The Urinary System

Introduction Function of Urinary System Cellular metabolism produces wastes Urea Uric Acid Ammonia Creatinine Kidneys rid the body of most nitrogenous wastes Kidneys regulate the chemical make-up of blood Regulate blood volume as well as RBC production Blood Pressure Regulate electrolytes

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

The Urinary System FG26_01A1.JPG Title: An Introduction to the Urinary System Notes: (a) Anterior view, posterior view; urinary system components. (b)Sectional view. Keywords: urinary system, kidney, ureter, urinary bladder, urethra, inferior vena cava, adrenal gland, renal artery, vein, aorta, parietal peritoneum, adipose capsule, renal capsule

Location of Kidneys Lie against the dorsal body wall Covered in adipose tissue In the superior lumbar region Protected by the lower part of the rib cage

The Urinary System FG26_01A2.JPG Title: An Introduction to the Urinary System Notes: (a) Anterior view, posterior view; urinary system components. (b)Sectional view. Keywords: urinary system, kidney, ureter, urinary bladder, urethra, inferior vena cava, adrenal gland, renal artery, vein, aorta, parietal peritoneum, adipose capsule, renal capsule

External Structure of the Kidney Renal capsule Connective tissue Renal artery Blood (oxygenated) to the kidney Renal vein Receives blood from kidney Ureter Drains urine

Internal Structure of the Kidney Renal cortex Renal medulla Renal pyramids Renal pelvis Continuous with ureter Calyces Extensions of the pelvis Function – collect urine

Structure of the Kidney FG26_03A1.JPG Title: Structure of the Kidney Notes: (a)Frontal section through kidney. (b)Shadow drawing showing arrangement of calyces and renal pelvis. (c)Urogram showing calyces, renal pelvis, and ureter. Keywords: kidney, frontal, cortex, medulla, renal sinus, renal capsule, hilus, ureter, renal papilla, renal capsule, renal columns, minor calyx, major calyx, renal pelvis, renal pyramids

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

Blood Supply of the Kidney FG26_07A.JPG Title: Blood Supply to the Kidneys Notes: The flow chart summarizes the pattern of renal circulation. (a) Sectional view. (b)Circulation in the cortex. (c)Circulation to a cortical nephron. (d)Blood vessels at a juxtamedullary nephron. Keywords: kidneys, blood supply, circulation, artery, vein, renal, semental, interlobar, arcuate, interlobular, afferent, efferent, peritubular capillaries, arterioles, venules, cortex, pyramid, interlobular, peritubular capillaries, glomerulus, suprarenal artery

Nephrons and Urine Formation Nephrons form the urine product Filtration Reabsorption Secretion Each kidney contains about 1 million nephrons

Structure of a Nephron 2 main structures Glomerulus – a knot of capillaries Renal tubule (about 2 inches long) 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

A Typical Nephron FG26_04.JPG Title: A Typical Nephron Notes: Diagrammatic view indicating major functions of each segment of the nephron and collecting system. Keywords: nephron, renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting system, papillary duct

A Typical Nephron FG26_05A.JPG Title: The Renal Corpuscle Notes: (a) A juxtamedullary nephron. (b)SEM of several renal corpuscles. (c)Renal corpuscle. (d)Diagrammatic view of filtration apparatus. (e)Electron micrograph of glomerular surface. Keywords: nephron, juxtamedullary, renal corpuscle, loop of Henle, convoluted tubule, proximal, distal, juxtaglomerular apparatus, macula densa, arteriole, glomerulus, podocyte, capsular space, filtration apparatus, mesangial cell, lamina densa

Renal Corpuscles FG26_05B.JPG Title: The Renal Corpuscle Notes: (a) A juxtamedullary nephron. (b)SEM of several renal corpuscles. (c)Renal corpuscle. (d)Diagrammatic view of filtration apparatus. (e)Electron micrograph of glomerular surface. Keywords: nephron, juxtamedullary, renal corpuscle, loop of Henle, convoluted tubule, proximal, distal, juxtaglomerular apparatus, macula densa, arteriole, glomerulus, podocyte, capsular space, filtration apparatus, mesangial cell, lamina densa

Blood Supply of the Nephron FG26_07C.JPG Title: Blood Supply to the Kidneys Notes: The flow chart summarizes the pattern of renal circulation. (a) Sectional view. (b)Circulation in the cortex. (c)Circulation to a cortical nephron. (d)Blood vessels at a juxtamedullary nephron. Keywords: kidneys, blood supply, circulation, artery, vein, renal, semental, interlobar, arcuate, interlobular, afferent, efferent, peritubular capillaries, arterioles, venules, cortex, pyramid, interlobular, peritubular capillaries, glomerulus, suprarenal artery

Urine Formation Filtration Blood in vessels is under high pressure Glomerulus acts as a filter Filtrate = the substance that is filtered from the blood into the renal tubule Reabsorption Filtrate contains useful substances which are returned to the blood Most occurs in the proximal convoluted tubules Secretion Substances move from blood (capillaries) into the filtrate Important in controlling pH of blood Acid-base balance of blood Blood pH must be 7.35 – 7.45 (very narrow range) Tubule cells secrete whatever is necessary into filtrate Urine pH = 4.5 – 8.0

Summary of Urine Flow Kidneys produce urine Filtration Reabsorption (active transport) Secretion Ureters Bladder Urethra