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Anatomy of the Lungs

A spongy organ that moves oxygen through the bloodstream

Associated Conditions

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.

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.

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.

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.

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.

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.

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).

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. 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.

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.

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.

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:

• 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.
• 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. Sarcoidosis is considered a rare disease, affecting fewer than 200,000 in the U.S.
• 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. 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%.

Your lung function hits max capacity between the ages of 20 to 25 years old, but after age 35 it naturally (and slightly) declines. 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:

• 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.

National Cancer Institute SEER Training Modules. Anatomy of the lung .

Kids Health from Nemours. Your lungs & respiratory system .

Teach Me Anatomy. The lungs .

Chaudhry R, Bordoni B. Anatomy, thorax, lungs . StatPearls.

Poe E, Granite G. Anatomical lung variations: A study conducted on cadaveric specimens . International Journal of Anatomical Variations.

George BM, Nayak SB, Marpalli S. Morphological variations of the lungs: a study conducted on Indian cadavers . Anat Cell Biol . 2014;47(4):253-258. doi:10.5115/acb.2014.47.4.253

Kc S, Shrestha P, Shah AK, Jha AK. Variations in human pulmonary fissures and lobes: a study conducted in Nepalese cadavers . Anat Cell Biol . 2018;51(2):85-92. doi:10.5115/acb.2018.51.2.85

The Lung Association. How the lungs work .

Medline Plus. Lung disease .

World Health Organization. The global impact of respiratory disease .

NIH U.S. National Library of Medicine Genetics Home Reference. Idiopathic pulmonary fibrosis .

American Lung Association. Learn about sarcoidosis .

Hoeper MM, Ghofrani HA, Grünig E, Klose H, Olschewski H, Rosenkranz S. Pulmonary hypertension . Dtsch Arztebl Int . 2017;114(5):73-84. doi:10.3238/arztebl.2017.0073

Bĕlohlávek J, Dytrych V, Linhart A. Pulmonary embolism, part I: Epidemiology, risk factors and risk stratification, pathophysiology, clinical presentation, diagnosis and nonthrombotic pulmonary embolism . Exp Clin Cardiol . 2013;18(2):129-38.

American Lung Association. Lung capacity and aging .

MedlinePlus. Lung function tests .

By Colleen Travers Travers is a freelance writer and editor specializing in health, wellness, and fitness based in New York City. 

22.2 The Lungs

Learning objectives.

By the end of this section, you will be able to:

• Describe the overall function of the lung
• Summarize the blood flow pattern associated with the lungs
• Outline the anatomy of the blood supply to the lungs
• Describe the pleura of the lungs and their function

A major organ of the respiratory system, each lung houses structures of both the conducting and respiratory zones. The main function of the lungs is to perform the exchange of oxygen and carbon dioxide with air from the atmosphere. To this end, the lungs exchange respiratory gases across a very large epithelial surface area—about 70 square meters—that is highly permeable to gases.

Gross Anatomy of the Lungs

The lungs are pyramid-shaped, paired organs that are connected to the trachea by the right and left bronchi; on the inferior surface, the lungs are bordered by the diaphragm. The diaphragm is the flat, dome-shaped muscle located at the base of the lungs and thoracic cavity. The lungs are enclosed by the pleurae, which are attached to the mediastinum. The right lung is shorter and wider than the left lung, and the left lung occupies a smaller volume than the right. The cardiac notch is an indentation on the surface of the left lung, and it allows space for the heart ( Figure 22.2.1 ). The apex of the lung is the superior region, whereas the base is the opposite region near the diaphragm. The costal surface of the lung borders the ribs. The mediastinal surface faces the midline.

Each lung is composed of smaller units called lobes. Fissures separate these lobes from each other. The right lung consists of three lobes: the superior, middle, and inferior lobes. The left lung consists of two lobes: the superior and inferior lobes. A bronchopulmonary segment is a division of a lobe, and each lobe houses multiple bronchopulmonary segments. Each segment receives air from its own tertiary bronchus and is supplied with blood by its own artery. Some diseases of the lungs typically affect one or more bronchopulmonary segments, and in some cases, the diseased segments can be surgically removed with little influence on neighboring segments. A pulmonary lobule is a subdivision formed as the bronchi branch into bronchioles. Each lobule receives its own large bronchiole that has multiple branches. An interlobular septum is a wall, composed of connective tissue, which separates lobules from one another.

