The Heart
In this article general academic words, from the Academic Word List,
are highlighted in bold. It is important that you understand these words
and can use them. Study the words in bold carefully. Learn them.
The heart functions as a pump at the centre of the circulatory system. In humans it is
located in the chest cavity, between the lungs, slightly to the left. The heart consists
of four chambers surrounded by a very strong muscular wall, the myocardium. The
upper chambers, the right and left atria, receive blood entering the heart, and the
lower chambers, the right and left ventricles pump the blood out of the heart, via the
pulmonary and the systemic circulatory systems.
The two systems work as follows. Blood from the body enters the right atrium, is
passed into the right ventricle and from there is propelled through the pulmonary
artery to the lungs. In the lungs the blood releases carbon dioxide and absorbs oxygen
and is then transported back to the heart into the left atrium. From here it passes into
the left ventricle, which pumps the oxygenated blood around the body.
The heartbeat is caused by the alternating contractions and relaxations of the muscles
of the myocardium. The heart rate varies, increasing temporarily during periods of
exercise and emotion and decreasing during sleep. Babies have a heart rate of 130
beats per minute but this diminishes progressively until the average adult rate of 70
is reached.
© Sandra Haywood, University of Nottingham