Session 11 - Development Of the Midline Structures Flashcards
Where does the pituitary gland sit?
Pituitary fossa of sphenoid bone
What are the 2 parts of the pituitary gland?
Anterior and posterior
What is the precursor of the anterior lobe of the pit gland and its origin?
Precursor - Rathke’s pouch
Origin - ectoderm
What is the origin of posterior lobe of pit gland?
Origin - neuroectoderm
Which lobe is derived from the brain?
POsterior lobe
Describe how the pituitary gland is formed.
- Infundibulum extends down towards roof of oral cavity
- Outpushing from roof grows up to meet it (Rathke’s Pouch) and it oses its connection with roof of mouth
- Pouch comes to lie anterior to infundibulum
- Pouch differentiates to cells of ant pit.
- Hypophyseal portal system links hypothalamus to pituitary gland.
What might happen to any remnants of rathke’s pouch?
Could form cysts
What week does the tongue appear in?
4th
How many lateral and medial lingual swellings are there? What are they each derived from?
2 lateral - 1st PA
3 medial - 1st to 4th PA
Whats the name of the 3 medial lingual swellings and which PA is each derived from?
1st PA - Tuberculum impar
2nd and 3rd PA - cupola
4th PA - Epiglottal swelling
Describe the development of the tongue
- Lateral swelling overgrow tuberculum impar
- 3rd Arch part of cupola overgrows its second Arch component
- Degeneration occurs, freeing tongue from floor of oral cavity except lingual frenulum
What innervates the special sensation of tongue?
anterior 2/3rds - Chorda Tympani
posterior 1/3rd - Glossopharyngeal
What is the general innervation of the tongue?
Anterior 2/3rds - Lingual (comes from mand branch of trigeminal)
Posterior 1/3rd - Glossopharyngeal
What innervates the muscles of the tongue?
All muscles except palatoglosssus - Hypoglossus nerve
Palatoglosssus - Vagus nerve
Where does the thyroid gland first appear in development?
Between tuberculum Impar and cuploa of tongue at site called foramen cecum
Describe the descent of the thyroid gland
Thyroid bifurcates and descends as bi-lobed
During descent remains connected to tongue by thryoglossal duct
What are the 2 cell types in the thyroid gland and their secretions?
Follicular cells - T3 and T4
Parafolicular cells - Calcitonin
where can ectopic thyroid tissue be found?
anywhere along path of descent of thyroid gland
What is first arch syndrome? What is the usual result
failure of colonisation of 1st arch with neural crest cells
Usual result is hypoplasia of mandible and facial bones
What is DiGeorge Syndrome?
CATCH 22
Cardiac abnormalities
Abnormal facies
Thymic hypoplasia
Cleft palate
Hypocalcaemia
Chromosome 22 abnormalities
What is CHARGE syndrome? What is it caused by?
CHARGE
Coloboma (hole in iris
Heart defects
Atresia (blockage of posterior nasal cavity)
Retardation of growth and development
Genital hypoplasia
Ear defects
CHD7 mutation, essential for production of multipotent nerual crest cells