Blood Supply and Nervous Innervation of the Lungs

The blood supply of the lungs plays an important role in gas exchange and serves as a transport system for gases throughout the body. In addition, innervation by the both the parasympathetic and sympathetic nervous systems provides an important level of control through dilation and constriction of the airway.

Blood Supply

The major function of the lungs is to perform gas exchange, which requires blood from the pulmonary circulation. This blood supply contains deoxygenated blood and travels to the lungs where erythrocytes, also known as red blood cells, pick up oxygen to be transported to tissues throughout the body. The pulmonary artery is an artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli. The pulmonary artery branches multiple times as it follows the bronchi, and each branch becomes progressively smaller in diameter. One arteriole and an accompanying venule supply and drain one pulmonary lobule. As they near the alveoli, the pulmonary arteries become the pulmonary capillary network. The pulmonary capillary network consists of tiny vessels with very thin walls that lack smooth muscle fibers. The capillaries branch and follow the bronchioles and structure of the alveoli. It is at this point that the capillary wall meets the alveolar wall, creating the respiratory membrane. Once the blood is oxygenated, it drains from the alveoli by way of multiple pulmonary veins, which exit the lungs through the hilum .

Nervous Innervation

Dilation and constriction of the airway are achieved through nervous control by the parasympathetic and sympathetic nervous systems. The parasympathetic system causes bronchoconstriction , whereas the sympathetic nervous system stimulates bronchodilation . Reflexes such as coughing, and the ability of the lungs to regulate oxygen and carbon dioxide levels, also result from this autonomic nervous system control. Sensory nerve fibers arise from the vagus nerve, and from the second to fifth thoracic ganglia. The pulmonary plexus is a region on the lung root formed by the entrance of the nerves at the hilum. The nerves then follow the bronchi in the lungs and branch to innervate muscle fibers, glands, and blood vessels.

Pleura of the Lungs

Each lung is enclosed within a cavity that is surrounded by the pleura. The pleura (plural = pleurae) is a serous membrane that surrounds the lung. The right and left pleurae, which enclose the right and left lungs, respectively, are separated by the mediastinum. The pleurae consist of two layers. The visceral pleura is the layer that is superficial to the lungs, and extends into and lines the lung fissures ( Figure 22.2.2 ). In contrast, the parietal pleura is the outer layer that connects to the thoracic wall, the mediastinum, and the diaphragm. The visceral and parietal pleurae connect to each other at the hilum. The pleural cavity is the space between the visceral and parietal layers.

The pleurae perform two major functions: They produce pleural fluid and create cavities that separate the major organs. Pleural fluid is secreted by mesothelial cells from both pleural layers and acts to lubricate their surfaces. This lubrication reduces friction between the two layers to prevent trauma during breathing, and creates surface tension that helps maintain the position of the lungs against the thoracic wall. This adhesive characteristic of the pleural fluid causes the lungs to enlarge when the thoracic wall expands during ventilation, allowing the lungs to fill with air. The pleurae also create a division between major organs that prevents interference due to the movement of the organs, while preventing the spread of infection.

Everyday Connection –  The Effects of Second-Hand Tobacco Smoke

The burning of a tobacco cigarette creates multiple chemical compounds that are released through mainstream smoke, which is inhaled by the smoker, and through sidestream smoke, which is the smoke that is given off by the burning cigarette. Second-hand smoke, which is a combination of sidestream smoke and the mainstream smoke that is exhaled by the smoker, has been demonstrated by numerous scientific studies to cause disease. At least 40 chemicals in sidestream smoke have been identified that negatively impact human health, leading to the development of cancer or other conditions, such as immune system dysfunction, liver toxicity, cardiac arrhythmias, pulmonary edema, and neurological dysfunction. Furthermore, second-hand smoke has been found to harbor at least 250 compounds that are known to be toxic, carcinogenic, or both. Some major classes of carcinogens in second-hand smoke are polyaromatic hydrocarbons (PAHs), N-nitrosamines, aromatic amines, formaldehyde, and acetaldehyde.

