2016年3月16日 星期三

F4 Biology teaching notes Ch 8: 2nd Term NE 7

Ø  Capillary (微血管)   CE-2005-I-B-Q8a
n  connect the arterioles (小動脈) to the venules (小靜脈).
n  form (13) capillary beds (微血管床)
in the body tissue to allow exchange of materials between
blood and body cells.

n  Structure of a capillary:

(14) one-cell
(15) differentially

n  adaptive features of capillary to facilitate (16) exchange of materials:

Feature
Description
Branched into an extensive network
increase the surface area for efficient exchange of materials
Large cross-section area
Reduce the blood flow rate, thus increasing the time of material exchange between the blood and the body cells
Thin wall (only (17) one-cell thick)
reduce the (18) diffusion distance across the blood vessels

Ø  The change in blood pressure along different blood vessels:           CE-2008-IB-Q9b
Blood vessel
Blood pressure
Arteries and arterioles
n (19) High due to the pumping action of the heart
n Changes (20) periodically as the heart contracts and relaxes
Capillaries
n Drops significantly because the small diameter of the capillaries offers a
high (21) resistance to blood flow
Veins and venules
n Much lower because the blood has overcome great resistance of the blood vessel walls after travelling a long distance

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