Muscular breathing movements and recoil of elastic tissues create the changes in pressure that result in ventilation. Pulmonary ventilation involves three different pressures: When the respiratory system is mentioned, people generally think of breathing, but breathing is only one of the activities of the respiratory system. The body cells need a continuous supply of oxygen for the metabolic processes that are necessary to maintain life. The respiratory system works with the circulatory system to provide this oxygen and to remove the waste products of metabolism. It also helps to regulate ph of the blood. Respiration is the sequence of events that results in the exchange of oxygen and carbon dioxide between the atmosphere and the body cells. Every 3 to 5 seconds, nerve impulses stimulate the breathing process, or ventilation, which moves air through a series of passages into and out of the lungs. After this, there is an exchange of gases between the lungs and the blood. This is called external respiration. The blood transports the gases to and from the tissue cells. The exchange of gases between the blood and tissue cells is internal respiration. Finally, the cells utilize the oxygen for their specific activities: this is called cellular metabolism, or cellular respiration. Together, these activities constitute respiration. Mechanics of Ventilation Ventilation, or breathing, is the movement of air through the conducting passages between the atmosphere and the lungs. The air moves through the passages because of pressure gradients that are produced by contraction of the diaphragm and thoracic muscles. Pulmonary ventilation Pulmonary ventilation is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation). Air flows because of pressure differences between the atmosphere and the gases inside the lungs. Air, like other gases, flows from a region with higher pressure to a region with lower pressure. Atmospheric pressure Intraalveolar (intrapulmonary) pressure Intrapleural pressure Atmospheric pressure is the pressure of the air outside the body. Intraalveolar pressure is the pressure inside the alveoli of the lungs. Intrapleural pressure is the pressure within the pleural cavity. These three pressures are responsible for pulmonary ventilation. Inspiration Inspiration (inhalation) is the process of taking air into the lungs. It is the active phase of ventilation because it is the result of muscle contraction. During inspiration, the diaphragm contracts and the thoracic cavity increases in volume. This decreases the intraalveolar pressure so that air flows into the lungs. Inspiration draws air into the lungs. Expiration Expiration (exhalation) is the process of letting air out of the lungs during the breathing cycle. During expiration, the relaxation of the diaphragm and elastic recoil of tissue decreases the thoracic volume and increases the intraalveolar pressure. Expiration pushes air out of the lungs. Respiratory Volumes and Capacities Under normal conditions, the average adult takes 12 to 15 breaths a minute. A breath is one complete respiratory cycle that consists of one inspiration and one expiration. An instrument called a spirometer is used to measure the volume of air that moves into and out of the lungs, and the process of taking the measurements is called spirometry. Respiratory (pulmonary) volumes are an important aspect of pulmonary function testing because they can
provide information about the physical condition of the lungs. Respiratory capacity (pulmonary capacity) is the sum of two or more volumes. the maxillae form the bridge of the nose, which is the bony portion. The remainder of the framework is cartilage and is the flexible portion. Connective tissue and skin cover the framework. Factors such as age, sex, body build, and physical conditioning have an influence on lung volumes and capacities. Lungs usually reach their maximumin capacity in early adulthood and decline with age after that. Conducting Passages Air enters the nasal cavity from the outside through two openings: the nostrils or external nares. The openings from the nasal cavity into the pharynx are the internal nares. Nose hairs at the entrance to the nose trap large inhaled particles. The respiratory conducting passages are divided into the upper respiratory tract and the lower respiratory tract. The upper respiratory tract includes the nose, pharynx, and larynx. The lower respiratory tract consists of the trachea, bronchial tree, and lungs. These tracts open to the outside and are lined with mucous membranes. In some regions, the membrane has hairs that help filter the air. Other regions may have cilia to propel mucus. Click a menu item listed below to learn more about a component(s) of the conducting passages. Nose & Nasal Cavities Pharynx Larynx & Trachea Bronchi, Bronchial Tree, & Lungs Nose, Nasal Cavities, & Paranasal Sinuses Nose & Nasal Cavities Paranasal Sinuses Paranasal sinuses are air-filled cavities in the frontal, maxilae, ethmoid, and sphenoid bones. These sinuses, which have the same names as the bones in which they are located, surround the nasal cavity and open into it. They function to reduce the weight of the skull, to produce mucus, and to influence voice quality by acting as resonating chambers. Pharynx The pharynx, commonly called the throat, is a passageway that extends from the base of the skull to the level of the sixth cervical vertebra. It serves both the respiratory and digestive systems by receiving air from the nasal cavity and air, food, and water from the oral cavity. Inferiorly, it opens into the larynx and esophagus. The pharynx is divided into three regions according to location: the nasopharynx, the oropharynx, and the laryngopharynx (hypopharynx). The framework of the nose consists of bone and cartilage. Two small nasal bones and extensions of
