Category:Arterial Pathology

Functional Anatomy

Arteries, capillaries and veins form a continuous system lined by endothelium. The endothelial layer is low friction to allow smooth blood flow. The endothelium forms the innermost layer of arteries;

• Tunica intima.

The tunica intima is enclosed externally by the internal elastic membrane. The outer tunics are:

• Tunica media.

Composed of elastic tissue and smooth muscle, this layer is the most variable, depending on location but is often the thickest layer.

• Tunica adventitia.

Fibrous tissue limiting expansion and so guarding against rupture.

Classification of arteries:

• Large elastic arteries are required to expand considerably E.g. the aorta as it receives the ventricular outflow.
• Large muscular arteries consist mainly of smooth muscle, the arterial lumen diameter is controlled by the autonomic nervous system.
• Arterioles regulate resistance to the flow of blood and therefore regulate peripheral blood pressure. The muscle layer is smaller than that of the larger muscular arteries. Opening or closing of the arterioles directs flow to specific capillary beds.