Body cells produce wastes as they do their jobs. Cell
wastes are excreted from the body through the lungs
(respiratory system), skin, and kidneys.
Not all wastes are harmful but your body cannot use them.
Nitrogen is a waste produced by body cells; it is released
when cells break down protein. Protein is necessary for cell
growth and repair.
Blood carries oxygen to the body cells and wastes to the
organs that excrete them.
EXCRETORY SYSTEM
1- Blood containing cell wastes enters the kidneys
a-kidneys are the main organs of the excretory system
2- Blood is filtered in the kidneys - cell wastes are removed
These wastes include nitrogen wastes, some salts, and
excess water and form a liquid called urine.
3- Urine flows from the kidneys through tubes called
ureters.
4- The ureters empty into the urinary bladder. The bladder
is a muscular, baglike organ that stores urine until it
leaves the body.
5- When the bladder is full, a message is sent to the
brain. You know it's time to empty your bladder. Urine
leaves the body through the urethra.
Veins carry the cleaned blood away from the kidneys and
back to the heart to be pumped throughout the body.
The kidneys clean your blood about 40 times a day.
If the kidneys are unable to clean the blood, you would
rely on kidney dialysis where a machine would filter wastes
from the blood for you.
DIGESTIVE WASTES
1- Food you eat goes to the stomach where it is partly
digested.
2- The stomach pushed the partly digested food into the
small intestine. Digestion continues and nutrients are
taken into the blood.
3- Any undigested food passes into the large intestine
(colon). Salts and water are removed from wastes to
make it more solid.
4- Waste is eliminated from the body.
WATER EXCRETION AND REPLACEMENT
1- Water vapor is included in the air you exhale
e.g.- you can see your breath on a cold day
2- Water is part of urine
3- Water is lost through the skin - perspiration
a - glands in the skin make sweat
b - sweat evaporates on the skin to cool you off
c - perspiration helps maintain body temperature
The body rids itself of excess water through the kidneys,
skin, and lungs.
We need to replace the water our body loses to stay
healthy.
Our bodies excrete water to prevent water from building
up,
to help get rid of certain wastes, and to maintain normal body
temperature.