21. The structure of the capillary aids its function by the following means:
a) The lumen or space within the capillary is narrow (1 red blood cell wide) so the capillary can fit into small places within the body tissues.
b) Pores or gaps are found between the endothelial cells lining the capillary, allowing plasma to leak into adjacent tissues and keep the moist. In addition, the pores allow phagocytes to squeeze out of the capillaries into the tissues in search of pathogens.
c) The cells lining the capillary are thin, allowing easier diffusion of materials into and out of the capillary (due to the shorter distance).
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