15) Development of Midline Structures

Question 1

What are two tissue types of the pituitary lobes?

Answer 1

Endocrine and neuroendocrine

Question 2

Describe the infundibulum and the parts of the pituitary it forms:

Answer 2

Downward out-growth of forebrain that grows towards roof of pharynx
Forms posterior pituitary and stalk

Question 3

Describe Rathke’s pouch and the part of the pituitary it forms:

Answer 3

Invagination of ectoderm in region of stomatodeum that grows dorsally and upwards towards forebrain
Forms anterior pituitary

Question 4

What is the sulcus terminalis?

Answer 4

V-shaped boundary between anterior 2/3rds and posterior 1/3rd of tongue

Question 5

Where is the foramen cecum found?

Answer 5

At the point of the V-shaped sulcus terminalis

Question 6

What pharyngeal arch do the lateral lingual swellings form from?

Answer 6

Arch 1

Question 7

What are the 3 median lingual swellings and the pharyngeal arches they form from?

Answer 7

Tuberculum impar (arch 1)
Cupola (arches 2, 3 (+4))
Epiglottal swelling (arch 4)

Question 8

What changes occur to the median lingual swellings as the tongue develops?

Answer 8

Lateral lingual swellings over-grow tuberculum impar

3rd arch component of cupola over-grows 2nd arch component

Question 9

How is the lingual frenulum formed?

Answer 9

Extensive degeneration occurs, freeing tongue from floor of oral cavity, frenulum remains

Question 10

Describe how chorda tympani innervates the tongue:

Answer 10

Takes route through middle ear so passes into 1st arch and innervates taste buds

Question 11

How do the muscle of the tongue gain innervation?

Answer 11

Occipital somites give rise to myogenic precursors that migrate into developing tongue, innervated by CN XII

Question 12

Where does the primordium of the thyroid develop from?

Answer 12

Between tuberculum impar and cupola - foramen cecum

Question 13

How does the thyroid get to its adult location?

Answer 13

Bifurcates and descends as bilobed diverticulum connect by isthmus

Question 14

How is the thyroid connected to the tongue?

Answer 14

Thyroglossal duct

Question 15

What clinical conditions stem from problems in thyroid descent?

Answer 15

Thyroglossal cyst or fistula

Ectopic thyroid tissue

Question 16

Where do follicular cells develop from?

Answer 16

Thyroid diverticulum

Question 17

Where do parafollicular (C) cells develop from?

Answer 17

Ultimobranchial body of 4th pharyngeal pouch

Question 18

What is first arch syndrome?

Answer 18

Spectrum of defects in development of eyes, ears, mandible and palate
Failure of colonisation of 1st arch with neural crest

Question 19

What is Treacher-Collins syndrome?

Answer 19

Hypoplasia of mandible and facial bones

Question 20

What is DiGeorge syndrome?

Answer 20

Congenital thymic aplasia and absence of parathyroid glands

Question 21

What are the signs and symptoms of DiGeorge Syndrome?

Answer 21

CATCH22:
Cardiac abnormalities
Abnormal facies
Thymic aplasia
Cleft palate
Hypocalcaemia
Chromosome 22 microdeletion

Question 22

What is CHARGE syndrome?

Answer 22

Heterozygous mutation to CHD7 (neural crest production)

Question 23

What are the signs and symptoms of CHARGE syndrome?

Answer 23

Coloboma
Heart defects
Choanal atresia
Growth and development retardation 
Genital hypoplasia
Ear defects