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प्रश्न
Veins have valves that allow blood to flow only in one direction. Arteries do not have valves. Yet the blood flows in one direction only. Can you explain why?
उत्तर
Blood flow in arteries is rapid as the blood in them is under great pressure. Thick elastic walls of arteries are not collapsible and maintain one direction rapid flow.
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संबंधित प्रश्न
The liquid connective tissue A circulates in our body continuously without stopping. This tissue contains a pigment B which imparts it a colour C. The tissue A consists of four components D, E, F and G. The component D fights infection and protects us from diseases. The component E helps in the clotting of tissue A if a person gets a cut. The component F is a liquid which consists mainly of water with many substances dissolved in it and component G carries oxygen from the lungs to all the parts of the body.
(a) What is (i) tissue A (ii) pigment B, and (iii) colour C?
(b) Name (i) D (ii) E (iii) F, and (iv) G.
(c) Name one substance (other than oxygen) which is transported by tissue A in the human body.
(d) Which two components of tissue A are the cells without nucleus?
(e) Name any two organisms ( animals) which do not have liquid like A in their body.
A patient with blood group O was injured in an accident and has blood loss. Which group of blood should be used by the doctor for transfusion?
Match the following.
| 1. Leukaemia | (a) Thrombocytes |
| 2. Platelets | (b) Phagocyte |
| 3. Monocytes | (c) Decrease in leucocytes |
| 4. Leucopenia | (d) Blood Cancer |
| 5. AB blood group | (e) Allergic condition |
| 6. O blood group | (f) Inflammation |
| 7. Eosinophil | (g) Absence of antigen |
| 8. Neutrophils | (h) Absence of antibody |
Why is the colour of the blood-red?
Direction: In each of the following questions a statement of assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Mark the correct statement as.
Assertion: RBC plays an important role in the transport of respiratory gases.
Reason: RBC does not have cell organelles and a nucleus.
Direction: In each of the following questions a statement of assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Mark the correct statement as.
Assertion: Persons with AB blood group are called a universal recipient because they can receive blood from all groups.
Reason: Antibodies are absent in persons with AB blood group.
The volume of blood in human adults is ______.
Crab has blue blood.
Name the organ which is located in the chest cavity with its lower tip slightly tilted towards the left.
Name the only artery that carries carbon dioxide-rich blood.
