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Excretion The process by which the body rids itself of metabolic wastes 1. 2. Lungs eliminate carbon dioxide Large intestine eliminates toxic digestive waste 3. Liver deaminates amino acids to form ammonia (NH3) -Ammonia is toxic so it is converted into urea. -Nucleic acids break down into uric acid. 4. Kidneys-remove urea and uric acid The Urinary System Two kidneys Ureters – tubes from kidney to bladder Bladder – stores urine Urethra – from bladder to exterior The Kidneys Function: to remove metabolic wastes from blood Also regulate pH and water balance of blood The Nephron Microscopic filters – 1 million in each kidney! Each kidney has 3 regions: 1) Cortex – outermost Contains most parts of nephrons 2) The medulla: middle region Contains loops of Henle, collecting ducts of nephrons 3) The renal pelvis: the mostly hollow innermost region Collecting ducts merge to form ureter The Urinary System Ureters have muscular walls – peristalsis About 25 cm long The Urinary System The urinary bladder – holds up to 600 mL Urinary System Urethra is longer in males (20 cm vs. 4 cm)– thus less infections get to bladder The Urinary System Micturition: the voluntary release of sphincters controlling the urine output from bladder Also aided by contraction of bladder wall Formation of Urine done by the nephrons three stages: filtration, absorption and secretion. Filtration High blood pressure in the glomerulus forces small molecules out of the blood and into Bowman’s Capsule Water, ions like Na+, Cl- and H+, amino acids, urea and glucose can pass into Bowman’s capsule Filtration Red blood cells, white blood cells and platelets can not move into Bowman’s capsule. (If they do it is a sign that something is wrong.) Filtration About 45 gallons (180 L ) per day passes through Bowman’s capsule. But only 1-2 L of urine is formed so what happens next? Reabsorption Essential nutrients and water are reabsorbed into the blood stream and distributed to the body. main site: proximal convoluted tubule also occurs in the loop of Henle, distal tubule and collecting ducts Reabsorption Na+ is moved back into the blood by active transport- requires energy Negative ions like Cl- will follow the Na+ due to charge attraction Glucose and amino acids are also reabsorbed by active transport Active transport may form vesicles Reabsorption The movement of solutes back into the blood creates an osmotic gradient so that water also moves into the blood by osmosis. Secretion Secretion – actively transporting materials back into urine from the blood. Ex) nitrogenous waste, water Occurs in the proximal and distal tubules. Secretion Proximal tubule secretes H+ which helps maintain pH balance Blood is neutral and H+ makes it acidic so it must be removed. Secretion Other things secreted include ammonia, potassium ions, penicillin, histamines, creatine, etc. Penicillin capsules Histamine release from a WBC Hormonal Control 1) Aldosterone is secreted from the cortex of the adrenal glands when blood pressure is low. Hormonal Control Low B.P is monitored by kidneys (juxtaglomerular complex) Hormonal Control Aldosterone causes the DCT and collecting ducts to increase Na+ transport into blood Chloride ions and water follow passively Hormonal Control Net result: Blood pressure increases and urine output decreases Hormonal Control 2) Antidiuretic Hormone (ADH) Produced by hypothalamus, stored in posterior pituitary gland Hormonal Control Hypothalamus monitors water content of blood (osmoreceptors) When the body is dehydrated, ADH is released. Hormonal Control ADH makes the nephron more permeable to water so more water is reabsorbed into the blood. As a result, the urine becomes more concentrated. When the body is well hydrated, the hypothalamus does not release ADH Diuretics like alcohol and caffeine inhibit ADH production So urine output increases Diabetes Mellitis inadequate secretion of insulin without insulin, blood glucose levels are extremely high, and excess glucose remains in the nephron. The high osmotic gradient prevents water re-absorption and increases urine production. Sugar is found in the urine Diabetes Insipidus lack of ADH production urine output increases up to 20L/day no sugar in urine Nephritis inflammation of the nephrons Protein in the urine is a common symptom The osmotic gradient also causes an increase in urine production. Nephritis can lead to irreversible kidney damage and eventual kidney failure. Dialysis Hemodialysis Artificial kidney machine connects to a vein and pumps blood through semipermeable tubes submerged in a solution to remove waste Dialysis Peritoneal dialysis-a catheter is inserted through abdominal lining. Fluid is injected to collect waste and is drained Kidney Stones Crystallized oxalic acid and/or calcium and/or phosphate Painful! Kidney Stones Treatment: Surgical removal Drugs to dissolve Lithotripsy-shock waves Kidney Transplant In 2002 there were 48 transplants done in Edmonton.