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Chapter 16

Chapter 16. The Respiratory System. Objectives. Discuss the generalized functions of the respiratory system List the major organs of the respiratory system and describe the function of each

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Chapter 16

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  1. Chapter 16 The Respiratory System

  2. Objectives • Discuss the generalized functions of the respiratory system • List the major organs of the respiratory system and describe the function of each • Compare, contrast, and explain the mechanism responsible for the exchange of gases that occurs during internal and external respiration

  3. Objectives • List and discuss the volumes of air exchanged during pulmonary ventilation • Identify and discuss the mechanisms that regulate respiration • Identify and describe the major disorders of the upper respiratory tract • Identify and describe the major disorders of the lower respiratory tract

  4. Structural Plan • Basic plan of respiratory system would be similar to an inverted tree if it were hollow; leaves of the tree would be comparable to alveoli, with the microscopic sacs enclosed by networks of capillaries • Diffusion is the mode for gas exchange that occurs in the respiratory mechanism

  5. Respiratory Tracts • Upper respiratory tract—nose, pharynx, and larynx • Lower respiratory tract—trachea, bronchial tree, and lungs

  6. Respiratory Mucosa • Mucous membrane that lines the air distribution tubes in the respiratory tree • More than 125 mL of mucus produced each day forms a “mucus blanket” over much of the respiratory mucosa • Mucus serves as an air purification mechanism by trapping inspired irritants such as dust, pollen • Cilia on mucosal cells beat in only one direction, moving mucus upward to pharynx for removal

  7. Nose • Structure • Nasal septum separates interior of nose into two cavities • Mucous membrane lines nose • Nasal polyp–noncancerous growths that project from nasal mucosa (associated with chronic hay fever) • Frontal, maxillary, sphenoidal, and ethmoidal sinuses drain into nose

  8. Nose • Functions • Warms and moistens inhaled air • Contains sense organs of smell

  9. Pharynx • Structure • Pharynx (throat) about 12.5 cm (5 inches) long • Divided into nasopharynx, oropharynx, and laryngopharynx • Two nasal cavities, mouth, esophagus, larynx, and auditory tubes all have openings into pharynx

  10. Pharynx • Structure • Pharyngeal tonsils and openings of auditory tubes open into nasopharynx; other tonsils found in oropharynx • Mucous membrane lines pharynx

  11. Pharynx • Functions • Passageway for food and liquids • Air distribution; passageway for air • Tonsils—masses of lymphoid tissue embedded in pharynx provide immune protection

  12. Larynx • Structure • Located just below pharynx; also referred to as the voice box • Several pieces of cartilage form framework • Thyroid cartilage (Adam’s apple) is largest • Epiglottis partially covers opening into larynx • Mucous lining • Vocal cords stretch across interior of larynx; space between cords is the glottis

  13. Larynx • Functions • Air distribution; passageway for air to move to and from lungs • Voice production

  14. Larynx • Laryngeal cancer • Incidence increases with age and alcohol abuse • Occurs most often in men over age 50 • If larynx removed, “esophageal speech” or electric artificial larynx needed for speech

  15. Disorders of the Upper Respiratory Tract • Upper respiratory infection (URI) • Rhinitis—nasal inflammation, as in a cold, influenza, or allergy • Infectious rhinitis—common cold • Allergic rhinitis—hay fever • Pharyngitis (sore throat)—inflammation or infection of the pharynx

  16. Disorders of the Upper Respiratory Tract • Upper respiratory infection • Laryngitis—inflammation of the larynx resulting from infection or irritation • Epiglottis—life threatening • Croup—not life threatening

  17. Disorders of the Upper Respiratory Tract • Anatomical disorders • Deviated septum—septum that is abnormally far from the midsagittal plane (congenital or acquired) • Epistaxis (bloody nose) can result from mechanical injuries to the nose, hypertension, or other factors

  18. Trachea • Structure • Tube (windpipe) about 11 cm (4½ inches) long that extends from larynx into the thoracic cavity • Mucous lining • C-shaped rings of cartilage hold trachea open • Function—passageway for air to move to and from lungs

  19. Trachea • Obstruction • Blockage of trachea occludes the airway and if complete causes death in minutes • Causes more than 4000 deaths annually in the United States • Abdominal thrust maneuver is a lifesaving technique used to free the trachea of obstructions; also called abdominal thrusts • Tracheostomy—surgical procedure in which a tube is inserted into an incision in the trachea so that a person with a blocked airway can breathe

  20. Bronchi, Bronchioles, and Alveoli • Structure • Trachea branches into right and left bronchi • Right primary bronchus more vertical than left • Aspirated objects most often lodge in right primary bronchus or right lung • Each bronchus branches into smaller and smaller tubes (secondary bronchi), eventually leading to bronchioles • Bronchioles end in clusters of microscopic alveolar sacs, whose walls are made of alveoli

