Blood vessels: artery, vein and capillary layers !

Tissue

Arteries and veins share three wall layers; arteries have a thick muscle layer for pressure, veins a thin wall and valves, capillaries only endothelium.

Updated 2026-11-01

See it in 3D: Thoracic aorta · Superior vena cava · Femoral artery · Great saphenous vein

What it is

Every vessel larger than a capillary has three tunics: the intima (endothelium on a basement membrane), the media (smooth muscle and elastic fibres) and the adventitia (collagen-rich connective tissue). Their thickness changes with the job: elastic arteries store energy, muscular arteries and arterioles control flow and resistance, capillaries exchange, and veins hold most of the blood volume. Most vascular disease, such as atherosclerosis, starts in the intima.

Function

Elastic arteries stretch in systole and recoil in diastole, keeping flow continuous.
Arterioles change their diameter to set peripheral resistance and blood pressure.
The endothelium controls clotting, vascular tone (nitric oxide) and the passage of leukocytes.

Artery, vein and capillary compared

Feature	Artery	Vein	Capillary
Tunica intima	Endothelium plus a wavy internal elastic lamina	Endothelium; forms the valves in limb veins	Only endothelium on a basement membrane (with pericytes)
Tunica media	Thick: many layers of smooth muscle and elastic fibres	Thin: few smooth muscle layers	Absent
Tunica adventitia	Present, thinner than the media; external elastic lamina in muscular arteries	Thickest layer, collagen with some longitudinal muscle in large veins	Absent
Lumen on a slide	Small, round, keeps its shape	Large, irregular, often collapsed, may hold blood	Wide enough for one red cell at a time
Pressure and job	High pressure; conduct and distribute blood	Low pressure; return blood and store most of the volume	Lowest pressure; exchange of gases, nutrients and waste

Markers

CD31
CD34
Von Willebrand factor
Verhoeff-Van Gieson (elastic fibres)

Clinical notes

Atherosclerosis: lipid and foam cells collect in the intima and form a plaque under a fibrous cap.
Aortic dissection: blood tears through the intima and splits the media.
Varicose veins and venous ulcers follow valve failure and high venous pressure in the legs.
Deep vein thrombosis is favoured by stasis, endothelial injury and hypercoagulability.

Test yourself

Think of the answer, then tap the question to see it.

Which tunica is thickest in a medium-sized artery and which in a medium-sized vein?

The media in the artery (smooth muscle) and the adventitia in the vein (collagen-rich connective tissue).

Which type of capillary is found in the liver, spleen and bone marrow?

The sinusoidal capillary: wide, with large gaps and a discontinuous basement membrane, so proteins and cells can pass.

In which layer does atherosclerosis begin?

In the tunica intima, where lipids, foam cells and smooth muscle cells build the plaque under the endothelium.

Which vessels contribute most to peripheral resistance?

The arterioles, which have one or two smooth muscle layers and change their diameter to control flow.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of histology

Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.

Sources: 20.1 Structure and Function of Blood Vessels - Anatomy and Physiology 2e | OpenStax (OpenStax, Rice University, 2022); Classification & Structure of Blood Vessels (National Cancer Institute, SEER Training Modules, 2024).

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Representative model, for educational purposes only.