Lungs
Human lungs
The human lungs are the organs of respiration in humans. Humans have two lungs, with the left being divided into two lobes and the right into three lobes. Together, the lungs contain approximately2400 km (1500 mi) of airways and 300 to 500 million alveoli, having a total surface area of about 70 m2 (8,4 x 8,4 m) in adults roughly the same area as one side of a tennis court. Furthermore, if all of the capillaries that surround the alveoli were unwound and laid end to end, they would extend for about 992 km (620 mi). Each lung weighs 1.1 kilograms (2.5 pounds), therefore making the entire organ about 2.3 kilograms (5 pounds).
The conducting zone contains the trachea, the bronchi, the bronchioles, and the terminal bronchioles The respiratory zone contains the respiratory bronchioles, the alveolar ducts, and the alveoli. The conducting zone and the respiratory stuffers (but not the alveoli) are made up of airways. The conducting zone has no gas exchange with the blood, and is reinforced with cartilage in order to hold open the airways. The conducting zone warms the air to 37 degrees Celsius and humidifies the air. It also cleanses the air by removing particles via cilia located on the walls of all the passageways. The lungs are surrounded by the rib cage. The respiratory zone is the site of gas exchange with blood.
The conducting zone contains the trachea, the bronchi, the bronchioles, and the terminal bronchioles The respiratory zone contains the respiratory bronchioles, the alveolar ducts, and the alveoli. The conducting zone and the respiratory stuffers (but not the alveoli) are made up of airways. The conducting zone has no gas exchange with the blood, and is reinforced with cartilage in order to hold open the airways. The conducting zone warms the air to 37 degrees Celsius and humidifies the air. It also cleanses the air by removing particles via cilia located on the walls of all the passageways. The lungs are surrounded by the rib cage. The respiratory zone is the site of gas exchange with blood.
- The sympathetic nervous system via noradrenaline acting on the beta receptors causes bronchodilation.
- The parasympathetic nervous system via acetylcholine, which acts on the M-1muscarinic receptors, maintains the resting tone of the bronchiolar smooth muscle. This action is related, although considered distinct from bronchoconstriction.
- Many other non-autonomic nervous and biochemical stimuli, including carbon dioxide and oxygen, are also involved in the regulation process.
- The pleural cavity is the potential space between the parietal pleura, lining the inner wall of the thoracic cage, and the visceral pleura lining the lungs.
- The lung parenchyma is strictly used to refer solely to alveolar tissue with respiratory bronchioles, alveolar ducts and terminal bronchioles. However, it often includes any form of lung tissue, also including bronchioles, bronchi, blood vessels and lung interstitium.
Diseases
Diseases of the human lung belong to respiratory diseases. The following is a list of important medical conditions involving the lung. Many of these are caused or worsened by smoking. Lung disorders are generally handled by general practitioners, although patients may be referred to a pulmonologist.
Transplantation now allows for a person to have a single lung transplant, a double-lung transplant, or a transplant of both the heart and lungs.
- Lung cancer
- Emphysema is an enlargement of the air spaces in the lung, making it hard to breathe.
- Asthma is an immunological disease which causes the bronchioles to narrow by inflammation and spasm of the lining of the airway wall.
- Cystic fibrosis is a hereditary disease which causes the lung to produce abnormally viscous mucus.
- A pulmonary embolism occurs when a blood clot obstructs an artery leading to the lung.
- Tuberculosis is a transmittable bacterial infection of the lung, the most common infectious disease today.
- Pneumonia is an infection of the lung, caused by bacteria, viruses or fungi.
- Pneumoconiosis, an occupational lung disease caused by the inhalation of dust.
- Bronchitis is an inflammation of the bronchi.
- A collapsed lung (pneumothorax) can occur when one or both walls of the pleural cavity are penetrated by injury, allowing air to enter.
- In pulmonary edema fluid from the capillaries enters the alveoli. This can be caused by weakness of the left side of the heart (resulting in a blood holdup in the lung), altitude sickness, or rarely inhaling toxic gases.
- Lung pinprick condition is a hereditary disease which results in decreased lung capacity and occasional shortness of breath.
Transplantation now allows for a person to have a single lung transplant, a double-lung transplant, or a transplant of both the heart and lungs.
The Respiratory System
We breathe in, air flows through the nose or mouth, down the throat, through the voice box, and down the windpipe (trachea). The air then comes to two main large airways (the right and left bronchial tubes). These large airways branch into smaller and smaller airways (bronchioles). Wrapped around the airways are muscles which crisscross each other. We have no control over these muscles, and their exact purpose is not known. Air continues through these small airways until it finally reaches the tiny balloon-like air sacs (alveoli). It is at these air sacs that the oxygen is taken into the blood.
Cleaning of Air and Removal of Mucus
The air that we breathe contains many tiny particles that must be removed before the air reaches the air sacs deep in the lungs. The nose partially cleans the air by trapping dirt particles in its hairs. Located inside the airways are glands which produce a sticky fluid called mucus. Mucus coats the airways and traps dirt and germs found in the airways. Tiny broom-like structures (cilia) clear the dirty mucus from the airways. These sweep the mucus up toward the throat where it can be spit out or swallowed.
Moisturizing the Air We Breathe
If the air we breathe in is too dry, it can damage the tiny air sacs in our lungs. Therefore, the air must be made moist. This is done by absorbing water from the airways. The moisture in the airways comes from food and drink.
