Lungs Lungs Home > Respiratory System > Lungs and Respiratory System of the Chest > Lungs Lungs The human lungs are a pair of large, spongy organs optimized for gas exchange between our blood and the air. Our bodies require oxygen in order to survive. The lungs provide us with that vital oxygen while also removing carbon dioxide before it can reach hazardous levels. If the inner surface of the lungs could be stretched out flat, they would occupy an area of around 80 to 100 square meters – about the size of half of a tennis court! The lungs also provide us with the air we need in order to speak, laugh at jokes, and sing.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image Anatomy of the Lungs Pleura The pleura are double-layered serous membranes that surround each lung. Attached to the wall of the thoracic cavity, the parietal pleura forms the outer layer of the membrane. The visceral pleura forms the inner layer of the membrane covering the outside surface of the lungs.

Between the parietal and visceral pleura is the pleural cavity, which creates a hollow space for the lungs to expand into during inhalation. Serous fluid secreted by the pleural membranes lubricates the inside of the pleural cavity to prevent irritation to the lungs during breathing. External Anatomy Occupying most of the space within the thoracic cavity, the lungs extend laterally from the heart to the ribs on both sides of the chest and continue posteriorly toward the spine . Each soft, spongy lung is roughly cone-shaped with the superior end of the lung forming the point of the cone and the inferior end forming the base. The superior end of the lungs narrows to a rounded tip known as the apex. The inferior end of the lungs, known as the base, rests on the dome-shaped diaphragm . The base of the lungs is concave to follow the contour of the diaphragm. The left lung is slightly smaller than the right lung because 2/3 of the heart is located on the left side of the body. The left lung contains the cardiac notch, an indentation in the lung that surrounds the apex of the heart. Each lung consists of several distinct lobes.

The right lung (the larger of the two) has 3 lobes – the superior, middle, and inferior lobes. The horizontal fissure separates the superior lobe from the middle lobe, while the right oblique fissure separates the middle and inferior lobes. The smaller left lung only has 2 lobes – superior and inferior – separated by the left oblique fissure. Bronchi Air enters the body through the nose or mouth and passes through the pharynx, larynx , and trachea . Just before reaching the lungs, the trachea then splits into the left and right bronchi – large, hollow tubes made of hyaline cartilage and lined with ciliated pseudostratified epithelium. The hyaline cartilage of the bronchi forms incomplete rings shaped like the letter “C” with the open part of the ring facing toward the posterior end of the bronchi. The rigid hyaline cartilage prevents the bronchi from collapsing and blocking airflow to the lungs.

Pseudostratified epithelium lines the inside of the hyaline ring and connects the unfinished ends of the ring to form a hollow tube shaped like the letter “D” with the flat part of the tube facing the posterior direction. Each lung receives air from a single, large primary bronchus. As the primary bronchi enter the lungs, they branch off into smaller secondary bronchi that carry air to each lobe of the lung. Thus, the right bronchus branches off into 3 secondary bronchi while the left lung branches off into 2 secondary bronchi. The secondary bronchi further branch into many smaller tertiary bronchi within each lobe. The secondary and tertiary bronchi improve the efficiency of the lungs by distributing air evenly within each lobe of the lungs. The pseudostratified epithelium that lines the bronchi contains many cilia and goblet cells. Cilia are small hair-like cellular projections that extend from the surface of the cells. Goblet cells are specialized epithelial cells that secrete mucus to coat the lining of the bronchi. Cilia move together to push mucus secreted by the goblet cells away from the lungs.

Particles of dust and even pathogens like viruses, bacteria and fungi in the air entering the lungs stick to the mucus and are carried out of the respiratory tract. In this way mucus helps to keep the lungs clean and free of disease. Bronchioles Many small bronchioles branch off from the tertiary bronchi. Bronchioles differ from bronchi both in size (they are smaller) and in the composition of their walls. While bronchi have hyaline cartilage rings in their walls, bronchioles are made of elastin fibers and smooth muscle tissue. The tissue of the bronchiole walls allows the diameter of bronchioles to change to a significant degree. When the body requires greater volumes of air entering the lungs, such as during exercise, the bronchioles dilate to permit greater airflow. In response to dust or other environmental pollutants, the bronchioles can constrict to prevent the pollution of the lungs. The bronchioles further branch off into many tiny terminal bronchioles. Terminal bronchioles are the smallest air tubes in the lungs and terminate at the alveoli of the lungs. Like bronchioles, the terminal bronchioles are elastic, capable of dilating or contracting to control airflow into the alveoli.