Tobacco and second-hand smoke are considered to be carcinogenic. Exposure to second-hand smoke can cause lung cancer in individuals who are not tobacco users themselves. It is estimated that the risk of developing lung cancer is increased by up to 30 percent in nonsmokers who live with an individual who smokes in the house, as compared to nonsmokers who are not regularly exposed to second-hand smoke. Children are especially affected by second-hand smoke. Children who live with an individual who smokes inside the home have a larger number of lower respiratory infections, which are associated with hospitalizations, and higher risk of sudden infant death syndrome (SIDS). Second-hand smoke in the home has also been linked to a greater number of ear infections in children, as well as worsening symptoms of asthma.

Chapter Review

The lungs are the major organs of the respiratory system and are responsible for performing gas exchange. The lungs are paired and separated into lobes; The left lung consists of two lobes, whereas the right lung consists of three lobes. Blood circulation is very important, as blood is required to transport oxygen from the lungs to other tissues throughout the body. The function of the pulmonary circulation is to aid in gas exchange. The pulmonary artery provides deoxygenated blood to the capillaries that form respiratory membranes with the alveoli, and the pulmonary veins return newly oxygenated blood to the heart for further transport throughout the body. The lungs are innervated by the parasympathetic and sympathetic nervous systems, which coordinate the bronchodilation and bronchoconstriction of the airways. The lungs are enclosed by the pleura, a membrane that is composed of visceral and parietal pleural layers. The space between these two layers is called the pleural cavity. The mesothelial cells of the pleural membrane create pleural fluid, which serves as both a lubricant (to reduce friction during breathing) and as an adhesive to adhere the lungs to the thoracic wall (to facilitate movement of the lungs during ventilation).

Review Questions

Critical thinking questions.

1. Compare and contrast the right and left lungs.

2. Why are the pleurae not damaged during normal breathing?

Answers for Critical Thinking Questions

• The right and left lungs differ in size and shape to accommodate other organs that encroach on the thoracic region. The right lung consists of three lobes and is shorter than the left lung, due to the position of the liver underneath it. The left lung consist of two lobes and is longer and narrower than the right lung. The left lung has a concave region on the mediastinal surface called the cardiac notch that allows space for the heart.
• There is a cavity, called the pleural cavity, between the parietal and visceral layers of the pleura. Mesothelial cells produce and secrete pleural fluid into the pleural cavity that acts as a lubricant. Therefore, as you breathe, the pleural fluid prevents the two layers of the pleura from rubbing against each other and causing damage due to friction.

This work, Anatomy & Physiology, is adapted from Anatomy & Physiology by OpenStax , licensed under CC BY . This edition, with revised content and artwork, is licensed under CC BY-SA except where otherwise noted.

Images, from Anatomy & Physiology by OpenStax , are licensed under CC BY except where otherwise noted.

Access the original for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction .

Anatomy & Physiology Copyright © 2019 by Lindsay M. Biga, Staci Bronson, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Matern, Katie Morrison-Graham, Kristen Oja, Devon Quick, Jon Runyeon, OSU OERU, and OpenStax is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License , except where otherwise noted.

Learn more about the human body's respiratory system.

Our lungs fuel us with oxygen, the body's life-sustaining gas. They breathe in air, then extract the oxygen and pass it into the bloodstream, where it's rushed off to the tissues and organs that require it to function.

Oxygen drives the process of respiration, which provides our cells with energy. When we exhale, we produce carbon dioxide as a byproduct. Without this vital exchange, our cells would quickly die and leave the body to suffocate.

Since the lungs process air, they are the only internal organs that are constantly exposed to the external environment. Central to the human respiratory system, they breathe in between 2,100 and 2,400 gallons (8,000 and 9,000 liters) of air each day—the amount needed to oxygenate the 2,400 gallons (9,000 liters) or so of blood that is pumped through the heart daily.

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.

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.

The actual job of breathing is done mainly by the diaphragm , the sheet of muscles between the chest and abdomen. These muscles contract when we breathe in, expanding the lungs and drawing in air. We breathe out simply by relaxing the diaphragm; the lungs deflate like balloons.

