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10. The Respratory System

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10. The Respratory System

  1. 1. The Respiratory System
  2. 2. Learning Objectives <ul><li>Differentiate between internal and external respiration. </li></ul><ul><li>List the secondary functions of the respiratory system. </li></ul><ul><li>List the components of the upper respiratory tract and describe their structure and functions. </li></ul><ul><li>List the components of the lower respiratory tract and describe their structure and functions. </li></ul><ul><li>Describe the events that occur during inspiration and expiration. </li></ul><ul><li>List the muscles involved in inspiration and expiration. </li></ul><ul><li>Define the terms tidal volume, minute volume, and residual volume. </li></ul><ul><li>Describe the processes of oxygen and carbon dioxide exchange between the alveoli and the blood. </li></ul><ul><li>Describe the mechanical and chemical respiratory control systems. </li></ul>
  3. 3. Respiratory System <ul><li>Primary Function: bring O 2 into the body and CO 2 out of it </li></ul><ul><ul><li>Respiratory system works together with the cardiovascular system </li></ul></ul><ul><li>Secondary functions </li></ul><ul><ul><li>Phonation (voice production) </li></ul></ul><ul><ul><li>Regulation of body temperature </li></ul></ul><ul><ul><li>Regulation of acid-base balance </li></ul></ul><ul><ul><li>Sense of smell </li></ul></ul>
  4. 4. Respiration <ul><li>External respiration - exchange of O 2 and CO 2 between the inhaled air and the blood flowing through the pulmonary capillaries </li></ul><ul><li>Internal respiration - exchange of O 2 and CO 2 between the blood in the systemic capillaries and all the cells and tissues of the body </li></ul>
  5. 5. Structures of Respiratory System <ul><li>Upper Respiratory Tract (outside the lungs) </li></ul><ul><li>Nostrils </li></ul><ul><li>Nasal passages </li></ul><ul><li>Pharynx </li></ul><ul><li>Larynx </li></ul><ul><li>Trachea </li></ul>
  6. 6. Nose and Nasal Passages <ul><li>Nares (nostrils): external openings of the respiratory tube </li></ul><ul><ul><li>Lead into the nasal passages </li></ul></ul><ul><li>Nasal Passages: between the nostrils and the pharynx </li></ul>
  7. 7. Nose and Nasal Passages <ul><li>Nasal septum: separates the left and right nasal passage </li></ul><ul><li>Hard and soft palates: separate the nasal passages from the mouth. </li></ul>
  8. 8. Nose and Nasal Passages <ul><li>Turbinates (nasal conchae): </li></ul><ul><ul><li>Divide each nasal passage into 3 main passageways </li></ul></ul><ul><ul><li>Thin, scroll-like bones covered with nasal epithelium </li></ul></ul><ul><ul><li>Dorsal and ventral </li></ul></ul>
  9. 9. Nose and Nasal Passages <ul><li>Nasal passages lined with pseudostratified columnar epithelium </li></ul><ul><li>Cilia project from the cell surfaces up into a layer of mucus </li></ul><ul><li>Mucus is secreted by mucous glands and goblet cells </li></ul>
  10. 10. Nasal Passages Functions <ul><li>Warm, humidify, and filter inhaled air </li></ul><ul><li>Air is warmed by blood flowing through blood vessels just beneath the nasal epithelium. </li></ul><ul><li>Air is humidified by mucus and other fluids on the epithelial surface. </li></ul><ul><li>Air is filtered as it passes through the winding passages produced by the turbinates. </li></ul><ul><ul><li>Particles do not readily pass through but become trapped in the mucous layer; cilia move mucus and trapped foreign material upward to the pharynx, mouth </li></ul></ul>
  11. 11. Paranasal Sinuses <ul><li>Paranasal Sinuses: ciliated outpouchings of the nasal passages contained within spaces in certain skull bones </li></ul><ul><li>Most animals have two frontal sinuses and two maxillary sinuses within the frontal and maxillary bones </li></ul>