Alveoli Alveoli are the functional units of the lungs that permit gas exchange between the air in the lungs and the blood in the capillaries of the lungs. Alveoli are found in small clusters called alveolar sacs at the end of the terminal bronchiole. Each alveolus is a hollow, cup-shaped cavity surrounded by many tiny capillaries. The walls of the alveolus are lined with simple squamous epithelial cells known as alveolar cells. A thin layer of connective tissue underlies and supports the alveolar cells. Capillaries surround the connective tissue on the outer border of the alveolus. The respiratory membrane is formed where the walls of a capillary touch the walls of an alveolus. At the respiratory membrane, gas exchange occurs freely between the air and blood through the extremely thin walls of the alveolus and capillary. Septal cells and macrophages are also found inside the alveoli. Septal cells produce alveolar fluid that coats the inner surface of the alveoli.

Alveolar fluid is extremely important to lung function, as it is a surfactant that moistens the alveoli, helps maintain the elasticity of the lungs, and prevents the thin alveolar walls from collapsing. Macrophages in the alveoli keep the lungs clean and free of infections by capturing and phagocytizing pathogens and other foreign matter that enter the alveoli along with inhaled air. Physiology of the Lungs Pulmonary Ventilation Our lungs receive air from the external environment through the process of negative pressure breathing. Negative pressure breathing requires a pressure differential between the air inside the alveoli and atmospheric air. Muscles surrounding the lungs, such as the diaphragm, intercostal muscles , and abdominal muscles, expand and contract to change the volume of the thoracic cavity. Muscles expand the thoracic cavity and decrease the pressure inside the alveoli to draw atmospheric air into the lungs. This process of drawing air into the lungs is known as inhalation or inspiration. Muscles can also contract the size of the thoracic cavity to increase the pressure inside of the alveoli and force air out of the lungs. This process of pushing air out of the lungs is known as exhalation or expiration.

Normal breathing involves several different mechanisms. Shallow breathing is accomplished by the contraction of the diaphragm and the external intercostal muscles for inhalation. During exhalation, the muscles relaxing and the elasticity of the lungs returning to their resting volume expels air out of the lungs. Our bodies accomplish deep breathing by a pronounced inferior movement of the diaphragm towards the abdomen. The external intercostal muscles along with the sternocleidomastoid and scalene muscles in the neck expand the space between the ribs, increasing the volume of the chest. During deep exhalation, the internal intercostal muscles and abdominal muscles contract to decrease the volume of the thoracic cavity, forcing air out of the lungs. Eupnea is the quiet breathing that happens when the body is at rest. During eupnea, the body mostly depends on shallow breathing with occasional deep breaths as the body needs slightly higher levels of gas exchange. Lung Volume The total air volume of the lungs is about 4 to 6 liters and varies with a person’s size, age, gender, and respiratory health. Lung volumes are measured clinically by a device known as a spirometer.

Normal shallow breathing only moves a small fraction of the lungs’ total volume into and out of the body with each breath. This volume of air, known as tidal volume, usually measures only around 0.5 liters. Deep breathing can force more air into and out of the lungs than during shallow breathing. The volume of air exchanged during deep breathing is known as vital capacity and ranges between 3 to 5 liters, depending on the lung capacity of the individual. There is a residual volume of around 1 liter of air that remains in the lungs at all times, even during a deep exhalation. Fresh air entering the lungs with each breath mixes with the residual air in the lungs so that the residual air is slowly exchanged over time even at rest. External Respiration External respiration is the process of exchanging oxygen and carbon dioxide between the air inside the alveoli and the blood in the capillaries of the lungs. Air inside the alveoli contains a higher partial pressure of oxygen compared to the blood in the capillaries. Conversely, blood in the lungs' capillaries contains a higher partial pressure of carbon dioxide compared to the air in the alveoli.

