What is The Breathe of Human Life? Air is drawn through the pharynx, the larynx, and the trachea. This air enters and leaves each  lung through a single main tube that branches from the trachea and is called the primary bronchus. Each bronchus branches profusely within its lung, carrying air through smaller and smaller passages known as bronchioles and the smaller alveolar ducts.

Finally, the smallest branches terminate in air sacs called alveoli, which are laced with a dense network of the tiny blood vessels called capillaries. The walls of both alveoli and capillaries are so thin that gases can easily pass through them. It is here, in the body’s 300 million alveoli, that the lungs perform their function – the exchange of oxygen and carbon dioxide.

When you inhale, the air, one-fifth of which is oxygen, enters the air sacs, and the oxygen enters the blood in the capillaries. Some of the entering oxygen is dissolved in the blood, but most of it combines chemically with hemoglobin, and is carried by it to the tissues. When the capillary blood reaches the body regions that need it, it releases oxygen. At the same time, the blood picks up the carbon dioxide produced by cells, and returns it to the alveoli to be exhaled.

What Determines How Much You Breathe?

The Breathe of Human Life?The rate and depth of respiration vary, depending on how quickly the body uses up oxygen and how fast it accumulates carbon dioxide. This usually depends on activity level. The respiratory center in the brain sends out impulses that drive the respiratory muscles. Other parts of the nervous system monitor the level of carbon dioxide in the blood, and if it rises by even a minute amount, signal the respiratory center. The center immediately modifies the rate and depth of respiration so that the carbon dioxide level returns to normal. The system for regulating oxygen levels is less sensitive to small changes.

When you are engaged in a quiet pastime, you breathe about 15 times a minute. In each breath, perhaps a pint (.55 liter) of air moves in and out of the lungs. This represents no more than 12 percent of a healthy young adult’s maximum single breath. In a strenuous activity, your breathing rate may double, and the amount of air taken into your lungs per breath may increase more than five times. By breathing deeper and faster, you use your lungs’ reserve capacities.

What is the Diaphragm?

The lungs are enclosed in a kind of cage in which the ribs form the sides and the diaphragm, an upwardly arching sheet of muscle, forms the floor. When you take a breath, the diaphragm is drawn downward until it becomes flat. At the same time, the muscles that surround the ribs contract, lifting them up like the hoops of a hoop skirt. In this way, the chest cavity becomes deeper and wider, and its air capacity increases.

What Happens When You Hiccup?

A hiccup is a two-part phenomenon. First, the diaphragm contracts involuntarily because the nerves that control it have become irritated by eating too fast, or for some other reason. Then, as air is inhaled, the space between the vocal cords at the back of the throat snaps shut with a characteristic clicking sound.

There are many remedies for hiccups. Some people drink a glass of water without pausing for air. Others hold their breath until the hiccups stop. These techniques may restore the normal rhythm of the twitching diaphragm by reducing the oxygen supply and increasing the carbon dioxide level. Other “cures” attempt to trick the nervous system with diversionary tactics, such as tickling the nose to induce sneezing or pulling the tongue. If hiccups persist in spite of all efforts to stop them, medical attention should be sought.

Is It Ever Dangerous to Breathe Pure Oxygen?

Surprising as it may seem, too much oxygen is actually poisonous. Doctors do sometimes give 100 percent oxygen in certain health emergencies, such as severe lung disease. However, that is nearly five times the normal concentration of oxygen in the air. Continuous breathing of 100 percent oxygen for an extended period of time can cause accumulation of fluid in the lungs, collapse of air sacs, convulsions, and, in premature infants, even blindness. Much lower oxygen concentrations are used for prolonged treatment to treat asthmatics, victims of heart attacks, and patients recovering from lung surgery.

Exhausted football player inhales oxygen. This practice is widespread, but options differ as to its value.

Deep Chambers of the Respiratory System

The lungs are a pair of not-quite-identical, cone-shaped organs that lie within the chest cavity. They are protected by ribs, spine, breastbone, and respiratory muscles. Between the lungs lie the trachea and the heart. Not shown on this cutaway drawing is the esophagus, which also lies between the lungs, but behind the trachea. (The esophagus leads from the pharynx to the stomach.) A layer of moist membranes called the pleura covers the lungs, and another pleural layer covers the inside of the chest cavity.

These lubrication surfaces allow the lungs to inflate and deflate smoothly, without sticking to one another. The diaphragm, which forms the floor of the chest cavity (and the roof of the abdominal cavity), is  continuous structure. The diaphragm has a few openings – where the esophagus connects to the stomach and for blood vessels.

The site of oxygen intake and removal of carbon dioxide is in the capillaries surrounding the alveoli. When magnified, alveolar sacs look like clusters of grapes or bubbles. Something like 300 million alveoli are packed into each lung. If the alveoli from one lung were opened and spread flat, they would cover half a tennis court.

It is estimated that in an average, healthy person, the alveoli will expand and contract approximately 15,000 times a day. It should be noted that almost all alveoli remain open, even when contracted.