  21. Bronchi, Bronchioles, and Alveoli • Function • Bronchi and bronchioles—air distribution; passageway for air to move to and from alveoli • Alveoli—exchange of gases between air and blood

  22. Bronchi, Bronchioles, and Alveoli • Respiratory distress—relative inability to inflate the alveoli • Infant respiratory distress syndrome (IRDS)—leading cause of death in premature infants resulting from lack of surfactant production in alveoli • Adult respiratory distress syndrome (ARDS)—impairment of surfactant by inhalation of foreign substances or other conditions

  23. Lungs and Pleura • Structure • Size—large enough to fill the chest cavity, except for middle space occupied by heart and large blood vessels • Apex—narrow upper part of each lung, under collarbone • Base—broad lower part of each lung; rests on diaphragm

  24. Lungs and Pleura • Structure • Pleura—moist, smooth, slippery membrane that lines chest cavity and covers outer surface of lungs; reduces friction between the lungs and chest wall during breathing

  25. Lungs and Pleura • Function—breathing (pulmonary ventilation) • Pleurisy—inflammation of the pleura • Atelectasis—incomplete expansion or collapse of lung (alveoli); can be caused by: • Pneumothorax—presence of air in the pleural space • Hemothorax—presence of blood in the pleural space

  26. Respiration • Mechanics of breathing • Pulmonary ventilation includes two phases called inspiration (movement of air into lungs) and expiration (movement of air out of lungs) • Changes in size and shape of thorax cause changes in air pressure within that cavity and in the lungs because as volume changes, pressure changes in the opposite direction • Air moves into or out of lungs because of pressure differences (pressure gradient); air moves from high air pressure toward low air pressure

  27. Respiration • Inspiration • Active process—muscles increase volume of thorax, decreasing lung pressure, which causes air to move from atmosphere into lungs (down the pressure gradient) • Inspiratory muscles include diaphragm and external intercostals • Diaphragm flattens during inspiration—increases top-to-bottom length of thorax • External intercostals—contraction elevates the ribs and increases the size of the thorax from front to back and from side to side

  28. Respiration • Expiration • Reduction in the size of the thoracic cavity decreases its volume and thus increases its pressure, so air moves down the pressure gradient and leaves the lungs • Quiet expiration ordinarily a passive process • During expiration, thorax returns to its resting size and shape • Elastic recoil of lung tissues aids in expiration

  29. Respiration • Expiration • Internal intercostals and abdominal muscles— expiratory muscles used in forceful expiration • Internal intercostals—contraction depresses the rib cage and decreases the size of the thorax from front to back • Abdominal muscles—contraction elevates the diaphragm, thus decreasing size of the thoracic cavity from top to bottom

  30. Respiration • Exchange of gases in lungs • Carbaminohemoglobin breaks down into carbon dioxide and hemoglobin • Carbon dioxide moves out of lung capillary blood into alveolar air and out of body in expired air • Oxygen moves from alveoli into lung capillaries • Hemoglobin combines with oxygen, producing oxyhemoglobin

  31. Respiration • Exchange of gases in tissues • Oxyhemoglobin breaks down into oxygen and hemoglobin • Oxygen moves out of tissue capillary blood into tissue cells • Carbon dioxide moves from tissue cells into tissue capillary blood • Hemoglobin combines with carbon dioxide, forming carbaminohemoglobin

  32. Blood Transportation of Gases • Transport of oxygen • Only small amounts of oxygen can be dissolved in blood • Most oxygen combines with hemoglobin to form oxyhemoglobin to be carried in blood • Transport of carbon dioxide • Dissolved carbon dioxide—10% • Carbaminohemoglobin—20% • Bicarbonate ions—70%

  33. Blood Transportation of Gases • Volumes of air exchanged in pulmonary ventilation • Volumes of air exchanged in breathing can be measured with a spirometer • Tidal volume (TV)—amount normally breathed in or out with each breath • Vital capacity (VC)—largest amount of air that one can breathe out in one expiration • Expiratory reserve volume (ERV)—amount of air that can be forcibly exhaled after expiring the tidal volume

  34. Blood Transportation of Gases • Volumes of air exchanged in pulmonary ventilation • Inspiratory reserve volume (IRV)—amount of air that can be forcibly inhaled after a normal inspiration • Residual volume (RV)—air that remains in the lungs after the most forceful expiration

  35. Regulation of Respiration • Regulation of respiration permits the body to adjust to varying demands for oxygen supply and carbon dioxide removal • Central regulatory centers in the brainstem are called respiratory control centers (inspiratory and expiratory centers) • Medullary centers—under resting conditions these centers in the medulla produce a normal rate and depth of respirations (12 to 18 per minute)

  36. Regulation of Respiration • Central regulatory centers • Pontine centers—as conditions in the body vary, these centers in the pons can alter the activity of the medullary centers, thus adjusting breathing rhythm • Brainstem centers are influenced by information from sensory receptors located in other body areas

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