Question
Biology Question on body fluids and circulation
Blood capillaries are made of
endothelium, connective tissue and muscle fibres
endothelium and muscle fibres
endothelium and connective tissue
endothelium only.
endothelium only.
Solution
The wall of capillaries is very thin (usually less than one micron) and have numerous minute pores and made up of only endothelium. Exchange of material takes place between blood and tissue fluid across the endothelial membrane of capillaries through active diffusion. The wall of blood vessels (arteries and veins) is made up of mainly 3 layers - the outer most tunica externa has connective tissue, collagen fibres, lymph vessels and the middle tunica media has circular smooth muscle fibres some elastic fibres and the inner most tunica interna in a single layered endothelium of polyhedral squamous cells. If the arteries reach organs they form arterioles which are thinner and mainly consist smooth muscles and when they subdivide in the tissues they make capillaries..