These partial pressures cause oxygen to diffuse out of the air and into the blood through the respiratory membrane. At the same time, carbon dioxide diffuses out of the blood and into the air through the respiratory membrane. The exchange of oxygen into the blood and carbon dioxide into the air allows the blood leaving the lungs to provide oxygen to the body’s cells, while depositing carbon dioxide waste into the air. Control of Breathing Breathing is controlled by the brain and may be controlled both consciously and unconsciously. Unconscious control of breathing is maintained by the respiratory center of the brainstem . The respiratory center monitors the concentration of gases in the blood and adjusts the rate and depth of breathing as needed. During exercise or other exertion, the respiratory center automatically increases the breathing rate to provide constant levels of oxygen to the blood. During rest, the respiratory center reduces the breathing rate to prevent hyperventilation and maintain healthy oxygen and carbon dioxide levels in the blood. Conscious control of breathing is maintained by the cerebral cortex of the brain . The cerebral cortex may override the respiratory center and often does so during activities such as speaking, laughing, and singing.

Unconscious control of breathing resumes as soon as conscious control of breathing ends, preventing the body from suffocating from lack of breathing. Prepared by Tim Taylor, Anatomy and Physiology Instructor Why do you have two lungs but only one heart? | HowStuffWorks Why do you have two lungs but only one heart? Susana Gonzalez/AFP/ Getty Images Your body is pretty amazing. At any given point you have a great many biological processes going on, such as digestion, respiration, metabolism, and fighting off invading bacteria. Different regions and systems within your body work together to create a state of balance -- just the right amount of blood sugar here, just enough electrolytes there -- to keep you working at peak performance. But have you ever asked yourself how your body got to be the way it is? Why do you have two of some organs and just one of others? Take the heart and lungs , for instance -- why do you have two lungs but just one heart? Wouldn't it be better to have two hearts? Learn More 13 People with Extra Body Parts Your vital organs -- like your lungs, your heart, your pancreas, brain and liver -- are just that, vital.

Not only are they vital to life, they are also vital to one another. Your lungs, for example, breathe in oxygen and exhale carbon dioxide (one of your body's waste products). The lungs transfer oxygen to the blood, which is carried to the heart for distribution throughout the rest of the body. The blood carries waste carbon dioxide back to the lungs, where it is absorbed and exhaled. It's a beautiful system. But how did it come about? It's a very ancient system, says Rutgers University anthropologist Susan Cachel -- and it's not unique to humans. The organ systems we find in most animals contain one heart and two lungs. That is, with the exception of earthworms and cephalopods -- the invertebrate class which includes octopi and squid. Earthworms have five heart-like structures. Cephalopods have three hearts (two to send blood to the gills, and one to send blood to the rest of the body) and no lungs. Cachel says that the one heart/two lungs system began to emerge about 300 million years ago, when animals first moved from sea to land to escape predators and find new sources of food. From that point on, it's been the norm.

But why didn't it continue to change? In this case, Occam's razor provides the key -- the simplest explanation is usually the right one. Ultimately most animals developed a system of two lungs and one heart (along with the rest of their organs) because that's what was needed to survive and thrive on Earth . People didn't develop two hearts or eight legs or wings because we didn't need them for survival. And we developed two lungs because we need them. Phylogeny is the study of how the first ribonucleic acid (RNA) strands in Earth's primordial soup developed into humans and other animals. As these animals evolved into such divergent species as birds, insects and humans, the organ systems in those animals remained similar to one another. We still have stomachs to digest food , lungs to breathe air, and kidneys to filter waste. All of this indicates that species -- including humans -- have been shaped and molded specifically to live on Earth. So does this mean that our system of internal organs is perfect? We know through our study of disease that going from two lungs to one is detrimental to our health, but what about adding an extra heart? Wouldn't that make us better able to survive?