Cleaning of Air and Removal of Mucus
The air that we breathe contains many tiny particles that must be removed before the air reaches the air sacs deep in the lungs. The nose partially cleans the air by trapping dirt particles in its hairs. Located inside the airways are glands which produce a sticky fluid called mucus. Mucus coats the airways and traps dirt and germs found in the airways. Tiny broom-like structures (cilia) clear the dirty mucus from the airways. These sweep the mucus up toward the throat where it can be spit out or swallowed.
Moisturizing the Air We Breathe
If the air we breathe in is too dry, it can damage the tiny air sacs in our lungs. Therefore, the air must be made moist. This is done by absorbing water from the airways. The moisture in the airways comes from food and drink.
How the Lungs Function
Breathing is taken for granted by most people. It is one part of the process of respiration which provides our bodies with a continuous supply of oxygen. Oxygen is the fuel of life. It keeps us all alive.
Oxygen enters our lungs as part of the air that we breathe. It goes to the blood vessels deep in our lungs and then on to all parts of our body. As our body uses oxygen, it makes a waste product called carbon dioxide. We get rid of carbon dioxide when we breathe out.
1. How the Diaphragm Controls BreathingA large sheet of muscle, known as the diaphragm, lies beneath the lungs at the base of the ribcage. The lungs are not muscles, and by themselves, are incapable of drawing air into them. With the help of the diaphragm, the lungs can expand and contract during inhalation and exhalation. When the normally curved diaphragm flattens, it increases the size of the chest cavity. In response, the lungs expand by pulling air into them. Many refer to this as inhalation or inspiration. When the diaphragm relaxes, the air in the lungs exits the body through exhalation, which is also known as expiration.
2. Anatomy of the LungsThe purpose of the lungs and breathing is to bring oxygen into the body to send to the blood and remove carbon dioxide in the blood. Two lobes at the base of the bronchial tubes form the lungs. Protected by the rib cage, these lobes of soft tissue filter carbon dioxide from the air and blood, transferring the oxygen inhaled to the blood. A web of tiny blood vessels, known as capillaries, surrounds the nodes in the base of the lungs, which are the alveoli. Over 300 million of these tiny alveoli rest in the lungs. Inside these alveoli, the exchange of oxygen and carbon dioxide occurs.
3. Air Enters the LungsOxygen, carbon dioxide and other gases make up the air breathed into the lungs. The human body only needs oxygen, and the lungs act to filter it from the inspirited air and deliver it to the blood. Carbon dioxide from the blood also is filtered out of the air and blood and exhaled. Once inside the lungs, air moves through the large bronchial tubes which branch off into the smaller bronchioles. These smaller nodes at the ends are known alveoli.
So small and thin, oxygen and carbon dioxide molecules pass between the walls of the capillaries into the alveoli in the lungs. The blood vessels drop off carbon dioxide from the blood into the alveoli and pick up oxygen molecules. The newly oxygenated blood moves into the heart where it is pumped throughout the body. Carbon dioxide removed from the blood travels back up the bronchioles, through the bronchial tubes, up the trachea and out of the body when the diaphragm relaxes and the person exhales. The entire breathing process occurs in normal adults 15 times every minute and more often when the body needs more oxygen, such as with stress and physical activity. The lungs continue to filter the air and blood from birth to death in their unceasing action to keep the body functioning at its prime.
Oxygen enters our lungs as part of the air that we breathe. It goes to the blood vessels deep in our lungs and then on to all parts of our body. As our body uses oxygen, it makes a waste product called carbon dioxide. We get rid of carbon dioxide when we breathe out.
1. How the Diaphragm Controls BreathingA large sheet of muscle, known as the diaphragm, lies beneath the lungs at the base of the ribcage. The lungs are not muscles, and by themselves, are incapable of drawing air into them. With the help of the diaphragm, the lungs can expand and contract during inhalation and exhalation. When the normally curved diaphragm flattens, it increases the size of the chest cavity. In response, the lungs expand by pulling air into them. Many refer to this as inhalation or inspiration. When the diaphragm relaxes, the air in the lungs exits the body through exhalation, which is also known as expiration.
2. Anatomy of the LungsThe purpose of the lungs and breathing is to bring oxygen into the body to send to the blood and remove carbon dioxide in the blood. Two lobes at the base of the bronchial tubes form the lungs. Protected by the rib cage, these lobes of soft tissue filter carbon dioxide from the air and blood, transferring the oxygen inhaled to the blood. A web of tiny blood vessels, known as capillaries, surrounds the nodes in the base of the lungs, which are the alveoli. Over 300 million of these tiny alveoli rest in the lungs. Inside these alveoli, the exchange of oxygen and carbon dioxide occurs.
3. Air Enters the LungsOxygen, carbon dioxide and other gases make up the air breathed into the lungs. The human body only needs oxygen, and the lungs act to filter it from the inspirited air and deliver it to the blood. Carbon dioxide from the blood also is filtered out of the air and blood and exhaled. Once inside the lungs, air moves through the large bronchial tubes which branch off into the smaller bronchioles. These smaller nodes at the ends are known alveoli.
So small and thin, oxygen and carbon dioxide molecules pass between the walls of the capillaries into the alveoli in the lungs. The blood vessels drop off carbon dioxide from the blood into the alveoli and pick up oxygen molecules. The newly oxygenated blood moves into the heart where it is pumped throughout the body. Carbon dioxide removed from the blood travels back up the bronchioles, through the bronchial tubes, up the trachea and out of the body when the diaphragm relaxes and the person exhales. The entire breathing process occurs in normal adults 15 times every minute and more often when the body needs more oxygen, such as with stress and physical activity. The lungs continue to filter the air and blood from birth to death in their unceasing action to keep the body functioning at its prime.