2010 BGD Practical 6 - Week 6
Key Events of Human Development during the sixth week (week 6) following fertilization or Clinical week 8 (LMP).
BGD Cycle A 2010 Audio - Dr Mark Hill Monday 17th May 2010 3-5pm G2G4.
--Mark Hill 08:30, 18 May 2010 (EST) Note this page has been updated to add thyroid and gonad information.
These organs mainly develop in the embryonic period and function in the fetal period. (Covered in next practical)
- Thyroid - develops from thyroid median endodermal thickening in the floor of pharynx outpouch – thyroid diverticulum (day 24), functions from week 10
- Pituitary - develops from surface (anterior) and neural tube (posterior) ectoderm, connecting stalk between pouch and oral cavity degenerates
- Parathyroid - develop from endoderm of pharyngeal pouches, diverticulum elongate, hollow then solid, dorsal cell proliferation
- Thymus - develops from 2 origins for lymphoid thymocytes and thymic epithelial cells, diverticulum elongate, hollow then solid, ventral cell proliferation
- Adrenal - develops from 2 origins adrenal medulla (neural crest) and fetal cortex (surrounding mesenchyme), fetal cortex forms from mesothelium adjacent to dorsal mesentery, medulla neural crest cells from adjacent sympathetic ganglia
- Gonad - develops from 2 origins, germ cells migrate into the genital ridge (mesothelium and underlying mesenchyme)
- Humans (week 5-6), germ cells do not determine sex, it is the support cells
- germ cells migrate into gonadal ridge
- Gonads (male - testis, female - ovary) identical at this stage, termed "indifferent"
|Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.|
Detailed Week by Week
The following information is a detailed timeline of embryonic development between week 3 to 8 and content does not form part of the current practical class.
Embryo Stages and Events
|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)
|Stage 16|| Neural first parasympathetic ganglia, submandibular and ciliary, are identifiable PMID: 2751117
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.
|Heart separation of common cardiac outflow (aortic arch and pulmonary aorta)|
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Cite this page: Hill, M.A. (2019, November 21) Embryology 2010 BGD Practical 6 - Week 6. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2010_BGD_Practical_6_-_Week_6
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G