Week 8
Key Events of Human Development during the eighth week (week 8) following fertilization or Clinical week 10 (LMP).
| Event | ||
| Stage 20 | File:CST20.gif
Head scalp vascular plexus visible Limb upper limbs begin to rotate ventrally Neural amygdaloid body has at least four individual nuclei PMID: 2268071 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 | |
| Gastrointestinal Tract anal membrane perforates | ||
| Stage 21 | File:CST21.gif
Neural cortical plate appears in the area of future insula PMID: 2252222 Limb upper and lower limbs rotate Intraembryonic Coelom pericardioperitoneal canals close | |
| Stage 22 | File:CST22.gifNeural neocortical fibres project to epithalamus, to dorsal thalamus, and to mesencephalon PMID: 2252222
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 PMID: 15604533 | |
| 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) | ||
| Stage 23 | File:CST23.gif[1]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 PMID: 2244584 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 | |
| Week 8 | GIT - Stomach - Week 8 - Gastrin containing cells in stomach antrum. Somatostatin cells in both the antrum and the fundus. |
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Cite this page: Hill, M.A. (2024, April 16) Embryology Week 8. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Week_8
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