Lungs are delicate organs and vulnerable to a range of illnesses . The most common of these in Western countries are bronchitis and emphysema, which are often caused by smoking. Tubes inside the lung become chronically inflamed, producing excess mucus. Smoking can also lead to lung cancer, the world's major cancer, which is diagnosed in 1.4 million people a year.

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The lungs replenish the body with life-giving oxygen. Learn about the anatomy of the lungs, how the organs make respiration possible, and how they are vulnerable to illnesses.

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Lungs : Anatomy, Function and Related Diseases

Table of Contents

Introduction

Lung – anatomy, borders of lungs, surfaces of lungs, right and left lung, microanatomy, lung microbiota, blood supply, nerve supply, function of the lungs, related diseases, frequently asked questions.

Lungs are the primary respiratory organs found in humans and most animals. The respiratory system consists of lung parenchyma and airway. The airway consists of the bronchus, which bifurcates into trachea and further divides into bronchioles and alveoli.

Humans have two lungs – a right lung and a left lung. It is found in the thoracic cavity of the chest. It is found near the backbone on either side of the heart. The lungs function to draw oxygen from the air and transport into the bloodstream and to remove carbon dioxide from the blood. This whole process is known as gas exchange. Lungs also supply the airflow with the help of which human speech is possible.

The diaphragm is the muscle which is responsible for driving gaseous exchange in the lungs. Both the lungs together weigh around 1.3 kg, the right one being heavier than the left. The lungs are enclosed in a pleural cavity called pleurae that is filled with pleural fluid. The pleural fluid between the outer and inner membranes smoothes the process of breathing and prevents friction.

The lungs are conical in shape with a rounded narrow apex at the top. At the bottom is a broad concave base that lies on the convex surface of the diaphragm. Anatomically, lungs have an apex, three surfaces and three borders.

The three borders are anterior, posterior and inferior borders. The anterior border coincides with the pleural reflection and is known to form a cardiac notch in the left lung. The cardiac notch is a concavity that accommodates the heart. The posterior border extends from C7 to T10 and is a thicker structure. The inferior border is thin in nature and separates the base of the lung from the costal surface.

The three surfaces are medial, costal and diaphragmatic surfaces. The costal surface is layered by the costal pleura and is found along the lines of sternum and ribs. It connects the medial surface at the anterior and posterior borders and also joins the diaphragmatic surface at the inferior border. The medial surface is related to the sternum anteriorly and to the vertebrae posteriorly. The diaphragmatic surface is convex on the upper side forming the floor of the thoracic cavity and concave on the lower side, forming the roof of the abdominal cavity.

The lungs have a central recession called hilum from where the blood vessels and airway arrive into the lungs and make up the root of the lung. The pleural membranes that surround the lung are double serous membranes in between which the pleural fluid is present. Each of the lungs is divided into lobes and lobules.

The right lung has three lobes – an upper, middle and lower one. The right lung usually weighs between 155g – 720g in males and 100g to 590g in females.

The left lung has two lobes – an upper lobe and a lower lobe. It does not have a middle lobe like the right lung. It weighs between 110g – 675g in men and 100g – 590g in women.

The lungs are a part of the lower respiratory tract, and they house the bronchial tubes that branch from the trachea. The main bronchus tube divides multiple times after entering the lungs and forms bronchioles that eventually form the minute air sacs called alveoli. The alveoli is the location of gaseous exchange between the respiratory system and blood capillaries. From the hilum, the lymphatic vessels, nerves, bronchus, and pulmonary arteries and veins enter the lungs.

All portions of the respiratory tract such as the trachea, bronchi and bronchioles are lined with respiratory epithelium. The respiratory epithelium is ciliated and scattered with goblet cells that secrete mucus.

Alveoli, also known as air space or air sacs, are millions of hollow cup-shaped cavities found in the lungs where exchange of oxygen and carbon dioxide takes place. The alveoli makes up the functional tissue of the lungs called lung parenchyma that occupy around 90% of the total lung space.

The alveoli consists of two types of alveolar cells and an alveolar macrophage. The two types of cells, also known as pneumocytes, are denoted as type I and type II cells.