Read the next page to find out about what it would be like to have two hearts. The Lungs (Human Anatomy): Picture, Function, Definition, Conditions Human Anatomy Picture of the Lungs © 2014 WebMD, LLC. All rights reserved. The lungs are a pair of spongy, air-filled organs located on either side of the chest (thorax). The trachea (windpipe) conducts inhaled air into the lungs through its tubular branches, called bronchi. The bronchi then divide into smaller and smaller branches (bronchioles), finally becoming microscopic. The bronchioles eventually end in clusters of microscopic air sacs called alveoli. In the alveoli, oxygen from the air is absorbed into the blood . Carbon dioxide , a waste product of metabolism , travels from the blood to the alveoli, where it can be exhaled. Between the alveoli is a thin layer of cells called the interstitium, which contains blood vessels and cells that help support the alveoli. The lungs are covered by a thin tissue layer called the pleura. The same kind of thin tissue lines the inside of the chest cavity -- also called pleura.

A thin layer of fluid acts as a lubricant allowing the lungs to slip smoothly as they expand and contract with each breath. Lung Conditions Chronic obstructive pulmonary disease ( COPD ): Damage to the lungs results in difficulty blowing air out, causing shortness of breath. Smoking is by far the most common cause of COPD. Emphysema : A form of COPD usually caused by smoking . The fragile walls between the lungs' air sacs (alveoli) are damaged, trapping air in the lungs and making breathing difficult. Chronic bronchitis : Repeated, frequent episodes of productive cough, usually caused by smoking . Breathing also becomes difficult in this form of COPD. Pneumonia : Infection in one or both lungs. Bacteria, especially Streptococcus pneumoniae, are the most common cause. Asthma : The lungs' airways (bronchi) become inflamed and can spasm, causing shortness of breath and wheezing . Allergies , viral infections , or air pollution often trigger asthma symptoms . Acute bronchitis : An infection of the lungs' large airways (bronchi), usually caused by a virus. Cough is the main symptom of acute bronchitis .

Pulmonary fibrosis : A form of interstitial lung disease . The interstitium (walls between air sacs) become scarred, making the lungs stiff and causing shortness of breath. Sarcoidosis : Tiny areas of inflammation can affect all organs in the body, with the lungs involved most of the time. The symptoms are usually mild; sarcoidosis is usually found when X-rays are done for other reasons. Obesity hypoventilation syndrome: Extra weight makes it difficult to expand the chest when breathing. This can lead to long-term breathing problems . Pleural effusion : Fluid builds up in the normally tiny space between the lung and the inside of the chest wall (the pleural space). If large, pleural effusions can cause problems with breathing. Pleurisy : Inflammation of the lining of the lung (pleura), which often causes pain when breathing in. Autoimmune conditions, infections, or a pulmonary embolism may cause pleurisy . Bronchiectasis: The airways (bronchi) become inflamed and expand abnormally, usually after repeated infections. Coughing , with large amounts of mucus, is the main symptom of bronchiectasis.

Lymphangioleiomyomatosis ( LAM ): A rare condition in which cysts form throughout the lungs, causing breathing problems similar to emphysema . LAM occurs almost exclusively in women of childbearing age. Cystic fibrosis : A genetic condition in which mucus does not clear easily from the airways. The excess mucus causes repeated episodes of bronchitis and pneumonia throughout life. Interstitial lung disease : A collection of conditions in which the interstitium (lining between the air sacs) becomes diseased. Fibrosis (scarring) of the interstitium eventually results, if the process can't be stopped. Lung cancer : Cancer may affect almost any part of the lung. Most lung cancer is caused by smoking . Wikijunior:Human Body/Lungs - Wikibooks, open books for an open world Wikijunior:Human Body/Lungs This is the latest reviewed version , checked on 7 November 2012. (+) Quality: poor/unrated Jump to: navigation , search The lung is an organ we use when we breathe. It takes oxygen from the air and transports it to the blood. It also takes carbon dioxide from the blood and releases it into the air.

