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1. Urinary System Dr. Rukhsana Anwar

2. Function of Kidney Regulation of Blood ionic composition Maintenance of blood osmolarity Regulation of blood volume Regulation of blood pressure Regulation of blood pH Release of hormones Regulation of blood glucose level Excretion of wastes

3. Nephron

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5. Urine Formation 1 Glomerular Filtration 2 Tubular Reabsorption 3 Secretion

6. 1. Glomerular Filtration Water and most solutes in plasma pass from blood across the wall of glomerular capillaries into the glomerular capsule. Fluid that enters the capsular space is called glomerular filtrate. Endothelial cells of glomerular capillaries and podocytes form a leaky barrier known as filtration membrane.

7. 1. Glomerular Capsule

8. Filtration membrane

9. . Filtration membrane permits filtration of water and small size solutes including glucose, vitamins, amino acid, ammonia, urea & ions (diameter < 6 -7nm)  

10. Glomerular Filtration Rate GFR The amount of filtrate formed in all the renal corpuscles ( nephrons ) of both kidneys in each minute is called GFR. In adult male GFR is 125mL/min and female it is 105mL /min.

11. Regulation of GFR Regulation of GFR Three mechanism control GFR 1. Renal Auto regulation 2. Neural Regulation 3. Hormonal Regulation

12. Renal Auto regulation The kidneys themselves help to maintain a constant renal blood flow & GFR. This capability is called auto regulation and consist of a. Myogenic Mechanism b. Tubuloglomerular feed back

13. Stretching triggers contraction of smooth muscles in the wall of afferent arteriols. Elevated B.P stretches the walls of affrent arteriols-------- smooth muscles in the wall contract--------the arteriole's lumen become narrows-------renal blood flow decreases---------reduces GFR

14. a. Myogenic Mechanism Conversely, B.P lowers-----smooth muscle relax-------afferent arteriole dilate----- renal blood flow will increase and GFR increases

15. b. Tubuloglomerular feed back GFR above normal--------filtrate flows more rapidly along the renal tubules------- there is less time for tubular reabsorption of Na, Cl ions and water. Macula densa cells detect increase delivery of Na, Cl ions and water--------- juxtaglomerular apparatus secretes renin (vasoconstrictor)----------afferent arteriole constrict------- GFR decreases.

16. 2. Neural Regulation Blood vessels of the kidney are supplied by sympathetic nerve fibers that release NE. Alpha AD receptors activated and cause vasoconstriction of blood vessels. During exercise vasoconstriction of afferent arteriole predominates-------blood flow to glomerular capillaries greatly decreased and GFR drops. Sympathetic stimulation also stimulates renin release.

17. Hormonal Regulation of GFR Hormonal Regulation of GFR Renin stimulates the production of angiotensin II. Angiotensin is potent vasoconstrictor that narrows both afferent and efferent arteriols, decreasing renal blood flow and GFR

18. Hormonal Regulation of GFR Atrial natriurtic peptide(ANP) secreted by cardiac Atrial cells--------causes relaxation of glomerular mesengial cells---------increases the capillary surface area --------- increase GFR

19. Hormonal regulation of Tubular reabsorption and secretion

20. . Following hormones controlled tubular reabsorption and secretion Angiotensin II Aldosterone Anti diuretic hormone (ADH) Atrial N atriuretic Peptide (ANP) Parathyroid hormone Renin-Angiotensin –Aldosterone sysytem

21. . Concentrated Urine Formation Dilute Urine Formation