Adrenal Gland.pOWER POINT PRESENTATION PPT

ADRENAL GLAND

1. Structure and function of Adrenal Glands

2. Structure and Blood Supply of the Adrenal Gland • Anatomically, the adrenal glands (suprarenal) are located in the thoracic abdomen situated 'on' top of the kidneys one on each side, specifically on their antero superior aspect. • They are surrounded by the adipose capsule and the renal fascia. 2

3. •The adrenal glands are found at the level of the 12th thoracic vertebra and receive their blood supply from the adrenal arteries. • The adrenal gland is separated into two distinct structures, both of which receive regulatory input from the nervous system 3

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5. • They consist of two parts, The outer cortex The inner medulla. • It secretes hormones that influence the body's metabolism, blood chemicals, and body characteristics, as well as influence the part of the nervous system that is involved in the response and defense against stress 5

6. Adrenal Cortex • The adrenal cortex is devoted to the synthesis of corticosteroid hormones from cholesterol . It completes the hypothalamic-pituitary-adrenal axis The source of cortisol and corticosterone hormones 6

7. • Normal the adrenal glands produce approximately 35–40 mg of cortisol per day • Cortical cells produce androgens such as testosterone, aldosterone . • the medulla has direct innervation of the sympathetic the cortex is regulated by neuroendocrine hormones secreted by the pituitary gland and hypothalamus, as well as by the renin-angiotensin system 7

8. • The cortex is divided into three zones, or layers. • This division is sometimes referred to as ‘functional zonation ” Zona glomerulosa Zona fasciculata Zona reticularis 8

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10. Zona glomerulosa , is the main site for production of mineralocorticosteroids , namely aldosterone , which plays an important role in the body‘s sodium homeostasis 10

11. Zona fasciculata , is responsible for producing glucocorticoids , chiefly cortisol Cortisol secretion is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, by binding to a cell surface receptor and in turn increasing intracellular cAMP . In the absence of ACTH, the zona fasciculata secretes a basal level of cortisol 11

12. Zona reticularis , it produces androgens , mainly dehydroepiandrosterone (DHEA) and DHEA sulfate in humans 12

13. Adrenal Medulla • The adrenal medulla is the core of the adrenal gland, and is surrounded by the adrenal cortex. • The chromaffin cells of the medulla are the body's main source of the circulating catecholamines , adrenaline (epinephrine) and noradrenaline ( norepinephrine ). 13

14. • These water-soluble hormones, derived from the amino acid tyrosine , are part of the fight-or-flight response initiated by the sympathetic nervous system. • The adrenal medulla can be considered as specialized ganglion of the sympathetic nervous system, lacking distinct synapses, instead releasing secretions directly into the blood. 14

15. • Noradrenaline is the postganglionic neurotransmitter of the sympathetic division of the autonomic nervous system. • Adrenaline and some noradrenaline are released into the blood from the adrenal medulla during stimulation of the sympathetic nervous system they are structurally very similar and this explains their similar effects. 15

16. • Together they 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 by dilating their blood vessels and constricting those of less essential organs, such as the skin, GIT Increasing metabolic rate. Dilating the pupils 16

17. • Adrenaline has a greater effect on the heart and metabolic processes whereas noradrenaline has more influence on blood vessels 17

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 supply each adrenal gland: The superior suprarenal artery is provided by the inferior phrenic artery. The middle suprarenal artery is provided by the abdominal aorta. The inferior suprarenal artery is provided by the renal artery 18

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20. • Venous drainage of the adrenal glands is achieved via the suprarenal veins: The right suprarenal vein drains into the inferior vena cava. The left suprarenal vein drains into the left renal vein or the left inferior phrenic vein 20

21. • The suprarenal veins may form anastomoses with the inferior phrenic veins. • The adrenal glands and the thyroid gland are the organs that have the greatest blood supply per gram of tissue. Up to 60 arterioles may enter each adrenal gland 21

22. Hormones of the Adrenal Cortex • The adrenal cortex produces three groups of steroid hormones from cholesterol. • They are collectively called adrenocorticocoids (corticosteroids, corticoids). • They are: o Glucocorticoids o Mineralocorticoids o Sex hormones (androgens) 22

23. • The hormones in each group have different characteristic actions but due to their structural similarity the actions may overlap. 23

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 to stress 24

25. • Secretion is controlled through negative feedback system involving the hypothalamus and anterior pituitary. • It is stimulated by ACTH from the anterior pituitary and by stress. • In non stressful conditions, secretion has marked circadia variations. 25

26. • Glucocorticoids have widespread metabolic effects and these include: Gluconeogenesis (formation of new sugar from, for example, protein) and hyperglycaemia (raised blood glucose level). Lipolysis (breakdown of triglycerides into fatty acids and glycerol for energy production). Stimulating breakdown of protein, releasing amino acids, which can be used for synthesis of other proteins, e.g. enzymes, or for energy (ATP) production? Promoting absorption of sodium and water from renal tubules (a weak mineral corticoid effect). 26

27. • In pathological and pharmacological quantities glucoocorticoids also have other effects including: Anti-inflammatory actions Suppression of immune responses Delayed wound healing 27

28. Aldosterone ( Mineralocorticoids ) • Aldosterone is the main mineralocorticoid . • Its functions are associated with the maintenance of water and electrolyte balance in the body. • Through a negative feedback system it stimulates the reabsorption of sodium (Na+) by the renal tubules and excretion of potassium (K+) in the urine 28

29. • Sodium reabsorption is also accompanied by retention of water and therefore aldosterone is involved in the regulation of blood volume and blood pressure too. • The blood potassium level regulates the amount of aldosterone produced by the adrenal cortex 29

30. • When the blood potassium level rises, more aldosterone is secreted. • Low blood potassium has the opposite effect. • Angiotensin also stimulates the release of aldosterone 30

31. Renin-Angiotensin-Aldosterone System • When renal blood flow is reduced or blood sodium levels fall, the enzyme renin is secreted by kidney cells. • Renin converts the plasma protein angiotensinogen , produced by the liver, to angiotensin 1. 31

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 stimulates secretion of aldosterone . • It also causes vasoconstriction and increases blood pressure. 32

33. Sex Hormones • Sex hormones secreted by the adrenal cortex are mainly androgens (male sex hormones) and the amounts produced are insignificant compared with those secreted by the testes and ovaries in late puberty and adulthood 33