1. Anatomy and PhysiologyThe Urinary SystemChapter 18 Community Education Mr. Kestner

2. Information • The urinary system, also known as the excretory system, is responsible for removing certain wastes and excess water from the body • It also maintains the body’s acid-base balance • Helps maintain homeostasis • System consists of 2 kidneys, 2 ureters, 1 bladder, and 1 urethra

3. Renal Functions • Excretion – filters large amounts of fluid from bloodstream • Maintain Blood Volume – controls volume by regulating balance of salts and water • pH Regulation – controls balance of H+ and HCO3- ions in conjunction with respiratory system • Blood Pressure – produces renin, which helps adjust filtration pressure • Erythrocyte Concentration – produces erythropoietin, hormone which stimulates RBC production • Vitamin D Production – converts Vitamin D to calciferol (important for bone and teeth development)

4. Kidneys • Bean shaped organs located on either side of vertebral column • Behind upper part of abdominal cavity - retroperitoneal • Protected by ribs and heavy cushion of fat • About the size of a closed fist • Right kidney slightly lower due to liver • Each kidney divided into two main sections • Cortex – outer section containing most nephrons • Medulla – inner section containing most of collecting tubules

5. Nephrons • Microscopic filtering units located in kidneys • More than one million per kidney • Each nephron consists of: • Glomerulus • Bowman’s capsule • Proximal convoluted tubule • Distal convoluted tubule • Collecting duct (tubule)

6. Glomerulus • Cluster of capillaries inside Bowman’s Capsule • As blood passes through, water; mineral salts; sugar; metabolic products; and other substances are filtered out of blood • RBCs and proteins are not filtered out • Filtered blood leaves glomerulus and makes its way to renal vein, which carries it away from kidney

7. Renal Tubule • Proximal Convoluted Tubule • Filtration • Loop of Henle • Reabsorption • Distal Convoluted Tubule • Filtration/Reabsorption • Collecting Duct (Tubule) • Transportation to renal pelvis

10. Urine • Consists of water and solutes • Approximately 95% water • Daily production = 0.6 – 2.5L/day • Produces about 56mL/hour • <30mL/hour indicates possible renal failure

11. Ureters • Two muscular tubes, one extending from each kidney to the bladder • Peristalsis moves urine through ureter to bladder

12. Bladder • A hollow, muscular sac that lies behind the symphysis pubis and at the midline of pelvis • Mucous membrane lining with folds called rugae • Rugae disappear when bladder becomes full • Three layers of visceral (smooth) muscle form the walls of bladder • Three openings in interior of bladder • Urine expelled through process called micturition • Average capacity of bladder is 700 – 800mL • Urge to void happens 200 – 400mL of urine due to stretch receptors sending nerve impulses to brain

13. Urethra • Tube that carries urine from bladder to the outside • External opening called urinary meatus • Different in females and males • Females approx. 1 ½ inches in length • Males approx. 8 inches in length • Also used to carry semen from reproductive system out of the body, although not at the same time

14. Urine Terms • Polyuria – excessive urination • Oliguria – below normal amounts of urination • Anuria – absence of urination • Hematuria – blood in urine • Pyuria – pus in urine • Nocturia – urination at night • Dysuria – painful urination • Retention – inability to empty bladder • Incontinence – involuntary urination