19 Embryology 2 Flashcards
What is another name for the pituitary gland?
Hypophysis (cerebri)
Explain how the pituitary gland arises from neuroectoderm and ectoderm.
Neural tube component (neuroectoderm) grows down from forebrain- towards roof of pharynx
Evagiantion of roof of pharynx ( Rathke’s pouch) grows towards forebrain (dorsally)
Fill in the missing labels:
Sulcus terminalis= border between anterior 2/3 of tongue and posterior 1/3
Which of the pharyngeal arches are required to complete the formation of the tongue? What parts of the developing tongue are formed by:
Pharyngeal arch 1
Pharyngeal arch 2 and 3
Pharyngeal arch 4
All of them
What happens after this to form the tongue?
Extensive degeneration occurs- freeing tongue from floor of oral cavity- leaving lingual frenulum (causes difficulty speaking if too short)
What do both intrinsic and extrinsic muscles of the tongue develop from?
Where does the primordium of the thyroid gland first appear?
In floor of pharynx between tuberculum impar and cupola
Describe the descent of the thyroid primordium into its position in the neck?
Bifurcates
Descends as bi-lobed diverticulum connected by isthmus
Remains connected to tongue by thyroglossal duct
Migrates anterior to pharyngeal gut, hyoid bone and laryngeal arches
What is a pyramidal lobe (with relation to thyroid gland) ?
Anatomical variant- 50% of population
(remnant of thyroglossal duct)
First arch syndrome is thought to be caused by a failure of colonisation of the 1st arch with neural crest cells. Give an example of first arch syndrome and outline how it presents.
Treacher- Collins syndrome
defects in development of eyes, ears, mandible and palate
What is Di-George syndrome?
Congenital: thymic aplasia and absence of parathyroid glands
Deletion of chromosome 22
Disruption of 3rd and 4th pharyngeal pouches
What is CHARGE syndrome?
Mutations in the CHD7 gene- neural creast cells especially vulnerable to this mutation
