16. Development Of The Head And Neck 2

Question 1

What bone does the pituitary gland sit in?

Answer 1

Sphenoid bone.

Question 2

What is the function of the posterior pituitary and anterior pituitary?

Answer 2

Posterior - neuroendocrine.

Anterior - endocrine.

Question 3

What is the embryological origin of the anterior pituitary?

Answer 3

Rathke’s pouch - ectoderm.

Question 4

What is the embryological origin of the posterior pituitary and stalk?

Answer 4

Infundibulum - neurectoderm.

Question 5

How does the infundibulum develop?

Answer 5

Downward outgrowth of the forebrain towards the roof of the pharynx.

Question 6

How does rathke’s pouch develop?

Answer 6

Out-pouching of ectoderm of the stomatodeum, making an evagination of the roof of the oropharynx. Draws dorsally towards the developing forebrain.

Question 7

What structure ensures the tongue is highly mobile?

Answer 7

Lingual frenulum.

Question 8

What structure separates the tongue into an anterior oral portion and a posterior pharyngeal portion?

Answer 8

Sulcus terminalis.

Question 9

When does primordial of the tongue begin to appear in an embryo?

Answer 9

Appear at about the same time as the palate begins to form.

Question 10

What parts of the first 4 pharyngeal arches form the tongue?

Answer 10

2 lateral lingual swellings from Ph Arch 1.
3 median lingual swellings - tuberculum impar from Ph Arch 1, cupola from Ph Arch 2, 3 & 4, epiglottal swelling from Ph Arch 4.

Question 11

How does the tongue develop from the pharyngeal arches?

Answer 11

Lateral lingual swelling over-grow the tuberculin impar, and the 3rd arch component of the cupola over-grows the second arch component. Extensive degeneration occurs, freeing the tongue from the floor of the oral cavity, to form the lingual frenulum.

Question 12

From what pharyngeal arches is the mucosa of the anterior 2/3s of the tongue derived? What is the general sensory innervation of this part of the tongue?

Answer 12

Ph Arches 1 & 3.

CN V and IX.

Question 13

From what pharyngeal arches is the mucosa of the posterior 1/3 of the tongue derived? What is the general sensory and special sensory innervation of this part of the tongue?

Answer 13

Ph Arch 3 & 4.

CN IX and X.

Question 14

How do taste buds develop in the tongue and what is the special sensory innervation of them?

Answer 14

Taste buds develop in papillae.

CN VII.

Question 15

What is the general sensory innervation of each of the pharyngeal arches?

Answer 15

Ph Arch 1 - CN V.
Ph Arch 2 - CN VII.
Ph Arch 3 - CN IX.
Ph Arch 4 - CN X.

Question 16

What general sensory nerve innervates the chorda tympani, and where does this pass through?

Answer 16

Branch of CN VII which is a nerve of the Ph Arch 2, but this passes into the first arch, therefore it also passes through the middle ear.

Question 17

Where do the muscles of the tongue develop from, and therefore what is the motor innervation?

Answer 17

Both the intrinsic and extrinsic muscles of the tongue develop from the myogenic precursors that migrate into the developing tongue.
CN XII.

Question 18

The primordium of the thyroid gland appears in the floor of the pharynx, between the tuberculin impar and the cupola. How does the thyroid gland descent to be in front of the trachea?

Answer 18

The point of origin from the descent of the thyroid is later marked by the foramen cecum. The thyroid bifurcates and descends as a bi-lobed diverticulum connected by the isthmus.

Question 19

How does the thyroid gland remain connected to the tongue during its descent? What defect does this lead to in approximately 50% of the population?

Answer 19

By the thyroglossal duct.

Pyramidal lobe.

Question 20

What 2 thyroid abnormalities can occur during its decent?

Answer 20

Thyroglossal cysts (not midline) and fistulae. 
Ectopic thyroid tissue.