Excretory system
remove toxic by-products from metabolism, particularly nitrogenous wastes that result from breakdown of proteins and nuclei acids
What goes in must come out!
Types of metabolic wastes depend on evolutionary history and habitat.
• Ammonia • Urea – 100,000x less toxic – Most toxic so than ammonia so needs large needs relatively amounts of water little water to get rid to get rid of it. of it. – Highly soluble in – Highly soluble in water. water. – Most aquatic – Mammals, some animals. fish, most adult amphibians.
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• Uric acid –Relatively nontoxic so needs no water to get rid of it. –Largely insoluble in water. –Birds, insects, many reptiles, land snails, few amphibians living in desert.
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Different waste products removed from body.
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Liver
Worn out RBCs/excess amino acids. Mineral salts bile duct SI anus
• Lungs
– CO2, H2O (~350 mL daily), heat from cellular respiration.
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Spleen
Worn out RBCs. Minerals kidney/skin.
• Excretory system
– Nitrogenous wastes from protein metabolism. – Urine kidneys urethra
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Skin
Heat, urea, salts, water All pores
• Large intestines
– Solid wastes/some water. – All anus
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Four major processes of production and disposal of urine
• Filtration-water/molecules small enough to be forced through capillary wall enter nephron tubule from glomerulus. Reabsorption-water and valuable solutes, including glucose, salts, and amino acids, are reclaimed from filtrate and returned to blood. Secretion-certain substances removed from blood/added to filtrate.
– – Excess K+/H+ in blood removed. Excess H+ keeps blood from becoming too acidic.
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•
•
Excretion-urine passes from kidneys, to (c) and out urethra. ureters, bladder 2007 brainybetty.com ALL
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Nephrons (~1 million filtering units per kidney) and urine formation
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• • •
•
Renal arteries Capillaries Glomerulus (tightly coiled capillaries where blood is under high pressure Bowman’s capsule (cup-shaped swelling that collects fluid)
– Filtrate contains water, urea, solutes (Na+, K+, Cl-, HCO3-), glucose, amino acids RBCs, platelets, proteins, lipid molecules left in (c) 2007 brainybetty.com ALL blood
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Convoluted tubulefour parts:
1. Proximal tubulereabsorption of water, sodium, amino acids, glucose 2. Loop of Henlereabsorption of water, salt
– Descending limb freely permeable to water/not salt – Ascending limb less permeable to water/permeable to salt
3. Distal tubulereabsorption of water and salt, secretion of acids, toxins, ions into tubule 4. Collecting ductremaining water/salts, all urea stay and are carried out of kidneys as urine – Blood leaves kidneys thru venules to all body parts, free of wastes
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• Ureters-two tubes where wastes are funneled from kidneys • Urinary bladder-sac that stores urine until muscular contractions force the urine out of the body • Urethra-tube carrying wastes from urinary bladder out of body
• Kidneys produce ~1.5 liters of urine daily
– Straw color due to pigment (urochrome). – Average pH of urine is ~6.0 (slightly acidic).
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More H2O releaseddecreases rate of reabsorption
Promotes water retention by kidneys and concentrates urine.
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• Many diuretics interfere w/ADH production, increasing the volume of urine produced.
– Drinking beer (alcohol) or coffee (caffeine) both inhibit secretion of ADH, person urinate more frequently. – Eat salty foods-kidneys return less salt to blood by reabsorption and excess excreted in urine.
• Aldosterone stimulates reabsorption of sodium/chlorine ions. • Parathyroid hormone increases rate of reabsorption of Ca/Mg from urine.
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Homework:
Read 39.3, pp. 997-1000 1. Make a chart for the lungs, skin, liver, spleen, large intestines and kidneys. Fill in columns for what each excretes and where. 2. List the organs through which urine passes. 3. Describe how a nephron works. Include what is removed and returned to the blood. 4. What is the function of aldosterone? How is this different from parathyroid hormone? 5. Explain how the hypothalamus regulates urine output. pp. 1001-1003, #1-20; 21, 22, 24; 29, 31 (use chart #30); Assessing Knowledge & Skills #1-3 Do Worksheet, pg. 166 http://www.glencoe.com/sec/science/biology/bio2000/pdfs/bdol37-3.pdf Do quiz and submit as before. http://www.glencoe.com/qe/science.php?qi=2527
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