APPLIED ANATOMY & PHYSIOLOGY OF THE URINARY SYSTEM DR. S Chakradhar 1

Functional Anatomy and Physiology Kidney size = 11-14cm Kidney size = 11-14cm Located retro - peritoneally on either side of vertebral column, Located retro - peritoneally on either side of vertebral column, Extends from T12 to L3. Extends from T12 to L3. Left kidney is slightly higher than Right. Left kidney is slightly higher than Right. Kidneys receive about 20-25% of the cardiac output. Kidneys receive about 20-25% of the cardiac output. DR. S Chakradhar 2

Gross structure Gross structure 3 Dr S Chakradhar

Nephron It is the structural & functional unit of kidney. It is the structural & functional unit of kidney.Parts Glomerulus / Renal Corpuscles Glomerulus / Renal Corpuscles Renal tubule Renal tubule Bowman's Capsule / Glomerular Capsule Bowman's Capsule / Glomerular Capsule Proximal Convoluted tubule Proximal Convoluted tubule Descending limb of loop Descending limb of loop Loop of Henle Loop of Henle Ascending limb of loop Ascending limb of loop Distal convoluted tubule Distal convoluted tubule Collecting duct Collecting duct DR. S Chakradhar 4

Glomerulus Distal Convoluted Tubule Proximal Convoluted Tubule Loop of Henle Thin descending limb Loop of Henle Thin ascending limb Loop of Henle Thick ascending limb Collecting Duct

DR. S Chakradhar 6

Blood Supply Blood Supply

Glomerulus ( Renal Corpuscle) Capillary tuft surrounded by bowman’s capsule Capillary tuft surrounded by bowman’s capsule Bowmen’s space ( urinary space) Bowmen’s space ( urinary space) Components: Components: Capillaries: endothelial cells Capillaries: endothelial cells Podocytes ( visceral epithelium): podocytes foot processes Podocytes ( visceral epithelium): podocytes foot processes Mesengial cells Mesengial cells Parietal epithelium Parietal epithelium

Podocytes Dr S Chakradhar 10

Mesangial Cells Lie in the central region of the glomerulus. Lie in the central region of the glomerulus. Contraction of these cells decreases GFR while relaxation increases GFR Contraction of these cells decreases GFR while relaxation increases GFR Dr S Chakradhar 11

Filtration barrier Capillary endothelium, Capillary endothelium, Basement membrane, and Basement membrane, and Visceral Epithelium (podocytes) Visceral Epithelium (podocytes) Filtration slits Capillary Space Endothelium Urinary Space GBM Podocyte

Urine formation Urine formation DR. S Chakradhar 13

DR. S Chakradhar 14

Juxta - glomerular apparatus Macula densa – modified cells of distal tubule near afferent arteriole are taller Macula densa – modified cells of distal tubule near afferent arteriole are taller Juxtaglomerular cells are myoepithelial cells in afferent arteriole. They secrete rennin Juxtaglomerular cells are myoepithelial cells in afferent arteriole. They secrete rennin Polkissen cells/Lacis cells -outside the kidney glomerulus near the macula densa and bound laterally by afferent and efferent arterioles. Polkissen cells/Lacis cells -outside the kidney glomerulus near the macula densa and bound laterally by afferent and efferent arterioles.

Renin Angiotensin DR. S Chakradhar 16

Functions of the kidneys: Formation & secretion of urine Formation & secretion of urine Control of the internal environment Control of the internal environment Salt, water, osmolarity, plasma volume/ BP Salt, water, osmolarity, plasma volume/ BP Acid-base control; H +, HCO 3 - Acid-base control; H +, HCO 3 - Other ions; K +, Ca ++, phosphate, Mg ++ Other ions; K +, Ca ++, phosphate, Mg ++ Excretion; urea, creatinine, urates, drugs Excretion; urea, creatinine, urates, drugs Endocrine Endocrine Renin, angiotensin, aldosterone axis Renin, angiotensin, aldosterone axis 1,25 OH Vit D 3 1,25 OH Vit D 3 Erythropoietin Erythropoietin DR. S Chakradhar 17

Summary Think of the kidney as an organ of homeostasis not as an organ of excretion

Lower Urinary Tract Lower Urinary Tract DR. S Chakradhar 19

Micturation Micturation DR. S Chakradhar 20