Chapter 31

Chapter 31 - 03/12/08 Chapter 31 The Urinary System...

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03/12/08 Chapter 31 The Urinary System Digestive system is unselective The excretory system restores and maintains the proper internal amount minerals, water, sugar, protein, fat, etc. in the body despite differences in diet. Introduction Picture: Kangaroo rat- rodent- mammal with urine 3.5-4% more concentrated than ours, makes sense because it lives in dry place Functions of excretory system: All performed simultaneously as blood is selectively filtered by kidneys; water and nutrients returned to blood 1. Excretion of cellular waste products a. Urea + ammonia (predominate waste), toxins, excessive water and nutrients collected by the kidneys and eliminated from body as urine b. Urea (toxic) is removed as ammonia (toxic) from blood. Liver helps convert ammonia to urea and then kidneys filter out urea and other wastes. c. Fig 31-3 2. Regulation of fluid composition (ions, water, nutrients) 3. Secretion of hormones Simple excretory system 1. Flame cells in flatworms (simplest excretory system). Network of tubes through body that end in bulbs called flame cells. H2O and dissolved wastes filtered into bulbs. a. Return water and nutrients to body b. Waste directed to pores which release to outside of body c. Fig 31-1 2. Nephridia in worms and mollusks function as simple kidneys a. We have about a million of these structures in each one of our kidneys b. Leads to water and nutrient reabsorbed into blood c. Urine-like waste stored in a bladder-like portions and excretory through pores in body wall
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d. Fig 31-2 3. Vertebrate excretory system (renal system) a. Kidney (filter)-> i. Made out of several different types of tissues ii. Fig 31-5 iii. You have 2; as big as his hand and a little bit over an inch thick iv. Nephron- important- have over a million (see above)
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Chapter 31 - 03/12/08 Chapter 31 The Urinary System...

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