BIOLOGY [3 marks Question Answer]

Plasma: The plasma is a light-yellow coloured, alkaline liquid which mainly consists of:

1. Water- 90-92%
2. Proteins – 7-8%
3. Inorganic salts – 1%
4. Other substances – traces

Cellular elements : These elements are of three categories:

1. Red blood cells (erythrocytes)
2. White blood cells (leukocytes)
3. Blood platelets (thrombocytes)

During surgical operation or an accident when excess of bleeding takes place, the patient may be given blood from outside to save his life. The transfer of blood from the donor to the recipient is called blood transfusion.
The following precautions are taken before the blood is given to the needy person:

1. Matching of the donor’s blood with that of the recipient should be done.
2. It should be made sure clinically that blood of donor is free from any infection.
3. Sterilization of all the instruments to be used during the operation is must.

Transfer of blood from one person to another is called blood transfusion. Ill or seriously injured people may need it. But compatibility of the blood groups is checked first. People with blood group AB are called universal recipients and people with blood group O are called universal donors.

Blood group	Can donate blood to	Can receive blood from
A	A and AB	A and O
B	B and AB	B and O
AB	AB	All groups
O	All groups	O

The four types of blood in humans are called blood groups. These are A, B, AB and O. The blood is determined by the antigens present on the RBCs. RBCs also contain antibodies in the plasma.

Blood group	Antigens in RBCs	Anitbody in plasma
A	A	Anti-B
B	B	Anti-A
AB	A and B	None
O	None	Anti-A and Anti-B

The circulatory system in human beings consists of heart, blood vessels (arteries, veins and capillaries) and blood. Blood circulates throughout the body in blood vessels by the pumping action of the heart. The impure blood is carried by veins from all parts of the body to the heart. The heart pumps it into the lungs where blood is oxygenated and carried back to the heart. From heart, the oxygenated (pure) blood is pumped to all parts of the body through arteries.
Thus, the circulatory system forms the transport system carrying food, oxygen, waste products, nutrients etc. throughout the body.

Blood vessels are a necessaiy part of the body’s circulatory system. The blood vessels carry blood throughout the body.
Three types of blood vessels are :

1. Arteries: They carry oxygenated blood from the heart to all parts of the body.
2. Veins: They carry deoxygenated blood from the body cells to the heart.
3. Capillaries: They form the connection between the arteries and the veins where exchange of substances takes place

The heart is a pump that circulates blood to all parts of the body. It is about the size of a human fist and located to the left in chest cavity. It has four chambers – two upper chambers called auricles or atria and two lower chambers called ventricles. The auricles receive blood from different body parts and ventricles pump the blood out of the heart. The valves between auricle and ventricle on each side allow blood to flow in one direction only. Heart acts as a double pump. The right side of the heart carries deoxygenated blood to the lungs to be oxygenated. The left side of the heart pump oxygenated blood to the body.