1. Chapter 16 The Respiratory System

2. 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

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

4. Respiratory Mucosa Specialized 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 and pollen Cilia on mucosal cells beat in only one direction, moving mucus upward to pharynx for removal

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

6. Nose Functions –Warms and moistens inhaled air –Contains sense organs of smell

7. 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

8. Pharynx –Pharyngeal tonsils and openings of auditory tubes open into nasopharynx; tonsils found in oropharynx –Mucous membrane lines pharynx

9. Pharynx Functions –Passageway for food and liquids –Air distribution; passageway for air

10. Larynx Structure –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

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

12. 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

13. 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

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

15. 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

16. Trachea (Windpipe) Structure –Tube 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

17. Trachea (Windpipe) Obstruction –Blockage of trachea occludes the airway and if complete causes death in minutes –Tracheal obstruction causes more than 4000 deaths annually in the United States –Heimlich maneuver is a lifesaving technique used to free the trachea of obstructions –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

18. 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 eventually leading to bronchioles –Bronchioles end in clusters of microscopic alveolar sacs, the walls of which are made up of alveoli

19. 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

20. 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

21. 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

22. Lungs and Pleura –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

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

24. 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 –Air pressure differences actually cause air to move into and out of the lungs

25. Respiration Inspiration –Active process—air moves into lungs –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

26. Respiration –The increase in the size of the chest cavity reduces pressure within it, and air enters the lungs

27. Respiration Expiration –Quiet expiration is ordinarily a passive process –During expiration, thorax returns to its resting size and shape –Elastic recoil of lung tissues aids in expiration –Expiratory muscles used in forceful expiration are internal intercostals and abdominal muscles Internal intercostals—contraction depresses the rib cage and decreases the size of the thorax from front to back

28. Respiration Contraction of abdominal muscles elevates the diaphragm, thus decreasing size of the thoracic cavity from top to bottom –Reduction in the size of the thoracic cavity increases its pressure, and air leaves the lungs

29. 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

30. 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

31. Respiration 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

32. Respiration –Expiratory reserve volume (ERV)—amount of air that can be forcibly exhaled after expiring the tidal volume –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 –Rate—usually about 12 to 18 breaths a minute; much faster during exercise

33. Respiration Regulation of respiration –Permits the body to adjust to varying demands for oxygen supply and carbon dioxide removal –Most important central regulatory centers in medulla are called respiratory control centers (inspiratory and expiratory centers) Under resting conditions nervous activity in the respiratory control centers produces a normal rate and depth of respirations (12 to 18 per minute)

34. Respiration –Respiratory control centers in the medulla are influenced by “inputs” from receptors located in other body areas: Cerebral cortex—voluntary (but limited) control of respiratory activity Chemoreceptors—respond to changes in carbon dioxide, oxygen, and blood acid levels—located in carotid and aortic bodies Pulmonary stretch receptors—respond to the stretch in lungs, thus protecting respiratory organs from overinflation

35. Types of Breathing Eupnea—normal breathing Hyperventilation—rapid and deep respirations Hypoventilation—slow and shallow respirations Dyspnea—labored or difficult respirations Orthopnea—dyspnea relieved by moving into an upright or sitting position

36. Types of Breathing Apnea—stopped respiration Cheyne-Stokes respiration (CSR)—cycles of alternating apnea and hyperventilation associated with critical conditions Respiratory arrest—failure to resume breathing after a period of apnea

37. Disorders of the Lower Respiratory Tract Lower respiratory infection –Acute bronchitis or tracheobronchitis— inflammation of the bronchi or bronchi and trachea caused by infection (usually resulting from the spread of a URI) –Pneumonia—acute inflammation (infection) in which lung airways become blocked with thick exudates Lobar pneumonia—affects entire lobe of lung Bronchopneumonia—infection scattered along bronchial tree

38. Disorders of the Lower Respiratory Tract Tuberculosis (TB)—chronic, highly contagious lung infection characterized by tubercles in the lung; can progress to involve tissues outside the lungs and pleurae

39. Disorders of the Lower Respiratory Tract Restrictive pulmonary disorders reduce the ability of lung tissues to stretch (as during inspiration) –Factors inside the lungs, such as fibrosis (scarring) or inflammation, may restrict breathing –Factors outside the lungs, such as pain of injury or pleurisy, may restrict breathing

40. Disorders of the Lower Respiratory Tract Obstructive pulmonary disorders –Obstruct breathing –Chronic obstructive pulmonary disease (COPD) can develop from preexisting obstructive conditions Chronic bronchitis—chronic inflammation of the bronchial tree Emphysema—reduced surface area of lungs caused by rupture or other damage to alveoli Asthma—recurring spasms of the airways accompanied by edema and mucus production

41. Disorders of the Lower Respiratory Tract Lung cancer—malignant tumor of the lungs, occasionally treatable with surgery, chemotherapy, radiation, and photodynamic therapy