1. Excretion vs. Elimination

2. Excretion vs. Elimination
Your body makes several kinds of waste, which fall into two groups:
Undigested solid wastes
Wastes made by cells

3. Elimination
Undigested solid waste leaves your body through the large intestine
Water is removed from the wastes in the large intestine, which allows for the formation of a solid (feces).

4. The solid wastes moves from the large intestine to the rectum.
From the rectum, the solid waste is excreted through the anus.

5. Excretion
When waste products made by cells (water, heat, carbon dioxide, salts, urea) leave your body
In many animals, CO2 leaves the body through the lungs
The liquid waste, urine, is made in the kidneys

6. Urine: made up of water, heat, harmful chemicals (urea), and some salts
Perspiration: when heat, water, and salt are excreted by the body through skin (i.e. sweating)

7. Write the correct waste product next to the excretory organ:
1. Skin =
2. Large intestine =
3. Lungs =
4. Kidneys =
(word bank: carbon dioxide, solid wastes, salt, harmful chemicals, water, heat)

8. The waste products are:
Skin = water, heat, salt
Large Intestine = solid waste
Lungs = carbon dioxide
Kidneys = harmful chemicals, heat, salt

9. The Excretory System
The group of organs responsible for removing waste products from the body = the excretory system
The main organs are:
Lungs
Kidneys
Skin

11. Lungs
When we breathe, we excrete CO2 waste, and small amounts of heat and water
Fact: your lungs are capable of removing alcohol from the blood; this is how a breathalyzer is able to determine a person’s blood alcohol level

13. Skin Largest organ; excretes most of the body’s waste heat
Also removes some water, salts, and very small amounts of urea
Perspiration: helps the body ‘cool off’
When sweat evaporates from the skin, it cools the body, removing heat

15. Kidneys
Fist sized, bean shaped (i.e. kidney bean) organs found on either side of the lower spine
Main job is to filter out wastes from the blood, making them more concentrated in preparation for excretion and, in the process of doing this, retaining as much water as possible

17. The blood enters the kidney through the renal arteries; renal veins carry blood back from the kidneys to the body
A ureter connects each kidney to the urinary bladder; once urine has formed, the ureter carries the urine (produced after the blood has been filtered for wastes) from the kidney to the bladder

19. Another tube, the urethra, carries the urine out of the body
In males, the urethra passes through the penis; in females, it lies between the pubic bone and the front wall of the vagina

20. Label the diagram: bladder, kidney, renal artery and vein, ureter, urethra

22. Nephrons
The filtration of the blood takes place in minute structures called nephrons, found in the cortex, which is the outer layer of the kidney
The nephrons estimate at more than 1 million per kidney

25. In spite of their size, the kidneys filter more than 180 L of blood every 24 hours
Most is reclaimed by the body, only 1.5 L of urine is passed each day
Your blood passes through the kidneys 300 times per day

26. Label the Kidney: cortex, medulla, renal artery, renal pelvis, renal vein, ureter

28. Liver A secondary organ of excretion
Does not excrete wastes, but is important for excretion
Handles cell wastes in several ways:
1) Breaks down dead red blood cells: pass into digestive tract, then eliminated with solid waste by the bowels

29. 2) Weakens certain harmful substances
3) Changes some harmful substances
Ex: the liver makes bile from harmful substances – bile is important in fat digestion – after bile works on fat, it is eliminated from the bowels
4) Combines certain harmful chemicals
Ex) liver combines ammonia and some CO2 – forms urea, which the blood carries to the kidneys where it becomes part of the urine