1. Excretory System
Chapter 38
Section 3

2. Excretion
The process by which excess substances and waste products are removed from an organism
Organisms would die if wastes were not removed
Also removes excess heat from an organism to help maintain homeostasis by maintaining a constant temperature

3. Organs of Excretion
Lungs
Kidneys
Liver
Skin

4. Metabolic Wastes CO2 and H2O from cellular respiration
Nitrogen compounds (ammonia, urea, uric acid) produced during the breakdown of amino acids
Mineral salts (NaCl, K, sulfate)- are products of other metabolic reactions
REMEMBER- Egestion is the elimination of undigested food- NOT metabolic waste!!

5. Excretion in Protists Wastes diffuse out of the cell into water
CO2, mineral salts, ammonia (NH3) are the waste products
NH3 is soluble in water
Water is also a waste product and the removal of water requires active transport
Water collects in the contractile vacuole and is periodically expelled

6. Diagram of Paramecium
Biology A Paramecium Osmoregulation

7. Excretion in the Hydra Wastes diffuse out of the cells
Water is removed through active transport

8. Excretion in the Earthworm
Most cells are not in contact with the environment
Requires special organs- Nephridia
There are 1 pair of nephridia in each body segment
Cellular wastes diffuse into the body fluid which enters the nephridia
Cilia moves fluid through a tubule which ends in a bladder

9. Earthworm (continued)
The bladder opens to the environment through a nephridiopore
Wastes leave the earthworm as urine- made of water, mineral salts, NH3, and urea (made from NH3 and CO2 and is soluble in water)

10. Diagram of an Earthworm

11. Excretion in the Grasshopper
Excretory organs are the Malpighian tubules
Wastes in the blood enter tubules through diffusion and active transport
These wastes then enter the intestine
Uric acid is formed- dry nitrogenous waste product which is excreted through the anus and is not soluble in water
This conserves water in the grasshopper

12. Diagram of a Grasshopper

13. Excretion In Humans- Liver
Removes harmful substances (bacteria, drugs, hormones) from blood
Changes these substances to less harmful forms (detoxification)
These substances are then returned to the blood
Cirrhosis-
Liver becomes nonfunctional
Detoxification can not occur
Due to overloading the liver with toxins

14. Liver (continued) Jaundice- Build-up of metabolic wastes in the bile
Occurs when the liver is not functioning
Bile is not excreted properly
Skin looks yellow due to build-up of hemoglobin products

15. Liver (continued)
Excess amino acids are broken down in the liver form ammonia (very poisonous) to urea (less poisonous)
Urea diffuses into the blood and is brought to the kidneys

16. Urinary System Made up of- Kidneys- produce urine
Ureter- tube which takes urine to
Urinary bladder- stores urine
Urethra- tube through which urine is excreted to the environment

17. Kidneys 2 of them in the back, just below the diaphragm
Remove wastes of cellular metabolism
Regulate concentration of water, salts, other substances
Can not live without kidneys

18. Structure of the Kidneys
Cortex- outer part
Medulla- middle part
Pelvis- inner part
Blood is filtered through the cortex
Medulla is made up of tubes- collecting ducts
Collecting ducts carry filtered substances (filtrate) to pelvis

19. Kidney (continued) Pelvis is a cavity connected to the ureter
Urine is formed from the filtrate and drains into the ureter
Kidney is made up of many nephrons
Nephrons filter wastes from blood
One part of the nephron is in the cortex (glomerulus), the rest is in the medulla (loop of Henle)

20. Kidney (continued)
Renal arteries bring blood with the metabolic wastes to the kidney
These arteries branch into capillaries which form the glomerulus (part of the nephron)
Blood leaves the kidney through the renal vein
Wastes are left in the kidney

21. Diagram of Kidney
Diagram of Kidney

22. Urine Formation
1st stage- wastes AND useful substances are filtered out of the blood (filtration stage)
2nd stage- useful substances are reabsorbed by blood (reabsorption stage)
Reabsorption is important in conserving water
Increases the concentration of the filtrate

23. Urine Formation (continued)
Glucose, amino acids, Na+, K+ are reabsorbed
Kidneys can only reabsorb so much of a substance, if the blood has too much, it will be excreted (glucose in diabetes)
After reabsorption, urine remains
Urine is made up of water, urea, salts

24. Urine Formation (continued)
Kidney stones- substances which crystallize in the kidney or ureter
Dialysis- machine which filters blood when kidneys fail

25. Lungs
Excrete CO2 and H2O

26. Skin 2 Layers- Epidermis protects the dermis Dermis-
Epidermis- outer layer
Dermis- inner layer
Epidermis protects the dermis
Dermis-
Elastic connective tissue
Contains sebaceous glands, sweat glands, blood vessels, hair follicles

27. Skin (continued) Protects the body Is waterproof
Sweat contains water, small amount of urea, and salts
Removes excess heat by evaporation of sweat and opening of blood vessels
Shivering and muscle tension produces heat