Chapter 22: Respiration

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Chapter 22: Respiration
2011-04-10 10:35:21
Respiratory system

respiratory system
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  1. What would be the main anatomical features of a respiratory system?
    • moist membrane
    • opened pathway- trachea so gas can come in whenever it wants
    • lots of surface area for gas exchange
    • very thin membrane for diffusion
    • elastic response- to both empty & fill the lungs
    • highly vasculated- large amounts of capillaries
  2. Alveoli structure
    • walls are made of simple squamous epithelial cells
    • macrophages clean up particles that enter lungs
  3. Great alveoli cells
    • make surfactant
    • -surfactant decreases natural surface tension in a water film
  4. "basket of capillaries"
    • the capillary cells are "fused" to alveoli walls by an elastic basement membrane
    • entire thickness is 0.5 microns
    • BP is low so that osmotic pressure wins
  5. viseral pleura
    outter tissue of the lungs, very thin membrane
  6. parietal pleura
    lining under the rib cage, gives good surface tension
  7. pleural cavity
    • really not meant to be a "space"
    • -pleural cavity does have less pressure than in lungs
    • -surface tension b/w 2 tissue layers: "pulls" on lungs when ribs are raised
  8. Pulmonary ventilation: inhalation
    is active; need to create an internal pressure that is less than atmospheric pressure
  9. Pulmonary ventilation: exhalation
    at rest is passive
  10. Boyle's Law
    if you increase volume of a contained area you decrease pressure of gases w/in that area (inversely proportional)
  11. Charles's Law
    gas volume will expand as temp. rises (directly proportional)
  12. Dalton's Law
    • In a mixture of gases, each gas component exerts its own pressure
    • -partial pressures: oxygen and carbon dioxide
  13. Pressures involved:
    intrapulmonary pressure
    intrapleural pressure
    • atmospheric= 760 mm Hg
    • intrapulmonary pressure= inside expanded lungs: 757
    • intrapleural pressure= between ribs & visceral pleura 756-754
  14. Negative internal pressure
    • pressure by raising ribs (intercostal muscles) and lowering diaphragm
    • - as ribs move, they pull on lungs and aid in expansion due to surface tension b/w tissue
  15. Transpulmonary gradients
    differences in pressures allow air flow into lungs
  16. Compliance
    • ease of inhalation; little resistance to lung expansion
    • Need: lungs easily expanded, muscles easily working ribs. alveoli easily open
  17. Factors that affect compliance
    • elastic tissue in lungs
    • residual air volume
    • cartilage of ribs to be flexible
    • surfactant to decrease surface tension b/w alveoli
    • surface tension b/w viseral pleura and rib covering
    • for exhalation: ease of recoil and fast relaxation of muscles
  18. pneumothorax
    • increased pressure in pleural cavity
    • -may lead to atelectasis: collapsed lung
  19. Partial Pressure of gases
  20. Ventilation
    amount of air entering specific parts of lungs
  21. Perfusion
    amount of blood entering the capillaries of the same part of the lungs
  22. What controls Hgb's affinity for oxygen?
    • PO2 levels: higher pO2 means greater afinity
    • -as the first O2 adds, this increases the affinity for more to add
    • pH: increased acidity decreases affinity -H+ ions ling ot the Hgb; discourage affinity of O2
    • -most significant in tissues where there is low pO2
    • Temp: increased in temp decreases affinity
    • -metabolically active tissues generate heat and need more O2
  23. Role of the 'waste' CO2
    • very soluble in water
    • -most will form carbonic acid
    • -small percent stays as CO2 in the blood
    • -small percent is carried around by the protein regions of Hgb
  24. Carbonic buffer system
  25. Details of gas exchange w/in the RBC's
    • Shifting of H+ effects affinity of oxygen for Hgb
    • -H+ shifts due to action of carbonic buffer system
    • -H+ influences Hgb's affintiy for oxygen
    • -Note systemic gas exchange details
    • -Note alveolar gas exchange details
    • Shifting of Cl ions encourages the buffer system in the tissue to shift to the R and stay there
  26. Hypercapnia
    • leads to acidosis
    • EX: reduced breathing rate due to coma
    • CO2 levels and the buffer system go up and shift to the right
  27. Hypocapnia
    • alkalosis
    • EX: hyperventilation
    • CO2 levels and the buffer system go down and shift left
  28. Regulation of breathing
    • involuntary act over which you have voluntary control
    • -chemoreceptors- in aorta & carotids closerly monitor blood pH
    • -medulla oblongata- VRG & DRG
    • - Pons- PRG
  29. Ventral respiratory group (VRG)
    • has the inspiratory neurons
    • -controls rhythm of breathing
    • -at rest pace in about 12 breaths/min
    • -inhalation take about 2 seconds
    • -innervation from this region goes to diaphragm & external intercostals
    • -absence of signal is expiration which takes about 3 seconds
  30. Dorsal Respiratory group
    • used for heavy group
    • ex: forced exhalation: active event
    • can constrict the intercostals and abdominal muscles to force air out
    • integrates messages coming from various areas inside and outside CNS
  31. Pneumotaxic area
    • controls neurons in VRG
    • needed to limit length and degree of inhalation
    • impulses from VRG can be set at every 1/2 sec. (panting) to every 7 sec (prolonged inhalation)
  32. Other input to control centers that regulate breathing
    • CC has some voluntary control; you can decide to alter breathing rate or hold your breath
    • Chemoreptors for pH, also CO2 and oxygen levels
    • stretch receptors in thoracic cavity send signals if you try to breath in too much! cant over inflate lungs
    • changes in blood pressure and heart rate also have input
  33. COPD
    • Chronic obstructive pulmonary disease
    • Really 2 conditions combined: chronic bronchitis and emphysema
  34. bronchitis
    caused by: allergies & asthma, smoking damage, repeated infections, pollution
  35. emphysema
    • pulmonary fibrosis
    • loss of alveoli; replace w/ fibrous connective tissue
    • extreme increase in residual air volume
    • lungs can not recoil enough to get old air out
    • barrel chest results as patient struggles to expel air
    • causes: smoking, genetic factors
  36. Lung cancer
    • prolonged irritation from smoke means constantly replacing cells that line tubes
    • increased rate of mitosis: increased rish of mutation; smoke is known carcinogen
    • loss of cells impairs ability to clear lungs; smokers cugh and emphysema result
    • mucous membrane of the large bronchial tubes are the most freguent sources of cancer cells
    • spreads rapidly; poor prognosis
  37. infant respiratory distress syndrome
    • premature infants have not produced surfactant
    • -lungs close up after an exhale and infant can't re-inflate lungs
    • treatment: man- made surfactant and high oxygen levels
  38. Cystic fibrosis
    • msot common lethal genetic disease of Caucasians
    • Two problems:
    • 1.mucous produced in bronchial tubes is too thick
    • -genetic flaw in ion transport
    • -affects amount of fluid being put into mucous
    • 2. Pancreas digestive enzymes don't reach the small intestine due to block duct