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The Urinary System Glen Hookey Eric Kolker Justin Loeb Michael Ross Uston—Period 5 Overview Animals and Waste • Filter body fluid for toxins and unnecessary substances • Kidneys (bp, activation of vitamin D, erythropoietin, wastes) • Nitrogenous waste Transport Epithelium • • • • Manage solute levels Line many channels inside the body Comprised of special epithelial cells Can move solutes against gradient Nitrogenous Wastes • Three types: Ammonia, Urea, Uric Acid • Ammonia – Highly toxic, diluted with large supplies of water • Urea – Low toxicity, energy cost (used by mammals) • Uric Acid – Low toxicity, water insoluble, excreted as a paste Excretory Processes • Filtration – One layer of transport epithelium (large molecules removed); filtrate • Reabsorption – Active transport (glucose, amino acids, etc.) • Secretion – Materials added to excretory tubule • Excretion – Expelled as urine Filtrate/Urine Pathway Kidney • Filters substances form blood • Adjusts filtrate’s composition • Returns most substances to blood Nephron • Functional unit • Packed tubules • Surrounded by capillaries • Filters blood Bowman’s Capsule • Start of Nephron • Glomerulus • Filtration into lumen: – Water, salts bicarbonate, hydrogen ions, urea, glucose, amino acids Proximal Tubule • pH maintained • Reabsorption • Reabsorbs Na+ osmosis Loop of Henle • Descending – Water • Ascending – Thin & Thick – Passive & Active Distal Tubule • pH regulation • Sodium, calcium, potassium Collecting Duct • Subject to hormonal controls • Diseases • Concentration of filtrate Urine Composition • • • • • • Excess water and solutes Ions Urea Neurotransmitters Histamine Drugs/toxins Osmoregulation • Solute gradient • Bends in nephron • Membrane selective permeability • Diffusion • Active transport • Salt Solute Gradient • Membrane selective permeability • Interstitial fluid • Filtrate • Active transport • Diffusion Nephron Overview Proximal Tubule Distal Tubule Descending Loop of the henle Ascending Loop of the henle Collecting duct Gradient Overview Gradient #1: Proximal tubule • • • • • • Blood – ~300 mosm/L Interstitial fluid: – ~300 mosm/L Filtrate: – ~300 mosm/L – In: • Hydrogen ions • Ammonia – Out: • Bicarbonate • Salt • Water • Nutrients • Potassium ions In cortex Volume decreased Osmolarity stays constant Gradient #2: Descending Loop of the Henle – Interstitial fluid • 300 - 1200 mosm/L – Filtrate • 300 - 1200 mosm/L • In – N/A • Out – Water – Membrane permeable only to water – Salt concentration increases – Water diffuses out Gradient #3: Ascending Loop of the Henle • Ascending loop – Interstitial fluid • 1200 - 300 mosm/L – Filtrate • 1200 - 200 mosm/L • In – N/A • Out – Salt – Membrane permeable only to Salt – Salt concentration decreases – Filtrate osmolarity lowered to increase osmolarity of interstitial fluid Gradient #4: Distal tubule • Interstitial fluid – 300 mosm/L • Filtrate – 100 mosm/L – In • Potassium ions • Hydrogen ions – Out • Salt • Water • Bicarbonate • • Filtrate at lowest osmolarity Key role in determination of pH of urine Gradient #5: Collection duct • Interstitial fluid – 300 - 1200 mosm/L • Filtrate – 300 - 1200 mosm/L – In • N/A – Out • Salt • Urea • Water • • • • • Final stage Controls final salt output Low salt Water diffuses Concentrated filtrate Regulation #1: ADH • Antidiuretic hormone • Hormone • Activated by hypothalamus at high blood osmolarity • Decreases water loss – More permeability to water Regulation #2: RAAS • Renin-angiotensinaldosterone system • Angiotensin II • Activated at low blood pressure/volume • Decreases water loss – Constricts capillaries – More reabsorption of salt Regulation #3: ANF • Atrial natriuretic factor • Opposite of ADH and RAAS – Triggered by high blood pressure/volume – Inhibits NaCl absorption – Increased water loss through urine • Disables ADH Ureter • Lining of ureter • Smooth-muscle cells contractions • Ureter crosses bladder wall • Ureter in Micturition Urinary Bladder • • • • Storage organ Bladder in micturition Brain cells Structure Urethra • Function and location • Cells of Urethra • External Meatus Abnormalities of the Renal System • Acute • Chronic • Congenital Congenital Problems • Horseshoe kidneys – Functions as one kidney • Has to be cautious of rigorous activity Acute Problems • Usually reversible • Examples: stones, infections, tumors, inflammation, acute renal failure • Detected by urinalysis or by pain and fever Urinary Tract Infection (UTI) • Occurs anywhere along the urinary tract (kidneys, bladder) • Women more prone than men; shorter urethra • Pain and fever • Treated with antibiotics Tumors and Stones • Most tumors in kidneys and bladder are malignant • Smokers are prone to bladder tumors • Stones- intensely painful • Can be passed but some require surgery or ultrasound Trauma • Kidneys damaged by physical trauma • People with one kidney have to avoid potentially dangerous activities • Blood in urine Chronic Kidney Failure • Dialysis (3 days a week; 4 hours) – Cleans blood • Only cure is transplantation