The Urinary System

1. The Urinary System

3. Function • Maintain the consistency of fluids in the body • Similar to a water purification plant

4. Facts • Kidneys filter 200 liters of fluid every day • Removes metabolic waste, ions, toxins from the bloodstream • Help regulate blood pressure and secretes erythropoietin

5. Organs • Kidneys • Ureters • Urinary bladder • Urethra

6. Kidney Location • Superior lumbar region • T12 to L3 • Receive some protection from the lower ribs • Right kidney is crowded by liver so it lies slightly lower than left kidney • Weighs 150g (0.33 lbs) • 12cm long, 6cm wide, 3cm thick (about size of large bar of soap)

10. Internal Anatomy • Three regions: • Cortex • Medulla • Contains renal pyramids • Pelvis • Collects urine to send down ureter to bladder

11. Blood Supply • Under normal conditions, the renal arteries deliver approximately ¼ of blood supply to the kidneys every minute

12. Nephrons • Each kidney contains over one million tiny processing units called nephrons • They carry out the process of making urine • Each consists of: Glomerulus – mass of capillaries Bowman’s capsule – structure that collects filtrate from glomerulus

15. Glomerulus • Endothelium is very porous • Large amounts of solute-rich, protein free fluid pass from the blood to the Bowman’s capsule • This fluid (or filtrate) is raw material that is processed by the renal tubules to form urine

20. Renal Tubule • Filtrate leaves the glomerulus and travels through a set of small tubes = tubules • About 3 cm long • Three parts: • Proximal convoluted tubule (closer to glomerulus) • Loop of Henle • Distal convoluted tubule

21. Collecting Ducts • Receive filtrate from many nephrons • Give renal pyramids striped appearance

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26. Kidney Physiology • Of the approximately 1000mL of blood that passes through the glomeruli each minute, 650mL is plasma • About of 120mL of plasma is forced into the renal tubules • Equivalent to filtering entire blood plasma 60 times a day = 47 gallons • Kidneys consume 20-25% of all oxygen used by body at rest

27. Filtrate vs. Urine • Once filtrate has moved through the collecting ducts, it has lost most of its water, nutrients and essential ions • What remains is called urine and contains mostly metabolic wastes • About 1.5L of the 180L of filtrate leaves the body as urine • Rest is returned to circulation

28. Urine Formation Three processes: • Glomerular filtration • Tubular reabsorption • Tubular secretion

29. Glomerular Filtration • For the most part, filtration is a passive, nonselective process in which fluids and solutes are forced through a membrane by hydrostatic pressure • Very efficient because of high permeability and high blood pressure • 55mm Hg in contrast to other capillaries in body at 18mm Hg

31. Tubular Reabsorption • Our total blood volume is filtered into the renal tubules about every 45 minutes • If some was not reclaimed, all of our plasma would be drained away within an hour • This reclaiming process is called tubular reabsorption

32. Tubular Reabsorption • All organic nutrients (glucose, amino acids) are completely reabsorbed but the reabsorption of water and ions are regulated by hormones • Which hormone regulates the reabsorption of water by adjusting the permeability of the collecting ducts? Antidiuretic hormone • Reabsorption of: • Cations (Na+,K+,Mg2+, Ca2+) • Anions (HCO3-, Cl-) HCO3- is bicarbonate; where did that come from? Small Intestine

34. Tubular Secretion • Disposing of certain drugs (penicillin, phenobarbital – seizures and anxiety) • Eliminates urea • CO(NH2)2 • How body eliminates nitrogen • Eliminates uric acid • C5H4N4O3 • Uric acid is a product of the breakdown of purine nucleotides. Which ones are purines? adenine (A) and guanine (G) • High blood concentrations of uric acid can lead to a type of arthritis known as gout

35. GOUT Gout

36. Formation of Dilute Urine • Simple process because no water is absorbed in the renal tubules Formation of Concentrated Urine • Antidiuretic hormone (ADH) inhibits urine output by increasing reabsorption of water • During maximum ADH secretion, 99% of water is reabsorbed and returned to blood

37. Diuretics • Chemicals that increase urinary output • Alcohol inhibits ADH release • Caffeine, drugs for hypertension and edema from congestive heart failure inhibit sodium ion reabsorption which inhibits water reabsorption

38. Characteristics of Urine • Generally clear and pale to deep yellow in color • Color results from the body’s destruction of hemoglobin and creation of by-product bilirubin • More water = pale urine, and vice versa • Pink or brown urine can result from foods like beets or rhubarb or due to bile pigments or blood in urine • Cloudy urine may indicate infection of some part of urinary tract

40. Characteristics of Urine Odor • Fresh urine has a slight odor • Urine that is allowed to stand develops an ammonia odor due to bacteria • Some foods or drugs can create unusual odor • In persons with diabetes, urine can smell fruity when glucose is high

41. Chemical Composition • 95% of urine is water • 5% is solutes • Urea • breakdown of amino acids • Creatinine • Helps regenerate ATP, more in skeletal muscles • Uric acid • Breakdown of purines

42. Kidney Stones • Caused by Ca, Mg, or uric acid salts crystallizing in kidney • Most are smaller than 5mm so they pass without problems • Larger crystals can obstruct ureter • Prevention includes adequate hydration • Treatment includes shock wave lithotripsy (using ultrasound to break up stones)

47. Pyelonephritis • Infection of entire kidney • In females, usually caused by E. coli bacteria from anal area into urinary tract • Severe cases can result in abscesses that cause kidney to fill with pus • If left untreated, kidneys can be damaged

49. Renal Failure • Causes: • Repeated damage from infections • Physical injury to kidneys • Crush injury to skeletal muscles (releases myoglobin that clogs renal tubules) • Heavy metal poisoning (Hg or Pb) • Organic solvent poisoning (paint thinner, acetone, dry-cleaning fluid, etc.) • Inadequate blood supply (can occur in arteriosclerosis)

50. Physiology of Renal Failure • Filtrate formation decreases or stops • Nitrogen waste builds up • Blood pH becomes more acidic