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Cardiovascular System
Blood

Composition

Blood is the fluid circulating in the blood vessels of the cardiovascular system. It essentially consists of red and white blood cells and platelets suspended in a colourless liquid medium known as plasma.

The red blood cells are the most common cells in the blood and are the main agent that delivers nutrients including oxygen to tissues.
These cells get their red colour from hemoglobin, which is a protein containing iron that readily binds with oxygen.
Red blood cells are continuously produced in the marrow of body’s large bones.

About 1% of blood consists of white blood cells (leukocytes), which are the cornerstone of the body’s immune system. They are continuously produced in the bone marrow and are mainly present to fight diseases.

The third most notable blood constituents are platelets, whose main function is to aid coagulation of the blood as part of the body’s repair system.

The Nutrient Transporter

The cardiovascular system utilises blood in the following way.

Food, in the form of carbohydrates, protein, fat, vitamins, and minerals are introduced to the blood via the gastrointestinal tract. Oxygen is dissolved in the blood while it circulates the lungs.
Blood passes under pressure (generated by the heart beating) from the smallest arteries (called arterioles) into even smaller capillaries. The capillaries have walls that are so thin and permeable that molecules of oxygen, water, and the base constituents of food (all present in the blood) pass through them by diffusion and enter the cells.

Waste matter from the cellular metabolism such as carbon dioxide easily diffuse back across the capillary walls, and enter the blood, which is already on its way back to organs for cleansing via the tiny venules.
Blood, immediately after metabolism at the capillaries and laden with carbon dioxide is a dark maroon colour.

How Blood Impacts High Blood Pressure

With respect to high blood pressure or hypertension, the viscosity of blood can have an impact.

Viscosity is a measure of how much a liquid resists flowing. For example, treacle at normal room temperatures is very thick and flows very slowly and is said to be of high viscosity. Water however is of low viscosity in comparison and flows much faster in any conduit.
Similarly blood viscosity is an indication of how easily the blood flows in the blood vessels.

The viscosity of blood can be increased if a large amount of cholesterol or saturated fat is consumed which eventually finds its way into the blood stream. This will make the blood thicker and thus require more forceful impulses from the heart in order to move it at the correct rate, especially in the very thin blood vessels.
Such a situation will cause the cardiovascular system to err towards high blood pressure conditions.

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