Session 11 - Development Of the Midline Structures

Question 1

Where does the pituitary gland sit?

Answer 1

Pituitary fossa of sphenoid bone

Question 2

What are the 2 parts of the pituitary gland?

Answer 2

Anterior and posterior

Question 3

What is the precursor of the anterior lobe of the pit gland and its origin?

Answer 3

Precursor - Rathke’s pouch

Origin - ectoderm

Question 4

What is the origin of posterior lobe of pit gland?

Answer 4

Origin - neuroectoderm

Question 5

Which lobe is derived from the brain?

Answer 5

POsterior lobe

Question 6

Describe how the pituitary gland is formed.

Answer 6

1. Infundibulum extends down towards roof of oral cavity
2. Outpushing from roof grows up to meet it (Rathke’s Pouch) and it oses its connection with roof of mouth
3. Pouch comes to lie anterior to infundibulum
4. Pouch differentiates to cells of ant pit.
5. Hypophyseal portal system links hypothalamus to pituitary gland.

Question 7

What might happen to any remnants of rathke’s pouch?

Answer 7

Could form cysts

Question 8

What week does the tongue appear in?

Answer 8

4th

Question 9

How many lateral and medial lingual swellings are there? What are they each derived from?

Answer 9

2 lateral - 1st PA

3 medial - 1st to 4th PA

Question 10

Whats the name of the 3 medial lingual swellings and which PA is each derived from?

Answer 10

1st PA - Tuberculum impar

2nd and 3rd PA - cupola

4th PA - Epiglottal swelling

Question 11

Describe the development of the tongue

Answer 11

1. Lateral swelling overgrow tuberculum impar
2. 3rd Arch part of cupola overgrows its second Arch component
3. Degeneration occurs, freeing tongue from floor of oral cavity except lingual frenulum

Question 12

What innervates the special sensation of tongue?

Answer 12

anterior 2/3rds - Chorda Tympani

posterior 1/3rd - Glossopharyngeal

Question 13

What is the general innervation of the tongue?

Answer 13

Anterior 2/3rds - Lingual (comes from mand branch of trigeminal)

Posterior 1/3rd - Glossopharyngeal

Question 14

What innervates the muscles of the tongue?

Answer 14

All muscles except palatoglosssus - Hypoglossus nerve

Palatoglosssus - Vagus nerve

Question 15

Where does the thyroid gland first appear in development?

Answer 15

Between tuberculum Impar and cuploa of tongue at site called foramen cecum

Question 16

Describe the descent of the thyroid gland

Answer 16

Thyroid bifurcates and descends as bi-lobed

During descent remains connected to tongue by thryoglossal duct

Question 17

What are the 2 cell types in the thyroid gland and their secretions?

Answer 17

Follicular cells - T3 and T4

Parafolicular cells - Calcitonin

Question 18

where can ectopic thyroid tissue be found?

Answer 18

anywhere along path of descent of thyroid gland

Question 19

What is first arch syndrome? What is the usual result

Answer 19

failure of colonisation of 1st arch with neural crest cells

Usual result is hypoplasia of mandible and facial bones

Question 20

What is DiGeorge Syndrome?

Answer 20

CATCH 22

Cardiac abnormalities

Abnormal facies

Thymic hypoplasia

Cleft palate

Hypocalcaemia

Chromosome 22 abnormalities

Question 21

What is CHARGE syndrome? What is it caused by?

Answer 21

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