Part 1 Structure and Function of the Respiratory System

2. Part 1 Structure and Function of the Respiratory System When you can not breath, nothing else matters Slogan of the American Lung Association

3. Respiration is the process by which the body takes in and utilizes oxygen (O2) and gets rid of carbon dioxide (CO2).

4. An Overview of Key Steps in Respiration

5. Respiration can be divided into four major functional events • Ventilation: Movement of air into and out of lungs • Gas exchange between air in lungs and blood • Transport of oxygen and carbon dioxide in the blood • Internal respiration: Gas exchange between the blood and tissues

6. Respiratory System Functions • Gas exchange: Oxygen enters blood and carbon dioxide leaves • Regulation of blood pH: Altered by changing blood carbon dioxide levels • Voice production: Movement of air past vocal folds makes sound and speech • Olfaction: Smell occurs when airborne molecules drawn into nasal cavity • Protection: Against microorganisms by preventing entry and removing them • Metabolism: Synthesize and metabolize different compounds (Nonrespiratory Function of the Lung)

7. Section I ANATOMY OF THE RESPIRATORY TRACT

8. Respiratory System Divisions • Upper Airway • Nose, pharynx, larynx and associated structures • Lower Airway • trachea, bronchi, lungs

9. Conducting Zone • All the structures air passes through before reaching the respiratory zone. • Cartilage holds tube system open and smooth muscle controls tube diameter • Warms and humidifies inspired air. • Filters and cleans: Insert fig. 16.5

10. Respiratory Zone • Region of gas exchange between air and blood. • Includes respiratory bronchioles and alveolar sacs.

11. Airway branching

12. Section II BLOOD SUPPLY TO THE LUNG • Two separate blood supplies: pulmonary circulation and bronchial circulation • Pulmonary circulation • Bronchial circulation

13. Pulmonary circulation • Brings deoxygenated blood from the right ventricle to the gas-exchange units • At the gas-exchanging units, oxygen is picked up and carbon dioxide is removed from the blood • The oxygenated blood returned to the left atrium for distribution to the rest of the body

14. Bronchial circulation • Arise from the aorta • Provides nourishments to the lung parenchyma（肺实质）

15. Section III MUSCLES OF RESPIRATION • Inspiratory muscle: • Diaphragm and Abdominal breathing （腹式呼吸） • external intercostal muscle and thoracic breathing （胸式呼吸） • accessory muscle of inspiration • Expiratory muscle • relax during normal breathing • Internal intercostal muscle • Muscles of the abdominal wall

16. Thoracic Walls and Muscles of Respiration

17. Breathing Rate • At rest: 10-20 breaths / minute • During exercise: 40 - 45 at maximum exercise in adults

18. Thoracic Volume

19. Rib Cage Contract IntercostalsContractto Lift Spine Rib Diaphragm Volume Volume Ribs Mechanisms of Breathing: How do we change the volume of the rib cage ? • To Inhale is an ACTIVE process • Diaphragm • External Intercostal Muscles Both actions occur simultaneously – otherwise not effective

20. Pleura

21. Pleural fluid produced by pleural membranes • Acts as lubricant • Helps hold parietal and visceral pleural membranes together

22. Ventilation • Movement of air into and out of lungs • Air moves from area of higher pressure to area of lower pressure • Pressure is inversely related to volume

23. Alveolar Pressure Changes During Respiration

24. Conducting Airways Lungs Gas Exchange Pleural Cavity Very small space Maintained at negative pressure Transmits pressure changes Allows lung and ribs to slide Chest Wall (muscle, ribs) Diaphragm (muscle) Pleural CavityImaginary Space between Lungs and chest wall Principles of Breathing Functional Unit: Chest Wall and Lung Follows Boyle’s Law:Pressure (P) x Volume (V) = Constant

25. CW Principle of Breathing Follows Boyle’s Law: PV= C At Rest with mouth open Pb = Pi = 0 Pb Airway Open A Pi PS D 1

26. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Inhalation: • Increase Volume of Rib cage • Decrease the pleural cavity pressure- Decrease in Pressure inside (Pi) lungs Pb Airway Open A Pi PS CW D 2

27. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Inhalation: • Pb outside is now greater than Pi- Air flows down pressure gradient • Until Pi = Pb Pb Airway Open A Pi CW PS D 3

28. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Exhalation: Opposite Process • Decrease Rib Cage Volume Pb Airway Open A Pi CW PS D 4

29. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Exhalation: Opposite Process • Decrease Rib Cage Volume • Increase in pleural cavity pressure - Increase Pi Pb Airway Open A Pi CW PS D 5

30. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Exhalation: Opposite Process • Decrease Rib Cage Volume • Increase Pi • Pi is greater than Pb • Air flows down pressure gradient • Until Pi = Pb again Pb Airway Open A Pi CW PS D 6

32. Section IV SURFACTANT AND SURFACE TENSION • Surface tension (表面张力）: a measure of the attraction force of the surface molecules per unit length of the material to which they are attached

33. Surface Tension • Force exerted by fluid in alveoli to resist distension • Lungs secrete and absorb fluid, leaving a very thin film of fluid. • H20 molecules at the surface are attracted to other H20 molecules by attractive forces. • Force is directed inward, raising pressure in alveoli.

34. At surface Unbalanced forces Generate Tension Within Fluid All forces balance What is Surface Tension ?

35. Surface Tension • Law of Laplace: • Pressure in alveoli • directly proportional to surface tension • inversely proportional to radius of alveoli • if surface tension were the same in all alveolus.... Insert fig. 16.11

36. AirFlow Expand Collapse Effect of Surface Tension on Alveoli size

37. Surfactant (表面活性物质） • Phospholipid produced by alveolar type II cells. • Lowers surface tension. • Reduces attractive forces of hydrogen bonding • by becoming interspersed between H20 molecules. • Surface tension in alveoli is reduced.

38. Low S/unit Area Slider - Change Surface Area Increase Area DecreaseArea Surfactant High S/unit Area Area Saline Saline Tension Area dependence of Surfactant action

39. Surfactant prevents alveolar collapse

40. Normal (with surfactant) Saline Filled Volume L 6 3 Without surfactant RV Pleural Pressure 0 0 - 15 - 30 cm H2O Volume-pressure curves of lungs filled with saline and with air (with or without surfactant)

41. Physiology Importance of Surfactant • Reduce the work of breathing • Stabilize alveoli • Prevent collapse and sticking of alveoli • Maintain the dryness of the alveoli • Prevent the edema of the alveoli