Atherosclerosis - The basics.
Normal Function of the Arterial System
It is important to understand the meaning of atherosclerosis and definitions of the disease help to show the meaning.
Atherosclerosis - definition A form of atherosclerosis characterized by patchy subintimal thickening (atheromas) of medium and large arteries, which can reduce or obstruct blood flow.
Arteriosclerosis - definition A generic term for several diseases in which the arterial wall becomes thickened and loses elasticity.
Sclero - hardening Arterio - arteries
Arteries Large elastic arteries carry blood from the heart, they divide into medium sized, muscular arteries branching throughout the body. Medium sized arteries divide into small arteries which divide further into smaller arteries called arterioles. Arterioles entering tissues branch into many very small blood vessels called capillaries which, through their very thin walls allow exchange of substances between the blood and tissues.
Inside tissues, groups of capillaries unite to form small veins or venules. These venules merge to form veins. The veins return blood to the heart. Blood vessels, like all tissues, also need nutrients plus O2. The larger vessels are served by their own blood vessels terms vasa vasorum (vasculature of vessels). These are located within the walls of the major vessels.
Arterial Wall Composed of three coats (tunics)
Innermost Tunica intima (internal). Composed of a layer of simple squamous epithelium called endothelium, a basement membrane plus a layer of elastic tissue, the interal elastic lamina.
The endothelium lies in the inner surface of the entire cardiovascular system and is a continuous layer of cells. It is the only tissue that under normal conditions, makes contact with the blood inside the lumen (hollow centre of the vessels).
Middle Tunica Media Usually the thickest layer. Composed of elastic and smooth muscle fibres or cells extending in a circle around the tunica intima. Due to elastic fibres, arteries normally have high compliance or stretch as pressure varies.
Outer Tunica Externa Elastic and collagen fibres. In muscular arteries an external elastic lamina composed of elastic tissue separates the tunica externa from the tunica media.
Contraction and Dilation of Arteries Neurons of the autonomic nervous system innervate vascular smooth muscle causing vasoconstriction - narrowing of vessels. The smooth muscle fibres relax when sympathetic stimulation decreases or when some chemicals are present such as NO, K+, H+ and lactic acid.
Vaso Dilation Elastic arteries or large diameter arteries. The tunica media contains a large amount of elastic fibres. The arteries help propel the blood while the ventricles of the heart relax before the next cycle. The elastic fibres store mechanical energy for a short time and function as a pressure reservoir. The elastic arteries recoil and continue to deliver blood while the ventricles relax by converting potential energy to kinetic energy.
Blood keeps moving through the arteries even while the ventricles are relaxed. Cholesterol is a key player in the formation of arterial plaques.
A diet high in fats results in the reabsorption of cholesterol-containing bile back to the blood, so less of the cholesterol is lost in faeces.
Also, when saturated fats are broken down, hepatocytes (in the liver) use some of the breakdown products to make cholesterol.
So a diet high in saturated fats results in higher cholesterol in the blood. The lipid profile test measures Total Cholesterol (TC), High Density Lipoprotein (HDL) and Triglycerides (VLDL's) while the Low Density Lipoprotein (LDL) is calculated as: LDL = TC - HDL - (VLDL/S) mg/dL (mg/100ml blood) Adults levels are: TC 239 mg/dL and LDL>159 mg/dL are very high.
The ratio of Total Cholesterol to HDL cholesterol will predict the risk of coronary artery disease. A person with a Total Cholesterol of 180 mg/dL and HDL of 60 mg/dL has a risk ratio of 3. Ratios above 4 are not desirable and the higher the ratio the greater the risk of heart disease or coronary artery disease.
Pathogenesis of Atherosclerosis
Definition Arteriosclerosis - A generic term for several diseases in which the arterial wall becomes thickened and loses elasticity.
Atherosclerosis - A form of arteriosclerosis characterized by patchy subintimal thickening (atheromas) of medium and large arteries, which can reduce to obstruct blood flow.
Sclerosis - Fibrosis
Causes High circulation LDL, cytomegolovirus (a common herpes virus), high blood glucose (diabetes mellitus)
Thought to begin by one of the above causing injury to endothelium of an artery, promoting aggregation of platelets and attracting phagocytes.
The prevalence of clinical manifestations of artherosclerosis in general, increases in post menopausal women and begins to approach that in age-matched men.
Pathogenesis/Pathology
Atherosclerosis consists of an accumulation of intra and extra cellular lipids, connective tissue, glycosaminoglycans and smooth muscle cells.
Early detection of atherosclerosis plaque is in the form of lipid-laden foam cells. These are macrophages which have migrated as monocytes from circulation into the subendothelial layer of the intima, that later form into fibrous plaque. This consists of intimal smooth muscle cells surrounded by connective tissue and both intra and extra cellular lipids.
Atherosclerotic vessels have reduced systolic (contractile) expansion and high wave propagation. People with hypertension who have arterosclerotic arteries have reduced elasticity, further reduced when atherosclerosis develops.
There is a probable relation between two proposed hypotheses for the pathogenesis of atherosclerosis which are the lipid hypothesis and the chronic endothelial injury hypothesis.
