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Urinary System
Lecture Unit 3
Question | Answer |
---|---|
Urinary System functions | Remove waste products from bloodstream: converts plasma filtrate into urine. Storage 7 excretion of urine. Regulation of blood pressure & volume. Secretion of erythropoietin (EPO): Regulation of erythrocyte production. |
Kidneys | Located by the posterior abdominal wall, suspended by fat. Left kidney is 2cm superior to right. Retroperitoneal. Adrenal gland on top. Paired organ. Symmetrical, bean shaped & reddish brown. f |
Anatomy of the Kidney | Renal capsule, cortex, medulla, columns, pyramids (8-15 per kidney), papilla (apex of pyramid), Minor calyx-1 per pyramid, Major calyx-2-3 per kidney, Renal pelvis-collects urine & transports to ureter, bladder, urethra |
After what structure does urine not change anymore? (comes out of body the same). | Minor calyx |
Nephron | Functional unit of kidney. ~1mil in each. Consists of renal corpuscle-glomerulus & glomerular capsule. Renal tubule. Cortical nephrons (85%)-small ones. Juxtamedullary nephrons (15%)-long ones-dip down into medulla |
Glomerulus | Ball of capillaries |
Renal tubule | Proximal convoluted tubule (PCT). Nephron Loop (Loop of Henle). Distal convoluted tubule (DCT). |
Urine Formation | Filtration (blood to tubules). Tubular Reabsorption (tubules to blood). Tubular Secretion (blood to tubules). 180L of plasma leaves the bloodstream to kidney tubule system. 99% goes back into blood. |
Filtration | Water dissolved solutes in plasma passively move out of glomerular capillaries into the capsular space. Fluid called filtrate. |
Tubular Reabsorption | Substances move by diffusion or active transport from the tubule back to the blood. Called tubular fluid. 99% of blood plasma is reabsorbed. |
Tubular Secretion | Active transport of solutes out of blood into the tubules. 1% becomes urine. |
Renal Corpuscle | Composed of Glomerulus (Fenestrated capillaries), Glomerular (Bowman's) capsule. Site of filtration: afferent arteriole is wider than efferent. Passive filtration. Blood in efferent is cleaner & thicker than afferent. |
Proximal convoluted tubule | Simple cuboidal epithelium w/ microvilli (brush border)-increase surface for reabsorption. Actively reabsorbs from tubular fluid: nutrients, electrolytes, plasma proteins. Surrounded by peritubular capillaries. |
Nephron Loop (Loop of Henle) | Thick portions are simple cuboidal epithelium. Thin portions are simple squamous epithelium. Reabsorbs: water, sodium, and chloride. Surrounded by vasa recta capillary network. |
Distal Convoluted Tubule | Lined w/ simple cuboidal epithelium-contain less microvilli than the PCT. Regulated secretion of potassium & hydrogen. Regulated reabsorption of sodium & water-aldosterone & ADH. Surrounded by peritubular capillaries. |
Collecting ducts | Fluid from the distal convoluted tubule drains into collecting ducts. Water absorption by ADH occurs in collecting ducts when dehydrated. When tubular fluid leaves the duct it is called urine. |
Juxtaglomerular Apparatus (Label) | Juxtaglomerular cells & Macula Densa regulate blood pressure. When macula densa cells detect low bp or low solute concentration, they stimulate the JG cells to secrete renin which increases aldosterone secretion. |
Juxtaglomerular cells | Modified smooth muscle cells of the afferent arteriole. |
Macula Densa | Group of modified epithelial cells in a distal convoluted tubule. |
Ureters | Retroperitoneal. Carries urine from renal pelvis to bladder. Urine in renal pelvis causes peristaltic waves. 3 layers: mucosa-transitional epithelium. muscularis-longitudinal & circular layers. adventitia-connective tissue. |
Retroperitoneal | Behind parietal peritoneum. |
Urinary Bladder | Collapsible, muscular sac. Immediately posterior to pubic symphysis. Stores & expels urine. Trigone functions as funnel to direct urine into urethra as bladder contracts. Grows and shrinks. 4 layers. |
Four Layer of the Urinary Bladder | Mucosa-transitional epithelium. Submucosa-dense irregular CT. Muscularis-detrusor muscle-muscle of bladder-contracts to get urine out. Advenitia-areolar CT. |
Urethra | Drains urine from teh bladder. Fibromsucular tube lined w/ a mucous membrane. Internal & external urethral sphincters. External urethral orifice. |
Internal urethral sphincter | Thickening of detrusor muscle. Smooth muscle. Involuntary. Bottom of bladder. |
External urethral sphincter | Portion of urogenital diaphragm. Skeletal muscle. Voluntary. |
Three regions of the Male Urethra | 1. Prostatic urethra. 2. Membranous urethra-shortest; external urethral sphincter on either side. 3. Spongy urethra-longest. |
Micturition or Urination | Controlled by centers in the pons & sacral spinal cord. Parasympathetic division stimulates it. Sympathetic inhibits it. |
Micturition Reflex | Stretch receptors in the bladder are stimulated. Internal & external urethral sphincters relax. Detrusor & abdominal muscles contract. |
Urinary Incontinence | Inability to control urine expulsion. Most common-old women. 2categories: Stress incont-exercise/coughing. Urge incont-not getting warning message-immediate bladder contraction.Causes-weight gain/pelvic surgery/diabetes/constipation/pregnancy/bigprostate. |
Urinary Tract Infections (UTI) | Bacteria (E. coli) or fungi multiply in urinary tract. More common in women-short urethra, proximity to anus, sex. Symptoms: dysuria, urgency, pressure in pelvic region, fever, nausea, vomiting, back pain. Testing through urinalysis. |
Urethritis | Inflammation in urethra. |
Cystitis | Inflammation in bladder. |
Pyelonephritis | Inflammation in kidney. |
Urolithiasis or Kidney Stones | Formed from crystalline minerals-75%calcium. Causes-inadequate fluid intake, diet. Small stones can be asymptomatic & easily passed. Larger stones can become stuck in urinary tract. May cause severe cramping, nausea/vomiting, hematuria. Ultrasound/surgery |
Renal Failure | Dialysis: Blood cycled through a machine. Done several times/week. Kidney transplant: immunosuppressant drugs taken throughout life. You may donate a kidney while living. |
Kidney Variations and Anomalies | Renal agenesis. Pelvic kidney. Polycystic kidney. Horseshoe kidney. Supernumerary kidneys. duplicated or bifid ureter (divides). Multiple renal vessels. |
Kidney Development | Metanephros becomes adult kidney. Metanephric duct becomes ureter. |