  12. 12. Pharynx <ul><li>Common passageway for respiratory and digestive systems </li></ul><ul><li>Soft palate divides pharynx into the dorsal nasopharynx (respiratory passageway) and the ventral oropharynx (digestive passageway) </li></ul><ul><li>Caudal end of pharynx opens dorsally into the esophagus and ventrally into the larynx </li></ul>
  13. 13. Pharynx <ul><li>Reflexes control actions of the muscles around the pharynx. </li></ul><ul><li>Larynx and pharynx work together to prevent swallowing from interfering with breathing, and vice versa. </li></ul><ul><li>Swallowing - breathing stops, opening into larynx is covered, material to be swallowed moves to rear of pharynx, esophagus opens </li></ul><ul><li>After swallowing, larynx is reopened and breathing resumes </li></ul>
  14. 14. Larynx <ul><li>Short, irregular tube connecting pharynx with the trachea </li></ul><ul><li>Composed of segments of cartilage that are connected to each other and the surrounding tissues by muscles </li></ul><ul><li>Supported in place by the hyoid bone </li></ul><ul><li>Cartilage components - epiglottis, arytenoid cartilages, thyroid cartilage, cricoid cartilage </li></ul>
  15. 15. Larynx Cartilages <ul><li>Epiglottis - single, leaf-shaped; projects forward from the ventral portion of the larynx </li></ul><ul><ul><li>During swallowing, the epiglottis is pulled back to cover the opening of the larynx </li></ul></ul><ul><li>Arytenoid cartilages - paired; attachment is the site of the vocal cords </li></ul><ul><ul><li>Muscles adjust the tension of the vocal cords by moving the cartilages. </li></ul></ul><ul><ul><li>Arytenoid cartilages and the vocal cords form the boundaries of the glottis. </li></ul></ul>
  16. 16. Larynx Functions <ul><li>Voice Production </li></ul><ul><li>Vocal cords - two connective tissue bands attached to the arytenoid cartilages </li></ul><ul><ul><li>Stretched across lumen of larynx parallel to each other </li></ul></ul><ul><li>Vocal cords vibrate as air passes over them. </li></ul><ul><li>Muscles attached to the arytenoid cartilages control the tension of the vocal cords. </li></ul><ul><ul><li>Complete relaxation opens the glottis wide; no sound </li></ul></ul><ul><ul><li>Lessening the tension produces lower-pitched sounds </li></ul></ul><ul><ul><li>Tightening the tension produces higher-pitched sounds </li></ul></ul>
  17. 17. Larynx Function <ul><li>Prevention of foreign material being inhaled </li></ul><ul><ul><li>During swallowing, muscle contractions pull the larynx forward and fold the epiglottis back over its opening. </li></ul></ul><ul><li>Control airflow to and from the lungs </li></ul><ul><ul><li>Small adjustments in the size of the glottis aid movement of air. </li></ul></ul>
  18. 18. Trachea <ul><li>Short, wide tube </li></ul><ul><li>Extends from the larynx into the thorax </li></ul><ul><li>Divides into the two main bronchi that enter the lungs </li></ul><ul><ul><li>Bifurcation of the trachea </li></ul></ul><ul><li>Composed of fibrous tissue and smooth muscle held open by hyaline cartilage rings </li></ul><ul><li>Lined with ciliated epithelium </li></ul>
  19. 19. Trachea <ul><li>C-shaped rings of hyaline cartilage </li></ul><ul><li>Open part of tracheal rings face dorsally </li></ul><ul><li>Gap between the ends of each ring bridged by smooth muscle </li></ul>
  20. 20. Structures of Respiratory System <ul><li>Lower Respiratory Tract </li></ul><ul><li>Bronchi </li></ul><ul><li>Bronchioles </li></ul><ul><li>Alveolar ducts </li></ul><ul><li>Alveoli </li></ul>
  21. 21. Bronchial Tree <ul><li>Each bronchus divides into smaller bronchi, which divide into even smaller bronchi, and then tiny bronchioles </li></ul><ul><li>Bronchioles subdivide into alveolar ducts </li></ul>
  22. 22. Bronchial Tree <ul><li>Alveolar ducts end in groups of alveoli </li></ul><ul><li>Arranged like bunches of grapes </li></ul><ul><li>Alveolar sacs: groups of alveoli </li></ul>
