blood vessels

Pericytes

Contractile stem cells that can generate new vessels or scar tissue, stabilize the capillary wall, and help control capillary permeability.

Continuous capillary

The least permeable and most common type of capillary, abundant in skin, muscles, lungs, and CNS, characterized by intercellular clefts between endothelial cells.

Blood-Brain Barrier

Formed by tight junctions in brain capillaries that lack intercellular clefts, limiting permeability for protection of the brain.

Fenestrated capillary

Capillaries with pores (fenestrations) that increase permeability; found in areas of active filtration (like kidneys) or absorption (like intestines).

Sinusoid capillary

The most permeable type of capillary, located in limited areas such as the liver, bone marrow, spleen, and adrenal medulla, characterized by large intercellular clefts.

Vascular shunt

Direct connection that allows blood to bypass capillaries, linking terminal arterioles to post-capillary venules via metarterioles and a throughfare channel.

Precapillary sphincter

Acts as a valve to regulate blood flow into capillaries, controlled by local chemical conditions.

Chemical regulation in capillary beds

Local chemical conditions and arteriolar vasomotor nerve fibers regulate the amount of blood entering a capillary bed.