Biology of Disease

beats. The smaller arteries and arterioles have muscular walls and their

diameters can be adjusted to regulate blood flow to a particular region of the

body. Capillaries are thin-walled vessels that allow oxygen, nutrients and other

materials, for example hormones, to diffuse from the blood to the tissues and

waste products to pass from the tissues into the blood. The capillaries are links

between the arteries and arterioles and the venules and veins. Veins are, in

general, larger in diameter than arteries but have much thinner walls. They

transport blood back to the heart but at much lower pressures and speeds

than is found in arteries.

Arteries

Arteries are elastic tubes with circular cross-sections (Figures 14.7 (A)and

(B)). They are built up from three layers called tunics. The tunica intima is

X]VeiZg&)/ DISORDERS OF THE CARDIOVASCULAR SYSTEM

W^dad\nd[Y^hZVhZ

Aorta

Pulmonary

Left ventricle

Aortic arch

Hepatic

Renal

Commmon

carotid

Subclavian

Common iliac

Femoral

Tibial

Brachial

Ulnar

Radial

Figure 14.5 Schematic showing the main arteries of the body.

Hepatic

Renal

Subclavian

Femoral

Tibial

Brachial

Internal jugular

External jugular

Superior

vena cava

Inferior

vena cava

Right atrium

Figure 14.6 Schematic showing the main veins of the body.

X]VeiZg&)/ DISORDERS OF THE CARDIOVASCULAR SYSTEM

(-) W^dad\nd[Y^hZVhZ