The type I cells are made up of squamous epithelium — they are thin and enable gaseous exchange. They make up the alveolar septa that separates the alveoli from each other. The type II alveolar cells are smaller and line the alveoli. They secrete lung surfactant and epithelial lining fluid that decreases the alveolar surface tension.

The alveolar macrophage is important for immunity as they remove depositions from the alveolar surface such as loose RBCs.

The lung houses a complex variety of microbial communities. They include bacteria, bacteriophages, fungi and viruses. The core 9 bacteria are – Streptococcus, Staphylococcus, Veillonela, Megasphaera, Fusobacterium, Acinetobacter, Pseudomonas, Sphingomonas and Prevotella . These microbes interact with the epithelial cells of the airway and play a major role in maintaining homeostasis. The common fungal species found in the lung include Aspergillus, Saccharomyces, Candida and Malassezia .

Changes in the composition of the microbiota can cause diseases such as asthma, chronic obstructive pulmonary disease and cystic fibrosis.

The lungs are supplied with blood by both pulmonary and bronchial circulation. The pulmonary circulation carries deoxygenated blood from the heart to the lungs and transports back oxygenated blood to the heart that can be supplied to the body. The bronchial circulation, on the other hand, transports oxygenated blood to the airway of the lungs with the help of bronchial arteries that come from the aorta.

There are three bronchial arteries; two in the left lung and one in the right lung that branch along with the bronchi and bronchioles. The average blood volume of the lungs is about 450ml that accounts for 9% of the total blood supply.

The lung is innervated from two sources – the pulmonary plexus that is a combination of sympathetic and parasympathetic innervation, and the phrenic nerve. The pulmonary plexus has afferent and efferent autonomic nerve fibres and it sits at the root of the lung. The vagus nerve (parasympathetic) helps in the dilation of blood vessels, constriction of the bronchi and also increases gland secretion. The sympathetic nerve, on the other hand, helps in the constriction of pulmonary vessels and dilation of the bronchi.

Refer: Difference between Type 1 and Type 2 Pneumocytes

• Gaseous Exchange: The primary function of the lungs is to facilitate gaseous exchange. Alveoli, the functional unit of the lungs, have thin membranes that allow easy exchange of gases. But the lungs cannot expand or relax on their own during the breathing process . The diaphragm and intercostal muscles are two main respiratory muscles that help in inhalation and exhalation.

These muscles contract, pull up the rib cage and increase the volume of the lungs for inhalation. During breathing out, the diaphragm and intercostal muscles relax, bringing the rib cage back to its original position.

• Protection: The respiratory tract is lined with respiratory epithelium that is interspersed with goblet cells. The goblet cells secrete mucus which acts as an important barrier against air borne infections. The mucus also contains many antimicrobial compounds such as antioxidants, antiproteases, and defensins.

They have macrophages that destroy or engulf waste debris and microbes by the process of phagocytosis. They also have antigen presenting cells called dendritic cells that activate the T cells and B cells for adaptive immune response.

• Other Functions: The lungs help in regulating the blood pressure by becoming a part of the renin-angiotensin complex. It also maintains an acid-base homeostasis in the blood by expelling carbon dioxide during breathing.

Serotonin, bradykinin, leukotrienes and prostaglandins are excreted by the lungs. Drugs can be absorbed, modified and excreted via the lungs. They also filter out clots from veins that could otherwise cause a stroke.

• Asthma: It is a long-term inflammatory disease that affects the airways of the lung. It obstructs the airflow and triggers spasms in the bronchioles. It is caused either due to genetic reasons or environmental factors such as air pollution and allergens. Most common symptoms include wheezing, coughing, shortness of breath and chest tightness.
• COPD: Chronic obstructive pulmonary disease is a long term progressive respiratory condition that worsens with everyday activities. It is caused by smoking, pollution or even genetic factors. The common symptoms include coughing and shortness of breath.
• Bronchitis: It is the inflammation of the bronchioles that leads to coughing of sputum, shortness of breath, wheezing and chest pain. Bronchitis can be both acute and chronic.
• Cystic Fibrosis: It is a recessive autosomal genetic disorder that affects the lungs, pancreas, kidney, liver and intestine. It leads to difficulty in breathing frequent lung infections.
• Pulmonary hypoplasia: It is a congenital malformation which is a condition where the lungs are underdeveloped. It results in a low number of bronchioles and alveolar segments.

