The Respiratory System

1. The Respiratory System

2. The Respiratory System Functions: • To provide the body with means of taking in(O2) for the production of ATP and eliminating (CO2) a byproduct of aerobic respiration. • To help maintain the body’s pH, by regulating the blood CO2 levels in the body. • Work in conjunction with the cardiovascular system to move these gases from the lungs to the cells and from the cells to the lungs.

3. Organs of Respiratory System

4. Conducting Zone • Conducting zone • Provides rigid conduits for air to reach the sites of gas exchange • Respiratory structures include (nose, nasal cavity, pharynx, trachea, primary, secondary and tertiary bronchi) • No Gas exchange

5. Respiratory Zone • Respiratory zone: • begins as terminal bronchioles → respiratory bronchioles → alveolar ducts, → alveolar sacs composed of alveoli • This is where gas exchange occurs!

6. Nose • Functions • Nasal choanae creates turbulent air flow that allows air to contact mucus membranes and superficial nasal sinuses. • The result is cleaner, warmer more humidified inhaled air. • detects odors via the olfactory cranial nerve which also enhances our sense of taste. • Resonating chamber that amplifies the voice

7. Pharynx

8. Larynx • Larynx (“voice box”) • contains vocal cords allowing speech production • Glottis – vocal cords • Epiglottis • flap of tissue that guards glottis, directs food and drink to esophagus

9. Trachea • Flexible and mobile tube extending from the larynx to the carina (split into primary bronchi) • Composed of three layers • Mucosa – made up of pseudostratified ciliated epithelium that contain goblet cells that secrete mucus to trap dirt. • Mucociliary escalator: cilia beats in an upward fashion toward the pharynx where debris can be swallowed. • Submucosa – connective tissue deep to the mucosa • Adventitia – outermost layer made of C-shaped rings of hyaline cartilage which prevent the airway from collapsing.

10. Trachea

11. Respiratory Zone • Approximately 300 million alveoli: • Account for most of the lungs’ volume • Provide tremendous surface area for gas exchange • Equivalent to 2 tennis courts in surface area.

12. Respiratory Membrane

13. Respiratory Membrane Air-blood barrier is composed of alveolar and capillary walls. • Alveolar walls: contain 2 main types of cells • Type I epithelial cells (simple squamous epithelium) that permit gas exchange by simple diffusion • Type II cells (cuboidal epithelium ) secrete surfactant which enables the lungs to expand. • White blood cells are found in the lumen of the alveoli. • Function to protect against infections from inhaled pathogens

14. 4 Processes of Respiration • Pulmonary ventilation – air moving into and out of the lungs along their pressure gradients. • Inspiration – air(O2)flows into the lungs • Expiration – air (CO2) exit the lungs • External respiration – gas exchange between the lungs (alveolus) and the blood (pulmonary capillaries) 3. Transport – transport of oxygen and carbon dioxide between the lungs and tissues via the circulatory system. • Internal respiration – gas exchange between systemic blood vessels (capillaries) and the tissues (cells) • Gases must diffuse into interstitial fluid prior to any exchange between the tissue and the cell.

15. Pulmonary Ventilation • Taking of air into and out of the lungs. • A mechanical process that depends on respiratory muscles changing the size of the thoracic cavity • Because this cavity is connected to the lungs via the parietal membranes it may also influence the lung (alveolar )volume. • A increase in alveolar volume will move air into the lungs down it concentration gradient. • A decrease in alveolus volume will move air out of the lungs.

16. Boyle’s Law • The changes in thoracic volume is necessary to move air in and out of the lungs. The movement of air in dependant of: • Boyle’s law – Pressure and Volume are inversely proportional. • P ×V= Constant • If pressure increases volume decreases • If pressure decreases volume increases and vise versa • This mechanism is dependent on a double-layered membrane system called (Pleurae)

17. Pleurae Parietal pleurae Visceral pleurae Intrapleural space

18. Pleurae • Parietal pleura • Covers the thoracic wall and superior face of the diaphragm • Continues around heart and between lungs Visceral pleura • Covers the external lung surface • Intrapleural Space • Space between the parietal and visceral pleurae. • There is a small amount of fluid (pleural fluid) within the space that hold the 2 pleurae together • This will reduce friction between the lungs and the thoracic cavity. • Similar to a small amount of water between 2 plains of glass. • Slides easily but difficult to separate.

