بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم ﴿و ما أوتيتم من العلم إلا قليلا﴾ صدق الله العظيم الاسراء اية 85

2. Physiology of Nephron By Dr. Abdel Aziz M. Hussein Assist Prof of Medical Physiology

3. Kidneys Urinary System

4. Overall Functions of Kidneys

5. Overall Functions of Kidneys

6. 1. Homeostatic Function • Kidneys keep the constancy of the internal environment (ECF) regarding; • Total body water • Tissue fluid osmolarity • Electrolytes Na, K, Ca etc……. • pH

7. 2. Excretory Function • Kidneys get rid of • Metabolic waste products e.g. urea, uric acid & creatinine. • Many drugs and toxins Chronic renal failure→ accumulation of these metabolites (uremia)

8. 3. Regulation of ABP Through; a) Renin - angiotensin system ↑ ABP V.C. Aldosterone Angiotensin II ACE Angiotensin I Renin Drop of ABP Angiotensinogen

9. 3. Regulation of ABP b) Production of vasoactive substances e.g. PGs and kinins. c) Control of Na and Water excretion Vasoactive substances e.g. kinins and PGs Controlling of Na and Water excretion

10. 4. Endocrinal Function • Kidneys secrete; Erythropoietin from interstitial cells around PTC kinins and PGs Renin Activation of Vit D 1,25 DOCC

11. 5. Metabolic Functions Breakdown of insulin and glucagon Gluconeogenesis in fasting and starvation Do not Forget (RHEEM)

12. Functional Anatomy of Kidney

13. Functional Anatomy of Kidney Weight : 150 gm Capsule: tough and fibrous (limit its distension) Cross section: Capsule inner Medulla Outer Cortex

14. Functional Anatomy of Kidney • Glomeruli • PCT • DCT Cortex • LH • CDs • Vasa recta Medulla

15. Nephron

16. Nephron Def., • It is the structural and functional unit of the kidney Number: • one million nephrons in each kidney Components :

17. Nephron Components Renal Corpuscle Renal Tubule

20. Renal Blood Supply

21. Short • Wide • Direct branch of aorta

24. Renal Blood Flow Value: • 1200ml/min or 4 ml/ 1 gm kidney tissues Significance: • Is high to ensure high GFR NOT to supply excess O2 for excess metabolism

25. Juxta-glomerular Apparatus

26. Juxta-glomerular Apparatus Components:

27. Macula Densa Function • Monitor NaCl concentration in DCT (stimulated by low NaCl) ↓ GFR ↑ GFR

28. Juxta-glomerular cell Function • A) Synthesis, store and release of renin • B) acts as Baroreceptors (detect tension in wall of afferent arterioles) JG cells ↓ wall tension ↓ Renal Blood Flow Renin

29. Extra-glomerular Mesangial cell or Lacis (Polkisson) Function • Form functional syncitium with macula densa and JG cells

30. Functions of JGA • The only function of JGA is synthesis and secretion of renin Actions of Renin: Stimulates Na reabsorption from PT Stimulates Na and H2O reabsorption from intestine Stimulates ACTH, ADH, etc…. V.C. Thirst and salt appetite Increase force of myocardial contraction Angiotensin II ACE Aldosterone Angiotensin I Renin Angiotensinogen

31. Urine Formation

32. Urine Formation Filtration Reabsorption Secretion Urine

33. Glomerular Membrane

34. Glomerular Membrane Def., • It the membrane through which the plasma is filtered Composition: 3 layers; • Capillary endothelium • Basement membrane • Capsular epithelium

36. Glomerular Membrane

37. Glomerular Filtration Blood Capillary endothelium Basement Membrane Podocytes slits Blood Cells Bowman Capsule Plasma proteins Plasma solutes

38. Glomerular Filtration Blood Capillary endothelium Basement Membrane Podocytes slits Bowman Capsule

39. Glomerular Filtration Def., • It is an ultrafiltration since it is plasma minus plasma protein and cellular elements while simple filtration excludes only cellular elements.

40. Glomerular Filtration Dynamics: • Glomerular Filtration is formed by the forces of filtration as many capillary filtrate in the body (Starling's forces of filtration). • They are 4 forces; • 2 Hydrostatic pressures • 2 Oncotic pressures

41. Glomerular Filtration Glomerular Oncotic Pressure (Gπ) Glomerular Hydrostatic Pressure (Gp) Glomerular capillary Capillary endothelium Basement Membrane Podocytes slits Bowman Capsule Bowman oncotic Pressure (B π) Bowman Hydrostatic Pressure (Bp)

42. Glomerular Filtration Gπ = 32 mmHg Gp = 60 mmHg Gp = 18 mmHg Bπ = 0 mmHg Help Filtration Oppose Filtration

43. Glomerular Filtration Rate (GFR)

44. Glomerular Filtration Rate Def., • Volume of plasma filtered by both kidney per unit time Value: • 125 ml/min • 180 L/day Significance of High GFR: • To ensure processing of plasma (3L) about 60 times/day (since daily GFR = 180L/day  prevents accumulation of metabolites.

45. Glomerular Filtration Rate Causes of high GFR: 1) High capillary hydrostatic P.: • It is about 45- 60 mmHg in glomerular capillary High GP: • Efferent arteriole → narrower than afferent arteriole • Glomerular capillaries →present between two arteries

46. Glomerular Filtration Rate Causes of high GFR: 2) High KF (filtration coefficient) 3) High RPF.: • It is about 600ml/ min. RBF

47. Glomerular Filtration Rate Factors Affecting GFR:

48. Functions of Renal Tubules

49. Renal Tubules

50. Proximal Tubules