Excretion:
- Is a process of getting rid wastes resulted from food burning inside the body cells .
- How does a body get rid of harmful wastes?
- The body gets rid of these wastes through:
a- The respiratory system.
b- The urinary system .
c- The skin.
- As a result of breaking down of food in the cells, carbon dioxide and water vapour "wastes" are produced
- waste gases are carried by blood traveling through the veins to the lungs , where exhalation process takes place and gases are removed from the body .
The human urinary system:
It consists of:
- The two kidneys
- The ureters
- The urinary bladder.
- The kidneys are dark red and shaped like phallus seed
- they are located near the back of the abdomen
- one on each side of the vertebral column
- A tube " ureter" runs from each kidney .
Its function :
They filter the blood to separate the harmful substances "urea , uric acid, excess salts and water "
- They separate these waste substances from the blood to form "Urine".
_ they are two tubes that connect the kidneys to the urinary bladder .
- It stores the " urine " until it is released from the body through the urinary tract to outside .
Urine:
- A watery liquid containing urea , uric acid , excess salts and other excretory substances , produced by the kidneys .
- Factors affecting the amount of excreted urine:
1- Temperature
2- Activity of the body.
3- Amount of drink water.
The role of the skin in excretion process
The human skin structure:
1-Epidermis
- It contains pores
- Sweat comes out from the skin through the pores
2-Dermis
- Is the second layer
- It contains
- Blood vessels
- Sweat glands
- Nerve endings
- Hair follicles
The sweat
- It is excess salts dissolved in water.
Functions of the skin:
A - Excretory function:
- Because it removes excess salts and excess water from the blood in the form of sweat.
B- Protective function:
- Because it protects the body against microbes and dryness
c- Sensory function:
- Because it feels touch, pressure, pain and temperature.
