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| Heart and blood |
Blood cells carry nourishment to all parts of our body through a network of arteries and veins and an average adult body contains about 4.5 liters of blood. Blood is red in colour and is made up of three types of cells, i.e., Red cells White cells and Platelets and a watery liquid called Plasma. These cells are so small that a drop of blood may contain millions of them. The red blood cells carry oxygen to all parts of the body and are produced in the marrow inside bones. The white cells protect the body against illness and fight infection. The third type of cells are the smallest type, called Platelets, and they help the blood in clotting in case of an injury. When we get injured and blood begins to flow out of wound, large quantities of platelets stick to gather to form a fine mesh, thus holding back other blood cells and forming a clot.
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The mechanism which pumps blood to various parts of the body is the Heart. The heart works throughout our life and its stopping results in death. The heart is located almost in the center of our chest and is protected by the rib cage. An average adult heart would weigh about 300 gm and be as big as a clenche first. The heart can be divided into four chambers, two located on either side, and two pumps which work side by side. One of the pumps is responsible for pumping oxygen enriched blood into arteries which carry it around the body.
The other pump brings the same blood back, once it is exhausted of oxygen, back into the heart through a network of veins from where it is sent back into the lungs for oxygen. The heart beats at an average of between 60 to 70 times per minute. The phase in which the heart muscles are relaxed is called ‘Diastole’ and the phase in which they are expanded is called ‘Systole’. The heart is able to bring a blood cell back for oxygen, after a full journey of the body, within sixty seconds.
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Medical