RESPIRATORY SYSTEM ANATOMY AND PHYSIOLOGY REVIEW

Respiration is essential for life. The body can survive a fair length of time without food, a few days without water, but only minutes without air. Refer to Figure for a review of the structure of the respiratory system.

The respiratory system

FIGURE. The respiratory system.

There are two levels involved in the respiratory process: external and internal respiration. External respiration is the exchange of two gases within the lungs. Oxygen that is present in inhaled air is exchanged for carbon dioxide that diffuses from the blood, across cell walls, into the air spaces of the lungs. The carbon dioxide is then exhaled from the lungs. Internal respiration is the exchange of oxygen and carbon dioxide at the cellular level within the organs of the body. Carbon dioxide is a waste product that results when oxygen and nutrients are metabolized within body cells.

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The respiratory system is divided between the upper respiratory tract and the lower respiratory tract. The upper tract is composed of the organs located outside the chest cavity: the nose and nasal cavities, pharynx, larynx, and upper trachea. The lower tract is composed of the organs located inside the chest cavity: the lower trachea, bronchi, bronchioles, alveoli (microscopic air sacs in the lung), and lungs. Additional parts of the lower tract are the pleural membranes and the respiratory muscles that form the chest cavity.

Midsagittal section of the head and neck

FIGURE. Midsagittal section of the head and neck showing the structures of the upper respiratory tract. (From Scanlon, VC, and Sanders, T: Understanding Human Structure and Function, ed 5. FA Davis, Philadelphia, 2007, p 345, with permission.)

Air enters the nose, which is composed of bone and cartilage and contains ciliated epithelium and cells where the air is humidified and warmed. Tiny hairs just inside the nostrils help prevent particles of dust from entering the nasal cavities. The nasal septum separates the two sides of the nose. The nasal cavities are lined with a membrane that creates mucus designed to further trap bacteria and air pollutants. The upper nasal cavities contain the olfactory receptors that detect odors. Olfactory nerves pass through the ethmoid bone into the brain. The paranasal sinuses, the air cavities in the maxillae, frontal, sphenoid, and ethmoid bones, function to lighten the skull and provide resonance for the voice. These sinuses contain several drainage openings where mucus drains into the nasal cavity.

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The pharynx, or throat, is divided into three parts: the nasopharynx, the oropharynx, and the laryngopharynx. The nasopharynx is the passageway for air only. The adenoids are located in the nasopharynx. The soft palate within the nasopharynx prevents food from going up into the nasopharynx. The oropharynx contains the palatine tonsils at the base of the tongue; and the laryngopharynx opens into the larynx and into the esophagus.

The larynx, or voice box, serves as an air passageway and allows for speaking. Cartilage in the larynx prevents the collapse of the larynx, which must stay open for air passage. The epiglottis, located at the top of the larynx, closes over to prevent the entry of food into the larynx. The vocal cords are located on either side of the glottis.

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The trachea contains C-shaped cartilage that keeps the wind pipe open for air passage yet allows food to pass through to the esophagus, which is located behind the trachea. The trachea extends downward into the chest cavity where it splits into the right and left bronchus. These bronchi branch into secondary bronchi leading into the right and left lungs to form the bronchial tree. The branches become smaller, forming bronchioles that terminate in clusters of alveoli, the air sacs of the lungs. The millions of tiny alveoli (only one cell thick) in each lung are important for respiration. They house macrophages to phagocytize any foreign pathogens that might have made it all the way to the lungs. They also permit the diffusion of gases between air in the alveoli and blood in the pulmonary capillaries (also only one cell thick).

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The lungs, located on either side of the heart, are protected by the rib cage and rest on the diaphragm. They are lined with pleural membranes. The parietal pleura lines the chest wall, while the visceral pleura is on the surface of the lung. Pleura serve to prevent friction and keep the two membranes together during breathing. The lungs are soft and cone-shaped and take up most of the thoracic cavity. The lobes of the lung (three on the right and two on the left) contain the bronchial tree.

