The Thyroid Gland

Question 1

it has a follicular structure and is the only tissue of the body which is able to accumulate iodine in large quantities and incorporate it into hormones.

Answer 1

Thyroid gland

Question 2

Thyroid hormones have many functions in the body, in General;

Answer 2

✓ regulate growth
✓ differentiation
✓ metabolism of lipids, proteins and carbohydrates

Question 3

Thyroid hormones

Answer 3

✓ Triiodothyronine (T3)
✓ Tetraiodothyronine (T4)

Question 4

two thyroid lobes located on the lateral surfaces of the trachea;

Answer 4

✓ In pigs- midline of the ventral cervical region w/ dorso-lateral projections
✓ In dogs- cranial to the left lobe and almost touches the caudal aspect of the larynx

Question 5

major supply of blood

Answer 5

cranial thyroid artery

Question 6

principal venous drainage

Answer 6

caudal thyroid vein

Question 7

usually enter directly into the cervical lymphatic drunk or internal jugular vein

Answer 7

Efferent lymphatics

Question 8

has a rich supply of sympathetic nerves associated with blood vessels

Answer 8

thyroid

Question 9

affect the rate of synthesis of thyroid hormone

Answer 9

Thyrotropin or Thyroid-stimulating hormone (TSH)

Question 10

originates as a thickened plate of epithelium in the floor of the pharynx

Answer 10

Thyroid Gland

Question 11

Thyroid gland originates as a thickened plate of epithelium in the floor of the pharynx and in the adult animal consists of;

Answer 11

✓ follicular cells
✓ parafollicular cells or C-cells
✓ colloid
✓ interstitial connective tissue

Question 12

is common in the dog and may be located anywhere from the larynx to the diaphragm

Answer 12

Accessory Thyroid tissue

Question 13

is completely lacking in C-cells (parafollicular), which secrete calcitonin

Answer 13

accessory thyroid tissue

Question 14

in the dog, it is usually are not successful because the accessory thyroids readily respond to an increase in endogenous TSH secretion and undergoes sufficient hypertrophy and hyperplasia of follicular cells to sustain adequate thyroid hormone production

Answer 14

Induced Hypothyroidism

Question 15

thyroid gland contains follicles ranging from ____________um size and are filled with a __________ produced by the cells lining the follicle.

Answer 15

20-150
filled with COLLOID

Question 16

is stimulated by TSH and that microfilament integrity and phosphorylation of tyrosine are essential to thyroid cell response

Answer 16

Folliculogenesis

Question 17

the majority of the epithelial cells and the most important functional cells of the thyroid

Answer 17

follicular cells

Question 18

the histologic appearance of the thyroid is dramatically influenced by the level of circulating TSH from the?

Answer 18

Adenohypophysis

Question 19

binds to receptors of thyroid follicular cells

Answer 19

Thyrotropin

Question 20

what enzymes thyrotropin activates?

Answer 20

Adenylate cyclase

Question 21

caused by iodine deficiency in the diet

Answer 21

Diffuse thyroid hyperplasia (goiter)

Question 22

Example of goitrogenic substances include;

Answer 22

1. Thiouracil
2. Sulfonamides
3. Complex anions
4. plants from the family Brassicacceae

Question 23

is a peptide hormone of the mammalian thyroid that has been shown to be secreted by C-cells

Answer 23

Calcitonin (CT)

Question 24

are distinct from the follicular cells that secrete thyroid hormones (T3 and T4)

Answer 24

C-cells

Question 25

the assembly of thyroid hormones within the follicular lumen is made possible by a unique protein called?

Answer 25

thyroglobulin

Question 26

it synthesized by follicular cells

Answer 26

thyroglobulin

Question 27

is a high molecular weight glycoprotein synthesized in successive subunits on the ribosomes of the endoplasmic reticulum of follicular cells

Answer 27

Thyroglobulin

Question 28

an essential component of thyroid hormones, is incorporated within the molecular structure of thyroglobulin

Answer 28

Amino acid TYROSINE

Question 29

iodine if bound to ____________ residues in thyroglobulin at the apical surface of follicular cells to form successively ______________ and ___________.

Answer 29

Tyrosyl

Monoiodotyrosine
Diiodotyrosine

Question 30

the resulting MIT and DIT combine to form the biologically active iodothyronines;

Answer 30

✓ Thyroxine- T4
✓ Triiodothyronine- T3