Introduction To The Lungs

The lungs consist of two inflatable lobes that sit inside the rib cage in the thoracic cavity, just behind the heart. They supply the body with the air needed during rest and activity. Air reaches the lungs, primarily, via the nose. The nose is lined with mucus and fine hairs that act as filters to trap dust particles and stop them from entering the body. However, during exertion, when the demand for oxygen is high, if sufficient air is to be made available to meet the demands of the working muscles, it needs to be taken in through both the nose and mouth. From the nose and/or mouth the air passes through the Pharynx And Larynx (The Throat). The air is then drawn into the Trachea (Windpipe), which separates into two. These two tubes are called the Bronchi; one goes to feed the left lobe and one to the right. The bronchi then divide into smaller tubes called Bronchioles that run through the surface area of the lungs. At the end of the bronchioles are tiny air sacs called alveoli.

The structure of the lungs is sometimes compared to an upside down tree, the trachea being the trunk, the bronchi and bronchioles being the branches that divide and get smaller and smaller, and the alveoli being the leaves.

What are your lungs?

The lungs are a major component of your respiratory system, which is the network of organs and tissues that allows you to breathe.

You have two lungs, one on each side of your chest, commonly known as the thorax. The thorax is the region of your body that is between your neck and your abdomen.

Right lung

On your right side, the lung is divided into three lobes: superior, medium, and inferior. It is shorter than your left lung, but it is also wider. Pleural tissue is a protective coating that covers both of your lungs.

Left lung

Your left lung is divided into two lobes: superior and inner. Because your heart is located where the middle lobe of your left lung would be, your left lung is smaller than your right. The cardiac notch (where your heart fits) and the lingula, an extension of the superior lobe, are two features unique to the left lung.

What do the lungs do?

The lungs provide the body with oxygen and remove other gases, such as carbon dioxide, from the body. This procedure occurs between 12 and 20 times per minute.

When you breathe in through your nose or mouth, air travels down your pharynx, through your larynx, and into your trachea (windpipe).

Your trachea is separated into two airways known as bronchial tubes. One bronchial tract leads to the left lung, while the other leads to the right. For your lungs to function optimally, your airways must be open when you inhale and exhale. Additionally, they must be devoid of inflammation (swelling) and an aberrant amount of mucus.

Your bronchial tubes connect to bronchi, which are smaller air passages, and then to bronchioles. The bronchioles terminate in alveoli, where oxygen is conveyed from inhaled air to the bloodstream. Alveoli resemble clusters of tiny, spherical fruits.

Following oxygen absorption, the blood departs the lungs and is transported to the heart. It is then circulated throughout the body to supply oxygen to the cells of your tissues and organs.

When cells consume oxygen, they produce carbon dioxide, which is then transferred to the blood. The circulation transports carbon dioxide back to the lungs. When you exhale, carbon dioxide is eliminated.

Your respiratory system prevents harmful substances from entering your lungs by using:

• Small hairs in your nose that operate as an air-cleaning system, allowing large particles to pass through.
• Mucus produced in the trachea and bronchial tubes to keep the airways moist and to trap dust, bacteria, and other things.
• Cilia (small hairs in your respiratory tract) sweeping motion to keep air passages clean. Cigarette smoke is hazardous because it prevents cilia from functioning properly.

Where are your lungs located?

Your lungs are positioned in your chest (thorax). The thoracic cavity is the name given to the compartment that houses your lungs and other organs. Your lungs are supported by a muscle known as the diaphragm.

What do the lungs look like?

The colour of healthy lungs is pinkish-gray. You have likely seen photographs contrasting the lungs of smokers and non-smokers. Damaged lungs appear darker grey and may contain black patches.

Your right and left lungs, which are triangular in shape, resemble the ears of an elephant.

A typical lung in an adult human weighs approximately 2.2 pounds and measures approximately 9 inches in length when breathing normally and 10.5 inches when fully expanded.

Gaseous Exchange

Each alveolus (singular) looks like a tiny bubble and is covered by a network of tiny blood vessels called capillaries. The walls of alveoli (plural) and capillaries are only one cell thick. This allows the oxygen to diffuse (pass) easily through the walls of the alveoli and the capillaries, and into the bloodstream. The oxygen combines with haemoglobin, which is found in red blood cells. It is then carried to the heart which then pumps it around the body. Whilst the oxygen is leaving an alveolus, carbon dioxide, a waste product, is entering the alveolus ready to be breathed out.

This is called gas exchange or gaseous exchange.

The oxygen from the air passes through the thin walls of alveoli and then passes into the capillaries that surround them. The blood is now oxygenated.

As oxygen is diffused through the capillary walls from alveoli and into the bloodstream, carbon dioxide also diffuses via the capillaries from the bloodstream into the alveoli (gaseous exchange). The carbon dioxide is then exhaled.

Mechanisms Of Breathing

Air is sucked into the lungs by the contraction of the diaphragm muscle (sits at the bottom of the rib cage) and the intercostal muscles (situated between the ribs). During inspiration [breathing in] the diaphragm muscle contracts and flattens, pushing the rib cage out and the external intercostal muscles assist by contracting to lift the ribs up, sucking in the air. During expiration [breathing out] the diaphragm muscle relaxes, returning to a dome shape and the internal intercostal muscles contract, drawing the ribs in and down, forcing the air out. If you place your hands on the rib cage you can experience this, breathing in and feeling the rib cage lift expand and draw the air in and, breathing out and feeling the rib cage go in and down as the air is forced out.

Diaphragm muscle contracts and flattens. The external intercostal muscles contracting pulling the ribcage up and out sucking air in.

Diaphragm muscle relaxes and returns to a dome shape. The internal intercostal muscles contract, allowing the rib cage to move in and down

At rest the normal amount [volume] of air we breathe in is known as the tidal volume. When we try to force all the air out our lungs, there will still be a small amount left. This is known as the residual volume. The maximum amount we can breathe in (forced inspiration) and the maximum amount we can breathe out (forced expiration) is known as vital capacity. During exercise, our muscles need more oxygen and, in order to meet this increased demand, we start to breathe deeper and at a faster rate.

If the intensity of the exercise becomes so high that the respiratory system is unable to keep up with the increased demand, this will lead to an oxygen debt. In order for oxygen debt to be re-paid, the intensity of the exercise must be decreased. Breathing rate will continue to be high until sufficient oxygen is taken in to repay the debt. For example: running for a bus and having to stop to catch your breath.