What do lungs look like?[ edit ] The lungs flank the heart and great vessels in the chest cavity . (Source: Gray's Anatomy of the Human Body , 20th ed. 1918.) Your lungs are located in the chest on either side of the heart. There are two of them. They are similar in appearance, but not identical. Lungs have a spongy texture and a honeycomb pattern. They have much more surface area in total than just the outer surface the lung. Each lung is separated into lobes . There are three lobes on the right and two on the left. The left lung contains a dent called the " cardiac notch". The cardiac notch allows room for the heart. The lungs form the major part of thorasic cavity. What are the parts of the lungs?[ edit ] The two main bronchi are the tubes that enter the roots of the lungs. The bronchi continue to divide within the lung with each branch smaller than the last. At the end of the smallest bronchi (called terminal bronchioles) there are tiny sacks. These sacks are made up of clusters of alveoli, which look a little like grapes in a bunch. The individual alveoli are wrapped in blood vessels.

This is where the gas exchange actually occurs. Blood without much oxygen from the heart is pumped through the pulmonary artery to the lungs. Oxygen from the air diffuses into blood and carbon dioxide from the blood is released. The oxygen-rich blood returns to the vein via the pulmonary veins to be pumped back into the rest of the body. The process goes on until you die. What is the function of the lungs?[ edit ] The cells in our body need oxygen to produce energy. These same cells produce carbon dioxide as a by-product. So there has to be a way for the body to deliver oxygen to cells and carry carbon dioxide from cells. The lungs allow your body to trade its waste carbon dioxide for oxygen. The lungs also serve as a cushion or shock absorber for the heart. How do the lungs work?[ edit ] The diaphragm is a big muscle under your lungs. It pushes downward when you inhale , which enlarges the cavity in the chest and causes the lungs to expand. This causes air to flow into them. When the diaphragm relaxes, air flows out and you exhale . One name for this process is ventilation.

What organ systems are the lungs connected with?[ edit ] The lungs directly connect the respiratory system to the circulatory system, for in the lungs, oxygen will leave the air and enter the blood so that it can be transferred to all of the other cells in your body. Conversely, carbon dioxide is removed from blood back into the air, so that it does not poison the cells that produced it. How do the lungs interact with other parts of the body?[ edit ] Bronchi , bronchial tree, and lungs . (Cardiac notch labeled at bottom left.) Breathing is largely driven by the muscular diaphragm at the bottom of the thorax. Contraction of the diaphragm pulls the bottom of the cavity in which the lung is enclosed downward. Air enter through the oral and nasal cavities; it flows through the larynx and into the trachea, which branches out into bronchi. Relaxation of the diaphragm has the opposite effect, passively recoiling during normal breathing. During exercise, the diaphragm contracts, forcing the air out more quickly and forcefully. The rib cage itself is also able to expand and contract to some degree, through the action of other respiratory and accessory respiratory muscles.

As a result, air is sucked into or expelled out of the lungs, always moving down its pressure gradient. This type of lung is known as a bellows lung as it resembles a blacksmith's bellows. Lungs have a tremendous reserve volume as compared to the oxygen exchange requirements when at rest. How can you keep your lungs healthy?[ edit ] Vital capacity is the maximum volume of air that a person can exhale after maximum inhalation. A person's vital capacity can be measured by a spirometer (spirometry). In combination with other physiological measurements, the vital capacity can help make a diagnosis of underlying lung disease. The environment of the lung is very moist, which makes it hospitable for bacteria. Many respiratory illnesses are the result of bacterial or viral infection of the lungs. To keep your lungs healthy, you should not smoke cigarettes and avoid smoky environments. You should not work or live in environments where the air is contaminated with dust or chemicals. If you do have to go into those kinds of environments, wear a respirator. Aerobic exercise like swimming and running can increase your lungs' vital capacity. If the alveoli can't get enough air, a person may have asthma .

