Adrenal cortex
Friday, 19 November 2021 10:21 AM
Anatomy of adrenal gland
- Superior poles of two kidneys
- Adrenal medulla
○ Neuroectodermal origin
○ Chromaffin cells
○ Functions related to the sympathetic NS
○ Innervated by cholinergic preganglionic sympathetic neurons
§ ACH released binds to nicotinic receptors on
chromaffin cells
○ Secretes catecholamines
§ Epinephrine and norepinephrine
§ In response to sympathetic stimulation
- Adrenal cortex
○ Mesodermal origin
○ Produces steroids
○ 3 zones
§ Zona glomerulosa
□ Mineralocorticoids
§ Zona fasciculata
□ Glucocorticoids (cortisol)
§ Zona reticularis
□ Androgens (DHEAS)
- Adrenocortical hormones
○ All human steroid hormones are synthesized from
cholesterol
○ 3 categories
§ Mineralocorticoids
§ Glucocorticoids
§ Androgens
- Cholesterol uptake
○ 80% of cholesterol used for steroid synthesis is provided by
LDLL in circulating plasma
§ LDLS which have high concentration of cholesterol
diffuse from plasma into interstitial fluid and attach to
specific receptors on adrenocortical cell membranes
○ Once cholesterol enters cells, delivered to mitochondria
where is it cleaved by enzyme cholesterol desmolase to
form pregnenolone
, § LDLS which have high concentration of cholesterol
diffuse from plasma into interstitial fluid and attach to
specific receptors on adrenocortical cell membranes
○ Once cholesterol enters cells, delivered to mitochondria
where is it cleaved by enzyme cholesterol desmolase to
form pregnenolone
§ This is the rate limiting step in the eventually
formation of adrenal steroids
Aldosterone
- Major Mineralocorticoid secreted is aldosterone
® Very potent accounts for 90% of all Mineralocorticoid
activity
- Aldosterone's Mineralocorticoid activity is about 3000 times
greater than that of cortisol but plasma concentration of cortisol is
nearly 2000 times greater
- Aldosterone actions
® Decrease urinary secretion off NaCl by stimulating Na
reabsorption by distal tubules and collecting duct
◊ And a little at thick ascending limb of loop of henle
® Increase urinary reabsorption of water
® Increase urinary excretion of K and protons
® Increase cellular uptake of K
- Regulation of Aldosterone secretion
® Renin angiotensin Aldosterone system
® Plasma K
® Atrial natriuretic peptide ANP
® ACTH has little effect on aldosterone secretion
- renin angiotensin aldosterone system
® Renin release stimulated by decrease perfusion pressure
(dehydration hemorrhage) increases sympathetic
stimulation and decrease NaCl delivery to macula densa cells
® Renin converts angiotensinogen to angiotensin ! Which is
converted in lungs by ACE
◊ Angiotensin converting enzyme
® Angiotensin 2 increases growth and vascularity of zona
glomerulosa and increase aldosterone secretion
◊ Also causes vasoconstriction and increase BP
- Aldosterone escape
® Bodys most power sodium retaining hormones
® Only transient sodium retention occurs when excess
amounts are secreted
® An aldosterone mediated increase in extracellular fluid
volume lasting more than 1-2 days also leads to increase in
arterial pressure
◊ This increase kidney excretion of both salt and water
◊ Called pressure natriuresis and pressure diuresis
Friday, 19 November 2021 10:21 AM
Anatomy of adrenal gland
- Superior poles of two kidneys
- Adrenal medulla
○ Neuroectodermal origin
○ Chromaffin cells
○ Functions related to the sympathetic NS
○ Innervated by cholinergic preganglionic sympathetic neurons
§ ACH released binds to nicotinic receptors on
chromaffin cells
○ Secretes catecholamines
§ Epinephrine and norepinephrine
§ In response to sympathetic stimulation
- Adrenal cortex
○ Mesodermal origin
○ Produces steroids
○ 3 zones
§ Zona glomerulosa
□ Mineralocorticoids
§ Zona fasciculata
□ Glucocorticoids (cortisol)
§ Zona reticularis
□ Androgens (DHEAS)
- Adrenocortical hormones
○ All human steroid hormones are synthesized from
cholesterol
○ 3 categories
§ Mineralocorticoids
§ Glucocorticoids
§ Androgens
- Cholesterol uptake
○ 80% of cholesterol used for steroid synthesis is provided by
LDLL in circulating plasma
§ LDLS which have high concentration of cholesterol
diffuse from plasma into interstitial fluid and attach to
specific receptors on adrenocortical cell membranes
○ Once cholesterol enters cells, delivered to mitochondria
where is it cleaved by enzyme cholesterol desmolase to
form pregnenolone
, § LDLS which have high concentration of cholesterol
diffuse from plasma into interstitial fluid and attach to
specific receptors on adrenocortical cell membranes
○ Once cholesterol enters cells, delivered to mitochondria
where is it cleaved by enzyme cholesterol desmolase to
form pregnenolone
§ This is the rate limiting step in the eventually
formation of adrenal steroids
Aldosterone
- Major Mineralocorticoid secreted is aldosterone
® Very potent accounts for 90% of all Mineralocorticoid
activity
- Aldosterone's Mineralocorticoid activity is about 3000 times
greater than that of cortisol but plasma concentration of cortisol is
nearly 2000 times greater
- Aldosterone actions
® Decrease urinary secretion off NaCl by stimulating Na
reabsorption by distal tubules and collecting duct
◊ And a little at thick ascending limb of loop of henle
® Increase urinary reabsorption of water
® Increase urinary excretion of K and protons
® Increase cellular uptake of K
- Regulation of Aldosterone secretion
® Renin angiotensin Aldosterone system
® Plasma K
® Atrial natriuretic peptide ANP
® ACTH has little effect on aldosterone secretion
- renin angiotensin aldosterone system
® Renin release stimulated by decrease perfusion pressure
(dehydration hemorrhage) increases sympathetic
stimulation and decrease NaCl delivery to macula densa cells
® Renin converts angiotensinogen to angiotensin ! Which is
converted in lungs by ACE
◊ Angiotensin converting enzyme
® Angiotensin 2 increases growth and vascularity of zona
glomerulosa and increase aldosterone secretion
◊ Also causes vasoconstriction and increase BP
- Aldosterone escape
® Bodys most power sodium retaining hormones
® Only transient sodium retention occurs when excess
amounts are secreted
® An aldosterone mediated increase in extracellular fluid
volume lasting more than 1-2 days also leads to increase in
arterial pressure
◊ This increase kidney excretion of both salt and water
◊ Called pressure natriuresis and pressure diuresis
