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MIDS 227 (module 1 + 2) > Ch 2 Thyroid > Flashcards

Ch 2 Thyroid Flashcards

1
Q

What is the thyroid gland?

A

An endocrine gland (which releases hormones that go directly into the bloodstream)

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2
Q

What does the thyroid gland do?

A

-Synthesizes, stores + secretes thyroid hormones
-Functions to control the BMI (basal metabolic rate)

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3
Q

What shape is the thyroid?

A

Butterfly shaped (has 2 lobes + an isthmus)

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4
Q

Where is the thyroid located?

A

Lower neck

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5
Q

What is the echo texture of the thyroid?

A

-Very homogeneous (when normal)
-Medium-high level
-Has a fibrous capsule

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6
Q

What is the average size of the thyroid?

A

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

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7
Q

List the 4 main arteries supplying the thyroid?

A

-Paired superior thyroid arteries: arise off the ECA

-Paired inferior thyroid arteries: arise from the thyrocervical trunk of the subclavian artery

(sometimes the thyroid ima artery as well - it is an anomaly that only some pt’s have)

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8
Q

How many veins drain the thyroid plexus?

A

3: the superior, middle + inferior thyroid veins

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9
Q

The superior + middle thyroid vein come off of which vein?

A

The internal jugular vein (IJV)

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10
Q

The inferior thyroid veins come off of which vein?

A

The brachiocephalic vein (BCV)

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11
Q

What are the 3 thyroid hormones?

A

-T3 (triiodothyroine)
-T4 (thyroxine)
-Calcitonin (thyrocalcitonin)

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12
Q

Which thyroid hormones m/c affect the body’s metabolism?

A

T3 + T4

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13
Q

How is T3 + T4 made?

A

Follicular cells process iodine to secrete T3 + T4, this increases metabolism

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14
Q

Is there more T3 or T4 in the bloodstream?

A

-There is more T4
-The body converts T4 into T3
-T3 is more potent + is produced in lesser quantity

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15
Q

Calcitonin is secreted by what type of cells?

A

Parafollicular cells (c-cells), this lowers blood calcium levels

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16
Q

What are follicles?

A

-Many small sacs throughout the thyroid
-They are lined with follicular cells and contain colloid in the center

17
Q

How are thyroid hormones made?

A

-Iodine binds with thyroglobulin (a protein) within the colloid part of a follicle to form thyroid hormones
-The follicular cells reabsorb thyroglobulin + chemically processes T3 + T4

18
Q

Do thyroid hormones circulate freely or when bound to protein (TBG)?

A

Both!

19
Q

What are thyroid lab tests typically testing for?

A

-Both free + total T3, T4 + TSH
-Typically testing for conditions such as hyperthyroidism + hypothyroidism

20
Q

When would calcitonin be tested?

A

Specifically for cancers

21
Q

What does euthyroid mean?

A

Normal lab values

22
Q

What is thyrotropin-releasing hormone (TRH) released from?

A

The hypothalamus

23
Q

What is thyrotropin-stimulating hormone (TSH) released from?

A

The anterior pituitary gland

24
Q

What does TSH do?

A

Arranges thyroid hormone production

25
Q

TSH is regulated by what?

A

T3, T4 + TRH

26
Q

Explain the negative feedback loop of the thyroid in 5 steps?

A
  1. Decrease in thyroid hormone causes decreased BMR
  2. Decreased BMR stimulates release of TRH
  3. TRH induces the release of TSH
  4. Thyroid releases T3 + T4
  5. BMR returns to normal
27
Q

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

A

The thyroid

28
Q

When is the thyroid fully developed?

A

By the end of the 1st trimester

29
Q

Development of the thyroid begins at what level?

A

Level of the primitive pharynx

(corresponds to the base of the tongue in adults)

30
Q

As the thyroid develops, the cells migrate downwards in the neck through a canal called what?

A

The thyroglossal tract/duct

(this duct m/c disappears once the thyroid reaches its final position in the neck)

31
Q

What is athyrosis + what is it associated with?

A

-The most severe abnormality of the thyroid
-Associated with cretinism or congenital hypothyroidism

32
Q

What is a pyramidal lobe?

A

-The m/c variation of the thyroid
-Typically extends upward from the isthmus
-Can arise from either lobe

33
Q

What is the m/c ectopic location for the thyroid?

A

Lingual (very rare tho)

34
Q

List 3 other thyroid variations that exclude athyrosis, pyramidal lobe + ectopic locations?

A

-Absence of isthmus
-Absence of 1 lobe (results in compensatory hypertrophy)
-Continuity of 1 lobe to the other (no distinguishable isthmus)

35
Q

How common is thyroid pathology?

A

Very!!!

36
Q

How does the thyroid look when compared to the surrounding muscles?

A

Homogeneous + echogenic to muscles

37
Q

What are the 3 main hormones produced by the thyroid?

A

T3, T4 + calcitonin

38
Q

What is the m/c variation of the thyroid?

A

Pyramidal lobe

MIDS 227 (module 1 + 2) (14 decks)

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