Smoking and Your Lungs Smoking and Your Lungs What Cigarettes Do When you smoke cigarettes, many chemicals enter your body through your lungs. Burning tobacco produces more than 4,000 chemicals. Nicotine (NIK-uh-TEEN), carbon monoxide (muh-NOK-side), and tars are some of these substances. Smoking greatly affects your lungs and airways. Smokers get a variety of problems related to breathing. Problems range from an annoying cough to grave illness like emphysema (EM-fuh-ZEE-muh) and cancer. How Your Lungs and Airways Change Smoking cigarettes causes many changes in your lungs and airways. Some changes are sudden, last a short time, and then go away. Colds and pneumonia are examples of this. Other changes happen slowly and last a long time, often for the rest of your life. These are chronic changes. Emphysema is an example of a chronic change. Here is a list of the changes that happen in your lungs and airways when you smoke: The cells that produce mucus in your lungs and airways grow in size and number. As a result, the amount of mucus increases. The mucus is also thicker.

The cleaning system in your lungs does not work well. The lungs have broom-like hairs, called cilia (SILL-ee-uh). The cilia clean your lungs. A few seconds after you start smoking a cigarette, the cilia slow down. Smoking one cigarette can slow the action of your cilia for several hours. Smoking also reduces the number of cilia, so there are fewer cilia to clean your lungs. Your lungs and airways have more mucus, and the mucus is not cleaned out well. So the mucus stays in your airways, clogs them, and makes you cough. This extra mucus can easily get infected. Your lungs and airways get irritated and inflamed. They become narrow and reduce the air flow. Even one or two cigarettes cause irritation and coughing. As you age, it’s normal for your lungs not to work as well. When you smoke, your lungs age faster. Your lungs can be destroyed. When lung tissue is destroyed, the number of air spaces and blood vessels in the lungs decreases. Less oxygen is carried to your body. You are less protected from infection. When you smoke, the natural defenses your lungs have against infection do not work well.

Cigarette smoke has chemicals that can make normal cells change into cancer cells. Weigh the Benefits of Quitting Smoking When you smoke, you have a much greater chance of getting health problems. In this section, you will learn about the kinds of problems you can get from smoking. You will also learn how you benefit when you quit smoking. Breathing-related symptoms Fast decrease in breathing-related symptoms no matter how much or how long you smoked Easier breathing within 72 hours Marked decrease in cough, mucus, shortness of breath, and wheezing within 1 month Less irritated and inflamed airways Cilia growth in 1 to 9 months Lungs more able to handle mucus, self-clean, and fight infection Colds and lung infections More colds and lung infections Worse colds and lung infections When you quit: Fewer colds and lung infections Milder colds and lung infections Flu and pneumonia Smoking increases the number of deaths from flu and pneumonia (new-MONE-yuh). As fewer people smoke, the death rate from flu and pneumonia drops rapidly.

When you smoke: Poor response to flu vaccine When you quit: 50 percent less risk of pneumonia within 5 years Fewer and milder bouts of the flu Better response to flu vaccine Chronic Obstructive Pulmonary Disease (COPD) Cigarette smoking is a major cause of COPD. COPD stands for chronic (KRON-ick) obstructive (ob-STRUCK-tiv) pulmonary (PULL-muh-nair-ee) disease. COPD blocks the flow of air into and out of your lungs. It is a leading cause of death in the United States. More than 80 percent of COPD deaths are related to smoking. When you smoke, your risk of death from COPD is 10 times greater than if you did not smoke. COPD includes two diseases: chronic bronchitis (bronk-EYE-tis) and emphysema.

When you have chronic bronchitis: You get a long-lasting cough every year Your cough produces a lot of mucus that blocks air flow When you quit smoking: Symptoms of chronic bronchitis decrease Symptoms of chronic bronchitis may disappear over time When you have emphysema: Your lung tissue is destroyed over time Your lungs are less able to take in fresh air and let out stale air Your lungs and airways produce a lot of mucus that blocks air flow When you quit smoking: You have a better chance of living longer Asthma Asthma (AZ-muh) is a chronic airway disease. People with asthma have periods of shortness of breath, wheezing, chest tightness, and cough. When you smoke: Symptoms of asthma are harder to control; many inhalers aren't as effective When you quit: Symptoms of asthma decrease Cancer Lung cancer is the leading cause of cancer death in the United States. Smoking causes 85 percent of lung cancer. Smokers have a higher number of pre-cancer changes in their airways than non-smokers.