There is a close link between these two hypotheses. Modified LDL is cytotoxic to endothelial cells. This may induce injury, attracting monocytes and macrophages which develop into foam cells and become trapped in the endothelial space. The atherosclerotic plaque develops and grows slowly, taking decades. Over time, vessels become occluded and calcified. Plaques rich in lipids and inflammatory cells may be covered by a thin fibrous cap which may rupture, contacting the contents with blood.
The rupture in the plaque can stimulate thrombosis which may embolize (clot) and occlude the lumen of the vessel either locally (perhaps distally) or proximal to lung and heart vessels.
Atherosclerosis is characteristically silent until critical sclerosis, thrombosis, aneurysm or embolus manifests.
In the early stages, symptoms and signs reflect an inability of blood flow to the affected tissue to increase with demand eg angina when exerted. Symptoms develop gradually as the atheroma encroaches on the vessel lumen but symptoms may be dramatic if a main artery is occluded.
Basic Causes of Atherosclerosis - Roles of Cholesterol and Lipoproteins
The most important factor causing atherosclerosis is a high blood plasma count of cholesterol as LDL's. The blood plasma concentration of LDL Cholesterol is directly increased by eating saturated fats and any form of cholesterol.
Both can contribute to the development of atherosclerosis. It has been found by feeding rabbits cholesterol via their diet that serious atherosclerotic plaques developed throughout their arterial system.
Arteriosclerotic arteries lose most of their distensibility and because of the degenerative areas in their walls, they are easily ruptured. Where the plaques protrude in the flowing blood, the roughness of their surfaces causes blood clots to develop, resulting in thrombosis or embolus, which can suddenly block all blood flow in the artery.
Atheroma - a tumour Skleros - hard Sis - condition or process
Endocytosis - normal cholesterol entry to cell Cholesterol - receptor mediated endocytosis Cholesterol is essential for membrane structure and for synthesis of steroid hormones. However, elevated cholesterol can lead to heart disease. Cholesterol is a water soluble nonpolar molecule which needs to bind to a lipoprotein carrier molecule for transport in the blood.
The most common lipoprotein is LDL (low density lipoprotein). LDL cholesterol is taken into the cells by endocytosis when LDL receptors on the cell plasma membrane bind to the protein portion. People with an inherited genetic defect that decreases the number of LDL receptors on the cell membrane cannot transport enough cholesterol into their cells, so LDL cholesterol stays in the blood plasma. This may result in abnormally high blood levels of LDL cholesterol which predisposes the person to the development of atherosclerosis or commonly known as hardening of the arteries. The accumulation of cholesterol in blood blocks blood flow and contributes to heart attacks.
Help in removing cholesterol A substance known as beta glucan helps remove excess cholesterol from the gut. Beta Glucan is present in some foods eg oats, however, with the beta glucan carbohydrates are also supplied, so mopping up cholesterol with the aid of beta glucan in a food such as oats, may result in excess carbohydrate build up manifesting as fat, unless this is burnt by exercising.
Exercise is necessary to burn the calories present in the food. All foods have a listing of calories per weight of food on the package.
Summary
I have written an article titled 'Five Elements - the usefulness of Chinese Medicine'. In this article I mention that 'movement' is the key to wellbeing. Movement is necessary to keep stagnation from occurring. Atherosclerotic plaque is formed due to improper diet and a deficit of movement - over quite a long period of time.
From the 'insult' to the body caused by an imbalance in diet and movement, the mechanisms in the body will attempt to remove unwanted substances and store them - however where they are stored is due to an imbalance of reactions that are uncommon in a healthy body. Consequently, the normally clever body makes mistakes and forms plaques where they will cause health problems. In a similar way the body will store arachidonic acid (found in meats) in fat just to get rid of it from the blood - this causes a toxicity that builds up over time.
The removal or dislodgement of plaques can be dangerous as the solids which move may cause an embolism (blockage) somewhere else in the body. There is help to disintegrate solids but the problem usually does not manifest until it is very late. DVT (deep vein thrombosis) is one example of a blockage that has its source in the legs and can/will travel to the lungs causing the person to pass out at any time - without warning.
A further health risk from atherosclerosis may be other immune related diseases such as cancer. This happened to a family member who had DVT then a year later breast cancer - the person made a full recovery from both issues by changing lifestyle - vegetarian diet(mostly fresh uncooked food), fresh made at home juices, green barley drinks, reiki treatments daily, exercise daily (aerobic using a recumbent exercise bike with full display to track progress), breathing exercises and high doses of certain supplements(CoQ10Sport was one of these). No alcohol, coffee, tea, processed food of any kind, no chemotherapy, no radiation, no drugs of any kind, no pain killers (affect the liver and gut causing constipation). In short - back to basics using clean food and water and a change to lifestyle.
The way out of athersclerosis will be different for everyone. The difference lies in the extent of the problem and the length of abuse to the body. Above all, there must be a suitable practitioner involved in the recovery process which must be taken slowly. Detoxification must be slow and steady - do not rush into it.
Ron Campeanu
References:
1. Human Physiology, Dee Unglaub Silverthorn, p 145-146, Pearsons
2. Merck Manual of Diagnosis and Therapy, p 1654-1658, Merck
3. Principles of Anatomy and Physiology, Tortora,G.J & Grabowsky,S.R., p 697-699, 921, Wiley
4. Textbook of Medical Physiology, Guyton, A.C. MD and Hall,J.E. PhD, p 789, Saunders
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