5.2.3 Development of the Head and Neck 3

Question 1

What pharyngeal arches contribute to the tongue?

Answer 1

1st and 2nd
Anterior 2/3 of tongue

3rd
Posterior 1/3 of tongue

Question 2

What separates the anterior 2/3 of the tongue from the posterior 1/3?

Answer 2

Sulcus terminalis

Question 3

What part of the tongue that is the area where the thyroid gland starts to develop?

Answer 3

Foramen caecum

Question 4

How do muscles of the tongue form?

Answer 4

Arise from occipital somites that move anteriorly to the tongue from the base of the skull

Arise from level of hypoglossal nerve

Question 5

How does the thyroid develop?

Answer 5

Week 4

Thyroid diverticulum grows down from the foramen caecum of the tongue and forms the thyroglossal duct

At the start of week 5 the thyroglossal duct continues to grow down to the anterior trachea

Late week 5 the thyroglossal duct begins to break down

By week 7 the thyroid gland has formed and the thyroglossal duct has completely broken down

Question 6

What happens if the thyroglossal duct does not break down?

Answer 6

Can result in cysts and fistulae opening at the foramen caecum

Question 7

What can be found along the path of descent of the thyroid?

Answer 7

Ectopic thyroid gland tissue

Question 8

How can you test for a thyroglossal duct cyst?

Answer 8

Ask the patient to stick out their tongue

Cysts are still connected to the tongue by fibours bands

Cysts will therefore elevate with the tongue