The nasopharynx is the portion of the pharynx that is posterior to the nasal cavity and extends inferiorly to the uvula. The oropharynx is the portion of the pharynx that is posterior to the oral cavity. The most inferior portion of the pharynx is the laryngopharynx that extends from the hyoid bone down to the lower margin of the larynx. The upper part of the pharynx (throat) lets only air pass through. Lower parts permit air, foods, and fluids to pass. The pharyngeal, palatine, and lingual tonsils are located in the pharynx. They are also called Waldereyer's Ring. The retromolar trigone is the small area behind the wisdom teeth. Larynx & Trachea Larynx The larynx, commonly called the voice box or glottis, is the passageway for air between the pharynx above and the trachea below. It extends from the fourth to the sixth vertebral levels. The larynx is often divided into three sections: sublarynx, larynx, and supralarynx. It is formed by nine cartilages that are connected to each other by muscles and ligaments. The larynx plays an essential role in human speech. During sound production, the vocal cords close together and vibrate as air expelled from the lungs passes between them. The false vocal cords have no role in sound production, but help close off the larynx when food is swallowed. The thyroid cartilage is the Adam's apple. The epiglottis acts like a trap door to keep food and other particles from entering the larynx. Trachea The trachea, commonly called the windpipe, is the main airway to the lungs. It divides into the right and left bronchi at the level of the fifth thoracic vertebra, channeling air to the right or left lung. The hyaline cartilage in the tracheal wall provides support and keeps the trachea from collapsing. The posterior soft tissue allows for expansion of the esophagus, which is immediately posterior to the trachea. The mucous membrane that lines the trachea is ciliated pseudostratified columnar epithelium similar to that in the nasal cavity and nasopharynx. Goblet cells produce mucus that traps airborne particles and microorganisms, and the cilia propel the mucus upward, where it is either swallowed or expelled. Bronchi, Bronchial Tree, & Lungs Bronchi and Bronchial Tree
In the mediastinum, at the level of the fifth thoracic vertebra, the trachea divides into the right and left primary bronchi. The bronchi branch into smaller and smaller passageways until they terminate in tiny air sacs called alveoli. The cartilage and mucous membrane of the primary bronchi are similar to that in the trachea. As the branching continues through the bronchial tree, the amount of hyaline cartilage in the walls decreases until it is absent in the smallest bronchioles. As the cartilage decreases, the amount of smooth muscle increases. The mucous membrane also undergoes a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium. The alveolar ducts and alveoli consist primarily of simple squamous epithelium, which permits rapid diffusion of oxygen and carbon dioxide. Exchange of gases between the air in the lungs and the blood in the capillaries occurs across the walls of the alveolar ducts and alveoli. The right lung is shorter, broader, and has a greater volume than the left lung. It is divided into three lobes and each lobe is supplied by one of the secondary bronchi. The left lung is longer and narrower than the right lung. It has an indentation, called the cardiac notch, on its medial surface for the apex of the heart. The left lung has two lobes. Each lung is enclosed by a double-layered serous membrane, called the pleura. The visceral pleura is firmly attached to the surface of the lung. At the hilum, the visceral pleura is continuous with the parietal pleura that lines the wall of the thorax. The small space between the visceral and parietal pleurae is the pleural cavity. It contains a thin film of serous fluid that is produced by the pleura. The fluid acts as a lubricant to reduce friction as the two layers slide against each other, and it helps to hold the two layers together as the lungs inflate and deflate. Review: Introduction to the Respiratory System Here is what we have learned from Introduction to the Respiratory System: Lungs The two lungs, which contain all the components of the bronchial tree beyond the primary bronchi, occupy most of the space in the thoracic cavity. The lungs are soft and spongy because they are mostly air spaces surrounded by the alveolar cells and elastic connective tissue. They are separated from each other by the mediastinum, which contains the heart. The only point of attachment for each lung is at the hilum, or root, on the medial side. This is where the bronchi, blood vessels, lymphatics, and nerves enter the lungs. The entire process of respiration includes ventilation, external respiration, transport of gases, internal respiration, and cellular respiration. The three pressures responsible for pulmonary ventilation are atmospheric pressure, intraalveolar pressure, and intrapleural pressure. A spirometer is used to measure respiratory volumes and capacities. These measurements provide useful information about the condition of the lungs. The frontal, maxillary, ethmoidal, and sphenoidal sinuses are air-filled cavities that open into the nasal cavity. The pharynx, commonly called the throat, is a passageway that extends from the base of the skull to the level of the sixth cervical vertebra. The larynx, commonly called the voice box, is the passageway for air between the pharynx above and the trachea below. The trachea, commonly called the windpipe, is the main airway to the lungs.
