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The Urinary System. Function Maintain the consistency of fluids in the body Similar to a water purification plant.

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Presentation on theme: "The Urinary System. Function Maintain the consistency of fluids in the body Similar to a water purification plant."— Presentation transcript:

1 The Urinary System

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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)

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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

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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

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20 Renal Tubule Filtrate leaves the glomerulus and travels through a set of small tubes = tubules About 3 cm long Three parts: 1)Proximal convoluted tubule (closer to glomerulus) 2)Loop of Henle 3)Distal convoluted tubule

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

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25 Quiz Click HereHere

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: 1)Glomerular filtration 2)Tubular reabsorption 3)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

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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 +, Mg 2+, Ca 2+ ) – Anions (HCO 3 -, Cl - ) HCO 3 - is bicarbonate; where did that come from? Small Intestine

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34 Tubular Secretion Disposing of certain drugs (penicillin, phenobarbital – seizures and anxiety) Eliminates urea – CO(NH 2 ) 2 – How body eliminates nitrogen Eliminates uric acid –C5H4N4O3–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

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40 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 Characteristics of Urine

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)

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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

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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

51 Hemodialysis Artificial kidney Patient’s blood is passed through membrane tubing that is permeable and wastes diffuse out of blood Usually done 3-4 times per week and each session takes 4-8 hours Life threatening kidney failure only becomes obvious after about 75% of renal function has been lost Only permanent solution is kidney transplant

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55 Ureters Tubes that take urine from each kidney to bladder Each begins at L2 Stretching of ureters causes peristalsis to push urine down

56 Urinary Bladder Smooth, collapsible, muscular sac that temporarily stores urine A moderately full bladder holds about 500mL of urine (2 cups)

57 Urethra Thin walled muscular tube that drains urine from the bladder to outside the body Has sphincters: Internal – involuntary sphincter keeps urethra closed when urine is not being passed External – voluntary sphincter that relaxes during voiding of urine

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59 Urinary Tract Infections Overall, 40% of all women get UTIs – Urethra is only 3-4 cm long – Proximal to anal opening – Improper toilet habits – Sexual intercourse can cause vaginal bacteria to move into urethra

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61 Incontinence Inability to control urination – Infants have not learned to control external sphincter – In older adults, the sphincter malfunctions

62 Crash Course Video About 12 minutes


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