21 bf1c.jpg

neural - cortical plate appears in the area of future insula[2]

limb upper and lower limbs rotate

Intraembryonic Coelom pericardioperitoneal canals close

53
   
54
Stage 22 Stage22 bf1c.jpg

neural - neocortical fibres project to epithalamus, to dorsal thalamus, and to mesencephalon[2]

limb fingers and toes lengthen

Sense - Smell Stage 22 to early fetal period - migratory streams of neurons from the subventricular zone of the olfactory bulb towards the future claustrum[3]

55
Genital 8 Weeks Testis - mesenchyme, interstitial cells (of Leydig) secrete testosterone, androstenedione

Genital 8 to 12 Weeks - hCG stimulates testosterone production

Tongue Week 8 - nerves penetrate epitheilai basal lamina and synapse with undifferentiated, elongated, epithelial cells (taste bud progenitor cell)

56
Stage 23 Stage23 bf1c.jpg Stage 23 defines the end of the embryonic (organogenesis) period

mesoderm heart prominence, ossification continues

Head nose, eye, external acoustic meatus, eyelids, external ears, rounded head

Body - straightening of trunk, heart, liver, umbilical cord, intestines herniated at umbilicus

limb upper limbs longer and bent at elbow, hands and feet turned inward, foot with separated digits, wrist, hand with separated digits

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[4]

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)[5]

 
Week 8 stomach - Week 8 - Gastrin containing cells in stomach antrum. Somatostatin cells in both the antrum and the fundus.
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. Müller F & O'Rahilly R. (1990). The human brain at stages 18-20, including the choroid plexuses and the amygdaloid and septal nuclei. Anat. Embryol. , 182, 285-306. PMID: 2268071
  2. 2.0 2.1 Müller F & O'Rahilly R. (1990). The human brain at stages 21-23, with particular reference to the cerebral cortical plate and to the development of the cerebellum. Anat. Embryol. , 182, 375-400. PMID: 2252222
  3. Müller F & O'Rahilly R. (2004). Olfactory structures in staged human embryos. Cells Tissues Organs (Print) , 178, 93-116. PMID: 15604533 DOI.
  4. Müller F & O'Rahilly R. (1990). The human rhombencephalon at the end of the embryonic period proper. Am. J. Anat. , 189, 127-45. PMID: 2244584 DOI.
  5. O'Rahilly R, Muller F & Meyer DB. (1980). The human vertebral column at the end of the embryonic period proper. 1. The column as a whole. J. Anat. , 131, 565-75. PMID: 7216919