19. Pulmonary Pressures • Intrapulmonary pressure and intrapleural pressure fluctuate with the phases of respiration. • Intrapulmonary pressure aka. alveolar is the pressure with in the alveolus • Intrapleural pressure is the pressure within the pleural space • created by many hydrogen bonds between the water molecules of the pleural fluid. • Intrapleural pressure must always less than intrapulmonary pressure and atmospheric pressure

20. Pulmonary Pressures Intrapulmonary pressure Atmospheric pressure intrapleural pressure

21. Lung Collapse • Caused by equalization of the intrapleural pressure with the intrapulmonary pressure • Transpulmonary pressure keeps the airways open • Transpulmonary pressure – difference between the intrapulmonary and intrapleural pressures (Ppul – Pip)

22. Muscles of Respiration

23. Inspiration

24. Expiration Figure 22.13.2

25. Respiratory muscles • The muscles collectively work to change the volume of the thorax during ventilation. • Inspiration • Diaphragm via the phrenic nerve flattens out increasing thoracic volume depth • External intercostals via intercostal nerves pull the ribs up and out. • This collectively increase the size (volume) of the thorax and the lungs via its attachment to the pleura. • Expiration • Normal expiration is a passive process that involves the relaxation of the inspiratory muscles. • Forced expiration is an active process involving the internal intercostals and abdominals contracting forcing the ribs down decreasing the size (volume) of the thorax. • coughing

26. What is the mechanism of action for the Heimlich Maneuver?

27. Lung Compliance • The lungs ability to expand despite the lungs tendency to collapse. • Determined by two main factors: • Distensibility of the lung tissue and surrounding thoracic cage • Reducing surface tension of the alveoli: as the lungs expand it stretches the type II cell to produce more surfactant. • Surfactant is a detergent-like complex, reduces surface tension by breaking H-bonds allowing the lungs to expand.

28. Factors That Diminish Lung Compliance • Scar tissue or fibrosis that reduces the natural resilience of the lungs preventing them to expand during inhalation. • Blockage of the smaller respiratory passages with mucus or fluid • Reduced production of surfactant • Decreased flexibility of the thoracic cage or its decreased ability to expand • Examples include: • Deformities of thorax • Ossification of the costal cartilage • Paralysis of intercostal muscles

29. Deformities of Thorax • Barrel Chest Pectus Excavatum

30. Environmental Influences of Ventilation: • The amount of gas flowing into and out of the alveoli is directly proportional to  Pressure • The greater the pressure gradient between the atmosphere and the alveoli the more air will enter the lungs • Atmospheric pressure (Patm) • Pressure exerted by the air surrounding the body • Altitude and (Patm) are inversely proportional. • It is much easier to breath at sea level than it is a 10,000 ft above. Why?

31. Airway Resistance • Gas flow is inversely proportional to resistance • The resistance increases as vessel diameter decreases. • This will lead to less gas reaching the alveoli for exchange. • As airway resistance rises, breathing movements become more strenuous • Severely constricted or obstructed bronchioles: • Can occur during acute asthma attacks which stops ventilation . • Epinephrine released via the sympathetic nervous system or medically induced dilates bronchioles and reduces air resistance.

32. Dalton’s Law of Partial Pressures • The air that we breath is made up of 4 main gases • N2, O2, H2O and CO2 • There is a different % of each of the above gases in the atmospheric air. • Each gas therefore makes up a different proportion of the total mixture. • The sum of the partial pressures of each individual gas is equal to the total pressure of the air. • The partial pressure of the various gases are important in establishing the gradients which drives the gases throughout the system.

34. Partial Pressure Gradients

35. Partial Pressures Gradients During Internal Respiration • PCO2 (45mmHg)in peripheral tissues is higher than in the arteries returning from the lungs(40mmHG) because CO2 is a end product of cellular respiration. • The PO2(40mmHg)is lower in the tissues than the arterial blood (95mmHg) because O2is being continuously being used by the cells. • O2 and CO2will diffuse along their concentration gradients • O2 from blood to tissues • CO2from tissue to blood

36. Partial Pressure Gradients During External Respiration • Following (internal respiration)O2 unloading to the tissues and CO2uptake into the blood the (PO2) in venous blood decreases to40 mmHgand the PCO2 increases to 45mmHg • Following ventilation the PO2in the alveoli is104 mmHg and PCO2 decreases to 40mmHg • O2and CO2will diffuse along its pressure gradient from high to low • PO2 =lungs → blood • CO2 =blood → lungs • Diffusion will occur until equilibrium is met. • Blood PO2 and PCO2 will = the alveolus partial pressures.

