External Respiration Specifics

1
External Respiration Specifics

• Partial pressures in alveoli different from
  atmospheric partial pressures

2
External Respiration Reasons for Difference

• humidification of inhaled air
• gas movements
• increases alveolar PCO2
• decreases alveolar PO2
• mixing of old and new air (not all alveolar air
  is exchanged with each breath)

3
External RespirationGas Movements

• O2 loading (into blood)
• CO2 unloading (out of blood)

4
Ventilation-Perfusion Coupling

• circulatory system works in coordination with
  respiratory system to maximize effectiveness of
  exchange
• PO2 in bronchioles affects arteriolar diameter
  more blood goes to areas with higher oxygen
  levels
• decreased airflow ? decreased PO2 in airway ?
  vasoconstriction of pulmonary arterioles
• increased airflow ? increased PO2 in airway ?
  vasodilation of pulmonary arterioles

5
Ventilation-Perfusion Coupling

• PCO2 in bronchioles affects bronchiolar diameter
  areas that are stagnating build up CO2 ?
  increase flow through those areas
• decreased airflow ? increased PCO2 in airway ?
  bronchodilation
• increased airflow ? decreased PCO2 in airway ?
  bronchoconstriction

6
Internal Respiration Gas Movements

• O2 enters tissues from blood
• CO2 leaves tissues to enter blood

7
Factors Affecting Internal Respiration

• surface area for exchange
• size of capillary beds serving tissue
• varies from tissue to tissue
• partial pressure gradient between blood and
  tissue
• ventilation keeps arterial PO2 high, PCO2 low
• rate of blood flow
• varies with needs of tissue
• increases during activity
• decreases when tissue is inactive

8
Metabolism Review

• Aerobic Glucose 6 O2 --gt 6 CO2 6 H2O ATP
• Anaerobic Glucose --gt lactic acid ATP
• By-products of glucose catabolism include
• BPG (bis-phosphoglycerate intermediate of
  glycolysis)
• heat (reactions are inefficient)
• H (lowers pH), from
• CO2 combines with H2O to produce carbonic acid or
• lactic acid