Understanding Nosebleeds Nosebleed, or epistaxis, is more likely a symptom than a disorder or disease. Bleeding from the nose is more common in winter months that are likely cold and dry. It is more common in children and older adults. Nosebleeds are usually not considered serious, but some circumstances call for medical attention by a health-care professional because of possible underlying causes. They are: Repeated nosebleeds Syncope Hematemesis or hemoptysis Nosebleeds commonly occur due to nose picking or nose trauma but may be secondary to rhinitis, hypertension, chemotherapy treatment, certain illnesses, and blood-thinning medications. Secondary nosebleeds should be reported to a medical professional. To treat a nosebleed, have the client lean forward and press the soft portion of the nostrils against the septum for 10 minutes (pinch the nose). Apply cold, wet compresses. A vasoconstricting agent such as epinephrine on a cotton ball may be applied to the bleeding site. Cauterization or petr...
Respiratory acidosis (Hypercapnia) ICD-9: 276.4 Description Respiratory acidosis is excessive acidity of body fluids attributable to inadequate removal of carbon dioxide (CO2) by the lungs. Whenever CO2 cannot be adequately ventilated, the CO2 dissolved in the blood rapidly increases. As the level of CO2—called the partial pressure of carbon dioxide (PaCO2)—rises, so does the amount of CO2 that combines with water to form carbonic acid. Consequently, the acidity or alkalinity (pH) of the blood decreases. The condition may be acute or chronic. Etiology Acute respiratory acidosis occurs whenever there is a sudden impairment of ventilation resulting from airway obstruction. This may be due to such causes as a foreign object blocking the airway or to the effects of certain drugs, neuromuscular diseases, or cardiac arrest. Chronic respiratory acidosis is caused by pulmonary diseases that change the characteristics of lung tissue, impairing the ability to release CO2. Examples of such diseases include emphysema, bro...
Silicosis ICD-9: 502 Description Silicosis, also known as grinder’s disease and potter’s rot, results from the inhalation of crystalline silica dust. Silica is a common mineral found naturally in sand and rock. Silica scars lungs and creates small, discrete nodules in the upper lobes of the lungs. As the disease advances, a dense fibrosis of the lungs develops, and emphysema with respiratory impairment may result. The disease is chronic and progressive. Etiology Silica exposure is common in mines and quarries and in a number of occupations, such as sandblasting, foundry work, ceramics, and glassmaking. The occupations most prone to silica exposure are mining, drilling, blasting, grinding, and abrasive manufacturing. Required exposure varies from 2 to 30 years; the average is 10 years. Signs and Symptoms The disease may be asymptomatic even though x-rays exhibit evidence of nodule formation. Dyspnea on exertion generally is the first symptom. A chronic dry cough that later turns p...
Respiratory System – Definition, Functions, Organs & Diseases Respiratory System Definition The respiratory system consists of the set of organs involved in the uptake of oxygen from the atmosphere and the release of carbon dioxide generated during aerobic respiration. This gas exchange is also called breathing or external respiration. Organs specialized for breathing usually contain moist structures with large surface areas to allow the diffusion of gases. They are also adapted to protect the organism from the invasion of pathogens along those surfaces. In fish, this gas exchange occurs through gills. Some invertebrates, like cockroaches, have simple respiratory systems made of interconnecting tubules directly delivering oxygen to tissues. In humans and other mammals, there is an extensive, highly vascularized organ system specialized for gas exchange. It begins in the nose, continues into the pharynx and larynx, leads to the trachea which branches to create bronchi, and bronchioles. This respiratory tree ends in puffy structures called alve...
Respiratory alkalosis (Hypocapnia) ICD-9: 276.3 Description Respiratory alkalosis is excessive alkalinity of body fluids attributable to the excessive removal of carbon dioxide (CO2) by the lungs. When excessive amounts of CO2 are ventilated by the lungs, the PaCO2 in the blood decreases, initiating a series of chemical and metabolic changes that act to reduce the level of serum bicarbonate. Consequently, the pH of the blood increases. The condition may be acute or chronic. Etiology Respiratory alkalosis is caused by acute or chronic hyperventilation. Acute respiratory alkalosis may result from hyperventilation induced by anxiety or psychological trauma, fever, pain, salicylate poisoning, excessive exercise, or excessive use of mechanical ventilators. It is also associated with hypoxia due to pneumonia, asthma, or pulmonary edema. Chronic respiratory alkalosis from hyperventilation is typically associated with hypoxia due to chronic cardiopulmonary diseases or high altitudes. Signs and Symptoms The class...