What Does The Respiratory System Do?
The respiratory system brings air into the body and removes carbon dioxide.
When you breathe in, air enters your nose or mouth and goes down a long tube called the trachea. The trachea branches into two bronchial tubes, or primary bronchi, which go to the lungs. The primary bronchi branch off into even smaller bronchial tubes, or bronchioles. The bronchioles end in the alveoli, or air sacs.
Oxygen follows this path and passes through the walls of the air sacs and blood vessels and enters the blood stream. At the same time, carbon dioxide passes into the lungs and is exhaled.
What Makes Up The Respiratory System?
The respiratory system can be divided into the upper and lower respiratory tracts.
Upper Respiratory Tract
- Mouth, nose & nasal cavity
The function of this part of the system is to warm, filter and moisten the incoming air.
Here the throat divides into the trachea (wind pipe) and esophagus (food pipe). There is also a small flap of cartilage called the epiglottis which prevents food from entering the trachea.
This is also known as the voice box as it is where sound is generated. It also helps protect the trachea by producing a strong cough reflex if any solid objects pass the epiglottis.
Lower Respiratory Tract
Also known as the windpipe, this is the tube which carries air from the throat into the lungs. It ranges from 3/4 inch to 1 inch in diameter and 4 inches to 6 inches in length. The inner membrane of the trachea is covered in tiny hairs called cilia, which catch particles of dust which we can then remove through coughing. The trachea is surrounded by 15-20 C-shaped rings of cartilage at the front and side which help protect the trachea and keep it open. They are not complete circles due to the position of the esophagus immediately behind the trachea and the need for the trachea to partially collapse to allow the expansion of the esophagus when swallowing large pieces of food.
The trachea divides into two tubes called bronchi, one entering the left and one entering the right lung. The left bronchi is narrower, longer and more horizontal than the right. Irregular rings of cartilage surround the bronchi, whose walls also consist of smooth muscle. Once inside the lung the bronchi split several ways, forming tertiary bronchi.
Tertiary bronchi continue to divide and become bronchioles, very narrow tubes, less than 1 millimeter in diameter. There is no cartilage within the bronchioles and they lead to alveolar sacs.
Individual hollow cavities contained within alveolar sacs (or ducts). Alveoli have very thin walls which permit the exchange of gases Oxygen and Carbon Dioxide. They are surrounded by a network of capillaries, into which the inspired gases pass. There are approximately 3 million alveoli within an average adult lung.
The diaphragm is a broad band of muscle which sits underneath the lungs, attaching to the lower ribs, sternum and lumbar spine and forming the base of the thoracic cavity.
How Does The Respiratory System Work?
At the top of the respiratory system, the nostrils act as the air intake, bringing air into the nose, where it’s warmed and humidified. Tiny hairs called cilia protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose through the breathed air.
Air can also be taken in through the mouth. These two openings of the airway (the nasal cavity and the mouth) meet at the pharynx, or throat, at the back of the nose and mouth. (The pharynx is part of the digestive system as well as the respiratory system because it carries both food and air.)
At the bottom of the pharynx, this pathway divides in two, one for food (the esophagus, which leads to the stomach) and the other for air. The epiglottis, a small flap of tissue, covers the air-only passage when we swallow, keeping food and liquid from going into the lungs.
The larynx, or voice box, is the uppermost part of the air-only pipe. This short tube contains a pair of vocal cords, which vibrate to make sounds.
The trachea, or windpipe, extends downward from the base of the larynx. It lies partly in the neck and partly in the chest cavity. The walls of the trachea are strengthened by stiff rings of cartilage to keep it open. The trachea is also lined with cilia, which sweep fluids and foreign particles out of the airway so that they stay out of the lungs.
At its bottom end, the trachea divides into left and right air tubes called bronchi, which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles. Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each lung houses about 300-400 million alveoli.
The alveoli are surrounded by a mesh of tiny blood vessels called capillaries. Oxygen from the inhaled air passes through the alveoli walls and into the blood.
After absorbing oxygen, the blood leaves the lungs and is carried to your heart. Your heart then pumps it through your body to provide oxygen to the cells of your tissues and organs.
