Flashcards in 15) Development of Midline Structures Deck (23):
What are two tissue types of the pituitary lobes?
Endocrine and neuroendocrine
Describe the infundibulum and the parts of the pituitary it forms:
Downward out-growth of forebrain that grows towards roof of pharynx
Forms posterior pituitary and stalk
Describe Rathke's pouch and the part of the pituitary it forms:
Invagination of ectoderm in region of stomatodeum that grows dorsally and upwards towards forebrain
Forms anterior pituitary
What is the sulcus terminalis?
V-shaped boundary between anterior 2/3rds and posterior 1/3rd of tongue
Where is the foramen cecum found?
At the point of the V-shaped sulcus terminalis
What pharyngeal arch do the lateral lingual swellings form from?
What are the 3 median lingual swellings and the pharyngeal arches they form from?
Tuberculum impar (arch 1)
Cupola (arches 2, 3 (+4))
Epiglottal swelling (arch 4)
What changes occur to the median lingual swellings as the tongue develops?
Lateral lingual swellings over-grow tuberculum impar
3rd arch component of cupola over-grows 2nd arch component
How is the lingual frenulum formed?
Extensive degeneration occurs, freeing tongue from floor of oral cavity, frenulum remains
Describe how chorda tympani innervates the tongue:
Takes route through middle ear so passes into 1st arch and innervates taste buds
How do the muscle of the tongue gain innervation?
Occipital somites give rise to myogenic precursors that migrate into developing tongue, innervated by CN XII
Where does the primordium of the thyroid develop from?
Between tuberculum impar and cupola - foramen cecum
How does the thyroid get to its adult location?
Bifurcates and descends as bilobed diverticulum connect by isthmus
How is the thyroid connected to the tongue?
What clinical conditions stem from problems in thyroid descent?
Thyroglossal cyst or fistula
Ectopic thyroid tissue
Where do follicular cells develop from?
Where do parafollicular (C) cells develop from?
Ultimobranchial body of 4th pharyngeal pouch
What is first arch syndrome?
Spectrum of defects in development of eyes, ears, mandible and palate
Failure of colonisation of 1st arch with neural crest
What is Treacher-Collins syndrome?
Hypoplasia of mandible and facial bones
What is DiGeorge syndrome?
Congenital thymic aplasia and absence of parathyroid glands
What are the signs and symptoms of DiGeorge Syndrome?
Chromosome 22 microdeletion
What is CHARGE syndrome?
Heterozygous mutation to CHD7 (neural crest production)