  23. 23. Bronchial Tree <ul><li>Autonomic nervous system controls smooth muscle fibers in wall of bronchial tree </li></ul><ul><li>Bronchodilation - bronchial smooth muscle relaxes </li></ul><ul><ul><li>Aids respiratory effort during intense physical activity </li></ul></ul><ul><li>Bronchoconstriction - bronchial smooth muscle partially contracts </li></ul><ul><ul><li>Reduces size of the air passage </li></ul></ul><ul><ul><li>Irritants in inhaled air can cause bronchoconstriction </li></ul></ul>
  24. 24. Alveoli <ul><li>Site of external respiration </li></ul><ul><li>Tiny, thin-walled sacs of simple squamous epithelium </li></ul><ul><li>Surrounded by networks of capillaries </li></ul><ul><li>Lined with fluid that contains surfactant </li></ul>
  25. 25. Lungs <ul><li>Each lung has a base, an apex, and a convex lateral surface. </li></ul><ul><li>Base is in caudal part of thoracic cavity </li></ul><ul><ul><li>Lies directly on cranial surface of diaphragm </li></ul></ul><ul><li>Apex lies in cranial portion of thoracic cavity </li></ul>
  26. 26. Lungs <ul><li>Convex lateral surface lies against inner surface of the thoracic wall </li></ul><ul><li>Mediastinum - area between the lungs </li></ul>
  27. 27. Lungs <ul><li>Lungs are divided into lobes (in most species) </li></ul><ul><ul><li>Pattern varies with species </li></ul></ul><ul><li>Lobes are distinguished by the major branches of the bronchi </li></ul><ul><li>Hilus - small, well-defined area on medial side of lung </li></ul><ul><ul><li>Site where air, blood, lymph, and nerves enter and leave the lung </li></ul></ul>
  28. 28. Pulmonary Circulation <ul><li>Deoxygenated blood enters the lungs from right ventricle of heart through the pulmonary artery </li></ul><ul><ul><li>Pulmonary artery splits into left and right pulmonary arteries that enter the two lungs </li></ul></ul><ul><ul><li>Pulmonary arterioles enter capillary networks around the alveoli </li></ul></ul><ul><li>Oxygenated blood returns to the left side of heart in the pulmonary veins. </li></ul>
  29. 29. Thoracic Cavity <ul><li>Bound by thoracic vertebrae dorsally, ribs & intercostal muscles laterally, the sternum ventrally </li></ul><ul><li>Mediastinum – area between lungs </li></ul><ul><ul><li>Contains heart, trachea, esophagus, blood vessels, nerves, lymphatic structures </li></ul></ul>
  30. 30. Pleura <ul><li>Thin membrane that lines thoracic cavity and covers organs and structures in the thorax </li></ul><ul><ul><li>Visceral layer covers thoracic organs and structures </li></ul></ul><ul><ul><li>Parietal layer lines the cavity </li></ul></ul><ul><li>Space between the two pleural layers is filled with a small amount of pleural fluid </li></ul><ul><ul><li>Helps ensure that surfaces of organs slide smoothly along the lining of the thorax during breathing </li></ul></ul>
  31. 31. Diaphragm <ul><li>Thin, dome-shaped skeletal muscle sheet </li></ul><ul><li>Forms caudal boundary of thorax </li></ul><ul><li>Important respiratory muscle </li></ul><ul><ul><li>Flattens when it contracts </li></ul></ul><ul><ul><li>Enlarges volume of the thorax and aids inspiration </li></ul></ul>
  32. 32. Process of Respiration <ul><li>Pressure within the thorax is negative with respect to atmospheric pressure. </li></ul><ul><ul><li>Pulls lungs tight out against the thoracic wall </li></ul></ul><ul><ul><li>Lungs follow passively as movements of the thoracic wall and diaphragm alternately enlarge and reduce the volume of the thorax. </li></ul></ul><ul><ul><li>Negative intrathoracic pressure helps draw blood through veins and into the atria </li></ul></ul>
  33. 33. Inspiration <ul><li>Process of drawing air into lungs (inhalation) </li></ul><ul><li>Results from enlargement of the volume of the thoracic cavity by the inspiratory muscles </li></ul><ul><li>Main inspiratory muscles: diaphragm and external intercostal muscles </li></ul><ul><ul><li>External intercostal muscles located in the external portion of the intercostal spaces (between ribs) </li></ul></ul>