As the cells use the oxygen, carbon dioxide is produced and absorbed into the blood. Your blood then carries the carbon dioxide back to your lungs, where it is removed from the body when you exhale.
The breathing process is aided by a large dome-shaped muscle under the lungs called the diaphragm.
When you breathe in, the diaphragm contracts downward, creating a vacuum that causes a rush of fresh air into the lungs.
The opposite occurs with exhalation, where the diaphragm relaxes upwards, pushing on the lungs, allowing them to deflate.
What Can Go Wrong With Your Respiratory System?
Asthma is a chronic inflammatory lung disease that causes airways to tighten and narrow. Often triggered by irritants in the air such as cigarette smoke, asthma involve contraction of the muscles and swelling of the lining of the tiny airways. The resulting narrowing of the airways prevents air from flowing properly, causing wheezing and difficulty breathing, sometimes to the point of being life-threatening.
Not to be confused with bronchitis, bronchiolitis is an inflammation of the bronchioles, the smallest branches of the bronchial tree. Bronchiolitis affects mostly infants and young children, and can cause wheezing and serious difficulty breathing.
Chronic Obstructive Pulmonary Disease (COPD)
COPD is a term that describes two lung diseases — emphysema and chronic bronchitis:
- Long-term smoking often causes emphysema. In emphysema, the lungs produce an excessive amount of mucus and the alveoli become damaged. It becomes difficult to breathe and get enough oxygen into the blood.
- In bronchitis, a common disease of adults and teens, the membranes lining the larger bronchial tubes become inflamed and an excessive amount of mucus is produced. The person develops a bad cough to get rid of the mucus. Cigarette smoking is a major cause of chronic bronchitis.
Caused by over 200 different viruses that cause inflammation in the upper respiratory tract, the common cold is the most common respiratory infection. Symptoms may include a mild fever, cough, headache, runny nose, sneezing, and sore throat.
A cough is a symptom of an illness, not an illness itself. There are many different types of cough and many different causes, ranging from not-so-serious to life-threatening. Some of the more common causes aare the common cold, asthma, sinusitis, seasonal allergies and pneumonia. Among the most serious causes of cough are tuberculosis (TB) and whooping cough (pertussis).
Cystic Fibrosis (CF)
Cystic fibrosis is the most common inherited disease affecting the lungs. Affecting primarily the respiratory and digestive systems, CF causes mucus in the body to be abnormally thick and sticky. The mucus can clog the airways in the lungs and make a person more vulnerable to bacterial infections.
Caused by an abnormal growth of cells in the lungs, lung cancer is a leading cause of death in the United States and is usually caused by smoking cigarettes. It starts in the lining of the bronchi and takes a long time to develop, so it’s generally a disease in adults. Symptoms include a persistent cough that may bring up blood, chest pain, hoarseness, and shortness of breath.
This inflammation of the lungs usually occurs because of bacterial or viral infection. Pneumonia causes fever and inflammation of lung tissue, and makes breathing difficult because the lungs have to work harder to transfer oxygen into the bloodstream and remove carbon dioxide from the blood. Common causes of pneumonia are influenza and infection with the bacterium Streptococcus pneumoniae.
This condition occurs when the blood pressure in the arteries of the lungs is abnormally high, which means the heart has to work harder to pump blood against the high pressure.
How Do Your Keep Your Respiratory System Healthy?
To keep your respiratory System healthy, don’t smoke, of course. In addition, be sure to do these things . . .
- Live plants. Keeping lots of live plants in your home to increase oxygen levels and absorb CO2 and toxins will contribute to your respiratory health.
- Eat a diet rich in nutrients necessary for a healthy respiratory system. According to the University of Maryland Medical Center, low levels of certain nutrients have been linked to lung diseases. It recommends eating foods rich in vitamins A, C and E and the minerals zinc, potassium, selenium and magnesium.
- Drink plenty of water. This helps thin mucus secretions that accumulate in your lungs, making it easier to breathe. You typically lose about 6 cups of fluids daily, so you should take in at least this much water each day.
This article is part of a series called “Your Body: An Owner’s Manual” which explains how your body systems work and how to maintain them. The first article in the series included a picture of my wife, fitness coach Kathie Lamir, who exemplifies a healthy body. Pictures of Kathie were so well received that I have included one with each article in the series