Thyroid Hormone

Question 1

What is the shape of the thyroid gland and where is it located?

Answer 1

The thyroid gland is located in the front of the neck above the trachea.

Question 2

What is the first endocrine to develop?

Answer 2

Thyroid gland

Question 3

State the Embryological origin of the thyroid gland

Answer 3

It originates as proliferation of Endoderm all epithelial cells on the median surface of the developing pharyngeal floor.

Question 4

Which pharyngeal arch does the thyroid gland arise from?

Answer 4

1st pharyngeal arch

Question 5

Fill in the following blank spaces

The thyroid precursor develops from the _____, a diverticulum that appears in the floor of the _____.

Answer 5

Thyroglossal Duct

Pharynx

Question 6

Describe the descent of the thyroid gland embryologically

Answer 6

The thyroid gland grows and descents in the neck as an initially hollow structure which later solidifies and becomes bilobed connected by an isthmus.

Initial descent is anterior to the pharyngeal gut but still connected to the tongue by the thyroglossal duct which then obliterates. The thyroid gland then forms its mature shape with its location anterior to the trachea

Question 7

Give 2 examples of clinical pathologies related to thyroid gland embryology. Briefly explain each

Answer 7

1. Ectopic Thyroid Gland: Thyroid is not located in its usual position. It is associated with congenital hypothyroidism. It could occur either due to failure to descend (rests at base of tongue) or incomplete descent where it rests high in the neck below the hyoid bone
2. Thyroglossal Duct Cyst: If the thyroglossal duct does not degrade, the remnants manifest clinically as a cyst.

Question 8

What clinical pathology is associated with congenital hypothyroidism?

Answer 8

Ectopic Thyroid gland

Question 9

What associated glands or cells are located on the thyroid gland?

Answer 9

Parathyroid glands

Parafollicular or C cells

Question 10

How many parathyroid glands are located on a thyroid gland?

Answer 10

4 or 2 pairs

Question 11

What is the role of the parathyroid gland? What does it regulate?

Answer 11

Parathyroid glands synthesize and secrete parathyroid hormones. Parathyroid hormones increase blood calcium levels

Question 12

What are C cells? What do they secrete? And what does it regulate?

Answer 12

C cells are single cells in the epithelial lining of follicles (or between follicles). They secrete Calcitonin which lowers blood calcium levels

Question 13

The thyroid gland is divided into follicles by connective tissue. List the 2 constituents of a follicle along with their role.

Answer 13

Ok