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2 ENDOCRINE > Thyroid Anatomy and Physiology > Flashcards

Thyroid Anatomy and Physiology Flashcards

1
Q

What structure joins to two lobes of the thyroid

A

isthmus

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2
Q

where are the parathyroid glands

A

the posterior 4 corners of the thyroid gland

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3
Q

what does the thyroid secrete

A

thyroid hormone

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4
Q

what does the parathyroid secrete

A

parathyroid hormone

controls calcium

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5
Q

what does the thyroid hormone do

A

allows you to convert what you eat into energy

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6
Q

where does the thyroid sit

A

between 5th cervical and 1st thoracic vertebrae

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7
Q

What nerve supplies the thyroid

A

parasympathetic from vagus nerve

sympathetic from superior, inferior and middle ganglia fo the sympathetic trunk

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8
Q

what nerve is at risk of being damaged near the thyroid

A

recurrent laryngeal nerve

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9
Q

what do the follicular cells of a thyroid follicle surround

A

colloid-tyrosine-containing thyroglobulin filled spheres

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10
Q

what do parafollicular C cells secrete

A

calcitonin

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11
Q

what do follicular cells synthesise

A

thyroid hormones

T3 and T4

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12
Q

what is needed to create thyroid hormone

A

iodine

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13
Q

what is the structure of the thyroid hormone

A

4 iodine molecules stuck to tyrosine residues on thyroglobulin

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14
Q

What is T3

A

coupling of MIT and DIT

monoiodotyrosine unit and di-iodntyrosine unit

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15
Q

what is T4

A

coupling of 2 DITS

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16
Q

what hormone is 90% of the hormone produced in the thyroid gland

A

T4 (4 iodines)

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17
Q

what hormone is 10% of the hormone produces in the thyroid

A

T3 (3 iodines)

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18
Q

how much more potent is T3 than T4

A

4 times more potent

19
Q

which thyroid hormone is more biologically active

A

T3

20
Q

why do T3 and T4 bind to plasma proteins in the blood

A

they are hydrophobic so cannot dissolve in the blood

21
Q

what proteins do the thyroid hormone bind to

A

Albumin (5%)
thyroxine binding globulin (70%)
thyroxine binding prealbumin (20%)

22
Q

what happens to T4 when it arrives at the cell

A

its changed to T3 by removal of an iodine

23
Q

what is unbound thyroid hormone in the blood

A

biologically active form

24
Q

what is measures in a blood test for thyroid hormone

A

just the free unbound hormone as thats the bit thats biologically active

25
Q

what puts you’re thyroxine binding globulin up

A

pregnancy
newborn state
OCP and other sources of oestrogen
others

26
Q

what does hyperthyroidism do

A 
affects every tissue in the body 
CNS- anxiety, sweating 
Heart- increased HR, palpitations 
GI- loose bowels, diarrhoea 
loose periods
27
Q

what does thyroid hormone affect

A 
metabolism 
growth 
development 
reproduction 
behaviour
28
Q

what affect to thyroid hormones have on metabolic rate and thermogenesis

A

increases them

29
Q

thyroid hormone affects of metabolism of carbs, lipids and proteins

A

increases all 3

30
Q

why is the thyroid important in children

A

growth hormone production and secretion
development of foetal and neonatal brain
normal central nervous system activity

31
Q

what affect does hypothyroidism have on the brain

A

slow intellectual functions

32
Q

what affect does hyperthyroidism have on brain

A

nervousness, hyperkinesis and emotional liability

33
Q

what do thyroid hormones increase responses to

A

adrenaline
sympathetic NS neurotransmitter
noradrenaline

by increasing number or receptors

cardiovascular responsiveness also increased

34
Q

what stimulates thyroid hormone release

A

thyrotrophin releasing hormone (TRH) from hypothalamus stimulates thyroid

this causes thyroid stimulating hormone (TSH) release from anterior pituitary

this stimulates release of T3 and T4

35
Q

how is thyroid hormone release controlled

A

negative feedback from T3 and T4 controls release of TRH and TSH

36
Q

what external factors affect thyroid hormone release

A

cold terperatures stimulate TRH release in babies and young children

stress inhibits TRH and TSH release

Circadian rhythms - thyroid hormones highest late at night

37
Q

what do de-Iodinase enzymes do

A

addition or removal of an iodine atom to change T4 to T3 or vis versa

38
Q

where is de-iodinase type 1 found

A

liver and kidney - reserves incase there isn’t enough in other cells

39
Q

where is de-iodinase type 2 found

A

in the heart and skeletal muscle, CNS, fat, thyroid and pituitary

40
Q

Where is type 3 de-iodinase found

A

in fatal tissue and placenta and brain

41
Q

what is hypothyroidism

A 
not enough thyroid hormone 
no negative feedback 
TRH and TSH increase
T3 and T4 decrease 
can be caused by lack of iodine in diet (can be associated with goitre, swollen neck?)
42
Q

symptoms of hypothyroidism

A

reduced basal metabolic rate
slow pulse rate
fatigue, lethargy, slow response times and mental sluggishness
cold intolerance
tendency to put on weight easily
in adults - myxoedema (puffy face, hands and feet)

in babies- cretinism (dwarfism and limited mental functioning due to deficiency of thyroid hormones present at birth)

43
Q

what is graves disease

A

autoimmune disease- thyroid stimulating immunoglobulin that acts like TSH but doesn’t have negative feedback by T3 and T4
can cause bulging eyes due to water retaining carb built up behind eyes
goitre -enlarged thyroid gland

44
Q

symptoms of hyperthyroidism

A 
increases basal metabolic rate 
fast pulse rate 
increased nervousness and excessively emotional 
insomnia 
sweating and heat intolerance 
tendency to loss weight easily

2 ENDOCRINE (32 decks)

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