THE BLOOD AND WHAT IT IS MADE OF
Some of us have played either the football or netball. Occasionally, we have obtained some wounds or have seen someone wounded. Others have had accidents when they cut their hands with blade or knife. This is bad and should be avoided. But, where there is a cut what do you notice?
A red liquid comes out of the body. This red liquid is known as blood.
you can read about blood circulation here
After a few minutes what happens? The blood forms a red solid part and a watery part which looks yellowish in colour.
This watery part is called plasma.
The solid part contains two types of cells which is
BLOOD AND WHAT IT CONTAINS
WHAT ARE THE BLOOD CORPUSCLES?
a. The red blood corpuscles: These are small rounded cells which appear red. They contain a substance called the haemoglobin. This haemoglobin likes oxygen. In the lungs, it takes up oxygen and is carried by the red blood corpuscles to all part of the body. In the body, oxygen is set free for the body to make use of.
The body has about 30,000,000 million red blood corpuscles
b. The white blood corpuscles: these cells, like soldiers, defend the body against some germs which cause diseases. They are bigger than the red blood corpuscles and can move about slowly in the blood. About 42,000 million white blood cells are found in the body.
FUNCTIONS OF THE BLOOD
The blood does a lot of work in the body
i. The blood carries digested food substances such as glucose (sugar) and amino-acid (proteins) from the intestines to all parts of the body where they are needed.
ii. The red blood corpuscles of the blood take oxygen from the lungs to other part of the body. The waste products such as urea and carbon dioxide are carried in the blood. Urea is removed from the body as urine while carbon dioxide is expelled when we breathe out.
iii. The white blood corpuscles fight and destroy germs in the body. They can also prevent them from entering the body especially at wounded areas.
HOW THE BLOOD MOVES ROUND THE BODY
Our body is like a small town. Just as water in the town travels to all houses through pipes, the blood in the body travels to all houses through pipes, the blood in the body travels to all parts through its own small pipes called the blood vessels. The vessels that carries pure blood are called arteries while those that carries impure blood are called veins. The smallest blood vessels are called capillaries.
In towns, water is pumped to houses at the power station. In the body, the power station from where blood is pumped to all parts of the body is called the heart.
THE HEART IS THE ORGAN THAT PUMPS BLOOD
The heart is found inside the chest. Touch the left side of your
chest with your hand. You will notice the beating of the heart. This beating continues throughout life. When it stops death occurs.
The heart is like a `top’ or cone. Its walls are very thick. The thick walls help to pump blood round the body.
the heart is divided into four chambers.
These are the left and right auricles and the left and right ventricles. The walls of the ventricles are thicker than those of auricles.
From the heart arise a number of blood vessels or pipes which bring in or take away blood during its journey round the body. The most important of these blood vessels are the aorta and the pulmonary artery. The aorta takes blood to all parts of the body while the pulmonary artery takes impure blood from the body into the lungs where it is purified. The heart has some valves which prevent blood from moving backwards.
BLOOD ROUND THE BODY
When the left ventricle contracts the pure blood is pumped from the ventricle into the aorta which takes it to all parts of the body such as the head, arms, intestines, kidneys and legs. From all these places blood which is now impure is brought back into right auricle of the heart.
From the right auricle the impure blood is pumped into the right ventricle from where it is pumped again into the lungs to obtain fresh oxygen.
Pure blood from the lungs returns to the left auricle of the heart. From the left auricle it passes into left ventricle for the journey round the body to start again.
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