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.

Arterial Hypertrophy

Degeneration

Arteriosclerosis

Atherosclerosis

Arterial Calcification

Amyloidosis

Inflammatory-Arteritis

Aneurysm and Rupture

Dissecting aneurysm. Courtesy of A. Jefferies

Aneurysm is a local abnormal dilation of a vessel due to weakening of loss of elasticity of the vessel wall.

Dissecting aneurysm. Courtesy of A. Jefferies

Seen proximal to a stenotic lesion. If the wall partially ruptues blood can track within the wall producing a dissecting aneurysm. Verminous anurysm occurs in horses with strongylus vulgaris infestation.

Rupture of the vessels is rare. aortic rupture may occur in some situations:

• Traumatic.
• Dog: Spirocerca lupi (NOT IN UK)
• Horse: Verminous aneurysms which rupture. Rupture within the pericardium leads to haemopericardium and Cardiac tamponade.

Vascular Pathology

Pulmonary artery thrombus. Courtesy of A. Jefferies

Thrombosis may be due to:

• Endothelial injury.
• Altered blood flow E.g. abnormal stasis.
• Hypercoagulability.

Often associated with other disease processes for example Disseminated intravascular coagulation.

Commonly see posterior paralysis of cats with cardiomyopathy.

Nasal thrombosis.

Sarcoma embolus (dog). Courtesy of T. Scase

DIC thrombus. Courtesy of A. Jefferies