1. Introduction to the excretory system

2. What is HOMEOSTASIS?

3. What is HOMEOSTASIS?
Homeostasis is the process by which the body maintains “balance”. It describes the body’s ability to recover from some form of disturbance.

4. Example of homeostasis related to the musculoskeletal system
Homeostasis ensures that your internal body temperature is always 37°C.
Example of a way in which the body responds to extreme heat to maintain homeostasis:
Example of a way in which the body respond to extreme cold to maintain homeostasis:

6. Homeostasis
Internal temperature is not the only thing that the body must keep constant. Other aspects of homeostasis:
Concentration of solutions within the body
pH of substances within the body
Water
Blood pressure

7. If you’ve just eaten lunch, you’ve probably ingested a whole bunch of products that your body does not need. Rather than hold onto them and let them pile up, unwanted products are filtered out of your blood.
This is done by the kidneys.

8. Some notable waste products:
Mineral salts (such as potassium and sodium)
Nitrogenous waste (waste products that develop from the breakdown of proteins, such as urea).
Excess water

9. Review from sec 1/2
What is osmosis?

10. Review from sec 1/2 What is osmosis?
Osmosis is when a solvent moves across a semi-permeable membrane from an area of low concentration to an area of high concentration.

13. Using the concept of osmosis, explain what happens if you eat a lot of very salty food.
The salt concentration inside your body will go up. So, by osmosis, water will leave your cells to preserve the proper salt concentration.

14. Fun with osmosis #1
What would happen if you gave someone medicine via an IV bag of pure water?
Red blood cells have semipermeable membranes. Water will want to move toward the area of higher concentration (inside your salty red blood cells). They’ll expand and burst, and you’ll die 

15. Fun with Osmosis #2 How do plants absorb water?
Water moves into roots (semi- permeable) because the salt concentration in the roots is higher than the soil around it.

16. Fun with Osmosis #3
If you own a clownfish as a pet, what do you have to be careful about? Clownfish are saltwater fish. If they are put in freshwater, water will diffuse into their bodies, causing their organs to swell up.

17. Is it bad to drink too much water?

18. Where are the kidneys?

19. Where are the kidneys?
Behind your liver, at the height of your lower two ribs, protected by fat.

20. You can see how this works by looking very closely at the inside of a kidney.

21. Nephrons filter blood
Each kidney has over 1 million nephrons (very thin, long, twisty tubes)
At the glomerular capsule, water, glucose, vitamins, salt, urea, and other products are squeezed out of the blood.
They are reabsorbed in the Loop of Henle, as needed. Water moves in and out by osmosis.
Once the fluid has moved through the nephrons, it is collected into another tube called the ureter, and eventually becomes urine.

22. What does the colour of urine indicate?

23. How does this work?

24. Kidney Video

25. Excretory system… draw it!

26. Excretory system… draw it!
Urine goes from the ureter to the bladder where it is stored. It is then voluntarily released. The bladder can hold up to 1 L of urine.

27. What is Dialysis?
If your kidneys do not function properly, you can use machinery to filter your blood. It takes blood out of your body, filters out waste products, and then puts it back in.