Vessel Diseases Flashcards
Describe the exogenous and endogenous lipoprotein metabolism pathways.
cholesterol from the diet is packaged into chylomicrons in the gut containing ApoB-48, ApoC and ApoE. This gives off FAs to muscle and adipose then goes to the liver. The liver sends out VLDL with ApoB-100 to pick up lipids from the periphery and the lipoprotein becomes IDL, even more pick up becomes LDL and that is uptaken by the liver and peripheral tissues.
Primary chylomicronemia
Defective removal of chylomicrons due to ApoC-II and LPL defect. Seen as elevated chylomicrons & VLDL, plus pancreatitis.
Familial hypertriglyceridemia
Defective metabolism of VLDL due to LPL defect. Seen as elevated VLDL & triglycerides, plus pancreatitis.
Familial dysbetalipoproteinemia.
Defective metabolism of VLDL and chylomicrons due to ApoE defect (E2/E2 alleles, causes decreased binding of E to its liver receptors). Seen as elevated VLDL and chylomicron remnants (IDL); elevated cholesterol and triglycerides 1:1 ratio; plus atherosclerosis.
Familial Combined Hyperlipidemia (FCH)
Overproduction of ApoB (means more VLDL). Seen as elevated VLDL, LDL, or both; also premature atherosclerosis.
Familial Hypercholesterolemia (FH)
Decreased receptor-mediated removal of LDL from plasma due to defective LDL receptor and ApoB. Seen as increased LDL and premature atherosclerosis.
What is the desirable range for cholesterol levels?
Total Cholesterol - 40, Women >50
Triglycerides -
Xanthoma
cutaneous manifestations of lipidosis, an accumulation of lipids in foam cells within the skin; associated with hyperlipidemias
Fibromuscular dysplasia
Focal irregular artery wall thickening with intimal and medial hyperplasia and fibrosis, leading to luminal stenosis. Typically in renal, carotid, splanchnic, or vertebral arteries; young women.
Hyperplastic arteriolosclerosis
*smooth muscle growth
concentric wall thickening due to hyperplasia and hypertrophy of the smooth muscle cells in the t. media (onion layers), also thickened reduplicated basement membrane
Hyaline arteriolosclerosis
*protein leak + ECM secretion
wall thickening due to leakage of plasma proteins from lumen into wall, as well as ECM secretion by smooth muscle cells. Caused by HTN.
Fibrinoid change (±necrosis)
*protein leak
Wall thickening due to leakage of plasma protein into wall with or without necrosis; often associated with vasculitis so will see surrounding inflammation as well
Medial calcific sclerosis
*calcium in elastic lamina
Calcification of internal elastic lamina spreading into tunica media
Atherosclerosis
thickening of tunica intima due to lipid accumulation, chronic inflammation, and repair response. This is a chronic inflammatory disease of response to endothelial cell injury.
SHODDY
five major modifiable risk factors for atherosclerosis: Smoking, Hypertension, Obesity, Diabetes, DYsplipidemia
+Inflammation/CRP
Pathogenesis of atherosclerosis/plaque formation
- malfunction of injured endothelial cells (HLD, HGlu, HTN, etc) –> increased permeability, cell adhesion
- lipoproteins (LDL and oxidized LDL, cholesterol, and C-esters) accumulation in intima
- leukocytes/monocytes come to intima to help, become MPs and [dysfunctional] foam cells (take up too much LDL/lipid)
- factors released (from plt, MPs, and endo cells) that recruit smooth muscle cells and T cells
- smooth muscle cell proliferation (PDGF, FGF, TGF-alpha) with ECM/collagen deposition
* then: inflammatory cells may initiate breakdown of ECM and lead to plaque break-off; often undergo calcification
Mechanism by which HLD contributes to atherogenesis
- impairs endo cell function by increasing ROS production when lipids are oxidized
- free radicals cause membrane and mitochondrial damage, as well as accelerate NO decay (decreased vasodilation effect)
- ROS/oxidized lipids are scavenged by MPs but there’s no feedback in this system so that’s how foam cells form; smooth muscle cells can also take up lots of lipid
- the modified lipids can’t be degraded so they sit within cells and cytokines are released –> inflammation/problems
Atherosclerotic plaques have 3 main components:
- cells - smooth muscle, MP, T cells
- ECM - collagen, elastic fibers, PGs
- lipid - IC and EC
What is contained in the: - fibrous cap - necrotic core - periphery of an atherosclerotic plaque?
Cap: smooth muscle cells and relatively dense collagen
Core: lipid, dead cell debris, foam cells, fibrin, thrombus, plasma proteins, EC cholesterol crystals
Periphery: neovascularization (weak, prone to rupture)
Difference between lesion, fatty streak, intermediate lesion, atheroma, fibroatheroma, and complicated lesion.
Lesion - histologically normal but with MPs and some foam cells
Fatty streak - IC lipid accumulation
Intermediate lesion - fatty streak with EC lipid pools
Atheroma - IC lipid and core of EC lipid
Fibroatheroma - 1/more lipid cores, fibrotic/calcific layers, increased smooth muscle/collagen
Complicated lesion - surface defect, hematoma/hemorrhage, thrombosis
Vulnerable plaque
thin fibrous cap overlying the lipid core of atheroma (as opposed to stable plaque, which has a thick fibrous cap)
Intraplaque hemorrhage
blood within the lipid core that got there either by rupture of the neovessels or rupture of the fibrous cap; this may expand the plaque or induce plaque rupture
Plaque rupture
break in fibrotic cap that allows communication of core contents with circulation, causing thrombus formation
The most extensively involved vessels in atherosclerosis (in order) are:
- aorta (lower abdominal)
- coronary arteries
- popliteal arteries
- cerebral arteries
Atherosclerotic stenosis
Critical stenosis (enough to cause tissue ischemia) is 70% decrease in cross-sectional area of the lumen. Prior to that the artery will remodel/expand outward to accommodate the plaque build up while not reducing the lumen size. The effects of vascular occlusion depend on the metabolic demand of the affected tissue as well as the arterial supply
Stable angina
predictable chest pain with a fixed amount of exertion
Acute plaque changes fall into 3 categories:
- rupture - release thrombus
- erosion - exposing thrombogenic SEC to blood
- hemorrhage - expands volume of atheroma
* adrenergic stimulation associated with circadian waking and emotional stress can contribute to plaque disruption
Potential causes of acute coronary syndromes
- thrombosis formed on disrupted plaque
- thromboemboli in coronary artery
- vasoconstriction which decreases lumen and potentiates plaque disruption (can be stimulated by adrenergic agonists, platelet content release, endothelial cell dysfunction, perivascular inflammatory cells’ mediator release)
Dissection
tear in the tunica intima that lets luminal blood get in between the intima and media where it tunnels out a second lumen