  34. 34. Expiration <ul><li>Process of pushing air out of lungs (exhalation) </li></ul><ul><li>Results from decrease in size of thoracic cavity </li></ul><ul><li>Main expiratory muscles: internal intercostal muscles and abdominal muscles </li></ul><ul><ul><li>Internal intercostal muscles located between the ribs, deep to the external intercostal muscles </li></ul></ul><ul><li>Contraction of abdominal muscles pushes abdominal organs against the diaphragm and pushes diaphragm back into its full dome shape. </li></ul>
  35. 35. Respiratory Volumes <ul><li>Tidal volume - volume of air inspired and expired during one breath </li></ul><ul><ul><li>Varies according to the body's needs </li></ul></ul><ul><li>Minute volume - volume of air inspired and expired during 1 minute of breathing </li></ul><ul><li>Residual volume - volume of air remaining in the lungs after maximum expiration </li></ul>
  36. 36. Alveolar Gas Exchange <ul><li>Simple diffusion of gas molecules according to concentration gradient </li></ul><ul><li>O 2 diffuses from the alveolar air into the blood of the alveolar capillary </li></ul><ul><li>CO 2 diffuses from the blood into the alveolus </li></ul>
  37. 37. Partial Pressure of Gases <ul><li>Pressure of each individual gas in a mixture of gases </li></ul><ul><li>Example: </li></ul><ul><ul><li>Atmospheric air ~ 21% O 2 </li></ul></ul><ul><ul><li>Total atmospheric pressure ~ 760 mm of mercury (Hg) </li></ul></ul><ul><ul><li>Partial pressure of oxygen (PO 2 ) in atmosphere: </li></ul></ul><ul><ul><ul><li>21% × 760 mm Hg = 159.6 mm Hg </li></ul></ul></ul><ul><li>Partial pressures of O 2 and CO 2 in the blood of alveolar capillaries is determined by the partial pressures of O 2 and CO 2 in alveolar air </li></ul>
  38. 38. Respiratory Center <ul><li>Area in the medulla oblongata of the brain stem </li></ul><ul><li>Controls respiratory muscle contractions </li></ul><ul><ul><li>Directs timing and strength of contraction </li></ul></ul><ul><li>Individual control centers - inspiration, expiration, breath holding </li></ul><ul><li>Can be consciously controlled for brief periods </li></ul>
  39. 39. Mechanical Control System <ul><li>Stretch receptors in the lungs set limits on routine resting inspiration and expiration. </li></ul><ul><li>Respiratory center sends out nerve impulses when lungs inflate to a certain point </li></ul><ul><ul><li>Stops muscle contractions that produce inspiration and starts contractions to produce expiration </li></ul></ul><ul><li>Another set of nerve impulses sent when lungs deflate sufficiently </li></ul><ul><ul><li>Stops expiration and starts the process of inspiration again </li></ul></ul>
  40. 40. Chemical Control System <ul><li>Adjusts the normal rhythmic breathing pattern produced by the mechanical control system </li></ul><ul><li>Chemical receptors in carotid artery and aorta monitor blood CO 2 , pH, and O 2 </li></ul>
  41. 41. Chemical Control System <ul><li>Blood level of CO 2 and blood pH are usually linked </li></ul><ul><li>Increased CO 2 in blood and decreased blood pH triggers respiratory center to increase rate and depth of respiration </li></ul><ul><li>Decreased CO 2 in blood increases blood pH; increased blood pH level triggers respiratory center to decrease rate and depth of respiration </li></ul>
  42. 42. Chemical Control System <ul><li>Hypoxia - decrease in blood O 2 level </li></ul><ul><li>Slight hypoxia triggers respiratory center to increase the rate and depth of breathing </li></ul><ul><li>Severe hypoxia - neurons of the respiratory center can become so depressed that adequate nerve impulses cannot be sent to the respiratory muscles </li></ul><ul><ul><li>Can cause breathing to decrease or stop completely </li></ul></ul>

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