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The Respiratory System

This chapter explores the operations of the respiratory system, including pulmonary ventilation, gas exchange, and pH control. It covers the anatomical components of the upper and lower respiratory tracts, as well as the processes of voice production, breathing, and lung volumes.

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The Respiratory System

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  1. The Respiratory System Chapter 18

  2. Operations • Pulmonary ventilation • Moving air in & out • External respiration • Gas exchange between alveoli & blood • Internal respiration • Gas exchange between blood & cells Helps pH control

  3. Anatomical Components • Upper respiratory tract • nose, pharynx • Lower Respiratory System • Trachea, larynx & bronchi & lungs • Conducting zone = tubing • Respiratory Zone= Gas exchange • Bronchioles, alveolar sacs & alveoli

  4. Figure 18.1

  5. Nose • Nose: external nares nasal cavity internal nares • Nasal septum splits in two • Nasal conchae swirl air over mucus membrane • Designed to: Filter, Warm, Humidify • Trap dust and infectious agents • Detect olfactory stimuli • Modify vocal sounds

  6. Pharynx • Funnel shaped tube from internal nares to larynx = “throat” • Upper = naso pharynx • Middle = oropharynx • Between uvula & top of epiglottis • lower = laryngeal pharynx • Connects with both esophagus & larynx • Thus both air & food & drink

  7. Figure 18.2

  8. Larynx • Short tube of cartilage • Thyroid cartilage- • anterior = “Adam's apple” • Epiglottis – upper leaf-shaped piece • During swallowing larynx moves up and epiglottis covers opening to trachea • Cricoid cartilage- forms inferior wall • Paired arytenoids- above cricoid • attach to vocal cords & pharyngeal muscles

  9. Figure 18.3

  10. Voice Production • Mucous membrane of larynx  two pairs of folds • Upper = false vocal cords • Lower = true vocal cords • Contain elastic ligaments stretched between cartilage • Move out into air way and vibrate • Pitch adjusted by tension and diameter of ligaments

  11. Trachea • Trachea- larynx  upper part of T5 vertebra R. & L. primary bronchus • Lined with pseudostratified ciliated mucous membrane  • dust protection – move toward pharynx • C-shaped cartilage rings keep lumen open

  12. Bronchi & Bronchioles • Bronchi also contain cartilage rings • Primary bronchi enter the lungs • Blood vessels, lymphatic vessels & nerves enter lungs with bronchi • In lungs branch secondary bronchi • one for each lobe of lung •  tertiary bronchi  terminal bronchi • Smaller bronchi have less cartilage and more smooth muscle • ANS can adjust diameter = resistance to flow

  13. Lungs • Two organs (R. & L) • Surrounded by pleural membrane • Parietal pleura attached to diaphragm & thoracic wall • Visceral pleura attached to lungs • Between is pleural cavity filled with fluid • Broad bottom = base; Pointy top = apex • Right lung has 3 lobes • Left lung has 3 lobes & cardiac notch

  14. Lung Lobes • Divided in lobules fed by tertiary bronchus • Further divisions terminal bronchiole •  respiratory bronchiole • Lined with non-ciliated cuboidal epithelium •  alveolar ducts  alveolar sacs 

  15. Figure 18.4

  16. Alveoli • Cup-shaped out pouch of sac • Lined with thin alveolar cells (simple squamous) • Scattered surfactant secreting cells • Lowers surface tension & humidifies • Alveolar macrophages- “cleaners” • Gases diffuse across combined epithelia of alveolus & capillary • Combination called: Respiratory Membrane

  17. Figure 18.5

  18. Figure 18.6

  19. Pulmonary Ventilation • Air flows between atmosphere & lungs due to difference in pressure • Caused by respiratory muscles • Inhalation: diaphragm & external intercostals • Diaphragm contracts  lung volume • Lung moves due to seal between parietal & visceral plura

  20. Exhalation • Resting exhalation due to muscle relaxation= passive process • Diaphragm rises & ribs fall   lung volume • Can be active using internal intercostals & abdominal muscles • Push diaphragm up & pull ribs in  • More  lung volume

