the Body
Think of the body as divided into seven systems:
(click on the underlined links to learn more)
- [ bones ]
- [ brain and nerves ]
- [ muscles ]
- [ respiration ]
- [ circulation ]
- [ digestion ]
- [ glands ]
All are connected and interdependent, though each has a special network of its own.
On average there are 5 litres of blood in your body constantly being pumped through the circulatory system by the heart. Blood accounts for about 10% of body weight. It is a tissue consisting of red cells, white cells, platelets and plasma, with the plasma occupying a little more than half the volume.
Red corpuscles contain haemoglobin, which picks up oxygen from the lungs and delivers it to the tissues; when carrying oxygen, blood and arteries are bright red. White corpuscles are lighter and fairly transparent; they are less numerous than the red and more varied; they primarily combat infection by their mobility and ability to ingest or absorb bacteria and other foreign elements. Too many white cells, however can be as disastrous as too few; leukaemia is an overproduction. Blood platelets are smaller than the corpuscles but much more numerous. They influence the clotting of the blood, keeping us from bleeding to death from a nick or cut. They take care of immediate needs at the site of injury. Plasma is not made up of cells; it is 90% water and the balance is proteins, salts and most of the blood cargo such as nutrients, hormones, waste-products and antibodies. Quite often an ill person needs the plasma more than the corpuscles.
Bloods most important job is transportation. During all its travels it carries water, vital to every cell; it takes oxygen from the lungs and carbon dioxide to them; it carries nutrients to the cells and waste products away; it is a distributor of hormones, a circulator of antibodies and it transports heat from the hot to the cool regions. Blood plays a part in every body function and reflects its condition; of all the substances used for testing, blood is by far the most indicative of your health.
The main pumping station, the heart, is the size of a fist and weighs less than 1/2 kilogram. It doesn't lie entirely on the left side of the chest as is often supposed, but fairly near the centre with about one-third of its bulk over on the right. It has two pumps, each having a similar output; one sends blood through the pulmonary system, the other through the rest of the body. It beats a two-fold sound, roughly seventy times a minute, or four times for each normal breath. With increased physical demand its beat quickens and it pumps blood faster.
Blood pressure is the pressure of blood in the arteries together with a measure of the tension in the arterial wall produced by the blood forced through from the heart. It depends on the output of the heart (systolic pressure) and the resistance to flow by smaller arteries (diastolic pressure). The former is always greater than the latter, and the two are always recorded in that order. An average combination in the twenties would be 120:80. It increases with age and should be frequently checked. Lack of blood pressure can be more rapidly fatal than excess of it. Fainting occurs when there is a short-lived decrease in blood flow to the brain; a stoppage, no matter how brief, would cause brain damage.
A body can lose a quarter of its blood without any apparent severe consequences. One pint can be given at a transfusion and you can donate a pint of blood three or four times a year without ill effects.
[ the Body ]
Think of the body as divided into seven systems:
(click on the underlined links to learn more)
- [ bones ]
- [ brain and nerves ]
- [ muscles ]
- [ respiration ]
- [ circulation ]
- [ digestion ]
- [ glands ]
All are connected and interdependent, though each has a special network of its own.
Return to [ the Body ] Index page!