Today is

By: Ikedi Ani-okoye

Cardiovascular system

The cardiovascular system is made up of the heart ("cardiac) and the blood vessels (avascular"). The heart - whlch is essentially a large, powerful muscle about the size of your clenched Fist - pumps blood at an average rate of 60-80 times a minute for a person's entire lifespan. The heart and the circulatory system can develop a range of disorders, due to the great demands placed on them. A number of these problems call for prompt emergency first-aid techniques in order to save the casualty's life.

The heart

Situated between the lungs, the heart is sfightly to the left side of the body. The hollow area inside the heart muscle is made up of two separate compartments: one on the left and one on the right.

In healthy people, these separate heart compartments leave no communication with each other. However, some babies are born with a communication between the two - a condition known as having a "hole in the heart",

Each of the compartments has two chambers, an upper atrium and a lower ventricle, giving four compartments in total: the left ventricle and atrium, and the right ventricle and atrium.

The blood vessels

The ventricles send blood to all parts of the body through the arteries, which branch out all over the body into smaller vessels called arterioles. These then become minute vessels called capillaries, which form a network that bathes all body tissues allowing easy exchange of oxygen, nutrients, carbon dioxide and other waste products. The capillaries then join with tiny vessels called venuses, which form larger and larger veins, until the vena cavae arrive back at the right side of the heart.

The circulation

The blood arriving at the right side of the heart has been around the body and therefore has a low oxygen content. This deoxygenated blood is a dark red colour, rather than the bright red colour it will turn when it has been through the lungs and has filled up with oxygen. This blood arrives back at the heart through the veins. The two veins that Iead into the heart are the vena cavae. Deoxygenated venous blood arrives in the right atrium, moves down into the right ventricle, and is then pumped through the lungs and back into the left atrium. This fresh, oxygenated blood passes into the left ventricle and then exits the heart via the aorta (the body's biggest vessel), starting its journey round the body.

The whole process - including the time taken for the chambers to
fill with blood and then contract and circulate the blood- takes about 0.8 seconds at rest, or less when the pulse is rapid.

The blood

Blood carries nutrients around the body, as well as taking oxygen from, and carbon dioxide to, dle lungs. It protects against blood loss through its clotting ability ;and infection through its white blood cells.

Fifty-five per cent of blood is made up of a straw-coloured clear fluid called plasma, which is also rich in proteins. When bleeding occurs, we lose plasma, and the blood volume drops. Eventually, there is not enough blood for the heart to pump, and the circulatory system collapses. Death swiftly follows. Within the plasma float red and white blood cells, plus substances (such as platelets) that are needed for clot-forming. White cells are mainly involved in fighting infection, while red cells carry oxygen.

What is the pulse?

Our pulse is caused by the aorta springing back down to its nonnd size, having been filled with blood from the heart. This drives oxygen-rich blond around the body, and the force of the aorta recoil travels along the large aneries - it can be felt wherever an artery lies dose to dle surface of the skin. Use two fingers to feel for an adult's or child's pulse at the thumb side of the wrist, at the neck or on the front of the arm at the elbow joint. A baby's phase is best felt on the inside of the upper arm.

It can be much trickier than most people imagine to determine whether someone has a pulse, so this check is often best left to those with medical experience. Remember that vital signs such as coughing, gasping, twitching or blinking also indicate a circulation, and anyone can check for those.