Endocrine system - thyroid gland

Question 1

Where is the thyroid gland located? What is the morphology of the thyroid gland?

Answer 1

• Anterior and inferior to the larynx

- The thyroid gland is butterfly shaped and comprises two lobes connected by an isthmus

Question 2

What hormones do the thyroid glands produce?

Answer 2

• triiodothyronine (T3)
• tetraiodothyronine/thyroxine (T4)
• calcitonin

Question 3

In terms of embryology, where does the thyroid gland originate from?

Answer 3

• the endoderm of the foregut, near the base of the developing tongue.

Question 4

How does the thyroid gland appear histologically?

Answer 4

A histological section of the thyroid gland shows many thyroid follicles encapsulation a gelatinous fluid within each follicle, known as colloid.

Question 5

Amongst all the endocrine glands, the product of teh thryodice cells not stored inside the cell - instead, they are stored extracellularly. Where?

Answer 5

The products of the thyroid follicular cells (T3, T4, calcitonin) are stored inside the colloid.

Question 6

What is thyroglobulin and where is it stored?

Answer 6

Thyroglobulin is the precursor of the thyroid hormones and is stored in the colloid.

Question 7

The thyroid cells (thyrocytes) adopt either a squamous form or columnar form, and this is dependent on the activity of the thyroid gland. In what conditions will the cells be squamous or columnar ?

Answer 7

• squamous is squishy and lazy (hypoactive thyroid gland)

- columnar cells are more rigid (active thyroid gland)

Question 8

What are parafollicular cells / C cells? Where are they derived from? What do they do? How do parafollicular cells differ from thyroid follicular cells histologically?

Answer 8

Parafollicular cells / C cells belong to the thyroid gland. They are derived from the neural crest. They produce calcitonin (to reduce blood Ca2+]. The parafollicular C cells are larger and stain lighter than the thyroid follicular cells.