Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HMS302 Endocrine System > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

The thyroid is a _________-shaped gland

A

butterfly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The thyroid gland is located where? Composed of?

A

Located just inferior to the larynx (voice box) and composes of right & left lateral lobes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

It is connected by an _________ (narrow passage) ________ to the _________.

A

Isthmus, anterior, trachea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where does it embryologically originate from?

A

It originates from the base of the tongue & descends to the middle of the neck.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

It has a rich blood supply from?

A

Superior & inferior thyroid arteries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Approx. 50% of thyroid glands have a small…

A

Third lobe - pyramidal lobe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Normal mass of the thyroid gland

A

Approx. 10 - 20g

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Extends from the isthmus _____ to the _________ cartilage & laterally to the ______ ________ arteries.

A

superiorly, mid-thyroid, common carotid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The thyroid lobes can be ______ or ______.

A

flat, globular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Discuss the thyroid isthmus

A
  • usually a narrow band of thyroid tissue
  • connects the 2 lobes of the thyroid
  • overlies the 2nd & 3rd tracheal rings
  • can be wide, long, or even absent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The thyroid is one of the most ______ organs in the body.

A

vascular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Medial border of the thyroid

A

Trachea & esophagus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Lateral border of the thyroid

A

Carotid sheath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Anterior & Lateral border of the thyroid

A

Sternocleidomastoid muscle & the 3 strap muscles
- sternohyoid
- sternothyroid
- superior belly of the omohyoid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

3 strap muscles

A
  • sternohyoid
  • sternothyroid
  • superior belly of the omohyoid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the Tubercle of Zuckerkandl

A

A posterior extrusion of the lateral thyroid lobes & is a pointer to the recurrent laryngeal nerve and inferior parathyroid glands.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What can help the surgeon find & identify the recurrent laryngeal nerve (RLN)?

A

The tubercle of zuckerkandl because the RLN usually traverses (across) the posterior aspect of the tubercle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the thyroid hormones & how many are there?

A

2 Thyroid hormones:
- Thyroxine aka tetraiodothyronine (T4)
- Triiodothyronine (T3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What cells produce the thyroid hormones? (T3 & T4)?

A

Follicular cells

20
Q

Why are the thyroid hormones called thyroxine & triiodothyronine?

A

This is due to the number of iodine atoms it contains.

21
Q

What cells produce calcitonin (hormone)?

A

Parafollicular or C cells
- lies between the follicles

22
Q

Thyroid gland is the only endocrine gland that?

A

Stores its secretory products in large quantities, which is normally about a 100 day supply.

23
Q

Steps in the synthesis & secretion of the thyroid hormones (T3 & T4)

A
  1. Iodide trapping
  2. Synthesis of thyroglobulin
  3. Oxidation of iodide
  4. Iodination of tyrosine
  5. Coupling of T1 & T2
  6. Pinocytosis & digestion of colloid
  7. Secretion of thyroid hormones
  8. Transport in the blood
24
Q

Synthesis & secretion of T3 & T4
1. Iodide trapping

A
  • Thyroid follicular cells trap iodide ions by actively transporting them from the blood into the cytosol.
  • As a result, the thyroid gland normally contains the most of the iodide in the body.
25
Q

Synthesis & secretion of T3 & T4
2. Synthesis of thyroglobulin

A
  • While the follicular cells are trapping iodide ions, they are also synthesizing thyroglobulin (TGB), a large glycoprotein that is produced in the rough ER, modified in the Golgi complex, & packaged into secretory vesicles.
  • Vesicles then undergo exocytosis, which releases TGB into the lumen of the follicle.
26
Q

Synthesis & secretion of T3 & T4
3. Oxidation of iodide

A
  • Some of the amino acids in TBG are tyrosines that will become iodinated.
  • Negatively charged iodide ions can’t bind to tyrosine until they undergo oxidation (removal of electrons) to iodine.
  • As the iodide ions are being oxidized, they pass through the membrane into the lumen of the follicle.
27
Q

Synthesis & secretion of T3 & T4
4. Iodination of tyrosine

A
  • As iodine molecules, they react with tyrosines that are part of TGB molecules.
  • Binding of 1 iodine atom yields monoiodotyrosine (T1) & a second iodination produces diiodotyrosine (T2).
  • Colloid - the TGB with attached iodine atoms, a sticky material that accumulates & is stored in the lumen of the thyroid follicle.
28
Q

Synthesis & secretion of T3 & T4
5. Coupling of T1 & T2

A

During the last step in the synthesis of thyroid hormone,
2 T2 molecules join to form T4
1 T1 & 1 T2 molecules join to form T3

