The capillary bed is an interlaced network of capillaries that services an organ. The network size of the capillary bed depends on how active the particular organ is. Usually, the more active organs require more nutrients and produce more waste products.
Two kinds of vessels make up the capillary bed, namely, true capillaries and vascular shunt. The true capillary provides exchange between the cells and blood while vascular shunt is the vessel that connects the arteriole and the venule from both sides of the capillary beds. Capillary transport is basically done by bidirectional diffusion on the capillary beds.
Blood flow in the capillary beds is controlled by autoregulation. Constant flow is kept even when there is change in the central blood pressure because the arterioles are stretched then constricted to counteract the consequent increase of blood flow due to high blood pressure.
Thus, this is basically how blood flows. Blood from the heart flows through the artery then to the arterioles then to the capillaries. Exchange happens in the capillary bed. After the exchange between the capillary and the cell, the capillaries branch and widen into venules where blood carrying wastes products is transported. From the venules blood is carried to the veins. Veins then return this blood to the heart then the heart will pump this blood to the designated excretory organ.
There are two types of capillaries, the continuous and the fenestrated. Continuous capillaries are found in the skeletal muscles, lungs, skin, gonads and the central nervous system. Fenestrated capillaries are found in the kidney, endocrine glands, intestines, and pancreas.