AN69.1-3 | Blood Vessels — Glossary

The innermost layer of a blood vessel wall consisting of endothelium, subendothelial connective tissue, and the internal elastic lamina

The middle layer of a blood vessel wall containing smooth muscle cells and elastic/collagen fibres; responsible for vasomotion and structural strength

The outermost layer of a blood vessel wall composed of loose connective tissue, fibroblasts, vasa vasorum, and nervi vasorum

A fenestrated elastic sheet at the junction of intima and media; most prominent in muscular arteries where it appears as a crisp wavy line on H&E

An elastic sheet at the junction of media and adventitia; present in muscular arteries but not distinct in elastic arteries

A single layer of flattened squamous cells lining the entire cardiovascular system; secretes NO, endothelin, clotting factors, and von Willebrand factor

Small blood vessels in the adventitia and outer media of large arteries and veins that supply the vessel wall with oxygen and nutrients

Large artery (e.g., aorta) with 40-70 elastic lamellae in the media; functions as a pressure buffer via the Windkessel effect

Medium-sized artery (e.g., femoral, radial) with prominent IEL and 10-40 smooth muscle layers in the media; regulates blood distribution

The ability of elastic arteries to stretch during systole and recoil during diastole, converting pulsatile flow to continuous flow

The smallest artery with 1-3 layers of smooth muscle; the primary site of peripheral resistance regulation and blood pressure control

The smallest blood vessel consisting of endothelium and basement membrane only; the site of gas, nutrient, and waste exchange

A capillary with uninterrupted endothelium and complete basement membrane; found in muscle, skin, lungs, and brain (BBB)

A capillary with small pores (fenestrae) in the endothelium; found in kidney glomerulus, intestinal villi, and endocrine glands

A wide, irregular capillary with large gaps between endothelial cells and discontinuous basement membrane; found in liver, spleen, and bone marrow

A small vein that collects blood from capillary beds; postcapillary venules are the site of leukocyte emigration in inflammation

A disease of arterial intima characterised by lipid accumulation, foam cells, fibrous cap formation, and plaque development leading to luminal narrowing

Tearing of blood between the layers of the aortic wall through a weakened tunica media; associated with Marfan syndrome and hypertension

Dilated, tortuous superficial veins with incompetent valves; common in lower limbs due to prolonged standing and venous hypertension

A contractile cell wrapping around capillaries and venules outside the endothelium; regulates blood flow, vessel stability, and may be a stem cell source

A vessel connecting an arteriole to a capillary bed; has discontinuous smooth muscle and a precapillary sphincter controlling capillary perfusion

A histological stain that stains elastic fibres black; used to visualise elastic lamellae in blood vessel walls