Embryology Flashcards
Anterior Pituitary Development
4 wks - oral ectoderm from upper mouth evaginates (Rathke’s pouch) –> contacts w/neural ectoderm & pinches off.
Posterior Pituitary Development
4 wks - evagination of lower neural ectoderm of primitive diencephalon –> beginning post. pituitary & central infundibular stalk
Pituitary 3 month Dev
More normal shape. Connective tissue around pituitary = sella turcica (pocket part of sphenoid bone)
Pituitary Vasculature Dev
Mesoderm infiltrates –> hypophyseal portal system & small vessels of post.
Pituitary Dev Overview
Thyroid Dev
Evagination of endoderm b/w 1st & 2nd pharyngeal pouches –> thryoid diverticulum –> enlarages & descends along pharynx (initially attached to thryoglossal duct) to in front of trachea. Contacts primordia of parathyroids & ultimobranchial body which embed themselves.
Inferior Parathyroids Dev
From clefts b/w 3rd & 4th pouches
Superior Parathyroid Dev
From cleft just after 4th pouch
Ultimobranchial Body
Develops just after the 4th pouch. Populated by cells from neural crest –> calcitonin-secreting parafollicular cells
Thyroid Vascularization
infiltrated with mesoderm –> vessels. Intersperses endoderm to cords of cells to small clumps that vesiculate into epithelia of follicles.
Adrenal Cortex Dev
From mesothelium (coelomic epithelium) in cleft b/w gut & urogenital ridge. At 4 wks mesonephric duct induces the cleft to prolif & migrate into dorsal mesenchyme –> cup shaped = reticularis
2-3months another wave of cells surround cup = new layer = fasciculata & glomerulosa
Adrenal Medulla Dev
Neural crest (ectoderm) migrate to become sympathetic ganglia (sympathogonia) & then some to center of cup = medulla (chromaffin cells) progenitors of Epi & NE cells
