Review Exam 3 PSIO 420
Ventilation - moving air in and out of the lungs which allows for external respiration
pH regulation - removal of CO2 and how it contributes to acid/base balance
Respiration: External vs. Internal
• External - diffusion of gasses from tissues to blood in the lungs.
• Internal - Diffusion of gasses from blood to tissues in the muscles, skin, organs
Well why do we breath?? - we do it to get gas exchange so that aerobic respiration can be
performed. This exchange is called diffusion of gasses.
KEY POINT: Respiratory system is not limiting factor during exercise!!
Family tree of AIR way:
The last section is alveoli - 24
- Diameter decreases as you move from top to
- Length also decreases moving from top to
bottom, with the alveoli being 1/3 mm.
- The number of each increased moving from
top to bottom, causing the number of alveoli to
be about 300 million.
- Lastly total cross sectional area decreased
from 0 to 3, however increased from 3 to 24.
The alveoli was about 50 -100m in total cross
- The conducting zone is also called anatomical
dead space, due to no gas diffusion in this area.
Anatomy of Lungs: Function is to help expand and relax the lungs, inhale and exhale.
- Visceral pleura is outer layer on the lungs.
-Parietal pleura is attached to the chest wall.
-Pleural cavity is the space in-between the visceral pleura and parietal pleura.
- Alveoli sac • very well vascularized
• Large surface area for gas exchange
• Very thin respiratory membrane: Has to cross three barriers
Alveolar cell membrane (Type 1 alveolar cell simple squamous) - epithelial
Capillary (endothelial cell) - also a basement membrane
• Type II cells - secrete surfactant (3%)
allows for alveoli so expand - no collapsing
There is also a thin layer of water present in the alveoli which causes the cell to
want to collapse, surfactant stops this from happening.
• Velocity of gas diffusion is proportional to the AREA, D is a constant, and Driving
pressure(P1-P2) and is inversely proportional to Thickness
• Thickness is proportional to Solubility and inversely proportional to square root of
Lecture 18: part 2
Mechanics of Breathing - Change in volume to effect pressure: The diaphragm, intercostal
muscles, and accessory muscles change volume that ultimately changes pressure.
• Air moves from areas of high pressure to areas of low pressure.
• Boyle's Law - Volume and pressure are inversely proportional - first change volume to
• Inspiration - takes place when alveolar pressure is lower than the outside pressure (this
only takes a couple of mm of Hg)
• Expiration - Takes place when alveolar pressure is higher than the atmospheric
pressure outside the body.