When you smoke: Pre-cancer tissue can change to cancer Your risk of lung cancer and death is 20 times greater than a non-smoker’s Your risk increases the more you smoke and the longer you smoke When you quit: Pre-cancer tissue may return to normal Your risk of lung cancer decreases within 5 years Your risk of lung cancer keeps decreasing over time How Second-hand Smoke Affects You When people are smoking, the air around them is polluted with tobacco smoke. This is called second-hand smoke. Second-hand smoke comes from two sources. The burning end of the cigarette produces smoke, and the smoker exhales smoke. When near a person smoking, non-smokers breathe second-hand smoke. Other names for breathing second-hand smoke are “passive smoking” and “involuntary smoking.” Passive smoking has bad effects on the lungs and airways in both adults and children. Researchers have studied adult non-smokers who breathe cigarette smoke in the work place. Results show these adults have impaired lungs. Second-hand smoke is a carcinogen (car-SIN-oh-jin). A carcinogen is a substance known to cause cancer. When you breathe second-hand smoke, your risk of lung cancer increases.

In the United States each year, an estimated 3,000 people die from lung cancer caused by second-hand smoke. When you breathe second-hand smoke, you can get: Wheezing Lungs, Lungs Information, Breathing Facts, News, Photos -- National Geographic This requires the latest version of Flash Player. Click here to download. 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. The waste gas carbon dioxide is produced as a byproduct and disposed of when we exhale. 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. This waste gas is expelled as we breathe out. 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. In and Out 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. Kids' Health - Topics - Your lungs Dr Kim says Have you ever looked at the sky and thought about whether there are other people living out there? Well, according to those scientists who study these things, there are no other people, animals or plants like us out there in our solar system, because no other planet has air like ours. Why do we need air? Because we could not survive without the oxygen in the air that we breathe. We could not take in the oxygen if we didn't have lungs. What are lungs? You have two lungs, which together form one of the largest organs in your body. The lung on your left is a bit smaller than the lung on the right because it has to make room for your heart to fit in your chest too. They need to be close together because they work together.

Your rib cage goes around your lungs and heart to protect them from damage. Your ribs also move when you breathe in and out. Below your lungs is the diaphragm (say dye-a-fram). This is a big muscle that works with your lungs to get air in (inhale) and out (exhale). You can feel how they work together. Put one hand on your chest and the other on the upper part of your tummy. Now breathe in deeply. You will feel your chest and your tummy get bigger as the air goes into your lungs. When the diaphragm contracts (gets tighter) it pushes some of the organs in your tummy down so that there is more space in your chest. What lungs look like Here is a diagram of the lungs. If you could see them, they would look pink and rubbery on the outside. Inside they look a lot like sponges. Air comes down the trachea (say trak-ee-a), or windpipe, into two large tubes called the bronchi (say bron-key). One bronchus (say bron-kuss) goes into the left lung and the other into the right.

Each bronchus is rather like the trunk of a tree because it has what look like branches and twigs growing from it. The smallest 'twigs' are called bronchioles (say bron-key-oles). They are so tiny that they are like hairs. At the end of these bronchioles there are little bunches of alveoli (say al-vee-o-lie). These are sacs, or little bags, full of air. There are about 600 million of them in your lungs, so you can imagine how very tiny they must be and what a powerful microscope you would need to look at them! Each tiny alveolus (that's the name for one of them) is covered in even tinier blood vessels called capillaries (say ca-pill-a-riz). Each part of your lungs has an important role to play. Breathing in When you inhale, or breathe in, the air goes in through your nose or mouth. Little hairs called cilia (say silly-a) inside your nostrils catch tiny particles of dust.

