Ch. 22: The Respiratory System

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Ch. 22 The Respiratory System

• I. Anatomy
• II. Pulmonary Ventilation
• III. Gas Exchange Transport
• IV. Respiratory Disorders

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III. Gas Exchange Transport

• A. Composition of Air
• B. The Air-Water Interface
• C. Alveolar Gas Exchange
• D. Gas Transport
• E. Systemic Gas Exchange
• F. Alveolar Gas Exchange Revisited
• G. Adjustment to the Metabolic Needs of
  Individual Tissues
• H. Blood Gases the Respiratory Rhythm

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A. Composition of Air

• Gas Laws Table 22.1
• Partial pressures Table 22.4
• Daltons Law
• total pressure sum of partial pressures
• alveolar air composition is different because of
• a. humidification by airway
• b. exchanges of O2 CO2 at respiration membrane
• c. mixing of inspired residual air

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B. The Air-Water Interface

• diffusion down conc. gradients
• O2 alveolar air-gtblood (O2 loading)
• CO2 blood-gtalveolar air (CO2 unloading)
• diffusion of each is independent of other

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C. Alveolar Gas Exchange

• principles
• depends on equilbrium time for O2 CO2 in blood
• 0.25 second
• depends on time RBCs spend in alveoli
• at least 0.3 second

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• gas exchange efficiency depends on
• concentration gradients of gases
• solubility of gases
• membrane thickness
• membrane area
• ventilation-perfusion coupling

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concentration gradients

• alveolar arterial blood
• high CO2 and low O2
• alveolar venous blood
• low CO2 and high O2
• hyperbaric chambers
• high atmospheric O2 pressure
• treatment for gangrene
• See Fig. 22.20 for comparison of gradients

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solubility of gases

• CO2 is more soluble than O2
• concentration gradients are different for each
• net effect ? equal exchange of CO2 and O2

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membrane thickness surface area

• Fig.22.21
• 150 x 106 alveoli
• 70m2 of surface area (total respiration membrane
  area) for gas exchange

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ventilation-perfusion coupling

• matching ventilation w. perfusion
• good ventilation in alveolus ? ? perfusion at
  that site
• poor ventilation in alveolus ? ? perfusion at
  that site
• mechanism
• chemoreceptors for CO2 and O2
• ? CO2 leads to bronchodilation for increased
  airflow
• ? CO2 leads to bronchoconstriction for decreased
  airflow
• ? O2 leads to bronchodilation for increased
  airflow
• ? O2 leads to bronchoconstriction for decreased
  airflow

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D. Gas Transport

• O2 transport
• 98.5 bound to Hb
• 1.5 dissolved in plasma (H2O)
• non-linear binding

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• CO2 transport
• 70 reacts with water
• H20 CO2 ? H2CO3 ? HCO3- H
• 23 binds to Hb and plasma proteins
• ? carbaminoHb
• Hb transports both CO2 and O2 simultaneously
• 7 carried as dissolved gas

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E. Systemic Gas Exchange (exchange at body tissue
capillaries)

• CO2 loading
• tissues dump CO2 into blood (Hb)
• hemoglobin ? carboxyhemoglobin
• O2 unloading
• blood dumps O2 into tissues cells
• RBC oxyhemoglobin ? deoxyhemoglobin
• venous reserve
• whats left of oxyhemoglobin after unloading

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F. Alveolar Gas Exchange Revisited (exchange at
alveoli)
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G. Adjustment to the Metabolic Needs of
Individual Tissues

• O2 needs of different tissues varies
• delivery of O2 requires dissociation from oxy-Hb
• factors in adjustment to needs
• ambient PO2
• tempterature
• the Bohr effect (pH)
• BPG (bisphosphoglycerate)
• the Haldane effect (re blood CO2)

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ambient PO2

• the more O2 a tissue uses, the more O2 flows into
  tissue from blood

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temperature
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pH
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metabolic needs (BPG)

• RBCs are anaerobic (no mitochondria)
• DPG - an intermediate in anaerobic metabolism
• when tissue is active ? ? BPG
• BPG binds Hb and promotes O2 unloading

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H. Blood Gases the Respiratory Rhythm

• Background
• Hydrogen Ions
• Carbon Dioxide
• Oxygen

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Background

• respiration for maintaining
• PO2, PCO2, pH
• detection receptors ? info to brainstem
• peripheral chemoreceptors
• aortic bodies
• carotid bodies
• central chemoreceptors
• info via vagus nerve glossopharyngeal nerve
• ? medulla oblongata receptors

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• MAIN STIMULUS TO PULMONARY VENTILATION IS H
  IN THE CSF

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H and CO2

• H does NOT cross BBB easily
• CO2 crosses BBB easily
• CSF grows acidic-gt stimulates the respiratory
  center
• blood pH 7.4 0.05
• when pH lt 7.35 ? acidosis
• hypercapnia (high PCO2)
• when pH gt 7.45 ? alkalosis
• hypocapnia (low PCO2)

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• hypercapnia triggers hyperventilation
• hypocapnia inhibits respiration
• other factors
• diabetes mellitis ? ketoacidosis
• hyperpnea is symptom of untreated DM

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O2

• PO2 has little effect on respiration - READ

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IV. Respiratory Disorders

• A. Oxygen Imbalances
• B. Chronic Obstructive Pulmonary Diseases
• C. Smoking Lung Cancer

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A. Oxygen imbalances

• Hypoxemic hypoxia
• Low arterial PO2
• Ischemic hypoxia
• Inadequate circulation
• Anemic hypoxia
• Low oxy-Hb
• Histotoxic hypoxia
• Metabolic poisoning (of aerobic machinery)

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B. COPD

• chronic obstructive pulmonary diseases
• asthma
• chronic bronchitis
• emphysema
• long-term airflow reduction due to obstruction ?
  ? pulmonary ventilation
• sputum
• cor pulmonale hypertrophy/failure of right heart
  due to obstructed pulmonary circulation

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C. Smoking Lung Cancer

• squamous cell carcinoma epithelial tissues
• adenocarcenomamucous glands
• small cell carcinoma primary bronchi

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INSIGHT

• Diving Physiology Decompression Sickness - read