The document summarizes key aspects of the respiratory system, including: - External respiration involves gas exchange between the lungs and blood, transporting oxygen to tissues and carbon dioxide away. Internal respiration occurs via cellular respiration in mitochondria. - The respiratory tract involves the nose, pharynx, larynx, trachea, bronchi and bronchioles leading to alveoli where gas exchange occurs by diffusion across pulmonary capillaries. - Breathing is driven by changes in thoracic pressure and lung volumes via contraction of respiratory muscles and elastic recoil of the lungs and chest wall. Inspiration occurs as lungs fill a expanded chest cavity, expiration when it relaxes.

3. Atmosphere Tissue cell Alveoli of lungs Pulmonary circulation Systemic circulation CO 2 O 2 Food + O 2 CO 2 + H 2 O + ATP O 2 CO 2 CO 2 O 2 1 External respiration Breathing --Gas exchange between the atmosphere & (alveoli) in the lungs Exchange of O 2 & CO 2 between air in the alveoli and the blood Transport of O 2 & CO 2 between the lungs and the tissues Exchange of O 2 & CO 2 between the blood and the tissues Internal respiration 2 3 4 The term respiration has a broad meaning

5. Nasal passages Mouth Pharynx Larynx Trachea Right bronchus Bronchiole Terminal bronchiole Terminal bronchiole Respiratory bronchiole Alveolar sac Respiratory airways conduct air between the atmosphere & alveoli. reinforced with rings of cartilage. Below the trachea, the respiratory tract forms progressively smaller and more numerous airways (bronchi to bronchioles to alveoli).

11. Vacuum 760 mm Mercury (Hg) Pressure exerted by atmospheric air above Earth’s surface Pressure is measured in mm of mercury.

13. 760 760 760 Collapsed lung 760 760 756 760 Puncture wound in chest wall 760 760 760 Traumatic pneumothorax 760 756 756 760 760 760 Spontaneous pneumothorax 760 756 760 756 Hole in lung

15. Equilibrated; no net movement of air 760 756 Before inspiration 759 754 During inspiration 760 761 756 During expiration 760 760 Inspiration & expiration are dependent on changing the size of the the thorax: Increasing throcic volume Decreasing throcic volume

16. Intra-Aveolar and Intrapleural Pressures Inspiration Expiration Atm pressure Intra-alveolar pressure Intraplural pressure Transmural pressure gradient across the lung wall

18. External intercostal muscles (relaxed) Contractions of external intercostal muscles causes elevation of ribs, which increases side-to-side dimension of thoracic cavity Lowering of diaphragm on contraction increases vertical dimension of thoracic cavity Elevation of ribs causes sternum to move upward and outward, which increases front-to back dimension of thoracic cavity Before inspiration Inspiration Elevated rib cage Contraction of external intercostal muscles Sternum Diaphragm (relaxed) Contraction of diaphragm

20. Relaxation of external intercostal muscles Return of diaphragm, ribs, and sternum to resting position on relaxation of inspiratory muscles restores thoracic cavity to preinspiratory size Contractions of abdominal muscles cause diaphragm to be pushed upward, further reducing vertical dimension of thoracic cavity Contraction of internal intercostal muscles flattens ribs & sternum, further reducing side- to-side and front to-back dimensions of thoracic cavity Passive expiration Active expiration Contraction of internal intercostal muscles Relaxation of diaphragm Contraction of diaphragm Position of relaxed abdominal muscles

26. Aveoli are interconnected. Thus aveoli must expand & contract as a unit. Interconnected alveoli Alveolus starts to collapse Collapsing alveolus pulled open

27. Airways Alveoli Pulmonary surfactant molecule Airways Alveoli Surfactant equalizes the inward pressure differences in between large & small aveoli created by surface tension

28. Variations in lung volume Total lung capacity at maximum inflation Variation in lung with normal, quiet breathing Minimal lung volume (residual volume) at maximum deflation Normal expiration (average 2,200 ml) normal inspiration (average 2,200 ml) Avg. 500 ml

29. Figure 13.19b Page 477 TV = Tidal volume (500ml) IRV = Inspiratory reserve volume (3,000 ml) IC = Inspiratory capacity (3,500 ml) ERV = Expiratory reserve volume (1,000 ml) RV = Residual volume (1,200 ml) FRC = Functional residual capacity (2,200 ml) VC = Vital capacity (4,500 ml) TLC = Total lung capacity (5,700 ml) Time Time (sec)

