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Endo > Endocrine glands in detail 2 > Flashcards

Endocrine glands in detail 2 Flashcards

1
Q

What is produced by the zona glomerulosa of the adrenal cortex?

A

Mineralocorticoids e.g. aldosterone

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2
Q

What is produced by the zona fasciculata of the adrenal cortex?

A

Glucocorticoids e.g. cortisol (and some androgens)

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3
Q

What is produced by the zona reticularis of the adrenal cortex

A

Androgens e.g. testosterone (and some glucocorticoids)

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4
Q

In what proportions are the regions of the adrenal cortex?

A
  • Most: fasciculata (60%)
  • Middle: glomerulosa (25%)
  • Least: reticularis (15%)
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5
Q

Describe the blood supply to the adrenal gland

A
  • High blod volume for size
  • Superior, middle and inferior suprarenal artereis
  • Branch before entering adrenal capsule
  • Within capsule, branch to give 3 patterns of blood distribution: capsular capillaries, cortical fenestrated capillaries and medullar arterioles
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6
Q

Describe the cortical fenestrated capillaries of the adrenal cortex

A
  • Supply cortex

- Drain into medullar fenestrated capillaries

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7
Q

Describe the medullary arterioles of the adrenal cortex

A
  • Direct to medulla

- No supply to cortex or branching prior to medulla

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8
Q

What are corticosteroids?

A

Gluco and mineralocorticoids (but ofen used as synonym for glucocorticoid)

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9
Q

Describe glucocorticoids

A
  • e.g. cortisol
  • Steroid hormones that bind to glucocorticoid receptor
  • Role in regulation of metabolism of glucose
  • Synthesis in adrenal cortex and steroidal role
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10
Q

Describe mineralocorticoids

A
  • e.g. aldosterone

- Class of steroid hormone characterised by effects on salt and water balance

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11
Q

Describe the control of glucocorticoid release

A
  • PVN of hypo. synthesises and release CRH
  • Control partly diurnal and in response to stress
  • CRH down axons to median eminence, terminate in portal capillary bed
  • CRH released, into pituitary portal blood system to pars distalis
  • Stimulates ACTH production and secretion (POMC)
  • ACTH then through systemic circulation to adrenal glands where stimulates adrenal cortex to make glucocorticoid steroid hormones esp cortisol
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12
Q

Outline mineralocorticoid release

A
  • Low blood pressure main stimulus via RAAS

- High serum potassium also stimulates release

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13
Q

Describe steroid hormone synthesis

A
  • Begin with cholesterol
  • Converted to pregnenlone by P-450-side-chain cleavage enzyme
  • P450 activated by ACTH
  • Pregnenloone converted to different corticoids according to zone, due to presence of different enzymes in each zone
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14
Q

What enzyme is required to convert pregnenolone to glucocorticoid, androgen and oestrogen substrates?

A

17-alpha-hydroxylase

- Lacking in zona glomerulosa

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15
Q

What hormone is required to convert corticosterone to aldosterone?

A

Aldosterone synthase

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16
Q

What is zonation of the adrenal cortex dependent on in dogs and why?

A
  • 17-alpha-hydroxylase

- Only have one type of 11-hydroxylase

17
Q

Describe the intracellular mechanisms of cortisol

A
  • Binds to intraccellular receptor
  • Cytoplasmic activation produces active GR monomer and another molecule
  • Dimerisation of active GR monomer
  • Binds to glucocorticoid response elements (GRE) on gene to alter gene expression
18
Q

What are the effects of glucocorticoids on metabolism?

A
  • Stimulate gluconeogenesis and glycogenolysis
  • Stimulate proteolysis and lipolysis
  • Inhibit insulin
19
Q

Describe cortisol in the early fasting state

A
  • Cortisol stimulates gluconeogenesis (formation of glucose)
  • Activates anti-stress and anti-inflammatory pathways
  • Indirect role in liver and muscle glycogenolysis
  • Via passive influence on glucagon
20
Q

Desribe cortisol in the late fasting state

A
  • Increases glycogenesis
  • Allows liver to take up glucose not being used by peripheral tissues and turn into liver glycogen fo use if move into starvation state
  • Prolonged elevated cortisol can lead to proteolysis and muscle wasting
21
Q

Describe the effect of cortisol on fat

A
  • Mobilisation from peripheral stores

- manifests as redistribution of body fat causing altered body shape

22
Q

Describe the effect of cortisol on muscle

A
  • Catabolism
  • Muscle weakness, poor exercise tolerance
  • Panting
  • Pot belly
23
Q

Describe the effect of cortisol on the liver

A
  • Gluconeogenesis

- Antagonise insulin

24
Q

Describe the effect of cortisol on the kidney

A
  • Increase GFR

- Block ADH action (increased excretion of water)

25
Q

Describe the effect of cortisol on the ski

A
  • Follicular atrophy
  • Sebaceous gland atrophy
  • Pyoderma
  • Calcinosis cutis
  • Collagen
26
Q

Describe the effect of cortisol on bone

A
  • Reduce calcium levels

- Osteopaenia

27
Q

Describe the effect of cortisol on the brain

A

Stimulates hunger and thirst

28
Q

Describe the effect of cortisol on the immune system

A
  • Release of neutrophils from marginated pool

- Downregulates immune responses (T cell function and recruitment, B cell activation)

29
Q

Desribe the actions of aldosterone

A
  • Central role in BP regulation
  • Acts on cells in distal tubule and collecting duct to increase reabsorption of NA, Cl and hence water
  • Stimulates K+ secretion into tubular lumen
  • Stimulates secretion of H+ in exchange for K+ in collecting tubules
  • Overal increased water retention and increased blood volume and pressure
30
Q

Describe androgens

A
  • Steroid hormones
  • Stimulate or control development and maintenance of male characteristics by binding to androgen receptors
  • Are precursors for all oestrogens
31
Q

Name the most improtant androgens

A
  • Testosterone
  • Dihydrotestosterone (DHT)
  • Dehydroepiandrosterone (DHEA)
32
Q

What are the anabolic effects of androgens?

A
  • Protein syntehsis from AAs
  • Increase muscle fibre size
  • increase bone growth and remodelling
  • Stimulate bone marrow
33
Q

Give examples of glucocorticoid diseases

A
  • Hyperadrenocorticisim (akak Cushing’s in small animas)

- Primary and secondary hypoadrenocorticism

34
Q

What is primary hypoadrenocorticism?

A

Undresecretion of the glucocorticoids and mineralocorticoids due to pathology of the adrenal glands themselves
- Aka Addison’s disease

35
Q

What is secondary hypoadrenocorticism?

A
  • Just under-secretion of glucocorticoids

- Due to pathology of the pituitary preventing ACTH release

Endo (30 decks)

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