Outline - 4, BIO 3360, Respiration II - Gas Transfer
I. Gas Transport in Air Breathing Animals
A. Oxygen and Carbon Dioxide move from high to low pressure
B. Lung ventilation (breathing) (convection)
C. Lung diffusion
D. Blood circulation (convection)
E. Tissue diffusion
F. Mammalian Lung
1. Gas exchange occurs between the blind-ended alveoli and respiratory capillaries
2. Surface area is enormous and wall of alveoli and blood capillaries is thin
II. Inspiration = Inhalation - breathing in - per Boyle's law as the closed container increases in size and volume, the pressure decreases to below atmospheric pressure, therefore air flows in.
III. Expiration = Exhalation - breathing out - per Boyle's law, as the closed container decreases in size and volume, the pressure increases to above atmospheric pressure, therefore air flows out. Quiet expiration is passive.
IV. Lung Distensibility or Compliance- how easy it is to stretch a structure due to elastic fibers in the lungs, elastic recoil is opposite of distensibility in how readily structure returns to resting shape
V. Surface Tension - resists lung inflation and reduces lung compliance
A. Thin layer of fluid lining alveoli resulting from hydrogen bonding between water molecules leading to two wet surfaces wanting to stick together
B. Surfactant reduces surface tension
C. Surfactant increases lung compliance
VI. Dead Space
A. Tidal volume is amount of air moving in or out of lung with each breath
B. Dead air volume is that volume not in the alveoli and therefore not useful for gas exchange
C. Volume of air in alveoli = Tidal Volume - Dead Air volume
D. Alveolar Ventilation rate is related to breaths per minute;
(V A )f =(V T – V D ) f
VII. Alveolar Blood Gas Exchange
A. Oxygen and Carbon Dioxide will diffuse according to their pressure gradients
B. Hemoglobin inside RBCs carries oxygen. Hb presence allows diffusion of more oxygen into the blood.
VIII. Tissue Blood Gas Exchange - follows the same principles