Urinary System II PDF

1. Nephrons, tiny structures in the renal pyramids, filter gallons of blood each day. 2. The kidneys are located behind the peritoneum, and so are called retroperitoneal organs. 3. The right kidney is slightly lower than the left kidney to accommodate the liver. 4. Nephrons perform the primary funct...

1. Nephrons, tiny structures in the renal pyramids, filter gallons of blood each day. 2. The kidneys are located behind the peritoneum, and so are called retroperitoneal organs. 3. The right kidney is slightly lower than the left kidney to accommodate the liver. 4. Nephrons perform the primary function of the kidneys: regulating the concentration of water and other substances in the body. 5. There are 3 main steps of urine formation: Glomerular filtration. Reabsorption. Secretion. 6. The glomerulus is a network of capillaries surrounded by a cuplike structure, the glomerular capsule (or Bowman s capsule). 7. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. 8. The internal sphincter is involuntary. 9. It surrounds the opening of the bladder to the urethra and relaxes to allow urine to pass. 10.The external sphincter is voluntary. 11.It surrounds the urethra outside the bladder and must be relaxed for urination to occur.  Functions of Urinary System: A. REGULATION OF BLOOD PRESSURE Kidneys play an important role in the long-term regulation of arterial blood pressure by two ways: 1. By regulating the volume of extracellular fluid. 2. Through renin-angiotensin–aldosterone mechanism. B. Hormones secreted by kidneys. 1. Erythropoietin 2. Thrombopoietin 3. Renin 4. 1,25-dihydroxycholecalciferol (calcitriol) 5. Prostaglandins. C. Regulation of blood glucose level. 1. Kidneys can use the amino acid glutamine in gluconeogenesis, the synthesis of new glucose molecules. 2. They can then release glucose into the blood to help maintain a normal blood glucose level. D. Maintenance of Acid-Base Balance Along with the respiratory system, the kidneys regulate the acid-base balance of the blood. pH is kept at around 7.4. Accomplished by excretion of H+ and reabsorption of bicarbonate(HCO3-)