What are the components of blood?
The average adult person has about 4 to 6 litres of blood and the study of blood is known as haematology. Four component of blood are as follows:
1. PLASMA: Plasma is pale yellow in colour, slightly alkaline and viscous fluid. It has fixed chemical composition: 90% water and 1% inorganic salts; and inorganic salts and 7 to 8% proteins. The remaining 1- 2% of the plasma is formed by food materials and waste products, dissolved gases, regulatory substances, anticoagulants cholesterol and the antibodies.
2. RED BLOOD CELLS (RBC): Red blood cells are red in colour due to the presence of a red, oxygen carrying pigment called haemoglobin; in the cytoplasm and are most abundant cells in the human body. Their shape varies in different vertebrate classes. In some like fishes, amphibians, reptiles, they are oval, biconvex and nucleated. In mammals, they are circular, biconcave, de-nucleated discs etc.
3. WHITE BLOOD CELLS (WBC): The white blood cells are also known as leucocytes; it fights from the infection and protect us from diseases that may occurs from the pathogens. White blood cells make chemicals ‘antibodies’ which usually fights against infection. They lack haemoglobin and are rounded irregular shaped cells which changes their shape and capable of doing amoeboid movement.
4. PLATELETS: Platelets are pale yellow in colour and are also called thrombocytes; are the tiny fragments of megakaryocyte cells in which cytoplasm remains enclosed by the piece of plasma membrane but lacks nuclei. Thrombopoietin hormone is produced by the liver which increases the number of megakaryocytes in the bone marrow and which automatically stimulates platelets production. Platelets are mainly involved in blood clotting (transformation of blood from liquid into solid gel). They helps to stop blood loss from the damaged blood vessels by forming platelet plus (thin layer). Their granules contains chemical when they released which promotes blood clotting.
Popular Questions of Class 7 Science
- Q:-
Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food - Q:-
Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.
Down Across
(D) 1 : Thorough washing (A) 1 : Keeps warm
2 : Animal fibre 2 : Its leaves are eaten by silkworms
3 : Long thread like structure 3 : Hatches from egg of moth
- Q:-
Sketch the cross section of soil and label the various layers.
- Q:-
Here is a crossword puzzle: Good luck!
Across
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from human bodyDown
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water - Q:-
Take three test-tubes. Fill æth of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2?
- Q:-
Sketch the reproductive parts of a flower.
- Q:-
Solve the following crossword puzzle with the clues given:
Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil. - Q:-
Describe how crystals of copper sulphate are prepared.
- Q:-
Match the items in Column I with those in Column II:
Column I Column II
(i) A home for living organisms (a) Large particles
(ii) Upper layer of the soil (b) All kinds of soil
(iii) Sandy soil (c) Dark in colour
(iv) Middle layer of the soil (d) Small particles and packed tight (v) Clayey soil (e) Lesser amount of humus - Q:-
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
Recently Viewed Questions of Class 7 Science
- Q:-
Fill in the blanks :
(a) The hotness of an object is determined by its __________.
(b) Temperature of boiling water cannot be measured by a _____________ thermometer.
(c) Temperature is measured in degree ______________.(d) No medium is required for transfer of heat by the process of __________.
(e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of ______________.
(f ) Clothes of ______________ colours absorb heat better than clothes of light colours. - Q:-
Show the shape of the distance-time graph for the motion in the following cases:
(i) A car moving with a constant speed.
(ii) A car parked on a side road. - Q:-
Fig.14.22 shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.
- Q:-
Match the following :
(i) Land breeze blows during (a) summer
(ii) Sea breeze blows during (b) winter
(iii) Dark coloured clothes are preferred during (c) day
(iv) Light coloured clothes are preferred during (d) night - Q:-
Match the items in Column I with those in Column II:
Column I Column II
(i) A home for living organisms (a) Large particles
(ii) Upper layer of the soil (b) All kinds of soil
(iii) Sandy soil (c) Dark in colour
(iv) Middle layer of the soil (d) Small particles and packed tight (v) Clayey soil (e) Lesser amount of humus - Q:-
Make a sketch showing groundwater and water table. Label it.
- Q:-
Which of the following relations is correct?
(i) Speed = Distance × Time (ii) Speed = Distance
Time(iii) Speed = Time (iv) Speed = 1
Distance Distance × Time - Q:-
Which type of lens forms always a virtual image?
- Q:-
11. A virtual image larger than the object can be produced by a
(i) concave lens (ii) concave mirror
(iii) convex mirror (iv) plane mirror - Q:-
Distinguish between a parasite and a saprotroph.
- NCERT Chapter