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Human Anatomy Chapter 26 The Urinary System Human Anatomy, 3rd edition Prentice Hall, © 2001 Introduction – Cellular metabolism produces wastes • CO2 • Urea • Ammonia – Kidneys rid the body of most nitrogenous wastes – Kidneys regulate the chemical make-up of blood Human Anatomy, 3rd edition Prentice Hall, © 2001 General Functions – Serves as a blood filter – Toxins, metabolic wastes leave the body in urine – H2O, glucose, and amino acids are returned to blood Human Anatomy, 3rd edition Prentice Hall, © 2001 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 The Urinary System Human Anatomy, 3rd edition Prentice Hall, © 2001 Location of 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 Location of the Kidneys Human Anatomy, 3rd edition Prentice Hall, © 2001 External Structure of the Kidney – – – – – Hilus Renal capsule Renal artery Renal vein Ureter Human Anatomy, 3rd edition Prentice Hall, © 2001 Internal Structure of the Kidney – Renal cortex – Renal medulla • Renal pyramids • Renal papilla – Renal pelvis – Calyces Human Anatomy, 3rd edition Prentice Hall, © 2001 Structure of the Kidney Human Anatomy, 3rd edition Prentice Hall, © 2001 Blood Supply of the Kidney – Approximately ¼ of the total blood supply of the body passes through the kidneys each minute – Renal artery branches inside the kidney • Supplies the pyramids and the cortex – Venous blood leaves the cortex and medulla • Small veins join the renal vein Human Anatomy, 3rd edition Prentice Hall, © 2001 Blood Supply of the Kidney Human Anatomy, 3rd edition Prentice Hall, © 2001 Blood Supply of the Kidney 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 Structure of a Nephron – 2 main structures • Glomerulus – a knot of capillaries • Renal tubule – – – – Bowman’s capsule surrounds the glomerulus Proximal convoluted tubule Henle’s Loop Distal convoluted tubule – Renal tubule enters collecting duct • Receives urine from nephrons • Delivers final urine product into the calyces Human Anatomy, 3rd edition Prentice Hall, © 2001 A Renal Corpuscle Human Anatomy, 3rd edition Prentice Hall, © 2001 Renal Corpuscles Human Anatomy, 3rd edition Prentice Hall, © 2001 A Typical Nephron Human Anatomy, 3rd edition Prentice Hall, © 2001 A Typical Nephron Human Anatomy, 3rd edition Prentice Hall, © 2001 Blood Supply of the Nephron Human Anatomy, 3rd edition Prentice Hall, © 2001 Urine Formation – Filtration • Blood in afferent arteriole is under high pressure • Glomerulus acts as a filter • Filtrate = the substance that is filtered from the blood into the renal tubule • Blood leaves the glomerulus through the efferent arteriole – Reabsorption • Filtrate contains useful substances (as well as wastes) which are returned to the blood • Most depends on active transport – Transported into peritubular capillaries – Most occurs in the proximal convoluted tubule – Secretion • Substances move from cells or blood (peritubular capillaries) into the filtrate • Important in controlling pH of blood Human Anatomy, 3rd edition Prentice Hall, © 2001 Control of Blood Composition – Excretion of nitrogen-containing compounds • Urea • Uric acid – Water and electrolyte balance • Regulated by hormones Human Anatomy, 3rd edition Prentice Hall, © 2001 Summary of Urine Flow – Kidneys produce urine • Filtration • Reabsorption • Secretion – Ureters – Bladder – Urethra Human Anatomy, 3rd edition Prentice Hall, © 2001