Adrenal glands ppt

1. Dr. Moses Kayungi, MD

2. Structure and Blood Supply of the Adrenal Gland
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⚫• Anatomically, the adrenal glands (suprarenal) are
located in the thoracicabdomen situated 'on' topof
the kidneys one on each side, specifically on their
anterosuperioraspect.
⚫• They are surrounded by theadiposecapsuleand the
renal fascia.

3. ⚫•The adrenal glands are found at the level of the 12th
thoracicvertebraand receive their blood supply from
theadrenal arteries.
⚫• Theadrenal gland is separated into twodistinct
structures, bothof which receive regulatory input from
the nervoussystem
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5. ⚫• Theyconsistof twoparts,
⚫Theoutercortex
⚫The inner medulla.
⚫• It secretes hormones that influence the body's
metabolism, blood chemicals, and bodycharacteristics,
⚫as well as influence the partof the nervoussystem that
is involved in the responseand defenseagainststress
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6. ⚫Adrenal Cortex
⚫• Theadrenal cortex is devoted to the synthesisof
corticosteroid hormones from cholesterol.
⚫Itcompletes the hypothalamic-pituitary-adrenal
axis
⚫The sourceof cortisol and corticosterone hormones
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7. ⚫• Normal theadrenal glands produceapproximately
35–40 mg of cortisol perday
⚫• Cortical cells produceandrogens such as
testosterone, aldosterone.
⚫• the medulla has direct innervation of the
sympathetic
⚫thecortex is regulated by neuroendocrine hormones
secreted by the pituitary gland and hypothalamus, as
well as by the renin-angiotensinsystem
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8. ⚫• Thecortex is divided into three zones, or layers.
⚫• This division is sometimes referred toas ‘functional
zonation”
1. Zonaglomerulosa
2. Zona fasciculata
3. Zonareticularis
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10. ⚫Zonaglomerulosa, is the main site forproductionof
mineralocorticosteroids, namely aldosterone,
which playsan important role in the body‘s sodium
homeostasis
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11. ⚫Zona fasciculata, is responsible forproducing
glucocorticoids, chiefly cortisol
⚫Cortisol secretion is stimulated byadrenocorticotropic
hormone (ACTH) from the anterior pituitary, by
binding toa cell surface receptorand in turn
increasing intracellularcAMP
.
⚫In theabsenceof ACTH, the zona fasciculatasecretesa
basal level of cortisol
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12. ⚫Zona reticularis, it produces androgens, mainly
dehydroepiandrosterone (DHEA) and DHEA sulfate in
humans
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13. ⚫Adrenal Medulla
⚫• The adrenal medulla is thecore of theadrenal gland,
and is surrounded by theadrenal cortex.
⚫• Thechromaffin cells of the medullaare the body's
main sourceof thecirculating catecholamines,
adrenaline (epinephrine) and noradrenaline
(norepinephrine).
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14. ⚫• These water-soluble hormones, derived from the
amino acid tyrosine, are part of the fight-or-flight
response initiated by the sympathetic nervoussystem.
⚫• Theadrenal medullacan beconsidered as specialized
ganglion of the sympathetic nervous system, lacking
distinct synapses, instead releasing secretions directly
into the blood.
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15. ⚫• Noradrenaline is the postganglionic neurotransmitter
of the sympatheticdivision of theautonomic nervous
system.
⚫• Adrenaline and some noradrenaline are released into
the blood from theadrenal medulla
⚫during stimulation of the sympathetic nervous system
theyare structurallyvery similarand thisexplains their
similareffects.
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16. ⚫• Togetherthey potentiate the fight or flight response
by:
⚫Increasing heart rate.
⚫Increasing blood pressure.
⚫Diverting blood to essential organs including the heart,
brain and skeletal muscles bydilating their blood vessels
and constricting those of less essential organs, such as
theskin, GIT
⚫Increasing metabolicrate.
⚫Dilating the pupils
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17. ⚫• Adrenaline has a greater effect on the heart and
metabolicprocesseswhereas noradrenaline has more
influence on blood vessels
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18. ⚫Blood supply to Adrenal Gland
⚫• Although variations of the blood supply to the
adrenal glands (and indeed the kidneys themselves)
are common, there are usually three arteries that
supplyeach adrenal gland:
