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3.12 The Excretory System. Pages 210-214. Kidneys. The kidney is the size of a fist and a mass of approximately 500 grams. Metabolic Waste. Waste is produced from the break-down of proteins. Deamination. We eat protein. We use protein for building and repair. - PowerPoint PPT Presentation
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3.12 The Excretory System
Pages 210-214
Kidneys
• The kidney is the size of a fist and a mass of approximately 500 grams.
Metabolic Waste
• Waste is produced from the break-down of proteins.
Deamination
• We eat protein.• We use protein for building and repair.• The liver breaks down extra protein.• The amino group, NH2 , is converted to
ammonia, NH3 ,
Toxic
• The amino group, NH2 , is converted to ammonia, NH3
• Ammonia is toxic! 0.005 mg can kill you!
Solution…
• Combining ammonia with carbon dioxide makes urea, [NH2]2CO
• Urea is less toxic than ammonia• The blood carries urea to the kidneys where it
is excreted in the urine
Kidneys
• Filter blood
Renal arteries
• Bring blood to the kidney.
Renal Veins
• Return “cleaned” blood to the circulatory system.
Ureters
• Carry urine from the kidneys to theBladder.
Bladder control
• A sphincter at the base controls the bladder• 200 mL …signal sent “Go to the bathroom”
• 400 mL …urgent signal sent “ Go to the bathroom right now!”
• 600 mL …too late
Ureter
• The tube that carries urine from the bladder to the exterior of the body.
Urine formation
• Step #1 filtration• Step #2 reabsorption• Step #3 secretion
Nephrons
• One million per kidney
Bowman’s capsule
• The cup-like structure that surrounds the glomerulus.
The glomerulus
• Cluster of capillaries• The area of fluid filtration
Proximal tubule
• a hollow, winding large diameter tube • for the reabsorption of glucose, sodium,
amino acids • these are pumped back into the capillaries• urea stays in the tube
Descending loop of Henle
• Straight part of the loop moving away from the proximal tubule
• Water flows out by osmosis
Ascending Loop of Henle
• Straight part of loop heading to distal tubule• Sodium pumped out of tube
Distal tubule
• A hollow winding large diameter tube.• Reabsorption of water if needed.
Collecting Duct
• System of urine collecting ducts that widen as they near the renal pelvis
• Wastes are transferred from the capillary network to the duct.
• Water moves by osmosis from the duct to the surrounding blood.
#1 Filtration
Moves from glomerulus to Bowman’s capsule:• Water• Salt• Glucose• urea
#1 Filtration
Does not move from glomerulus to Bowman’s capsule:• Plasma proteins• Blood cells• Large platelets
volume
• 600 mL blood through each kidney per minute
Reabsorption
• 119 of every 120 mL of fluid is returned to the blood
Urine
• 95% water• 5% salts, urea etc.