18.4 & 18.5 Thyroid & Parathyroid

Question 1

thyroid gland location

Answer 1

anterior surface of trachea, inferior to thyroid cartilage

Question 2

isthmus

Answer 2

slender connection between two lobes of thyroid gland

Question 3

thyroid follicles

Surround what?

Answer 3

hollow spheres lined by simple cuboidal epithelium.. surround follicle cavity.
-each follicle is surrounded by a network of capillaries

Question 4

follicle cavity

Answer 4

holds colloid, fluid containing dissolved proteins

Question 5

thyroglobulin

Secreted by?

Answer 5

globular protein secreted by follicle cells into the colloid

Question 6

thyroid gland requires _____ for hormone synthesis

Answer 6

iodide

Question 7

thyroid hormone synthesis

Answer 7

TSH-sensitive proteins transports iodide into cytoplasm. I- is converted to I+ by thyroid peroxidase at apical membrane surface. Iodide is attached to tyrosine portions of thyroglobulin. these are linked together to form hormones

Question 8

thyroid peroxidase

Answer 8

converts I- to I+, and attaches iodide to tyrosine portions of thyroglobulin at apical membrane surface

Question 9

thyroxine AKA, % of thyroid secretion?

Answer 9

tetraiodothyronine (T4)

-makes up 90% of all thyroid secretions

Question 10

Thyroid-binding globulins (TBG)

Answer 10

transport proteins in the bloodstream that ~70% T3 and T4 attach to.

Question 11

transthyretin

Answer 11

AKA thyroid-binding prealbumin (TBPA)… most of remaining T3 and T4 binds to this in circulation

Question 12

thyroid hormones bind to receptors…where?

Answer 12

in cytoplasm (storage), on mitochondrial surfaces (increase ATP production), and in nucleus (activates genes involved in energy utilization)

Question 13

calorigenic effect of thyroid hormones

Answer 13

cell consumes more energy and generates more heat due to an increased metabolic rate

Question 14

observed effects of thyroid hormones.. Which hormone is most responsible?

Answer 14

strong, immediate, and short-lived increase in rate of cellular metabolism
-T3 is primarily resposible

Question 15

minimum amount of iodine needed each day to maintain normal thyroid funtion

Answer 15

120-150 micrograms I-

Question 16

C cells

Aka?

Answer 16

(clear cells) aka parafollicular cells

-produce the hormone calcitonin

Question 17

CT stimulation, effects, and target cells

Answer 17

• stimulated by elevation of Ca2+ in blood
• CT inhibits osteoclasts, slowing the rate of Ca2+ release from bone, and stimulates Ca2+ secretion by kidneys
• stimulates bone growth & mineral deposition in children
• targets bone and kidneys

Question 18

Four parathyroid glands are embedded in the ____ surface of thyroid gland

Answer 18

posterior

Question 19

parathyroid (chief) cells produce..

Answer 19

parathyroid hormone PTH

Question 20

two cell populations in parathyroid glands

Answer 20

parathyroid (chief) cells and oxyphils

Question 21

PTH stimulation, effects, and target cells

Answer 21

• stimulated by low Ca2+ levels
• mobillizes calcium from bone, enhances reabsorption of Ca2+ by kidneys, stimulates secretion of calcitrol by the kidneys (also enhances reabsorption)
• targets bone and kidneys

Question 22

T3 & T4 stimulation, effects, and target cells

Answer 22

• stimulated by TSH
• increases energy utilization, oxygen consumption, growth, and development
• targets most cells