30. Lung volumes and capacities can be measured by a spirometer. Spirogram Floating drum Air Water Expired air Inspired air

31. Figure 13.22a Page 479 Obstructive lung disease

32. Figure 13.22b Page 479 Restrictive lung disease Normal total lung capacity

33. “ Old” alveolar air that has exchanged O 2 and CO 2 with the blood Fresh atmospheric air that has not exchanged O 2 and CO 2 with the blood 150 During expiration 350 150 500 ml “old” alveolar air expired Fresh air from inspiration 150 dead space volume (150 ml) After inspiration, before expiration Alveolar air 150 350 150 During inspiration Alveolar ventilation is less because of the anatomic dead space.

37. Composition and partial pressure in atmospheric air Total atmospheric pressure = 760 mm Hg 79% N 2 Partial pressure N 2 = 600 mm Hg 21% O 2 Partial pressure O 2 = 160 mm Hg Partial pressure of N 2 in atmospheric air: P N2 = 760 mm Hg X 0.79 = 600 mm Hg Partial pressure of O 2 in atmospheric air: P O2 = 760 mm Hg X 0.21 = 160 mm Hg

38. Across pulmonary capillaries: O 2 partial pressure gradient from alveoli to blood = 60 mm Hg (100 –> 40) O 2 partial pressure gradient from blood to alveoli = 6 mm Hg (46 –> 40) Across pulmonary capillaries: O 2 partial pressure gradient from blood to alveoli = 6 mm Hg (46 –> 40) O 2 partial pressure gradient from tissue cell to blood = 6 mm Hg (46 –> 40) Inspiration Expiration Pulmonary circulation Systemic circulation Alveoli Diffusion gradients for O 2 & CO 2 between the lungs & tissues Tissue cell Atmospheric air

39. Area in which blood flow (perfusion) is greater than airflow (ventilation) Helps balance Helps balance Small airflow CO 2 in area Relaxation of local-airway smooth muscle Dilation of local airways Airway resistance Airflow O 2 in area Contraction of local pulmonary smooth muscle Constriction of blood vessels Vascular resistance Blood flow Large bloodflow

40. Area in which blood flow (ventilation) is greater than blood (perfusion) Helps balance Helps balance Large airflow Small blood flow CO 2 in area Contraction of local airway smooth muscle Constriction of local-airway Airway resistance Airflow O 2 in area Relaxation of local pulmonary smooth muscle Dilation of local blood vessels Vascular resistance Blood flow

45. Alveoli Pulmonary capillary blood = O 2 molecule = Partially saturated hemoglobin molecules = Fully saturated hemoglobin molecules Hemoglobin increases the concentation gradient of O 2 in pulmonary capillaries.

48. Figure 13.30 Page 491 Arterial P CO2 & acidity, normal body temperature (as at pulmonary level) P CO2 Acid (H + ) Temperature or 2,3-Bisphosphoglycerate (from normal tissue levels)

50. CO 2 transport Tissue cell Alveolus Plasma From systemic circulation to pulmonary circulation

52. Effects of hyperventilation and hypoventilation on arterial P O2 & P CO2 Hypoventilation Hyperventilation Normal alveolar and arterial P O2 Normal alveolar and arterial P C O2 P CO2 P O2

53. Output from the DRG goes through the phrenic nerve to the diaphagm Input from other areas– some excitatory, some inhibitory Inspiratory neurons in DRG (rhythmically firing) Phrenic nerve Diaphragm Spinal cord Medulla

55. Arterial P CO2 Relieves Brain ECF P CO2 Brain ECF H + Central Chemo-receptors Medullary respiratory center Ventilation Arterial P CO2 Peripheral Chemo-receptors Weakly Brain ECF  when arterial P CO2 >70-80 mm Hg

56. Low levels of O2 can trigger increased external respiration Arterial P O2 <60 mm Hg Emergency life-saving mechanism Medullary respiratory center Ventilation Arterial P O2 Central chemoreceptors Peripheral chemoreceptors No effect on Relieves

57. Figure 13.38 Page 5O2 Acidosis Arterial non-CO 2 -H + Peripheral Chemo-receptors Medullary respiratory center Central Chemo-receptors Cannot penetrate blood-brain barrier No effect on Ventilation Arterial P CO2 Arterial -CO 2 -H + Relieves