Blood Circulation

Introduction:

I know you have wondered what blood is, what is does in the body and how it is distributed. After reading this article, I know your questions would be answered.

The heart:

This is one of the organs that make up the circulatory system of the body. The heart is made up of a muscle called myocardium, comparably large tubes called blood vessels, valves, cusp, and also small vessels. The heart is the blood pumping machine of the body and when it stops because of a disease condition or any other cause, death is inevitable.

Blood vessels:

They are the transporter, the channel or the tunnel by which blood gets to the targeted tissues or cells. There are 3 main types of blood vessels and they are; artery- channels blood from the heart to the tissues and cells, pulmonary artery is excluded from this function. Vein- channels blood from the cells and tissues to the heart, the pulmonary vein is excluded from this function. Capillaries- they form intermediate channels between the arteries and veins.

How to differentiate an artery from a vein:

The lumen or center of the vein is larger than that of an artery.

The wall of an artery is thicker than that of a vein.

Veins are seen on the surface, close to the skin while arteries are deep seated.

Veins are used for intravenous injections while arteries are used to take pulsation.

What is blood?

Blood is a thick reddish liquid found in the body of humans. Their reddish color is due to the red color of cells (erythrocyte) present in it. This cell is called the red blood cell.

There are other cells in the blood and they are; white blood cells, also called leucocytes. Platelets also called thrombocytes. A liquid called blood plasma.

Red blood cells or erythrocytes convey oxygen and carbon dioxide using hemoglobin (an iron-containing compound).

White blood cells fight germs and infections.

Platelets help the blood to clot when one has wound.

Blood plasma is liquid that enables these cells swim to their destination.

Functions of the blood:

There are many functions of the blood but I will list some of them.

Transports oxygen and carbon dioxide- carries oxygen from air to the cells of the body while carbon dioxide from cells are taken out into the surroundings in a process called respiration or breathing.

Transports absorbed nutrients- nutrients from the digestive system are sent to cells where they are needed for metabolism.

Fight infections- white blood cells in the blood helps the body to fight infections.

Prevents too much bleeding- the platelets in blood helps to make sure one do not bleed to death by helping the blood in the area to clot, stopping the bleeding.

Remove harmful substances- harmful substances produced or removed from one part of the body is transferred to another part where it is excreted.

Keeps the body warm- heat generated by the blood helps to keep the body warm.

How blood circulate in the body:

This is a continuous cycle that starts in the heart through a blood vessel called aorta (artery) and ends in the heart through blood vessels called inferior and superior vena cava. Details on circulation;

When oxygen is added to the blood and the carbon dioxide removed in the lungs, the oxygenated (rich in oxygen) is transported to back to the heart through a vessel called pulmonary vein (that is why I made that exception above) into the left atrium (a compartment in the heart). This blood flows into the left ventricle (a compartment in the heart) across a valve (bicuspid or mitral), from there through the aorta to the rest of the body.

From the aorta, the blood is distributed to the head via the carotid artery, to the upper limb (hand) via subclavian artery, to the body via abdominal or descending artery and to the lower limbs or legs via femoral artery.

The blood from these arteries gets to smaller artery (called arterioles) and from there to the capillaries. From the capillaries to the tissues and cells where exchange takes place (the tissues and cells receives oxygen and nutrients from the blood while the blood receives carbon dioxide and toxic waste products from the cells).

The deoxygenated blood (blood without oxygen) and the waste products leave the capillaries to the smaller veins (called venules), from venules to veins, from veins to superior and inferior vena cava, and from there to the right atrium (a compartment in the heart) of the heart.

Blood from the right atrium flows down into the right ventricle across a tricuspid valve, from there through the pulmonary artery (that is why I made the exception above) to the lungs for oxygenation (adding of oxygen and removal of carbon dioxide).

Note that blood from the head, neck and upper limb (hands) region returns through the superior vena cava while blood from the body (trunk) and lower limb (legs) region returns via the inferior vena cava.

Inferior and superior vena cava are larger veins while the aorta is a larger artery.

Next time we would discuss on the exchange of gases in the lungs. In the mean time, learn health, live healthy and think healthy.