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Body Talk

Lungs - the breathing machines

We cannot survive without breathing, but how do we breathe and which organs in our body help us to breathe in the oxygen so vital for our survival? In the introductory Body Talk page, we examined how the brain functioned and what it looked like. Today we will check out how the lungs act as breathing machines to keep us alive with the help of the heart and other organs.

The lungs are like two spongy bags that can be filled with water and then squeezed dry again. Our lungs fill with air when we breathe in, and release most of the air again when we breathe out.

Human beings have two lungs - a left lung and a right lung which fill up most of the chest cavity. The somewhat bullet shaped lungs are suspended within the rib cage. They extend from just above the first rib down to the diaphragm, a muscular sheet that separates the chest cavity from the abdomen.

The lungs which are a pinkish white at birth, turns into a dark, slaty grey, mottled in patches, as people age. Spongy and porous in texture, the lungs are about 10-12 inches long, and is covered by a tough membrane called the Visceral Pleura.

The heart, large blood vessels and the tube connecting the mouth and stomach known as the Oesophagus, lie between the two lungs.

The air that you breathe through your nose and mouth, goes down the trachea which is also known as the windpipe (the hard tube in the front of your neck), to the lungs.

The air splits off into two tubes known as bronchial tubes at the end of the trachea. There is a bronchial tube in each lung, and these split into smaller and smaller tubes within the lung.

At the end of these smaller tubes there are air sacs known as alveoli. The very thin walls of each alveolus contain networks of extremely small blood vessels called pulmonary capillaries (tiny tubes carrying blood).

Once the air you breathe enters this area via the blood, the oxygen passes through the lining and into the blood.

All of you must be aware how important oxygen is to your bodies. The body contains millions of tiny cells, and the food energy they need to function - oxygen, is carried via the blood.

So, just as much as Oxygen gets into your body, when you breathe in, other waste products such as carbon dioxide too gets into your body. It is the lungs that help to pass it out of the body when you breathe out again.

This is why it is not good to hold your breath for too long because then, the cells wont get the Oxygen they need to function, and also the waste products will not get cleaned out. When you breathe, you take in about 16 kg of air everyday. When you are resting, you don't need to take in a lot of oxygen, so around a pint of air is taken in with each shallow breath. However, when you are running or exercising, you need more oxygen - as much as four quarts!

***

Clearing system

There is so much pollution in the air that we breathe, and the lungs have developed a special system to clean the dirt and germs that pass through our noses into them. Initially, the mucus produced by the mucus glands in our bodies act as defenders.

The dirt and germs get trapped in the mucus, but the mucus enters the lungs via the trachea. Then tiny hairs called cilia act as little brooms to sweep out the mucus out of your lungs. Without these tiny cilia you will be ill all the time.

How gas is exchanged

Gas is exchanged within the respiratory system, the primary function of which is to supply the blood in our body with oxygen. We know that when we breathe in (inhale) we take in oxygen, and when we breathe out (exhale), we send out carbon dioxide.

This is known as the exchange of gases. Inhaled air contains 20 per cent oxygen, 0.003 per cent carbon dioxide and the rest nitrogen. The air we exhale contains 16 per cent oxygen and the carbon dioxide is increased over a hundredfold to about four per cent.

Fact file

* You take 15-25 breaths per minute. In fact you breathe so regularly and so naturally, that you take your lungs for granted.

* The right lung is larger than the left lung. The right one weighs about 625 gm and the left lung about 567 gm, but the weight varies according to blood or serous fluids.

* The lungs of males are heavier than those of females.

* Volume wise, lungs are one of the largest organs in the body.

* The right lung has three lobes and the left has two lobes, which split into smaller lobes.

* The lungs and heart work as a team to keep us alive. See how vital team work could be, so, develop a team spirit and be like the heart and lungs in your body.

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