Chapter 25 The Urinary System

Introduction Cellular metabolism produces wastes CO2 Urea Ammonia Kidneys rid the body of most nitrogenous wastes Kidneys regulate the chemical make-up of blood

General Functions Serves as a blood filter Toxins, metabolic wastes leave the body in urine H2O, glucose, and amino acids are returned to blood

Organs of the Urinary System Kidneys (paired) Perform filtering functions and manufacture urine Ureters (paired) Transport urine Urinary bladder (single) Stores urine Urethra (single) Transports urine Human Anatomy, 3rd edition Prentice Hall, © 2001

Location of the Kidneys Lie against the dorsal body wall Beneath the parietal peritoneum In the superior lumbar region Protected by the lower part of the rib cage Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Anatomy of the Kidney External Anatomy Hilus Renal capsule Renal artery Renal vein Ureter Internal Anatomy Renal cortex Renal medulla Renal pyramids Renal papilla Renal pelvis Calyces Human Anatomy, 3rd edition Prentice Hall, © 2001

Blood Supply of the Kidney Approximately ¼ of the total blood supply passes through the kidneys each minute Renal artery branches Supplies pyramids and cortex Venous blood leaves the cortex and medulla Small veins join the renal vein Human Anatomy, 3rd edition Prentice Hall, © 2001

Nephrons and Urine Formation Nephrons form the urine product Filtration Reabsorption Secretion Each kidney contains about 1 million nephrons Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Structure of a Nephron 2 main structures Glomerulus Renal tubule Bowman’s capsule Proximal convoluted tubule Henle’s Loop Distal convoluted tubule Collecting duct Receives urine from nephrons Delivers final urine product into calyces Human Anatomy, 3rd edition Prentice Hall, © 2001

The Glomerulus - Filtration Blood enters glomerulus Afferent arteriole Glomerulus filters blood Forms filtrate Blood leaves glomerulus Efferent arteriole Human Anatomy, 3rd edition Prentice Hall, © 2001

Renal Tubule – Reabsorption & Secretion Substances move from filtrate into peritubular capillaries Active transport Most occurs in proximal convoluted tubule Secretion Substances move from peritubular capillaries into filtrate Control of blood pH http://home.earthlink.net/~dayvdanls/nephron.gif

Control of Blood Composition Excretion of nitrogen-containing compounds Urea Uric acid Water and electrolyte balance Regulated by hormones

Summary of Urine Flow Kidneys produce urine Ureters Bladder Urethra Filtration Reabsorption Secretion Ureters Bladder Urethra www.foxriverwatch.com/kidney_works.jpg