The Respiratory System
Whether you are aware of it or not, you breathe in and out 15 times each minute on average. This rate increases automatically if your physical activity increases. With normal breathing, the average person moves more than 10 000 L of air in and out of the lungs each day. The respiratory system is responsible for providing the oxygen needed by the body and for removing the carbon dioxide produced as your body uses energy for growth, repair, and movement. The respiratory system works in close collaboration with the circulatory system.
Whether you are aware of it or not, you breathe in and out 15 times each minute on average. This rate increases automatically if your physical activity increases. With normal breathing, the average person moves more than 10 000 L of air in and out of the lungs each day. The respiratory system is responsible for providing the oxygen needed by the body and for removing the carbon dioxide produced as your body uses energy for growth, repair, and movement. The respiratory system works in close collaboration with the circulatory system.
Structural Features
The respiratory system consists of the lungs and the other organs that connect the lungs to the outside (a). Air enters through the mouth and the nose, passes through the pharynx (throat), and travels down the trachea (commonly known as the windpipe). The trachea separates into two branches called bronchi (singular: bronchus). Some of the epithelial cells that line the trachea and bronchi produce mucus, similar to those in the digestive system. Many of the epithelial cells have cilia (hairlike projections). Cillia help move mucus and filter out any foreign material that might enter the system (b). Th e bronchi deliver air into the lungs.
The respiratory system consists of the lungs and the other organs that connect the lungs to the outside (a). Air enters through the mouth and the nose, passes through the pharynx (throat), and travels down the trachea (commonly known as the windpipe). The trachea separates into two branches called bronchi (singular: bronchus). Some of the epithelial cells that line the trachea and bronchi produce mucus, similar to those in the digestive system. Many of the epithelial cells have cilia (hairlike projections). Cillia help move mucus and filter out any foreign material that might enter the system (b). Th e bronchi deliver air into the lungs.
The trachea is supported by rings of cartilage. This keeps the trachea open and allows the air to fl ow freely. Cartilage is a special type of connective tissue
consisting of specialized cells embedded in a matrix of strong but flexible fibres. This matrix was formed by cells but is not actually living material.
consisting of specialized cells embedded in a matrix of strong but flexible fibres. This matrix was formed by cells but is not actually living material.
Gas Exchange
The main purpose of the respiratory system is gas exchange. Oxygen enters the bloodstream in the lungs by diffusion. Carbon dioxide leaves the blood in the same way. The respiratory system is adapted in several ways to make these processes as efficient as possible. Each of the bronchi branch again and again, ending in tiny air sacs called alveoli (singular: alveolus) (Figure 3(a)). The alveoli have very thin walls. Each alveolus is surrounded by a network of capillaries. Oxygen and carbon dioxide have only to diffuse through two thin walls: the walls of the capillaries and the walls of the alveoli (Figure 3(b)).The circulatory system provides a good blood supply to the lungs. This helps make the respiratory system very efficient. The concentration of oxygen in the blood that flows through the lungs is always less than the concentration of oxygen in the air in the alveoli. This means that oxygen always diffuses into the blood. As the blood picks up oxygen, it is quickly carried away to other parts of the body, where the oxygen diffuses out of the blood and into the cells. At the same time, excess carbon dioxide diff uses from the cells into the blood. It is then carried by the blood to the lungs, where it diff uses out into the air in the alveoli and is expelled to the outside.
The main purpose of the respiratory system is gas exchange. Oxygen enters the bloodstream in the lungs by diffusion. Carbon dioxide leaves the blood in the same way. The respiratory system is adapted in several ways to make these processes as efficient as possible. Each of the bronchi branch again and again, ending in tiny air sacs called alveoli (singular: alveolus) (Figure 3(a)). The alveoli have very thin walls. Each alveolus is surrounded by a network of capillaries. Oxygen and carbon dioxide have only to diffuse through two thin walls: the walls of the capillaries and the walls of the alveoli (Figure 3(b)).The circulatory system provides a good blood supply to the lungs. This helps make the respiratory system very efficient. The concentration of oxygen in the blood that flows through the lungs is always less than the concentration of oxygen in the air in the alveoli. This means that oxygen always diffuses into the blood. As the blood picks up oxygen, it is quickly carried away to other parts of the body, where the oxygen diffuses out of the blood and into the cells. At the same time, excess carbon dioxide diff uses from the cells into the blood. It is then carried by the blood to the lungs, where it diff uses out into the air in the alveoli and is expelled to the outside.
Breathing
The respiratory system includes a method of moving air into and out of the lungs. This process, which we call breathing, involves alternately drawing air into the lungs (inhalation) and then pushing air out (exhalation). This
process involves muscles that move the ribs, making the rib cage expand and contract. Breathing also involves the diaphragm, a large sheet of muscle underneath the lungs. Together, the diaphragm and the muscles between the ribs increase or decrease the volume of the lungs (Figure 4). As the volume of the lungs changes, the pressure inside them also changes. In this way, fresh air flows into and out of the alveoli.
The respiratory system includes a method of moving air into and out of the lungs. This process, which we call breathing, involves alternately drawing air into the lungs (inhalation) and then pushing air out (exhalation). This
process involves muscles that move the ribs, making the rib cage expand and contract. Breathing also involves the diaphragm, a large sheet of muscle underneath the lungs. Together, the diaphragm and the muscles between the ribs increase or decrease the volume of the lungs (Figure 4). As the volume of the lungs changes, the pressure inside them also changes. In this way, fresh air flows into and out of the alveoli.
Diseases of the Respiratory System
Because the respiratory system is constantly exposed to substances in the air, it is not surprising that is it affected by many different diseases. Tuberculosis (TB) is an infectious disease, which means that it is easily passed between people. It is caused by bacteria that enter your body when you breathe. The bacteria grow in your lungs, although the disease can spread to other parts of your body, including your nervous system and your bones. TB has fairly general symptoms: fever, cough, weight loss, tiredness, and chest pain. If untreated, the disease can be fatal. A chest X-ray is one of the tests used to diagnose TB (Figure 6). However, other conditions such as pneumonia may show similar results on an X-ray
Because the respiratory system is constantly exposed to substances in the air, it is not surprising that is it affected by many different diseases. Tuberculosis (TB) is an infectious disease, which means that it is easily passed between people. It is caused by bacteria that enter your body when you breathe. The bacteria grow in your lungs, although the disease can spread to other parts of your body, including your nervous system and your bones. TB has fairly general symptoms: fever, cough, weight loss, tiredness, and chest pain. If untreated, the disease can be fatal. A chest X-ray is one of the tests used to diagnose TB (Figure 6). However, other conditions such as pneumonia may show similar results on an X-ray
To confirm a diagnosis of TB, medical technicians examine samples of stomach or lung secretions. One of the problems with TB is that, after the
initial contact, the bacteria can remain dormant in the body for decades. Once diagnosed, however, the disease can be successfully treated with
medicine and a few weeks of hospitalization.
Cancers
Tobacco smoke, both first-hand and second-hand, is a serious threat to the health of the respiratory system. Tobacco smoke contains many known carcinogens. These chemicals contribute to cancers not only of the lungs but also of the mouth, esophagus, larynx, pancreas, and bladder.
initial contact, the bacteria can remain dormant in the body for decades. Once diagnosed, however, the disease can be successfully treated with
medicine and a few weeks of hospitalization.
Cancers
Tobacco smoke, both first-hand and second-hand, is a serious threat to the health of the respiratory system. Tobacco smoke contains many known carcinogens. These chemicals contribute to cancers not only of the lungs but also of the mouth, esophagus, larynx, pancreas, and bladder.