Anatomy and Physiology of the Thyroid (Unit 2A)

Question 1

What type of gland is the thyroid gland?

Answer 1

Endocrine gland

Question 2

What does the thyroid do?

Answer 2

Synthesizes, stores, and secretes thyroid hormones

Question 3

What does the thyroid gland function to control?

Answer 3

The basal metabolic rate

Question 4

What is the average size of the thyroid gland?

Answer 4

Length: 4-6cm
AP: 1.3-1.8 cm
Isthmus: 4-6cm

Question 5

Is the thyroid gland larger in males or females?

Answer 5

Males

Question 6

What are the 4 main arteries that supply blood to the thyroid?

Answer 6

Superior Thyroid Arteries (2 - paired) : arise from external carotid artery
Inferior Thyroid Arteries (2 - paired) : arise from right subclavian artery

Question 7

What artery can sometimes feed the thyroid?

Answer 7

Thyroid ima artery

Question 8

What are the 3 veins that drain the thyroid plexus?

Answer 8

Superior thyroid veins, middle thyroid veins, inferior thyroid veins

Question 9

Where do the superior and middle thyroid veins arise from?

Answer 9

The IJV

Question 10

Where do the inferior thyroid veins arise from?

Answer 10

Brachiocephalic Vein

Question 11

What are the 3 hormones that the thyroid secrete?

Answer 11

T3, T4 (thyroxine), Calcitonin (thyrocalcitonin)

Question 12

What secretes Calcitonin?

Answer 12

Parafollicular cells (c-cells)

Question 13

What does Calcitonin do?

Answer 13

Lowers blood calcium levels

Question 14

What do T3 and T4 cells do?

Answer 14

Process iodine to secrete T3 and T4

Question 15

What does the regulatory system involve? (3)

Answer 15

The hypothalamus, anterior pituitary, and thyroid gland

Question 16

What does Iodine bind with within a colloid to form thyroid hormones?

Answer 16

Thyroglobulin (protein)

Question 17

What do follicular cells reabsorb to process T3 and T4?

Answer 17

Thyroglobulin (protein)

Question 18

Follicular cells reabsorb thyroglobulin to process which thyroid hormones?

Answer 18

T3 and T4

Question 19

Where does TRH release from?

Answer 19

The hypothalamus

Question 20

Does TRH stand for?

Answer 20

Thyrotropin-releasing Hormone

Question 21

What does TSH stand for?

Answer 21

Thyroid Stimulating Hormone (aka Thyrotropin)

Question 22

What is regulated by T3, T4 and TRH?

Answer 22

TSH (Thyrotropin)

Question 23

Describe the Negative Feedback Loop for Thyroid hormones.

Answer 23

1. Decrease in thyroid hormone decreases the BMR
2. Decreasing BMR stimulates the release of TRH
3. TRH induces the release of TSH
4. Thyroid releases T3 and T4
5. BMR returns to normal

Question 24

What is the earliest endocrine gland to form in the human embryo?

Answer 24

Thyroid

Question 25

At what level does development begin for the thyroid?

Answer 25

Level of the primitive pharynx

Question 26

What is the thyroglossal tract (duct)?

Answer 26

A canal that usually disappears once the thyroid reaches its final position in the neck after the cells have migrated downwards in the neck

Question 27

By which trimester does the thyroid fully develop?

Answer 27

First trimester

Question 28

What is Athyrosis?

Answer 28

The most severe anomaly - associated with Cretinism or congenital hypothyroidism

Question 29

What is the most common variation of the thyroid?

Answer 29

Pyramidal lobe

Question 30

What is Pyramidal lobe?

Answer 30

An additional lobe that extends upwards from the isthmus. (can also arise from either lobe, left is more common than right)