Recommended Video:

This sums up the structure of the lungs. Keep visiting BYJU’S Biology for more information.

• Lung Volumes and Lung Capacity
• Difference between Right and Left Lung
• Lung Cancer

What is the shape of the lungs?

What is the root of the lung, how many lobes are there in the lungs.

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Class 10 Biology (India)

Course: class 10 biology (india)   >   unit 1.

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Video transcript

Clinical Benefit From Immunotherapy in Patients With SCLC Is Associated With Tumor Capacity for Antigen Presentation

Affiliations.

• 1 Thoracic Oncology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York; Department of Medicine, Weill Cornell Medical College, New York, New York; Druckenmiller Center for Lung Cancer Research, Memorial Sloan Kettering Cancer Center, New York, New York. Electronic address: [email protected].
• 2 Bristol-Myers Squibb, New York, New York.
• 3 Thoracic Oncology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York; Department of Medicine, Weill Cornell Medical College, New York, New York.
• 4 Marie-Josée and Henry R. Kravis Center for Molecular Oncology, Memorial Sloan Kettering Cancer Center, New York, New York.
• 5 Cancer Biology Program, Louis V. Gerstner Jr. Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, New York.
• 6 Druckenmiller Center for Lung Cancer Research, Memorial Sloan Kettering Cancer Center, New York, New York.
• 7 Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York.
• 8 Perlmutter Cancer Center, New York University Langone Health, New York, New York.
• PMID: 37210008
• PMCID: PMC10524620 (available on 2024-09-01 )
• DOI: 10.1016/j.jtho.2023.05.008

Introduction: A small percentage of patients with SCLC experience durable responses to immune checkpoint blockade (ICB). Defining determinants of immune response may nominate strategies to broaden the efficacy of immunotherapy in patients with SCLC. Prior studies have been limited by small numbers or concomitant chemotherapy administration.

Methods: CheckMate 032, a multicenter, open-label, phase 1/2 trial evaluating nivolumab alone or with ipilimumab was the largest study of ICB alone in patients with SCLC. We performed comprehensive RNA sequencing of 286 pretreatment SCLC tumor samples, assessing outcome on the basis of defined SCLC subtypes (SCLC-A, -N, -P, and -Y), and expression signatures associated with durable benefit, defined as progression-free survival more than or equal to 6 months. Potential biomarkers were further explored by immunohistochemistry.

Results: None of the subtypes were associated with survival. Antigen presentation machinery signature (p = 0.000032) and presence of more than or equal to 1% infiltrating CD8+ T cells by immunohistochemistry (hazard ratio = 0.51, 95% confidence interval: 0.27-0.95) both correlated with survival in patients treated with nivolumab. Pathway enrichment analysis revealed the association between durable benefit from immunotherapy and antigen processing and presentation. Analysis of epigenetic determinants of antigen presentation identified LSD1 gene expression as a correlate of worse survival outcomes for patients treated with either nivolumab or the combination of nivolumab and ipilimumab.

Conclusions: Tumor antigen processing and presentation is a key correlate of ICB efficacy in patients with SCLC. As antigen presentation machinery is frequently epigenetically suppressed in SCLC, this study defines a targetable mechanism by which we might improve clinical benefit of ICB for patients with SCLC.

Keywords: Antigen presentation; Epigenetics; Immune checkpoint blockade; Small cell lung cancer.

Copyright © 2023 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

Publication types

• Clinical Trial, Phase II
• Clinical Trial, Phase I
• Multicenter Study
• Research Support, Non-U.S. Gov't
• Research Support, N.I.H., Extramural
• Antigen Presentation
• Immunotherapy
• Ipilimumab / therapeutic use
• Lung Neoplasms* / pathology
• Nivolumab / therapeutic use
• Small Cell Lung Carcinoma* / pathology

Grants and funding

• P30 CA008748/CA/NCI NIH HHS/United States
• R01 CA258784/CA/NCI NIH HHS/United States
• R35 CA263816/CA/NCI NIH HHS/United States
• U24 CA213274/CA/NCI NIH HHS/United States

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Lung Inflammation: Pneumonia

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