HISTOLOGY OF ADRENAL GLAND & CORRELATION WITH FUNCTION

point of identification and clinical significant of adrenal gland

1. ADRENAL GLAND Izatty Lim Batch 4 (0308188) 5 th September 2014 HISTOLOGICAL STRUCTURE CORRELATION WITH FUNCTION

2. OVERALL ADRENAL GLAND

3. Cortex Zona glomerulosa mineralocorticoids (aldosterone) Zona fasiculata glucocorticoids (cortisol) Zona reticularis Androgens ( dehydroepiandosterone (DHEA)) Medulla catecholamines ( epinephrine & norepinephrine)

4. ADRENAL CORTEX HISTOLOGY Cells arranged into three concentric zones differentiated based on the pattern produced by cords of cells boundaries between zones are indistinct ZONA GLOMERULOSA: narrow outer zone that constitutes up to 15% of the cortical volume ZONA FASICULATA: thick middle zone that constitutes nearly 80% of the cortical volume ZONA RETICULARIS: inner zone that constitutes only 5% to 7% of the cortical volume but is thicker than the glomerulosa because of its more central location

5. ZONA GLOMERULOSA small columnar cells arranged in closely packed ovoid clusters & curved columns spherical nuclei appear closely packed and stain densely rich network of fenestrated sinusoidal capillaries surrounds each cell cluster lipid droplets are sparse SECRETES MINERALOCORTICOIDS ( ALDOSTERONE , DEOXYCORTICOSTERONE) Maintain fluid & electrolyte balance

6. ZONA FASICULATA large polyhedral cells arranged in long straight cords , one or two cells thick, separated by sinusoidal capillaries lightly staining spherical nucleus Binucleate cells are common numerous lipid droplets contain neutral fats, fatty acids, cholesterol, & phospholipids (precursors for the steroid hormones) SECRETES GLUCOCORTICOIDS ( CORTISOL , CORTICOSTERONE) Regulate metabolism of carbohydrate, protein & lipid (gluconeogenesis, proteolysis, lipolysis) Suppress inflammation & immune response Impair healing process

7. ZONA RETICULARIS dark acidophilic cells abundant lipofuscin pigment granules Smaller cells compared to cells in zona fasciculata , nuclei are more deeply stained less cytoplasm ; thus the nuclei appear more closely packed . arranged in anastomosing cords , separated by fenestrated capillaries cells have relatively few lipid droplets SECRETES ANDROGENS ( DEHYDROEPIANDOSTERONE , ANDROSTENEDIONE) Weak masculinizing effect Libido, body hair (female)

8. HORMONES OF ADRENAL CORTEX Hormone Composition Source Major Functions Adrenal cortex Mineralocorticoids ( 95% of mineralocorticoid activity in aldosterone) Steriod hormones (cholesterol derivatives) Parenchymal cells of the zona glomerulosa Aid in controlling electrolyte homeostasis (act on distal tubule of kidney to ↑ sodium reabsorption and ↓ potassium reabsorption); function in maintaining the osmotic balance in the urine and in preventing serum acidosis Glucocorticoids ( corticosterone , and cortisol; 95% of glucocorticoid activity in cortisol) Steriod hormones (cholesterol derivatives) Parenchymal cells of the zona fasciculata (and to a lesser extent of the zona reticularis ) Promote normal metabolism , particularly carbohydrate metabolism (↑ rate of amino acid transport to live, promote removal of protein from skeletal muscle and its transport to liver, ↓ rate of glucose metabolism by cells and stimulate glycogen synthesis by liver, stimulate mobilization of fats from storage deposits for energy use); provide resistance to stress ; suppress inflammatory response & some allergic reactions Gonadocorticoids ( dehydroepiandrosterone [DHEA] is a major sex steroid produced in both men and women) Steriod hormones (cholesterol derivatives) Parenchymal cells of the zona reticularis (and to a lesser extent of the zona fasciculata) Induce weak masculinizing effect ; at normal serum levels usually their function is insignificant

9. ADRENAL MEDULLA HISTOLOGY Consist of: Chromaffin cell (most abundant cell) CT Sinusoidal blood capilaries Nerves Myelinated Sympathetic ganglion cells round or polygonal with prominent nuclei May be in cluster

10. CHROMAFFIN CELL Pheochromocytes Large, pale-staining epithelioid cells Organized in ovoid clusters & short interconnecting cords Intimate relation with blood capillaries G ranular cytoplasm due to hormone-containing granules can be observed Stain intensely with Chromaffin salts SECRETES CATECHOLAMINES ( ADRENALINE , NORADRENALINE) Augment sympathetic system activity Major role in acute response to stress

11. Chromaffin cells arranged in clusters, usually around medullary veins Ganglion cells (round or polygonal with prominent nuclei)

12. HORMONES OF ADRENAL MEDULLA Hormone Composition Source Major Functions Adrenal medulla Norepinephrine and epinephrine (in human, 80% epinephrine) Catecholamines (amino acid derivatives) Chromaffin cells Sympathomimetic (produce effects similar to those induced by the sympathetic division of the autonomic nervous system) a ; ↑ heart rate , ↑ blood pressure , ↓ blood flow to viscera and skin ; stimulate conversion of glycogen to glucose ; ↑ sweating ; induce dilation of bronchioles ; ↑ rate of respiration ; ↓ digestion ; ↓ enzyme production by digestive system glands; ↓ urine production

13. CLINICAL IMPORTANCE Excessive cortical secretion Cushing’s syndrome  hypercortisolism Masculinization ( virilism )  excessive adrogens in women Feminization  excessive estrogens in men Adrenogenital syndrome  excessive sex hormone in children Insufficient cortical secretion Addison’s disease

14. CLINICAL IMPORTANCE Abnormal medullary secretion Hyposecretion Not much problem if sympathetic function is normal Some attenuation of acute response to stress Hypersecretion Pheochromocytoma  benign tumours of adrenal medulla The tumor cells in pheochromocytoma may be arranged in alveolar (nesting), trabecular, solid/diffuse, or mixed patterns. Alveolar pattern is shown here