If they don't catch all of them, there are more cilia and mucus inside your trachea, which trap the dust and stop it from getting into your lungs. Your diaphragm flattens out (contracts), your ribcage lifts and the air goes through all the little branches in your lungs to fill up the air sacs, or alveoli. Oxygen goes through the walls of the alveoli and into the capillaries where the oxygen enters the red blood cells in each tiny blood vessel. The blood carries the oxygen to the heart. The heart pumps all the oxygen-carrying blood to every cell in the body. Breathing out As each red blood cell empties its load of oxygen, it picks up carbon dioxide (say car-bon dye-ox-eyed) from the cells and heads back to the lungs. The carbon dioxide is carried by the red blood cells in the lungs' capillaries to the alveoli, where it is emptied into the air that leaves the body when you breathe out. For you to exhale, or breathe out, the diaphragm relaxes, muscles between the ribs relax and air is pushed out of the lungs.

This air then goes up through all the bronchioles, up the bronchi, up the trachea and out through the nose or mouth. Look after your lungs 1 Don't smoke and keep away from others who smoke. Lungs do not like cigarette smoke - it can damage them, and cause disease and even death. 2 Stay out of the workshop if someone is using chemicals, as some can damage your lungs. Remind mum she should wear a mask and have windows open if she is using some chemicals, like when she is cleaning the oven or using drain cleaner. 3 Get plenty of exercise. It makes the muscles around your lungs work harder and makes them stronger. 4 If there is a fire in your home or school, stand well back from the fire as breathing smoke can be bad for your lungs. Have you noticed how firemen wear special masks when they are fighting fires? The heat from smoke can burn the tiny bronchioles in your lungs and some chemicals that are made when plastics and other materials burn in a house fire can be poisonous. When lungs don't work well Some people have asthma .

Sometimes when they get a cold, are in contact with something they are allergic to, or exercise hard, the tiny tubes in their lungs get tighter and there is a lot more mucus. This makes it hard to get air into the alveoli. They can become very short of breath and sometimes they need medication to help their lungs work well. Our topics on Asthma can tell you more about it. Illnesses like bronchitis (say bron-kite-us) and pneumonia (say new-mow-nee-a) also make it hard for air to get into the alveoli. When lungs don't work well, that means there is not enough oxygen getting round to all the cells of the body, and the body systems don't work as well as usual. - You feel short of breath. - It feels like you don't have any energy and can't do things. - It feels like you just want to lie down and rest or sleep. How many calories does a person need daily? | HowStuffWorks How many calories does a person need daily? Digital Vision/ Getty Images The number of calories the body consumes in a day is different for every person.

You may notice on the nutritional labels of the foods you buy that the "percent daily values" are based on a 2,000 calorie diet -- 2,000 calories is a rough average of what people eat in a day. But your body might need more or less than 2,000. Height, weight, gender, age and activity level all affect your caloric needs. There are three main factors involved in calculating how many calories your body needs per day: basal metabolic rate physical activity thermic effect of food Your basal metabolic rate (BMR) is the amount of energy your body needs to function at rest. This accounts for about 60 to 70 percent of calories burned in a day and includes the energy required to keep the heart beating, the lungs breathing, the eyelids blinking and the body temperature stabilized. In general, men have a higher BMR than women .

One of the most accurate methods of estimating your basal metabolic rate is the Harris-Benedict formula: Food for Thought 45 Common Foods and the Number of Calories They Contain Adult male: 66 + (6.3 x body weight in lbs.) + (12.9 x height in inches) - (6.8 x age in years) Adult female: 655 + (4.3 x weight in lbs.) + (4.7 x height in inches) - (4.7 x age in years) The second factor in the equation, physical activity, consumes the next highest number of calories. Physical activity includes everything from making your bed in the morning to jogging. Walking, lifting, bending and just generally moving around burns calories, but the number of calories you burn in any given activity depends on your body weight. Click here for a great table listing the calories expended in various physical activities and for various weights. The thermic effect of food is the final addition to the number of calories your body burns. This is the amount of energy your body uses to digest the food you eat -- it takes energy to break food down to its basic elements in order to be used by the body.

To calculate the number of calories you expend in this process, multiply the total number of calories you eat in a day by 0.10, or 10 percent. If you need some help determining how many calories you eat in a day:

Question: How many lungs should a human have?
Answer: 2