A spongy organ that moves oxygen through the bloodstream

By Colleen Travers 

Updated on August 16, 2023

 Medically reviewed by Scott Sundick, MD

The lungs are a major organ that is part of the respiratory system, taking in fresh air and getting rid of old, stale air. This mechanism of breathing also helps to allow you to talk. By taking in fresh air, the lungs are able to help oxygenate blood to be carried around your body. This is done by inhaling the air and bringing it in toward the pulmonary capillaries, which then become oxygen-filled cells that help with respiration.

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Anatomy

Structure

There are two lungs (a right and left) in the body, but they are different sizes. The right lung is bigger and is divided into three lobes (separated by fissures), while the left lobe is smaller consisting of two lobes. The left lobe is also smaller as it has to make room for the heart.

The left and right lungs are suspended by the lung root and separated by a mediastinum, a partition between the two. Each lung has three surfaces, named after their location in the thorax. They are the mediastinal surface, diaphragmatic surface, and costal surface. Lungs are protected by pleura, a thin layer of tissue that provides cushion and a small amount of fluid to help the lungs breathe smoothly.¹

Inside the lungs are bronchi—tubes that run from the trachea into each lung. The bronchi branch off into smaller tubes called bronchioles which help air reach the alveoli, which are tiny air sacs in each lung. There are approximately 30,000 bronchioles in each lung and 600 million alveoli in each lung combined.²

The lungs also consist of pulmonary arteries, pulmonary veins, bronchial arteries, as well as lymph nodes. While most arteries carry oxygenated blood to the tissues and veins carry deoxygenated blood back, this is reversed in the lungs. Deoxygenated blood is sent from the right ventricle of the heart to the lungs via the pulmonary artery. The blood is oxygenated in the lungs and exits through the pulmonary vein to the left side of the heart, where it is pumped out to the circulate through the body. Bronchial arteries, which stem from the aorta, get blood supply to fuel areas like the bronchi, lung roots, and surrounding structures.³

Location

The lungs are guarded by the rib cage, and they are located right above the diaphragm. Each lung is located near different organs in the body. The left lung lies close to the heart, thoracic aorta, and esophagus, while the right lung is by the esophagus, heart, both vena cavas (inferior and superior), and the azygos vein.³

Looking at the lungs from the front they lie right above the collarbone and go halfway down the rib cage, although the back of the lungs are slightly longer, ending just above the last rib, while the pleura extends down the entirety of the rib cage. Together with your heart, the lungs take up almost the entire width of the rib cage.⁴

Anatomical Variations

It’s common to see anatomical variations when it comes to the lungs. For example, in one study of 50 cadavers, 26% had incomplete and absent fissures, extra lobes, and/or an azygos lobe (when the azygos vein creates an extra fissure in the right lobe).⁵

While these anatomical variations are common and often go unnoticed in otherwise healthy individuals, it’s important to distinguish them when reading radiological images as well as ahead of any surgery involving the lungs and monitoring for any post-operative complications like air leakage.⁶ These variations occur can happen for a number of reasons. According to research published in Anatomy & Cell Biology, the most common include genetic and environmental factors during development.⁷

Function

The lungs are responsible for bringing in fresh air into the body. As you breathe in the diaphragm helps move air up into the lungs by tightening its muscles (relaxing pushes air out). Once air enters the lungs by way of the mouth and nose (with the help of mucus which traps dust and dirt from entering with the air), the air travels through the trachea and into the bronchi, filling up alveoli. From there, air travels to the blood vessels surrounding the alveoli. The red blood cells release carbon dioxide and exchange it for oxygen, which binds to hemoglobin molecules. The oxygenated blood circulates through the body. Carbon dioxide and other gases the body doesn’t need are exhaled out by the lungs.⁸

The act of the lungs exhaling is also what helps you speak. The exhaled air goes back through the trachea to the larynx and finally the vocal cords, making them vibrate and produce sound.²

Associated Conditions

Lung disease is an extremely broad term, as it covers a plethora of conditions ranging from mild to severe. The three main types of lung disease include:⁹

• Airway diseases including chronic obstructive pulmonary disease (COPD), and asthma. COPD affects 65 million people and is the third leading cause of death worldwide. Asthma affects 334 million people and affects 14% of children worldwide, making it one of the most common chronic childhood conditions.¹⁰

• Lung tissue diseases like pulmonary fibrosis and sarcoidosis. There are 30,000 to 40,000 new cases of pulmonary fibrosis diagnosed in the U.S. each year, affecting 100,000 people in total.¹¹ Sarcoidosis is considered a rare disease, affecting fewer than 200,000 in the U.S. ¹²

• Lung circulation diseases (which frequently also affect the heart) like pulmonary hypertension or pulmonary embolism. There are many different types of pulmonary hypertension, but those with lung diseases like chronic obstructive and fibrotic disease make up the second-largest group that deals with pulmonary hypertension.¹³ Pulmonary embolisms also range in severity, with people who have chronic lung disease being at higher risk. If left untreated, pulmonary embolism has a mortality rate as high as 30%.¹⁴

Tests

Your lung function hits max capacity between the ages of 20 to 25 years old, but after age 35 it naturally (and slightly) declines.¹⁵ However, difficulty breathing or shortness of breath is not normal and should be discussed with your healthcare provider immediately. After discussing your symptoms along with your overall health history, your healthcare provider may order one or more of the below tests to determine the cause behind your breathing difficulty:¹⁶

• Spirometry: A test that measures how much and how quickly air can move in and out of the lungs.

• Lung plethysmography test: Measuring how much air you can hold in the lungs and the amount of air left after exhaling.

• Diffusing capacity of the lungs test: A test that tells how much oxygen and carbon dioxide gets diffused into the bloodstream.

• Exercise stress test: Also commonly used to diagnose cardiac diseases, this test shows the amount of air that moves in and out of the lungs during exercise like walking or riding a stationary bike.