  21. Figure 18.7a

  22. Figure 18.7b

  23. Pressure Changes •  lung volume   alveolar pressure • Atmospheric pressure is constant • Atmospheric > alveolar inhalation • During exhalation   lung rises • Alveolar> Atmospheric  exhalation

  24. Figure 18.8

  25. Air Flow Terms • Frequency (f) = breaths per minute • Normal ~12 breaths per min • Tidal volume (TV) = volume moved in one breath • Normal ~ 500 ml • Minute Ventilation (MV) = f x TV • ~ 70% of TV reaches alveoli (350 ml) • Only this involved in gas exchange • 30% in airways = Anatomic Dead Space

  26. Lung Volumes • Inspiration beyond resting = Inspiratory reserve volume • Expiration beyond resting (active) = Expiratory reserve volume • Air left after a maximum expiration = residual volume

  27. Lung Capacities • Inspiratory capacity= • TV + inspiratory reserve • Functional residual capacity = • Residual volume + expiratory reserve • Vital capacity (VC) = • Expiratory reserve + TV + Inspiratory reserve • Total lung capacity = VC + residual

  28. Figure 18.9

  29. Breathing Patterns • Eupnea = normal breathing • Highly variable in pattern • Special modifications for speech and emotional responses • Also variations fro coughing & sneezing to clear airways • See table 18.1

  30. Nature of Air • Mixture of gases (N2, O2,, CO2, H2O & others) • Each gas has own partial pressure (Px) • Each gas diffuses down partial pressure gradient • Total = sum of partial pressures = atmospheric pressure

  31. Pulmonary Gas Exchange: External Respiration • O2 diffuses from air (PO2 ~105mm Hg)  incoming blood (PO2 ~40mm Hg) • Continues until equilibrium (PO2 ~105mm Hg) • Some unexchanged mixture in out flow so Arterial blood is ~100 mmHg • Meanwhile blood (PCO2 ~45) diffuses to alveolar air (PCO2 ~40) • Again to equilibrium

  32. Systemic Gas Exchange: Internal Respiration • Occurs throughout body • O2 diffuses from blood to cells • PO2 lower in cells because of use • Meanwhile CO2 diffuses in opposite direction

  33. Figure 18.10

  34. Transport of Oxygen • O2 dissolves poorly 98.5% bound to hemoglobin in RBCs • Binding depends on PO2 • High at lung and lower at tissue PO2s • Tissue release of O2 increased by: • High CO2 • Acidity • Higher temperatures

  35. Transport of Carbon Dioxide • As comes in to blood from cells • Some dissolved (7%) • Bound to proteins including Hemoglobin (23%) • Becomes bicarbonate ions (70%) • CO2 + H2O <=> H+ + HCO3- • Process reverses at lungs

  36. Figure 18.11

  37. Control of Respiration • Medullary respiratory area in medulla • Contains both inspiratory & expiratory areas • Quiet breathing: • inspiratory area nerve signals to inspiratory muscles for ~2 sec • inspiration • Then becomes inactive & muscles relax • Expiration • Expiratory centre active only during forceful breathing • Area in pons adjusts length of inspiratory stimulation

  38. Figure 18.12a

  39. Figure 18.12b

  40. Regulation of Respiratory Center • Cortical input: voluntary adjustment of patterns • Protection & talking • Chemoreceptor input will override breath-hold • Chemoreceptor input • Central receptors in medulla • Peripheral receptors in arch of aorta • respond to increased H+ or PCO2increased ventilation • Thus negative feedback loop to maintain blood & brain pH • Significant falls in PO2 also stimulates breathing

  41. Figure 18.13

  42. Other Regulatory Factors • Limbic system- • anticipation of activity or emotion can stimulate • Proprioception stimulates on start of activity • Temperature  warming increases • Pain- Sudden pain  apnea • Prolonged somatic pain can increase rate • Airway irritation cough or sneeze • Inflation reflex- bronchi wall stretch receptors inhibit inspiration • Prevents overinflation

  43. Aging • Everything becomes less elastic  • Decrease in Vital capacity • Can decrease blood O2 level • Decreased exercise capacity • Decreased macrophage activity • Increased susceptibility to pulmonary disease

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