⚫The superiorsuprarenal artery is provided by the
inferiorphrenicartery.
⚫The middle suprarenal artery is provided by the
abdominal aorta.
⚫The inferiorsuprarenal artery is provided by the renal
artery
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20. ⚫• Venousdrainage of theadrenal glands is achieved via the
suprarenal veins:
⚫The right suprarenal vein drains into the inferiorvenacava.
⚫The leftsuprarenal vein drains into the left renal vein or
the left inferior phrenicvein
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21. ⚫• The suprarenal veins may form anastomoseswith the
inferior phrenicveins.
⚫• The adrenal glands and the thyroid gland are the
organs that have thegreatest blood supplypergram of
tissue.
⚫Up to 60 arterioles mayentereach adrenal gland
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22. ⚫Hormonesof the Adrenal Cortex
⚫• Theadrenal cortex produces threegroupsof steroid
hormones from cholesterol.
⚫• Theyare collectivelycalled adrenocorticocoids
(corticosteroids, corticoids).
⚫• Theyare:
⚫o Glucocorticoids
⚫o Mineralocorticoids
⚫o Sex hormones (androgens)
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23. ⚫• The hormones in each group have different
characteristic actions butdue to theirstructural
similarity theactions mayoverlap.
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24. ⚫Glucocorticoids
⚫• Cortisol (hydrocortisone), is the main glucocorticoid
but small amounts of corticosterone and cortisone are
also produced.
⚫• They are essential for life, regulating metabolism and
responses tostress
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25. ⚫• Secretion is controlled through negative feedback
system involving the hypothalamus and anterior
pituitary.
⚫• It is stimulated by ACTH from theanteriorpituitary
and by stress.
⚫• In non stressful conditions, secretion has marked
circadia variations.
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26. ⚫• Glucocorticoids havewidespread metaboliceffectsand
these include:
1. Gluconeogenesis (formation of new sugar from, for
example, protein) and hyperglycaemia (raised blood
glucose level).
2. Lipolysis (breakdown of triglycerides into fattyacids and
glycerol forenergyproduction).
3. Stimulating breakdown of protein, releasing aminoacids,
which can be used for synthesis of other proteins, e.g.
enzymes, or forenergy (ATP) production?
4. Promoting absorptionof sodium and water from renal
tubules (aweak mineral corticoid effect).
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27. ⚫• In pathological and pharmacological quantities
glucoocorticoidsalso haveothereffects including:
1. Anti-inf lammatoryactions
2. Suppressionof immune responses
3. Delayed wound healing
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28. ⚫Aldosterone (Mineralocorticoids )
⚫• Aldosterone is the main mineralocorticoid.
⚫• Its functions are associated with the maintenance of
waterand electrolyte balance in the body.
⚫• Through a negative feedback system it stimulates the
reabsorption of sodium (Na+) by the renal tubules and
excretionof potassium (K+) in the urine
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29. ⚫• Sodium reabsorption is also accompanied by
retention of water and therefore aldosterone is
involved in the regulation of blood volumeand blood
pressure too.
⚫• The blood potassium level regulates theamountof
aldosteroneproduced by theadrenal cortex
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30. ⚫• When the blood potassium level rises, more
aldosterone is secreted.
⚫• Low blood potassium has theoppositeeffect.
⚫• Angiotensinalsostimulates the releaseof
aldosterone
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31. ⚫Renin-Angiotensin-Aldosterone System
⚫• When renal blood flow is reduced or blood sodium
levels fall, theenzyme renin is secreted by kidneycells.
⚫• Renin converts the plasma protein angiotensinogen,
produced by the liver, toangiotensin 1.
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32. ⚫• Angiotensin converting enzyme (ACE), formed in
small quantities in the lungs, proximal kidney tubules
and other tissues converts angiotensin 1 to angiotensin
2, which stimulatessecretionof aldosterone.
⚫• It also causes vasoconstriction and increases blood
pressure.
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33. ⚫Sex Hormones
⚫• Sex hormonessecreted by theadrenal cortexare
mainly androgens (male sex hormones)
⚫and the amounts produced are insignificantcompared
with thosesecreted by the testesand ovaries in late
pubertyand adulthood
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