Atherosclerosis

Question 1

Briefly describe the 3 layers of a blood vessel

Answer 1

Tunica intima - endothelium, basal lamina and subendothelium
Tunica media - smooth muscle cells (thick in arteries as internal and external elastic membrane)
Tunica adventitia - outer layer composed of collagen and elastic fibres

Question 2

Describe the changes in vessel wall as arteries narrow to arterioles?

Answer 2

The ratio of wall thickness to lumen diameter increases to allow more precise regulation of intravascular pressures

Question 3

What properties do veins have (in their structure)?

Answer 3

Distensible, thin walled vessels with high capacitance

Question 4

Describe the difference between arteriosclerosis and atherosclerosis

Answer 4

Arteriosclerosis is hardening of the vessel walls
Arteriosclerosis = affects smaller arteries leading to hypertension
Atherosclerosis = affects larger, muscular arteries by plaque build up in tunica intima leading to endothelial damage

Question 5

What factors predispose endothelial injuries?

Answer 5

LDL cholesterol hyperlipidaemia
Hyperglycaemia (in Diabetes)
Hypertension
Increased toxin levels associated with smoking
Certain viral and bacterial infections

Question 6

Functions of vascular endothelium?

Answer 6

Maintain selective permeability barrier
Maintain non-thrombogenic barrier
Modulate blood flow and vascular resistance
Regulate immune responses (interaction of lymphocytes with endothelial surface)
Oxidise LDLS by free radicals released from endothelial cells

= all of these can be impaired in endothelial damage resulting in loss of function

Question 7

Outline the pathogenesis of an atheroma

Answer 7

Vascular endothelial damage leads to increased permeability to LDLs and increased adherence of WBCs to vessel wall
Increased production of ROS which oxidises LDLs in tunica intima = monocytes differentiate in macrophages
Macrophages phagocytose oxidised LDLs = foam cells
Foam cells + infiltrated T lymphocytes form initial lesion (fatty streak)
Fatty streak remodelled into fibrofatty plaque - fibroblasts form protective capsule = atheromatous plaque

Question 8

What does the final atheromatous plaque include?

Answer 8

Thick layer of fibrous connective tissue containing:
Scattered smooth muscle cells
Macrophages
Foam cells
T lymphocytes
Cholesterol crystals
Cell debris

Question 9

What are the clinical consequences of atheroma formation?

Answer 9

Infarction: myocardial, cerebral, renal, aortic aneurysm
Occlusion of smaller vessels = poor tissue perfusion
Plaque rupture = vascular thrombosis/distal embolus
Destruction of vessel wall can lead to aneurysm formation with secondary rupture and thrombosis

Question 10

What vessels are most commonly involved in atherosclerosis?

Answer 10

Large elastic arteries: aorta, carotid, iliac

Large/medium sized muscular arteries: renal, coronary