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.
Respiration is more than inhaling and exhaling, it is a very organised method of distributing oxygen around the body. All cells need oxygen around the body. All cells need oxygen to survive. A relaxed person breathes in and out some ten to fourteen times a minute drawing in between 4.5 to 6 litres of air. We carry meagre reserves of oxygen so for any physical activity there is an immediate need for more air. Strenuous exercise can require as much as 90 litres of air a minute with only a second between each breath.
Breathing is controlled by the diaphragm, a large flat muscle separating the chest from the abdomen. It contracts, moving downward - 8 mm in quiet breathing, almost 7.5 cm in deep breathing. This movement increases the capacity of the chest, while at the same time the ribs shift from a sloping position to a more horizontal one. Air rushes in to fill the vacuum in the lungs. For exhalation, the diaphragm relaxes and is pushed upward by abdominal muscles; the ribs return to their former position.
Air is taken in through the nostrils or the mouth or both. It is cleansed by the hairs at the entrance of the nose and by the thin hairs deeper inside. The mucous cells of the nose help to humidify the air, making it less irritating to the delicate structure inside the chest. This is why it is preferable to breathe through the nose rather than the mouth. Air then enters the pharynx, a fibro-muscular passage about 13 cm long; food also passes down it. Then food and air passages separate, the air going through the larynx at the front of the neck and into the windpipe (trachea), a 13 cm long elastic tube. Where there's a bump on your breastbone, the windpipe divides into two main bronchi, each subdividing into much smaller bronchioles which in turn divide into many small ducts that lead into the lungs and culminate in alveoli.
The lungs are a pair of large, spongy half cones almost filling the chest area and consisting entirely of air sacs. Together they weigh about 1 kilogram, the right one usually heavier than the left. Architecturally they are rather poor as they have the same entrance as exit. This means there is usually only a partial interchange of gas and about five-sixths of the air present in the lungs is still there when the next breath is taken. Hence recommendations to breathe deeply for good health, as only in this manner is there a chance of exchanging stale air; some molecules can stay in the lungs for life.
It is at the alveoli of the lungs where gaseous diffusion most easily occurs. Each one is covered with a tracery of blood capillaries through which blood cells pass giving off carbon dioxide and taking up the oxygen just breathed in. The two ventricles of the heart are responsible for the blood flow; the right one pumps its blood into the capillary network of the lungs, the left one pumps the oxygenated blood into the capillary network of the body.
Respiration can cause some oddities. Laughter is actually deep breathing followed by spasmodic breathings out. Maybe this way of really cleaning out the lungs is responsible for the belief that if you laugh you are healthy. Yawning is a prolonged deep breath to give the body a reviving and plentiful supply of oxygen. Sighing involves extra breathing out. Hiccups are spasmodic inhalations which end in a click due to a sudden closing of the vocal cords; either the diaphragm is at fault or the nerves controlling it.
[ 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!