Download Adrenal Glands

Adrenal Glands
Adrenal Glands
The adrenal glands (suprarenal glands) are located on top of each kidney.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Adrenal Gland – 2 Glands in 1
Cortex (outer) – bulk of gland (75%); glandular tissue
Medulla (inner) – nervous tissue; SNS
Cortex vs. Medulla
• Glandular vs. Nervous tissue
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Remind you of another endocrine gland??
• Blood flows from outside of adrenals inward
Adrenal Cortex Zones
Cortex - divided
histologically into 3
regions:
• ZG - “salt”
• Mineralcorticoids
• ZF – “sugar”
• Glucocorticoids
• ZR – “sex”
• Gonadocorticoids
Adrenal Cortex Hormones
• The zona glomerulosa secretes:
• Mineralocorticoids - used to regulate mineral homeostasis (electrolytes),
Na2+ K+
• Aldosterone
• The zona fasciculata secretes:
• Glucocorticoids - affect glucose homeostasis
• Cortisol
• The zona reticularis secretes:
• Weak androgens
• DHEA, androstenedione
Zona Glomerulosa - Mineralcorticoids
• Aldosterone is the major mineralocorticoid.
• Regulates sodium (Na2+) and potassium (K+) homeostasis.
• Controlled by renin-angiotensin-aldosterone (RAA)
pathway
• A.k.a. Renin Angiotensin System (RAS)
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Renin-Angiotensin-Aldosterone (RAA) Pathway
Zona Fasciculata - Glucocorticoids
• Stimulated by ACTH
• Secretion of cortisol is regulated by negative
feedback.
Glucocorticoids help control:
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Protein breakdown
Glucose formation
Lipolysis
Resistance to stress
Inflammation
Immune responses
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Glucocorticoids
Mostly permissive to actions of other hormones.
• Epi is ineffective w/out cortisol
• Under stress, w/out glucocorts, there is vascular
collapse.
• Maintain cardiac output; increase arteriolar tone; decrease
endothelial permeability; maintain normal vascular resistance
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Maintains normal BP (angiotensin II)
Modulate emotional tone, wakefulness; memory
High cortisol will ↓ muscle mass and bone formation
Inhibit inflammatory and immune response
Facilitate maturation of the fetus
• Develops fetal enzyme systems
• Growth and development
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Glucocorticoid
Feedback
Loop
Zona Reticularis - Gonadocorticoids
• Dehydroepiandrosterone (DHEA) – major androgen secreted.
• In males, after puberty the hormone testosterone is secreted in much larger
quantities so DHEA has virtually no effect.
• In females, DHEA and other adrenal androgens play a major role in promoting
libido and are converted to estrogens.
• In menopausal women, all female estrogens come from adrenal androgens.
Adrenal Medulla
• Stimulated by sympathetic preganglionic neurons of the
autonomic nervous system (ANS).
• Chromaffin cells store and secrete 2 catecholamines:
• epinephrine (adrenaline)
• norepinephrine (noradrenaline).
Both of which are involved in the fight-or-flight
response.
Catecholamines & Thyroid Hormone
• Sympathoadrenal activity is enhanced under
conditions of hyperthyroidism and depressed under
conditions of low levels of thyroid hormones.
• Major symptoms of patients with thyroid
dysfunction relate to functional alterations of those
organs regulated by the sympathetic nervous
system.