The trachea divides into the right and left primary bronchi, which branch into smaller and smaller passageways until they terminate in tiny air sacs called alveoli. The two lungs contain all the components of the bronchial tree beyond the primary bronchi. The right lung is shorter, broader, and is divided into three lobes. The left lung is longer, narrower, and is divided into two lobes. Disorders and Diseases of the Respiratory System Asthma When someone has asthma, his airways narrow and swell. They produce extra mucus, and breathing becomes difficult. The most common asthma signs and symptoms are coughing, wheezing and shortness of breath. For some people, asthma symptoms are a minor nuisance. For others, they're a major problem that interferes with daily activities. If you have severe asthma, you may be at risk of a life-threatening asthma attack. Asthma symptoms range from minor to severe and vary from person to person. One may have mild symptoms and asthma attacks may be infrequent. Between asthma flare-ups the person may feel normal and have no trouble breathing. He may have symptoms primarily at night, during exercise or when you're exposed to specific triggers. Or he may have asthma symptoms all the time. Asthma signs and symptoms include: Shortness of breath Chest tightness or pain Trouble sleeping caused by shortness of breath, coughing or wheezing An audible whistling or wheezing sound when exhaling (wheezing is a common sign of asthma in children) Bouts of coughing or wheezing that are worsened by a respiratory virus such as a cold or the flu Signs that your asthma is probably getting worse include: More frequent and bothersome asthma signs and symptoms Increasing difficulty breathing (this can be measured by a peak flow meter, a simple device used to check how well your lungs are working) An increasingly frequent need to use a quick-relief inhaler For some people, asthma symptoms flare up in certain situations: Exercise-induced asthma occurs during exercise. For many people, exerciseinduced asthma is worse when the air is cold and dry. Occupational asthma is asthma that's caused or worsened by breathing in a workplace irritant such as chemical fumes, gases or dust. Allergy-induced asthma. Some people have asthma symptoms that are triggered by particular allergens, such as pet dander, cockroaches or pollen. Pharyngitis A sore throat is pain, scratchiness or irritation of the throat that often worsens when swallowing. A sore throat is the primary symptom of pharyngitis inflammation of the pharynx, or throat. But the terms "sore throat" and "pharyngitis" are often used interchangeably. Symptoms of a sore throat may vary depending on the cause. Signs and symptoms may include: Pain or a scratchy sensation in the throat Pain that worsens with swallowing or talking Difficulty swallowing Dry throat Sore, swollen glands in your neck or jaw Swollen, red tonsils White patches or pus on your tonsils Hoarse or muffled voice Refusal to eat (infants and toddlers) Common infections causing a sore throat may result in other accompanying signs and symptoms:
Laryngitis Fever Chills Cough Runny nose Sneezing Body aches Headache Nausea or vomiting Laryngitis is an inflammation of the voice box (larynx) from overuse, irritation or infection. Inside the larynx are the vocal cords two folds of mucous membrane covering muscle and cartilage. Normally the vocal cords open and close smoothly, forming sounds through their movement and vibration. But in laryngitis, your vocal cords become inflamed or irritated. This swelling causes distortion of the sounds produced by air passing over them. As a result, the voice sounds hoarse. In some cases of laryngitis, the voice can become almost undetectable. In most cases laryngitis symptoms last less than a couple of weeks and are caused by something minor, such as a cold. Less often, laryngitis symptoms are caused by something more serious or long lasting. Laryngitis signs and symptoms can include: Bronchitis Hoarseness Weak voice or voice loss Tickling sensation and rawness of your throat Sore throat Dry throat Dry cough Bronchitis is an inflammation of the lining of the bronchial tubes, which carry air to and from the lungs. Bronchitis may be either acute or chronic. A common condition, acute bronchitis often develops from a cold or other respiratory infection. Chronic bronchitis, a more serious condition, is a constant irritation or inflammation of the lining of the bronchial tubes, often due to smoking. For either acute bronchitis or chronic bronchitis, signs and symptoms may include: Cough Production of mucus (sputum), either clear or white or yellowish-gray or green in color Shortness of breath, made worse by mild exertion Wheezing Fatigue Slight fever and chills Chest discomfort If one has acute bronchitis, he may have a nagging cough that lingers for several weeks after the bronchitis resolves. However, bronchitis symptoms can be deceptive. One doesn't always produce sputum when he has bronchitis, and children often swallow coughed-up material, so parents may not know there's a secondary infection. Person can develop chronic bronchitis without first developing acute bronchitis. And many smokers have to clear their throats every morning when they get up, which, if it continues for more than three months, may be chronic bronchitis. Symptoms of chronic bronchitis In case of chronic bronchitis, long-term inflammation leads to scarring of the bronchial tubes, producing excessive mucus. Over time, the lining of the bronchial tubes thickens, and the airways eventually may become scarred. Signs and symptoms of chronic bronchitis may also include: Cough that's worse in the mornings and in damp weather Frequent respiratory infections (such as colds or the flu) with a worsening productive cough. Emphysema Emphysema is a factor in the progression of chronic obstructive pulmonary disease (COPD), a condition that limits the flow of air during exhalation. Emphysema occurs when the air sacs at the ends of the smallest air passages (bronchioles) are gradually destroyed. Smoking is the leading cause of emphysema.
