biology 3 chapter 3.1

Controlling internal conditions 

• Waste products must be removed from the cells
• Internal conditions in the body must be kept constant

The human kidney 

• Chemical reactions in the body produces substances that are toxic eg: urea
• The kidneys excrete substances that the body does not want
• The kidneys first filter substances out of the blood, they reabsorb the substances that the body needs.

Dialysis

• When kidneys fail, the patient can be treated by dialysis
• A dialysis machine does the work of the kidneys and keeps patients alive
• …