29
Q

Synthesis & secretion of T3 & T4
6. Pinocytosis & digestion of colloid

A
  • Droplets of colloid reenter follicular cells by pinocytosis & merge with lysosomes.
  • Digestive enzymes in the lysosomes break down TGB, cleaving off molecules of T3 & T4.
30
Q

Synthesis & secretion of T3 & T4
7. Secretion of thyroid hormones

A
  • Because T3 & T4 are lipid-soluble, they diffuse through the plasma membrane into interstitial fluid & then into the blood.
  • T4 normally is secreted in greater quantity than T3, but T3 is several times more potent.
  • After T4 enters a body cell, most of it is converted to T3 by removal of one iodine.
31
Q

Synthesis & secretion of T3 & T4
8. Transport in the blood

A

More than 99% of both the T3 and the T4
combine with transport proteins in the blood, mainly thyroxine-binding globulin (TBG).

32
Q

Storage form of thyroid hormones

A

Thyroglobulin (TGB)

33
Q

Actions of thyroid hormones (T3 & T4)

A
  • Increase basal metabolic rate (BMR)
  • Maintenance of normal body temperature
  • Regulation of metabolism
  • Enhance actions of catecholamines
  • Accelerates body growth
34
Q

Actions of thyroid hormones (T3 & T4)
- Increase basal metabolic rate (BMR)

A
  • BMR = rate of energy expenditure under standard or basal conditions (awake, at rest, & fasting).
  • Increases rate of O2 consumption under standard or basal conditions by stimulating the use of cellular O2 to produce ATP.
35
Q

When basal metabolic rate (BMR) increases, what else increases?

A

The cellular metabolism of carbohydrates, lipids, & proteins increases.

36
Q

Actions of thyroid hormones (T3 & T4)
- Maintenance of normal body temperature

A
  • As cells produced & use more ATP, BMR increases, more heat is given off, & body temp rises = a calorigenic effect.
37
Q

Actions of thyroid hormones (T3 & T4)
- Enhance some actions of catecholamines (epinephrine/norepinephrine)

A
  • they have permissive effects on the catecholamines bc they up-regulate beta-adrenergic receptors.
  • catecholamines bind to beta-adrenergic receptors to promote sympathetic responses.
  • symptoms of excess levels of thyroid hormones = increased HR, increased BP.
38
Q

Actions of thyroid hormones (T3 & T4)
- Regulation of metabolism

A
  • stimulates protein synthesis & increases the use of glucose & fatty acids for ATP production.
  • increases lipolysis & enhances cholesterol excretion, thus decreasing cholesterol level.
39
Q

Actions of thyroid hormones (T3 & T4)
- Accelerates body growth

A
  • Nervous system = promotes synapse formation, myelin production & growth of dendrites.
  • Skeletal system = promotes formation of ossification centers in developing bones, synthesis of many bone proteins, & secretion of GH & insulin-like growth factors (IGF).
40
Q

_______ from the hypothalamus & ________ from the ________ pituitary stimulates the synthesis & release of thyroid hormones (T3 & T4).

A

TRH, TSH, anterior

41
Q

Steps in the control of thyroid hormones secretion

A
  1. Low blood levels of T3 & T4 OR lo metabolic rate stimulates the hypothalamus to secrete TRH.
  2. TRH enters the hypophyseal portal veins & flows to the anterior pituitary gland = which stimulates thyrotrophs to secrete TSH.
  3. TSH stimulates all aspects of thyroid follicular cell activity.
  4. The thyroid follicular cells release T3 and T4 into the blood until the metabolic rate returns to normal.
  5. An elevated level of T3 inhibits release of TRH
    and TSH (negative feedback inhibition).
42
Q

What conditions increase ATP, therefore increasing the secretion of thyroid hormones?

A
  • cold environment
  • hypoglycemia
  • high altitude
  • pregnancy
43
Q

What hormone is produced by the parafollicular cells of the thyroid gland?

A

Calcitonin (CT)

44
Q

Function of thyroid peroxidase

A
  • catalyzes iodide oxidation to form iodine atoms which are added onto tyrosine residues on thyroglobulin for the production of thyroxine or triiodothyronine.
45
Q

Function of Calcitonin (CT)

A

Decreases the level of Ca2+ in the blood by inhibiting the action of osteoclasts (breaks down bone extracellular matrix)

46
Q

Secretion of Calcitonin (CT) is controlled by a?

A

negative feedback system

47
Q

When Ca2+ levels are high in the blood, what does Calcitonin (CT) do?

A
  • decreases the amount of blood Ca2+ & phosphates by inhibiting bone resorption (breakdown of bone extracellular matrix) by osteoclasts.
  • by accelerating uptake of Ca2+ & phosphates into bone extracellular matrix.

HMS302 Endocrine System (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions