11. Explain briefly :
() Counting the pulse is counting the rate of heart
(ICSE 1995)
beat.
(ii) Why are capillaries thin walled ?
[ICSE 1997]
(iii) A matured mammalian erythrocyte lacks nucleus
and mitochondria.
(ICSE 2011, 2016]
(iv) Pulse.
[ICSE 2012, 2015)
() Blood flows in arteries in spurts and is under
pressure.
[ICSE 2016]
The figures given below are cross-sections of blood
Answers
Answer:
The capillaries are thin walled, because they help in the exchange of gases and diffusion of materials into the cells. This diffusion is possible due to the thinness of its walls.
Answer:
1--Your pulse is usually called your heart rate, which is the number of times your heart beats each minute (bpm). ... You check your pulse rate by counting the beats in a set period of time (at least 15 to 20 seconds) and multiplying that number to get the number of beats per minute. Your pulse changes from minute to minute.
2--The capillaries are thin walled, because they help in the exchange of gases and diffusion of materials into the cells. This diffusion is possible due to the thinness of its walls.
3--A mature erythrocyte lacks nucleus and mitochondria so as to make a place for the accommodation of more hemoglobin and hence more oxygen molecules. Lack of such organelles also provides the peculiar biconcave appearance of RBCs that aids in efficient diffusion. Young mammalian RBCs are nucleated.
4--As the ventricles of the heart contract, they push blood into the small lumen of the arteries with a great force, thus making the blood in the arteries flow in spurts and under pressure.
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