1. The Excretory System
Big Q: What is the principle role of the structures of the excretory system?

2. Engage - Drat I Smell Scat
What are some things a scientist can tell about an animal by studying its scat?
What does this mean about excreted wastes?

3. Elaborate - Animal Excretion
Aquatic Animals - diffuse waste through their skin or gills
Terrestrial Animals - use organs to eliminate waste and water
1. Annelids and Mollusks - use nephridia to concentrate waste as it moves through the tubes
2. Insects and Arachnids - use Malpighian tubules to combine excretory and digestive wastes together
3. Vertebrates - use an excretory system

4. Nitrogen waste The kind of waste you make depends on where you live
Freshwater
ammonia
Land
urea
Egg layer
uric acid
Mode of reproduction appears to have been important in choosing between these alternatives.
Soluble wastes can diffuse out of a shell-less amphibian egg (ammonia) or be carried away by the mother’s blood in a mammalian embryo (urea).
However, the shelled eggs of birds and reptiles are not permeable to liquids, which means that soluble nitrogenous wastes trapped within the egg could accumulate to dangerous levels (even urea is toxic at very high concentrations).
In these animals, uric acid precipitates out of solution and can be stored within the egg as a harmless solid left behind when the animal hatches.

5. Nitrogen waste disposal in water
Freshwater animals
If you have a lot of water you can dilute the waste before it poisons you
excrete ammonia through gills and as dilute urine
If you have a lot of water you can urinate out a lot of dilute urine.
Predators track fish by sensing ammonia gradients in water.
Transport epithelia in the gills of freshwater fishes actively pump salts from the dilute water passing by the gill filaments.

6. Nitrogen waste disposal on land
Land animals
need to save H2O
evolved less poisonous waste product
urea
excrete urea & H2O as urine
The salt secreting glands of some marine birds, such as an albatross, secrete an excretory fluid that is much more salty than the ocean.
The salt-excreting glands of the albatross remove excess sodium chloride from the blood, so they can drink sea water during their months at sea.
The counter-current system in these glands removes salt from the blood, allowing these organisms to drink sea water during their months at sea.

7. What liquid waste do we make?
Digesting protein makes poison
nitrogen waste = ammonia = poison
C—OH || O H |
—C—
CO2 + H2O H N H
NH2 = ammonia

8. Explore - Composition of Urine
Analyze the data to draw conclusions about urine production
****Answer questions on your lab sheet

9. Explain - Excretion
Excretory System - removal of metabolic wastes from the body in order to maintain homeostasis
Main Players:
1. Skin
2. Lungs
3. Liver
4. Kidneys
Urine - contains urea, salts, water, sugar, and nutrients

10. Elaborate - Skin, Lungs, and Liver
Skin - removes excess water, salt, and urea through sweat
Lungs - removes carbon dioxide and water vapor through exhalation
Liver - converts nitrogenous waste into urea

11. Human kidney Mammals have a pair of bean-shaped kidneys
supplied with blood by a renal artery and a renal vein
In humans, the kidneys account for less than 1% of body weight, but they receive about 20% of resting cardiac output

12. Nephron = Kidney’s filter
Not filtered out
cells
proteins
Filtered out
urea
sugars
salts
H2O
toxins from food
Makes
urine
Filtrate from Bowman’s capsule flows through the nephron and collecting ducts as it becomes urine.
Filtration occurs as blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule.
The porous capillaries, along with specialized capsule cells called podocytes, are permeable to water and small solutes but not to blood cells or large molecules such as plasma proteins.
The filtrate in Bowman’s capsule contains salt, glucose, vitamins, nitrogenous wastes, and other small molecules. ↓
to bladder

13. Elaborate - Nephron Structure
Glomerulus - a network of capillaries that filters blood
Bowman’s Capsule - takes in the materials from the glomerulus for urine production
Loop of Henle - conserves water and puts it back in the body
Collecting Duct - pass urine to the ureter for removal

14. Explain - Pathway of Urine
Ureter - tubes that transport urine from the kidney to the bladder
Bladder - storage site of urine
Urethra - pathway for urine out of the body

15. Elaborate - Diseases of the Excretory System
Urinary Tract Infection - bacterial infection
Gout - build up of uric acid in the blood
Acne - clogged pores
Kidney Stones - calcium or protein deposits in the kidney
Cirrhosis - damaged liver tissue due to toxins

16. Evaluate - Bioartificial Kidneys
Read the passage on page 799.
How does the artificial kidney dialysis help a person who has kidney failure?
Where do the living kidney cells in the RAD come from?
What do those cells do that an artificial dialysis machine cannot do?