Atherosclerosis

Arteriosclerosis: Systemic disease involving arterial tree
Commonly affects coronary, carotids, iliac + femoral
Three level pattern in lower limbs:
- Aorto-iliac
- Femoropopliteal
- Tibial segments (DM, ESRF, Older)
Atherosclerosis: Arteriosclerosis characterized by fibrous plaques in the intima (atheromas)
Layers of Arterial Wall:
Tunica Intima
- Endothelium: Single layer of squamous epithelial cells lining the lumen.
- Basement membrane: Provides structural support for the endothelium.
- Subendothelial layer: Contains loose connective tissue and elastic fibers (prominent in large arteries).
- Internal elastic lamina: A layer of elastic fibers separating the intima from the media.
Tunica Media
- Smooth muscle cells: Circularly arranged layers controlling vessel diameter.
- Elastic fibers: Provide flexibility and resilience, especially in larger arteries.
- External elastic lamina: Separates the media from the adventitia in larger arteries.
Tunica Adventitia
- Collagen fibers: Provide strength and structural support.
- Vasa vasorum: Small blood vessels supplying the artery wall in large vessels.
- Nerve fibers: Regulate smooth muscle contraction and relaxation.

Pathophysiology

Atherosclerosis is a chronic inflammatory response to endothelial injury in the intima
Endothelial damage (Hyperlipidaemia, HTN, cigarettes, high glucose)
- Injury increases permeability allowing LDL to penetrate arterial wall.
Lipid accumulation
- LDL enters the intima and becomes oxidised
Foam cell formation
- Macrophages engulf oxidised LDL forming foam cells - this forms a fatty streak - the earliest visible lesion in atherosclerosis.
Inflammation
- Foam cells and damaged endothelial cells release cytokines leading to inflammation within the vessel wall.
Smooth muscle migration and proliferation
- SMCs produce ECM (collagen and elastin) which forms a fibrous cap over the plaque.
Plaque maturation
- Plaque grows, fibrous cap thickens.