Chapter 26: Urinary System 1.26-1 Urinary System Functions a. Three primary functions of the Urinary System i. Excretion 1. Removal of organic wastes from body fluids ii. Elimination 1. Discharge of waste products iii. Homeostatic regulation 1. Of blood plasma volume and solute concentration b. Components of the Urinary system i. Kidneys – organs that produce urine ii. Urinary Tract – organs that eliminate urine 1. Ureters (paired tubes) 2. Urinary bladder (muscular sac) 3. Urethra (exit tube) iii. Urination – process of eliminating urine c. Homeostatic Functions of the Urinary System i. Regulates blood volume and blood pressure 1. Adjusting urine volume, releasing erythropoietin and renin ii. Regulates plasma ion concentrations 1. Controlling excretion of Na+, K+, and Cl- iii. Help stabilize blood pH 1. By controlling loss of H+ and bicarbonate ions in urine iv. Conserves valuable nutrients 1. Selective excretion of wastes only v. Assists liver in detoxifying poisons 2. 26-2 The Kidneys a. Each kidney is protected and stabilized by three concentric layers of connective tissue i. Fibrous capsule is a layer of collagen fibers that covers outer surface of entire organ ii. Perinephric fat capsule is a thick layer of adipose tissue that surrounds renal capsule iii. Renal fascia is a dense, fibrous outer layer that anchors kidney to surrounding structures b. Kidney anatomy i. Hilum, renal cortex, renal medulla, renal pyramids, renal papilla, renal columns, renal lobe ii. Urine collecting structures à minor calyx, major calyx, renal pelvis, ureter c. Blood Supply to the Kidneys i. Kidneys receive 20%–25% of total cardiac output d. Renal Nerves i. Innervate kidneys and ureters ii. Enter each kidney at hilum and follow tributaries of renal arteries to individual nephrons iii. Most nerve fibers are sympathetic
1. Adjust rate of urine formation by changing blood flow and blood pressure at nephron 2. Stimulates release of renin a. Which restricts losses of water and salt in urine by stimulating reabsorption at nephrons e. The Nephron is the functional unit of the kidney i. Nephron = renal corpuscle + renal tubule 1. Renal corpuscle consists of glomerular (Bowman’s) capsule and the glomerulus a. Capsule is a cup shaped structure b. Glomerulus is a capillary knot 2. Renal tubule is a long tubular passageway f. The renal corpuscle performs the function of filtration g. Blood pressure forces water and dissolved solutes out of glomerular capillaries into the capsular space i. Produces protein-free solution ( filtrate ) similar to blood plasma h. The renal tubule performs the functions of secretion and reabsorption i. Reabsorb useful nutrients that enter filtrate ii. Reabsorb more than 90% of water in filtrate iii. Secrete waste products that failed to enter renal corpuscle through filtration at glomerulus i. Renal Tubule i. As the filtrate flows through the tubule its chemical composition changes à tubular fluid ii. From the renal corpuscle, fluid flows through the proximal convoluted tubule, the nephron loop (loop of Henle), the distal convoluted tubule, and
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