The Respiratory System
The respiratory system is comprised of several structures that enable ventilation and oxygenation. Inhalation moves oxygen into the bloodstream. Blood cells pick up carbon dioxide, which is then excreted through exhalation. We’ll discuss the actual respiration process while reviewing the structures themselves.
The Upper Airway
The upper airway starts at the nose and mouth, and extends to the cricoid cartilage, the ring-shaped structure that forms the lower portion of the “voice box,” or larynx. Air entering the nostrils is warmed, moistened and filtered before it continues through the nasopharynx, the area directly posterior to the nose. Air also enters the mouth and through the oropharynx, the area directly posterior to the mouth. Together, the nasopharynx and oropharynx are called the pharynx, or the throat. (See Figure 1.)
The respiratory system is comprised of several structures that enable ventilation and oxygenation. Inhalation moves oxygen into the bloodstream. Blood cells pick up carbon dioxide, which is then excreted through exhalation. We’ll discuss the actual respiration process while reviewing the structures themselves.
The Upper Airway
The upper airway starts at the nose and mouth, and extends to the cricoid cartilage, the ring-shaped structure that forms the lower portion of the “voice box,” or larynx. Air entering the nostrils is warmed, moistened and filtered before it continues through the nasopharynx, the area directly posterior to the nose. Air also enters the mouth and through the oropharynx, the area directly posterior to the mouth. Together, the nasopharynx and oropharynx are called the pharynx, or the throat. (See Figure 1.)
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A small, leaf-shaped flap of tissue at the top of the trachea – the epiglottis – opens to allow breathing and closes during swallowing to prevent food and fluids from entering the trachea. |
At the lower portion of the pharynx, just below the thyroid cartilage (also known as the “Adam’s apple”) and the cricoid cartilage, are the trachea, which is the passageway for air to the lungs, and the esophagus, through which food and water travel to the stomach. A small, leaf-shaped flap of tissue at the top of the trachea, called the epiglottis, opens to allow breathing and closes during swallowing to prevent food and fluids from entering the trachea. It also helps keep air from entering the stomach through the esophagus. If the epiglottis fails to close, food, fluids, vomit, blood, secretions or a foreign object can enter the larynx and trachea, cause an obstruction and force a person to choke. Anything but air that reaches the lungs can also cause an infection.
The Lower Airway
The lower airway starts at the cricoid cartilage and extends to the alveoli in the lungs. The trachea, or windpipe, extends from the larynx to
the carina, the point at which it divides (bifurcates) into its to major branches, the right and left mainstem bronchi. These cartilaginous bronchi extend into the lungs, like tree branches, splitting into increasingly smaller sections called bronchioles. Lined with smooth muscle and mucus membranes, the bronchioles can contract. When the mucus membrane becomes irritated and swollen – as in asthma – it can lead to narrowing or constriction of the bronchiole and increased airway resistance that makes moving air in and out of the alveoli more difficult. Work of breathing (WOB) as a result of increased airway resistance can lead to fatigue and respiratory failure. At the end of the bronchioles are thousands of tiny air sacs called alveoli, where the gas exchange – oxygen and carbon dioxide – occurs with the bloodstream. Made of elastic tissue, the lungs expand and recoil. The right lung is divided into three lobes; the left lung into two lobes. Surrounding the lungs are two layers of connective tissue called the pleura. The visceral pleura is the moist, innermost membrane that adheres to the lung tissue. The parietal pleura is the moist, thicker, more-elastic membrane that adheres to the chest (thoracic) wall, diaphragm and mediastinum, the central compartment of the thoracic cavity. Between these two layers is the pleural space, which contains serous fluid that acts as a lubricant when the layers rub against each other. The diaphragm is a large muscle that separates the thoracic and abdominal cavities. During inhalation, the rib cage muscles (intercostal muscles) and the diaphragm contract. The diaphragm lowers and the ribs move upward and outward. This expands the size of the chest and creates negative pressure inside the chest cavity, pulling air into the lungs. During exhalation, the diaphragm and intercostal muscles relax. The ribs move downward and inward, and the diaphragm rises. With this, the chest becomes smaller and positive pressure builds inside the chest cavity, pushing air out of the lungs. During inhalation, air moves through the airway into the alveoli, where the gas and carbon dioxide are exchanged with the pulmonary capillaries
