the human body has how many lungs

The lungs are the primary organs of the respiratory system in humans and most other animals including a few fish, and some snails. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart.

Their function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. Respiration is driven by different muscular systems in different species.

Mammals, reptiles and birds use their different muscles to support and foster breathing. In earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech possible.

1.3 kilograms

Humans have two lungs, a right lung, and a left lung. They are situated within the thoracic cavity of the chest. The right lung is bigger than the left, which shares space in the chest with the heart. The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier.

The lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, and which receive air breathed in via the conducting zone. The conducting zone ends at the terminal bronchioles. These divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place.

pleurae

Alveoli are also sparsely present on the walls of the respiratory bronchioles and alveolar ducts. Together, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli. Each lung is enclosed within a pleural sac of two membranes called pleurae; the membranes are separated by a film of pleural fluid, which allows the inner and outer membranes to slide over each other whilst breathing takes place, without much friction.

The inner pleura also divides each lung into sections called lobes. The right lung has three lobes and the left has two. The lobes are further divided into bronchopulmonary segments and pulmonary lobules. The lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purposes of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the tissue of the lungs, in the bronchial circulation.

Lung diseases

The tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer. Chronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances. A number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust.

Diseases such as bronchitis can also affect the respiratory tract. Medical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων “lung”) as in pneumonia.

In embryonic development, the lungs begin to develop as an outpouching of the foregut, a tube which goes on to form the upper part of the digestive system. When the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe. Blood is also diverted from the lungs through the ductus arteriosus. At birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire. The lungs only fully develop in early childhood.

Intricate Construction

Our two lungs are made up of a complex latticework of tubes, which are suspended, on either side of the heart, inside the chest cavity on a framework of elastic fibers. Air is drawn in via the mouth and the nose, the latter acting as an air filter by trapping dust particles on its hairs. The air is warmed up before passing down the windpipe, where it’s divided at the bottom between two airways called bronchi that lead to either lung.

Within the lungs, the mucus-lined bronchi split like the branches of a tree into tens of thousands of ever smaller tubes (bronchioles), which connect to tiny sacs called alveoli. The average adult’s lungs contain about 600 million of these spongy, air-filled structures. There are enough alveoli in just one lung to cover an area roughly the size of a tennis court.

Transfer of oxygen to the heart

The alveoli are where the crucial gas exchange takes place. The air sacs are surrounded by a dense network of minute blood vessels, or capillaries, which connect to the heart. Those that link to the pulmonary arteries carry deoxygenated blood that needs to be refreshed. Oxygen passes through the incredibly thin walls of the alveoli into the capillaries and is then carried back to the heart via the pulmonary veins.

At the same time, carbon dioxide is removed from the blood through the same process of diffusion. The rate at which we breathe is controlled by the brain, which is quick to sense changes in gas concentrations. This is certainly in the brain’s interests—it’s the body’s biggest user of oxygen and the first organ to suffer if there’s a shortage.

Your lungs work hard. Even when you’re resting, they’re diligently transporting oxygen into your bloodstream and moving carbon dioxide out. They’re part of a serious business run by an intricate structure of organs and tissues—aka your respiratory system. To keep you alive and breathing, your lungs are on the clock 24/7, 365 days a year. Breathing 12 to 15 times a minute, translating to 17,000 breaths a day or more than 6 million breaths a year. And no vacation days! Here’s how they get the job done:

1,500 Miles of Airways

Your lungs are one of the largest organs in your body. The surface area of both lungs is roughly the same size as a tennis court and the total length of the airways running through them is 1,500 miles. That’s about the distance from Chicago to Las Vegas.

When you breathe in—either through your nose or mouth—air moves from the throat down to the windpipe and into two main bronchial tubes that lead to each lung. These tubes then branch out into smaller passages called bronchioles, which deliver the air to small air sacs called alveoli. It’s here where fresh oxygen from the air is exchanged for carbon dioxide in the blood.

Power of 2

You have two lungs, the left lung and the right lung. The left lung is slightly smaller and has a notch to give room for the heart. Each lung is divided into lobes—the left lung has two and the right lung has three—which are similar to balloons filled with sponge-like tissue. Each lobe receives air from its own branch of the bronchial tree, but they all have the same function: bringing oxygen into the bloodstream and removing carbon dioxide. That’s why it’s possible (but by no means ideal) to live with just one lung.

6 Liters of Capacity

When you inhale, your lungs expand to hold the incoming air. How much air they hold is called lung capacity and varies with a person’s size, age, gender and respiratory health. The maximum amount of air an average adult male’s lungs can hold is about six liters (that’s the same as about three large soda bottles). There’s some math involved to get to that number, but basically, it’s adding up air from a normal breath, extra air you can force in, additional air you can force out after regular exhaling and the air that’s left in the lungs after all that.

2,000 Gallons a Day

Every day, you breathe in just over 2,000 gallons of air—enough to almost fill up a normal-sized swimming pool. That’s a lot of air. It’s the amount needed to oxygenate approximately 2,000 gallons of blood pumped through your heart daily.

Because lungs are constantly exposed to the external environment, they need some protection from dust, germs and other unwanted matter. That’s where mucus comes in. Your bronchial tubes are lined with cilia (they’re like thin little hairs) that carry mucus up into your throat to trap those yucky intruders until you cough, sneeze, clear your throat or swallow to get rid of them.

80 Percent of the Work

The diaphragm is the chief muscle of breathing. This dome-shaped wall of muscle does the most of the breathing work by expanding and contracting the chest to draw air in and out of your lungs. If your lungs are healthy, that’s about 80 percent. When lungs need to be more efficient (e.g., you have a lung disease that impairs breathing or even if you’re an athlete or musician looking to boost performance) a common place to start is with breathing exercises, which are focused on the diaphragm.

Lung anatomy

This spongy, pinkish organ looks like two upside-down cones in your chest. The right lung is made up of three lobes. The left lung has only two lobes to make room for your heart.

Bronchial tree

The lungs begin at the bottom of your trachea (windpipe). The trachea is a tube that carries the air in and out of your lungs. Each lung has a tube called a bronchus that connects to the trachea. The trachea and bronchi airways form an upside-down “Y” in your chest. This “Y” is often called the bronchial tree.

The bronchi branch off into smaller bronchi and even smaller tubes called bronchioles. Like the branches of a tree, these tiny tubes stretch out into every part of your lungs. Some of them are so tiny that they have the thickness of a hair. You have almost 30,000 bronchioles in each lung.

Each bronchiole tube ends with a cluster of small air sacs called alveoli (individually referred to as alveolus). They look like tiny grape bunches or very tiny balloons. There are about 600 million alveoli in your lungs. The small bubble shapes of the alveoli give your lungs a surprising amount of surface area — equivalent to the size of a tennis court. This means there’s plenty of room for vital oxygen to pass into your body.

How your lungs stay healthy

The alveoli stay partly inflated like a balloon even when you exhale air. Your lungs make a fluid called surfactant to help them stay open. Surfactant also contains fatty proteins that help keep the lungs healthy.

Your lungs are self-cleaning.

They make mucus to trap germs and particles. The mucus is then swept up by cilia, small hairs that line the airways. Normally, you swallow this mucus without noticing. If you have a respiratory illness, your lungs may make too much mucus.

The alveoli also contain immune cells called macrophages. These cells “eat” germs and irritants before they can cause an infection in your lungs.

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