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Biology question(examination of capillary in a fish's tail)

Biology question(examination of capillary in a fish's tail)

1. Write a few points about the flow of blood in the capillary bed(e.g. fast/slow, direction of movement, the size of red blood cells compared to the diameter of the capillary, etc).

2. White blood Cells are larger than red blood cells. How are they moving in the capillaries which are of a smaller diameter without blocking them?

1 Answer

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  • 莫愁
    Lv 6
    1 decade ago
    Favorite Answer

    (1)The diameter of the capillary bed is smaller than that of RBC. RBC

    will be squeezed when passing through the capillary. This provides a

    larger surface area for material exchange.

    Besides, the narrower the diameter of the capillary, the slower will the

    blood flow the capillary bed. This increases the time for material exchange

    so that such action will become more complete.

    The capillary is made of arterioles and venules joined together and placed in

    interstitial fluid at tissue. The blood is thus flowing from arterioles to venules

    causing material to diffuse into and out of the interstitial fluid along the

    concentration gradient. Hence oxygen and nutrients at high concentration

    in arterioles diffuse into the interstitial fluid via the capillary wall, while

    carbon dioxide and metabolic wastes at high concentration in tissue diffuse

    from the interstitial fluid into the venules via the capillary wall.

    (2)The WBCs can move across the blood capillary wall by a process called

    diapedesis血球滲出. By means of diapedesis, WBCs can pass through the

    capillary without blocking themselves.

    WBC = white blood cell; RBC = red blood cell

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