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Histology Pt. 2 > Unit 2 - Thyroid gland > Flashcards

Unit 2 - Thyroid gland Flashcards

1
Q

What is the structure of the thyroid gland?

A

it is made up of follicular cells and parafollicular cells

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2
Q

What is in the lumen of follicular cells?

A

colloid

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3
Q

What do parafollicular cells produce?

A

calcitonin

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4
Q

What hormones are secreted from follicular cells?

A

thyroxine (T4) and triopdpthyronine (T3)

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5
Q

What is T3 and T4 synthesized from?

A

tyrosine and iodide

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6
Q

What are T3 and T4 bound to in colloid?

A

thyroglobulin

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7
Q

What is the main function of T3 and T4?

A

increase the basal metabolic rate (energy production at rest)

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8
Q

What is goiter?

A

Iodine deficiency that leads to the reduction in thyroid hormone production slowing the rate of oxidation of all cells which causes an enlarged thyroid gland

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9
Q

What synthesizes thyroglobulin?

A

follicular cells

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10
Q

What synthesizes ‘trap’ I?

A

follicular cells

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11
Q

When I- is released into the lumen of the follicle, what happens?

A

it is converted into highly reactive I^0

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12
Q

What does I^0 do?

A

it iodinates tyrosine molecules within the thyroglobulin protein

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13
Q

If iodinated tyrosinases are adjacent to one another what happens?

A

they condense and form T3 and T4

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14
Q

When T3 and T4 are needed, what occurs within follicular cells to free them?

A

TG containing T3 and T4 is taken up by phagocytosis and inside of follicular cells it is attacked by proteases, which free T3 and T4.

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15
Q

How is the secretion of thyroid hormones regulated?

A

deviations from homeostasis are detected by the hypothalamus and stimulate its release

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16
Q

When deviation from homeostasis is sensed, what is released by the hypothalamus?

A

TRH

17
Q

What does TRH do?

A

it stimulates the release of TSH from the anterior pituitary

18
Q

What does TSH do?

A

it enters the circulation which then tells the thyroid gland to release T3 and T4

19
Q

How do thyroid hormones effect calorigenesis?

A

increase O2 consumption, increase BMR, increase heat dissipation, increase beta adrenergic receptors, increase vasodilation, increase cardiac output

20
Q

How do thyroid hormones effect carbohydrate metabolism?

A

they provide more glucose

21
Q

How do thyroid hormones effect lipid metabolism?

A

provide more fatty acids

22
Q

How do thyroid hormones effect protein synthesis?

A

stimulates pre-adolescent growth and development and inhibits hyperthyroidism

23
Q

How do thyroid hormones effect bone?

A

maintain growth and epiphyseal closure

24
Q

How do thyroid hormones effect muscle?

A

they maintain muscle protein synthesis

25
Q

How do thyroid hormones effect skin?

A

maintain protein synthesis and turn over, maintain hair coat, and sebaceous gland activity

26
Q

How do thyroid hormones effect brain development?

A

increase fetal brain development, synapse formation, and myelination

27
Q

In which species will you most likely encounter hyperthyroidism?

A

older cats

28
Q

What are the most common causes of hyperthyroidism?

A

Thyroid gland tumors

29
Q

What are common physical manifestations of hyperthyroidism?

A

poor hair coat, diarrhea, weight loss, heat intolerance, increased nail growth, goiter, vomiting, weak, and nervousness

30
Q

What is hyperthyroidism treated with?

A

Methimazole, surgery, or radioactive I

31
Q

What does Methimazole do?

A

inhibits T4 formation

32
Q

In which species will you most likely encounter hypothyroidism?

A

dogs

33
Q

Are there breeds which are predisposed for hypothyroidism?

A

yes, especially golden retrievers and doberman pinchers

34
Q

What is primary hypothyroidism caused by and what happens after administering TSH?

A

it is a thyroid lesion; no increase in T4 after administering TSH

35
Q

What is secondary hypothyroidism caused by and what happens after administering TRH?

A

pituitary lesion, no increase in TSH after administrating TRH

36
Q

What is tertiary hypothyroidism caused by and what happens after administering TRH?

A

hypothalamic lesion, increase in TSH after administering TRH

37
Q

What is the most common type of hypothyroidism?

A

primary

38
Q

What is cretenism?

A

congenital hypothyroidism

39
Q

how is hypothyroidism treated?

A

replacement therapy with synthetic thyroxine-levothyroxine

Histology Pt. 2 (52 decks)

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