Capillaries are the smallest blood vessels in the body, they convey blood between the arterioles and venules. The capillaries contain only 5% of the circulatory blood, but this fraction is the most important part...
The circulatory system has the lymphatic system, which circulates lymph, It is known as the cardiovascular system or the vascular system, It is a vital organ system that delivers essential substances to all cells...
Animals obtain their requirements of energy in the form of food, after its digestion, the soluble food substances are absorbed, but still remains the problem of their transport and distribution to the various tissues...