37. Gas Transport: Role of Hemoglobin • Molecular oxygen is carried in the blood: • Bound to hemoglobin (Hb) within red blood cells (99%) • The hemoglobin-oxygen combination is called oxyhemoglobin (HbO2) • Dissolved in plasma (1%) • Carbon dioxide is transported in the blood in three forms • Dissolved in plasma – 7 to 10% • Chemically bound to hemoglobin – 20% is carried in RBCs as carbaminohemoglobin • Bicarbonate ion in plasma – 70% is transported as bicarbonate (HCO3–)

38. Internal Respiration

39. Internal Respiration At the tissues: • Carbon dioxide diffuses into RBCs • The high concentration of CO2 causes the above equation to shift to the right. • combines with water to form carbonic acid (H2CO3) • (H2CO3), which quickly dissociates into hydrogen ions and bicarbonate ions • Hydrogen ions attach to one of 4 heme molecules in the RBC dislodging on of the O2 (Bohr effect) • Oxygen travels down its concentration gradient to the tissues • Bicarbonate levels quickly build up and will quickly diffuses from RBCs into the blood plasma • The chloride shift – to counterbalance the out rush of negative bicarbonate ions from the RBCs, chloride ions (Cl–) move from the plasma into the erythrocytes

40. External Respiration

41. External Respiration • When the blood gets to the lungs these processes are reversed. • The above reaction will shift to the left. • Bicarbonate ions move into the RBCs and bind with hydrogen ions to form carbonic acid • Carbonic acid is then split by carbonic anhydrase to release carbon dioxide and water • CO2 levels quickly rise in the cell • CO2 diffuses from the blood into the alveoli along its concentration gradient.

42. Oxygen-Hemoglobin Dissociation Curve • The higher the PO2in the blood the greater the percent O2 saturation. • The percent O2 saturation plotted against blood PO2 • this tells us the amount of oxygen that is bound to hemoglobin at a particular PO2 in the blood • We monitor O2 saturation levels with patients with pulmonary issues • Below 90% is termed hypoxemia

43. Other Factors Influencing Hemoglobin Saturation • Increases in Temperature, H+, PCO2, and BPG increase O2 unloading from the hemoglobin. • This will result in a shift to the right on the curve • When the cells are more metabolically active there is a greater need for O2. • Temperature increases in metabolically activity, the tissues because heat is a byproduct of cellular respiration. • Active cells will also produce more CO2 and H20 which ultimately will lead to greater amounts of H+ • Both these byproducts ensure that O2 will be unloaded from the RBC and delivered to the tissues. • Decreases in Temperature, H+, PCO2, and BPG will act in the opposite manner • This will result in a shift to the left on the curve

44. Factors Influencing Hemoglobin Saturation

45. Medullary Respiratory Centers • Ventral Respiratory Group: Sets the underline breathing rate .It activates the • Diaphragm stimulated via the Phrenic Nerve • External Intercostals stimulated via the Costal Nerves • Dorsal Respiratory Group (DRG): receives input from multiple areas. • It modulates the breathing rate of the VRG so it can adapt to various situations.

46. Pons (Secondary Centers) • Apneustic Center • Stimulation of this center causes strong inspirations or aids in prolong inspiration. • stimulations the inspiratory center • Pneumotaxic Center • inhibits the VRG to end inspiration • provides for a smooth transition between inspiration and expiration • Stimulation of this center inhibits the Apneustic center • Contributes to expiration • Cortical control: we can actively effect our respiratory rate such as • holding breath under water • The Limbic system and hypothalamus also stimulate the respiratory centers. • Emotional effect on respiration

47. Depth and Rate of Breathing: Reflexes • Inflation reflex (Hering-Breuer) – stretch receptors in the lungs are stimulated by lung inflation • Upon inflation, inhibitory signals are sent to the medullary inspiration center to end inhalation and allow expiration • Pulmonary irritant reflexes – irritants promote reflexive constriction of air passages

48. Central Chemoreceptors • Changing PCO2 levels are monitored by Central chemoreceptors of the brain stem • Carbon dioxide in the blood diffuses into the cerebrospinal fluid •  CO2 + H2O  H2CO3  HCO3-+ H+ • PCO2 levels rise (hypercapnia) resulting in increase in H+ ion level concentration in the medulla. • This stimulations of( DRG) increased depth and rate of breathing • CO2 (expired) + H2O  H2CO3  HCO3-+ H+ • This will allow the body to blow off more CO2 thus reducing CO2 levels reestablishing homeostasis.

49. Depth and Rate of Breathing: PCO2

50. Peripheral Chemoreceptors • Arch of the Aorta • main vessel originating from the heart • Carotid sinus • main artery in the neck • Elevated arterial P CO2 and H+ ion concentration or decrease in PO2 will stimulate DRG to increase respiratory rate. • CO2 levels are the main driving force behind respiratory rate.