As it worsens, emphysema turns the spherical air sacs clustered like bunches of grapes into large, irregular pockets with gaping holes in their inner walls. This reduces the number of air sacs and keeps some of the oxygen entering the lungs from reaching the bloodstream. In addition, the elastic fibers that hold open the small airways leading to the air sacs are slowly destroyed, so that they collapse when breathing out, not letting the air in the lungs escape. Emphysema symptoms are mild to begin with but steadily get worse as the disease progresses. The main emphysema symptoms are: Shortness of breath Wheezing Chest tightness Reduced capacity for physical activity Chronic coughing, which could also indicate chronic bronchitis Loss of appetite and weight Fatigue Pneumonia Pneumonia is an inflammation of the lungs, usually caused by infection. Bacteria, viruses, fungi or parasites can cause pneumonia. Pneumonia is a particular concern if one is older than 65 or have a chronic illness or impaired immune system. It can also occur in young, healthy people. Pneumonia symptoms can vary greatly, depending on any underlying conditions the affected person may have and the type of organism causing the infection. Pneumonia often mimics the flu, beginning with a cough and a fever, so the patient may not realize he has a more serious condition. Common signs and symptoms of pneumonia may include: Fever Cough Shortness of breath Sweating Shaking chills Chest pain that fluctuates with breathing (pleurisy) Headache Muscle pain Fatigue Ironically, people in high-risk groups such as older adults and people with chronic illnesses or weakened immune systems may have fewer or milder symptoms than less vulnerable people do. And instead of having the high fever that often characterizes pneumonia, older adults may even have a lower than normal temperature. Lung cancer Lung cancer is a type of cancer that begins in the lungs. The lungs are two spongy organs in the chest that take in oxygen when one inhales and releases carbon dioxide when exhale. Lung cancer is the leading cause of cancer deaths in the United States, among both men and women. Lung cancer claims more lives each year than colon, prostate, ovarian, lymph and breast cancers combined. Lung cancer typically doesn't cause signs and symptoms in its earliest stages. Signs and symptoms of lung cancer typically occur only when the disease is advanced. Signs and symptoms of lung cancer may include: A new cough that doesn't go away Changes in a chronic cough or "smoker's cough" Coughing up blood, even a small amount Shortness of breath Chest pain Wheezing Hoarseness Losing weight without trying Bone pain Headache Pulmonary embolism Pulmonary embolism is a condition that occurs when one or more arteries in the lungs become blocked. In most cases, pulmonary embolism is caused by blood clots that travel to the lungs from another part of the body most commonly, the legs. Pulmonary embolism symptoms can vary greatly, depending on how much of the lung is involved, the size of the clot and the overall health
especially the presence or absence of underlying lung disease or heart disease. Common signs and symptoms include: Shortness of breath. This symptom typically appears suddenly, and occurs whether you're active or at rest. Chest pain. You may feel like you're having a heart attack. The pain may become worse when you breathe deeply, cough, eat, bend or stoop. The pain will get worse with exertion but won't go away when you rest. Cough. The cough may produce bloody or blood-streaked sputum. Other signs and symptoms that can occur with pulmonary embolism include: Wheezing Leg swelling Clammy or bluish-colored skin Excessive sweating Rapid or irregular heartbeat Weak pulse Lightheadedness or fainting