CH 18 Objectives 4, 5, 6, 7

Learning objective 6: Describe possible mechanisms involved in the development of Atherosclerosis

Atherosclerosis is a type of arteriosclerosis or hardening of the arteries. It denotes the formation of fibro-fatty lesions in the intimal lining of the large and medium sized arteries. The three lesions involved in atherosclerosis: 1.) Fatty streaks: thin, flat, yellow intimal discolorations that progressively enlarge by becoming thicker and slightly elevated as they grow in length. Consist of macrophages and smooth muscle cells that have become distended with lipid to form foam cells 2.) Fibrous atheromatous plaque: basic lesion of clinical atherosclerosis. Characterized by the accumulation of intracellular & extracellular lipids, proliferation of vascular smooth muscle cells, formation of scar tissue, and calcification. Lesions being as grey, pearl white, elevated thickening of the vessel intima with a core extracellular lipid covered by a fibrous cap of connective and smooth muscle tissue. As lesions increase in size, hey may encroach on the lumen and occlude the blood vessel, causing reduction in blood flow. 3.) Complicated lesion: more advanced lesions contain hemorrhage, ulceration, scar tissue deposits. Thrombosis is the most common complication.

Learning Objective 4: Describe the lipoprotein receptors in removal of cholesterol from the blood

Because lipids, namely, cholesterol and triglycerides, are insoluble in plasma, they are encapsulated by special fat carrying proteins called lipoproteins for transport in the blood. LDL(low density lipoprotein) is referred to as bad cholesterol. It is the main carrier of cholesterol. Some cells, phagocytic macrophages, have nonspecific receptors known as scavenger receptors that bind to various types of molecules, including, modified LDL. If extra LDL is presented as in hypercholesteremia, the receptor mediated uptake of LDL by hepatic and extrahepatic tissues becomes saturated the excess LDL is available for uptake by scavenger cells present near the cells of arteries HDL, aka good cholesterol is synthesized in the liver. It participates in the reverse transport of cholesterol, that is, carrying cholesterol from peripheral tissues back to the liver. It is thought that HDL, which is low in cholesterol and rich in phospholipids, facilitates the clearance of cholesterol from athermatous plaques and transports it to the liver, where it may be excreted rather than reused.

Learning objective 5: Cite the criteria for diagnosis of hypercholesterolemia

Hypercholesterolemia refers to increased levels of cholesterol in the blood with optimal to high levels of LDL cholesterol, triglycerides & low and high levels of HDL cholesterol. (Table 18-2)

Learning objective 7: List the risk factors of atherosclerosis

Increasing age, male gender, premature coronary artery disease, family history of heart disease or stroke due to atherosclerosis, cigarette smoking, hypertension, obesity, hyperlipidemia, diabetes mellitus, inflammation marked by elevated C-reactive protein levels, hyperhomocystinemia, & increased lipoprotein (a) levels