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Provide energy and remove waste

The job of the lungs is to bring oxygen into the body and remove carbon dioxide. Oxygen is a gas that provides us with energy, whilst carbon dioxide is a waste product or “exhaust” of the body.

Two lungs

The chest contains two lungs, one on the right side of the chest, the other on the left. Each lung is made up of sections called lobes. The lungs are soft and protected by the ribcage.

How does air get into the body?

Air is breathed in through the nose, mouth or both.

Nose or mouth

The nose is the best route for air to get into the lungs, as it is a better filter than the mouth. The nose decreases the amount of irritants that reach the lungs, whilst also heating and adding moisture to the air.
Mouth breathing is usually needed when exercising or when more air is needed, because the nose is not the most efficient way of getting large amounts of air into the lungs.

Journey down the windpipe

After entering the nose or mouth, air travels down the trachea or “windpipe”. The trachea is the tube lying closest to the neck.
Behind the trachea is the oesophagus or “food tube”. Air moves down the trachea when we inhale and food moves down the oesophagus when we eat.
The path air and food take is controlled by the epiglottis, a gate that prevents food from entering the trachea. Occasionally, food or liquid may enter the trachea, resulting in choking and coughing spasms.

Route into the lungs

The trachea divides into one left and one right breathing tube, termed bronchi. The left bronchus leads to the left lung and the right bronchus leads to the right lung. These breathing tubes continue to divide into smaller tubes called bronchioles.

The end of the trip

The bronchioles end in tiny air sacs called alveoli. Alveoli, which means “bunch of grapes” in Italian, look like clusters of grapes attached to tiny breathing tubes. There are over 300 million alveoli in normal lungs. If the alveoli were opened and laid out flat, they would cover the area of a doubles tennis court. Not all alveoli are in use at one time, so the lung has many to spare in the event of damage from disease, infection or surgery.   

 

What happens to oxygen and carbon dioxide?

Tiny blood vessels or capillaries surround every air sac in the lungs. The blood vessels surround the alveoli like a net, and this is where oxygen enters the blood and carbon dioxide leaves.

Trading places

Oxygen from the air enters the blood, and carbon dioxide from the body trades places with the oxygen by leaving the blood and entering the alveoli. Carbon dioxide is then exhaled out of the lungs. Oxygen must enter the blood and carbon dioxide must leave the blood at a regular rate for our body to function correctly.

Blood vessels

The lungs also have two sets of blood vessels. Blood vessels can be arteries or veins. One set of blood vessels feeds into and nourishes the lung, whilst the other set is responsible for transporting oxygen from the lung to the body via the heart.

Oxygen around the body

Blood that has collected oxygen from the lungs goes to the left side of the heart and is pumped around the body to deliver oxygen-rich blood (called arterial blood). After the blood has delivered oxygen to the cells of the body (skin, organs, etc.) it is called venous blood, and returns to the right side of the heart. Venous blood contains high amounts of carbon dioxide and small amounts of oxygen. The venous blood returns to the lungs to get rid of carbon dioxide and to pick up oxygen.

Not enough oxygen

When the lungs are unable to take in enough oxygen or oxygen is blocked from getting into the blood, the lung tries to protect itself by shutting down some blood vessels. The heart then has to pump the same amount of blood as usual through fewer blood vessels. This puts added stress on the heart. The back-up of blood causes the heart to work harder and often results in the heart becoming enlarged. This is termed cor pulmonale or right heart failure.

Which muscles help with breathing?

Many different muscles are used in breathing.

The diaphragm

The largest and most efficient muscle is the diaphragm. The diaphragm is a large muscle that lies under the lungs and separates them from the organs below.
As the diaphragm moves down or flattens, the ribs flare outward, the lungs expand and air is drawn in. This process is called inhalation or inspiration. As the diaphragm relaxes, air leaves the lungs and they spring back into their original position. This is called exhalation or expiration.
The lungs, like balloons, require energy to blow up but no energy is needed to get air out.

Other muscles

The other muscles used in breathing can be found between the ribs and between the neck and the upper ribs. The diaphragm, muscles between the ribs and one of the muscles in the neck, called the scalene muscle, are involved in almost every breath we take. If we need more help expanding our lungs, we “recruit” other muscles in the neck and shoulders.

When muscles don’t work

In some conditions, such as emphysema, the diaphragm is pushed down so that it doesn’t work properly. This means that the other muscles must work extra hard because they aren’t as efficient as the diaphragm. When this happens, patients may experience breathlessness or shortness of breath.

How do the lungs protect themselves?

The lungs have several ways of protecting themselves from irritants.

The nose

First, the nose acts as a filter when breathing in, preventing large particles of pollutants from entering the lungs.

Mucus

If an irritant does enter the lung, it will get stuck in the thin layer of mucus (also called sputum or phlegm) that lines the inside of the breathing tubes. An average of 85 grams of mucus are secreted onto the lining of these breathing tubes every day. The mucus is “swept up” toward the mouth by little hairs called cilia that line the breathing tubes.

Hairs in the throat

Cilia move mucus from the lungs upward toward the throat to the epiglottis. The epiglottis is the gate, which opens allowing the mucus to be swallowed. This occurs without us even thinking about it.
Spitting up sputum is not “normal” and does not occur unless the individual has chronic bronchitis or there is an infection, such as a chest cold, pneumonia or an exacerbation of chronic obstructive pulmonary disease (COPD).

Coughing

Another protective mechanism for the lungs is the cough. While coughing is a common event, is not a normal event and is the result of irritation to the bronchial tubes. A cough can expel mucus from the lungs faster than cilia.

Bronchospasms

The last of the common methods used by the lungs to protect themselves can also create problems.
The airways in the lungs are surrounded by bands of muscle.
When the lungs are irritated, these muscle bands can tighten, making the breathing tube narrower as the lungs try to keep the irritant out.
The rapid tightening of these muscles is called bronchospasm.
Some lungs are very sensitive to irritants and bronchospams may cause serious problems for people with COPD and they are often a major problem for those with asthma, because it is more difficult to breathe through narrowed airways.

Nguồn : ELF