that surround each alveolus. This is called ventilation. Oxygenated blood moves from the lungs to the heart, which pumps it into the body’s circulatory system. The blood travels through the arteries to, eventually, capillaries. Oxygen that was carried by the blood from the lungs is
transferred through the capillary walls into the cells. Carbon dioxide moves into the capillaries, then to the veins, which return to the heart and lungs, and the process begins anew. The process of moving gases and other nutrients between cells and the blood is called respiration. Breathing (inhaling and exhaling air) is either adequate – sufficient to support life – or inadequate. The EMT’s assessment involves not only counting patient respirations (not guessing a number), but also evaluating the patient’s breathing effort and chest movement. In addition, knowing normal respiratory rates. END
The Lower Airway
The lower airway starts at the cricoid cartilage and extends to the alveoli in the lungs. The trachea, or windpipe, extends from the larynx to
the carina, the point at which it divides (bifurcates) into its to major branches, the right and left mainstem bronchi. These cartilaginous bronchi extend into the lungs, like tree branches, splitting into increasingly smaller sections called bronchioles. Lined with smooth muscle and mucus membranes, the bronchioles can contract. When the mucus membrane becomes irritated and swollen – as in asthma – it can lead to narrowing or constriction of the bronchiole and increased airway resistance that makes moving air in and out of the alveoli more difficult. Work of breathing (WOB) as a result of increased airway resistance can lead to fatigue and respiratory failure. At the end of the bronchioles are thousands of tiny air sacs called alveoli, where the gas exchange – oxygen and carbon dioxide – occurs with the bloodstream. Made of elastic tissue, the lungs expand and recoil. The right lung is divided into three lobes; the left lung into two lobes. Surrounding the lungs are two layers of connective tissue called the pleura. The visceral pleura is the moist, innermost membrane that adheres to the lung tissue. The parietal pleura is the moist, thicker, more-elastic membrane that adheres to the chest (thoracic) wall, diaphragm and mediastinum, the central compartment of the thoracic cavity. Between these two layers is the pleural space, which contains serous fluid that acts as a lubricant when the layers rub against each other. The diaphragm is a large muscle that separates the thoracic and abdominal cavities. During inhalation, the rib cage muscles (intercostal muscles) and the diaphragm contract. The diaphragm lowers and the ribs move upward and outward. This expands the size of the chest and creates negative pressure inside the chest cavity, pulling air into the lungs. During exhalation, the diaphragm and intercostal muscles relax. The ribs move downward and inward, and the diaphragm rises. With this, the chest becomes smaller and positive pressure builds inside the chest cavity, pushing air out of the lungs. During inhalation, air moves through the airway into the alveoli, where the gas and carbon dioxide are exchanged with the pulmonary capillaries
that surround each alveolus. This is called ventilation. Oxygenated blood moves from the lungs to the heart, which pumps it into the body’s circulatory system. The blood travels through the arteries to, eventually, capillaries. Oxygen that was carried by the blood from the lungs is
transferred through the capillary walls into the cells. Carbon dioxide moves into the capillaries, then to the veins, which return to the heart and lungs, and the process begins anew. The process of moving gases and other nutrients between cells and the blood is called respiration. Breathing (inhaling and exhaling air) is either adequate – sufficient to support life – or inadequate. The EMT’s assessment involves not only counting patient respirations (not guessing a number), but also evaluating the patient’s breathing effort and chest movement. In addition, knowing normal respiratory rates. END
From the Gold Cross Magazine CEU Education Series, Fall 2015 edition, "Lung Diseases: When It Could Be Your Patient's Last Gasp" by Sylvie Mulvaney and Louis A. Sforza.
