Respiratory System – Varsity Education

What Happens During Respiration

Main Idea: The respiratory system provides oxygen to the blood and removes carbon dioxide from the body.

Your respiratory system removes carbon dioxide from the body and provides it with fresh oxygen. Inhaling and exhal- ing causes the lungs to expand and deflate slightly.

The process of respiration can be divided into two parts. In external respiration, oxygen moves from the lungs into the blood, and carbon dioxide moves from the blood into the lungs. In internal respiration, oxygen moves from the blood into the cells, and carbon dioxide moves from the cells into the blood. The continual exchange of gases in both external and internal respiration is essential for survival. Oxygen fuels the brain and allows your body to metabolize food for energy to move muscles.

How Respiration Works

Main Idea: The respiratory system consists of the lungs, trachea, and diaphragm.

Your lungs automatically fill with air and are emptied in a rhythmic way. This rhythm changes with the level of your activity. You’ve probably noticed that when you do aerobic exercises, like running or fast walking, you tend to breathe harder than when you’re sitting still. Breathing is regulated by the brain, which sends impulses to stimulate the muscles involved in respiration. This process provides your body with the oxygen it needs to keep going. It also removes carbon dioxide from the lungs. The lungs are found within the chest cavity and are protected by the ribs. In the base of the chest cavity is the diaphragm (DY-uh-fram), a muscle that separates the chest from the abdominal cavity.

AB you inhale, the diaphragm and the muscles between your ribs contract. This contraction expands your chest cav- ity and your lungs. The pressure inside your lungs is lower than the pressure outside your body, so air naturally flows into your lungs to equalize the pressure. AB you exhale, these same muscles relax and your chest cavity decreases. Pressure inside your lungs is higher, so air naturally flows out of your lungs to the outside, the area of lower pressure.

The Lungs

The structure ofthe lungs can be compared to the structure of a branching tree. Air moves into the lungs through thetrachea (TRAY-kee-uh), or the windpipe. The trachea branches out into two bronchi (BRAHN-ky), the main airways that reach into each lung. The airways become smaller as they branch out deeper into the lungs. A network of tubes calledbronchioles brings air closer to the site ofexternal respiration. At the end of each bronchiole are groups of microscopic structures called alveoli. Shown in Figure 15, alveoli are thin-walled air sacs covered with capillaries. Gas exchange takes place as oxygen and carbon dioxide spread across the walls of the capillaries and alveoli.

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Other Respiratory Structures

The respiratory system also includes structures in the upper airways. Air enters and exits your body through the nose and mouth. The membranes of the nose are lined with hairlike structures, called cilia, and with cells that produce mucus. The cilia and mucus work together to help prevent foreign particles such as dust, bacteria, and viruses from moving deeper into the respiratory system.

Theairthatenterstherespiratorysystemisfiltered,warmed, and moistened. The air then moves into the pharynx, or throat, and then into the trachea, or windpipe. The tissue that lines the trachea is also lined with mucus and cilia to trap particles and prevent them from going deeper into the respiratory system.

Other structures that are not directly involved in respiration, but have important functions in the respiratory system, arn the larynx and the epiglottis. The larynx, or voice box, connects the throat and the trachea. The larynx contains the vocal cor:ls, two bands of tissue that produce sound when air forced betv,;een them causes them to vibrate.

The epiglottis is a flap of tissue located above the larynx. It folds down to close off the entrance to the larynx and trachea when you swallow. This is an involuntary action that keeps food or drink from entering the respiratory system. If you eat too quickly or talk or laugh while eating, your food may get past the epiglottis and “go down the wrong pipe.” The piece of food stimulates the cough reflex to expel the material from your respiratory system.

Your Respiratory Health

Main Idea: Caring for your lungs can prevent many respiratory disorders.

Respiratory problems can affect the functioning of other body systems. Imagine not being able to climb a flight ofstairs without running out of breath. The single most important decision you can make for your respiratory health is not to smoke. Smoking damages all parts of the respiratory system and is the main cause of lung cancer. Smoking can also cause bronchitis and emphysema, and increase the likelihood of asthma in children. Tobacco use also reduces the rate of lung growth in teens. Avoiding tobacco use and exposure to secondhand smoke will decrease your risk. Air pollution also increases the risk of respiratory health problems and certain types of cancers.

Regular physical activity is also important for a healthy respiratory system. Increased respiration during exercise improves the capacity of the lungs to pass oxygen into the blood.

Washing your hands regularly can help prevent infec- tion. Bacteria and viruses can be easily transmitted to the respiratory system when contaminated hands touch the nose or mouth.

Respiratory System Problems

Main Idea: Problems of the respiratory system can be mild, such as a cold, or serious and even life threatening.

Problems of the respiratory system range from mild infec- tions to disorders that can damage lung tissue and alveoli and prevent proper ventilation. When severe disease occurs a lung transplant may be recommended.

A deceased donor may provide one or both lungs. Recent medical advances have enabled living donors to provide a portion of one lung to a recipient. Colds and influenza are common infections of the upper respiratory system. Other infections and disorders affect the lower respiratory tract.

Sinusitis is an inflammation of the tissues that line the sinuses, air-filled cavities above the nasal passages and throat. The inflammation can result from allergies or an infection. Symptoms include nasal congestion, headache, and fever. Treatment includes nasal decongestant drops or sprays and antibiotics.

Bronchitis is an inflammation of the bronchi caused by infection or exposure to irritants such as tobacco smoke or air pollution. In bronchitis, the membranes that line the bronchi produce excessive amounts of mucus in the airways. This blocks the airways and leads to symptoms such as coughing, wheezing, and shortness of breath that worsen with physical activity. Treatment includes avoiding exposure to the irritant and taking antibiotics.
Asthma (AZ-muh) is an inflammatory condition in which the trachea, bronchi, and bronchioles become narrowed, causing difficulty breathing. During an asthma attack, an involuntary contraction of smooth airway muscles leads to chest tightness and breathing difficulty. Acute asthma attacks can be relieved with an inhaler that dispenses medication to dilate, or widen, the airways.

Pneumonia is an inflammation of the lungs common! caused by a bacterial or viral infection. In a common type of pneumonia, the alveoli swell and become clogged withe mucus, decreasing the amount of gas exchange. Symptoms include cough, fever, chills, and chest pain. Bacterial pneumonia is treated with antibiotics.
Tuberculosis is a contagious bacterial infection that usually affects the lungs. When a person is infected with tuberculosis, the immune system surrounds the infected area and isolates it. In this inactive stage, which can last for many years, a person doesn’t show symptoms. How- ever, if the immune system is weakened by illness or age, the infection can become active. During this active stage, symptoms include cough, fever, fatigue, and weight loss. Treatment includes antibiotics and hospitalization.
Emphysema is a disease that progressively destroys the walls of the alveoli. Symptoms include breathing difficulty and chronic cough. Although the symptoms of emphysema can be treated, the tissue damage is perma- nent. Emphysema is almost always caused by smoking.

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