Respiratory System Flashcards
Ventilation
movement of air in and out of the lungs
- PV=nRT
- pressure is proportional to number of molecules and temperature
- P inversely related to V
- barometric P > alveolar P = air enter alveoli
General Gas Law (Boyle’s law)
pressure and volume are inverse of each other. A gas will move from an area of high pressure to an area of low pressure
- when alveolar volume increases due to pleural cavity expanding, the pressure decreases and air enters in. now that pressure is increasing the alveolar volume will decrease
Dalton’s Law
How gas will move across a membrane
each gas in a mixture of gases exerts its own pressure as if no other gases were present
greater the % of gas in a mixture the greater amount of pressure it exerts.
- gas moves from area of high conc to low conc
-Partial pressure is a gradient
Henry’s Law
Concentration of a gas in a liquid is determined by its partial pressure and its solubility coefficient. 02 has to work 24 times as hard to soluble than CO2
Meaning there must be a higher partial pressure difference to effectively move O2 from the lung to blood than CO2
alveolar pressure changes
alveolar pressure must be lower than barometric pressure (ambient air pressure) to bring air into the lung and alveolar pressure must be greater than barometric pressure to breath air out of the lung
Once P is the same in and out = No air movement
elastic recoil
elastic fibers in the alveolar walls that cause them to contract and recoil
surface tension
weak H bonds from water in alveolar walls are attracted to each others’ polarity causing the alveolar to try and close
surfactant
reduces surface tension and causes alveolar to remain their shape and not collapse
- made by type 2 pneumocytes
- respiratory distress syndrome (7mo infants not have surfactant and lungs collapse)
pleural pressure
Ribcage expands and takes parietal pleural with it, causing alveoli to expand = negative pressure
- pressure is low so gas enters (wants to go to area of low conc)
normal breathing cycle
Inspiration = decrease Pleural pressure
Expiration = increase PP
Inspiration = decrease alveolar pressure
Expiration = increase AP
Inspiration = increase volume
Expiration = decrease V
Compliance
a measure of the ease of expansion of the lungs and thorax
- more compliance = easier to expand and breathe
- factors inhibiting compliance: pulmonary edema, pulmonary fibrosis, asthma, bronchitis, kyphosis)
partial pressure
The pressure exerted by a particular gas in a mixture of gases
- % of each gas is proportional to its partial pressure (Dalton’s law)
-Water vapor pressure: pressure exerted by gaseous water in a mixture of gases
Principles of Gas Exchange
Diffusion of gas across membranes depends on:
- thickness of the membrane (thicker=lower diffusion)
- diffusion coefficient (how easily gas moves thru a membrane)
- surface area (how much is available)
- partial pressure differences (go to area of lower conc)
ventilation and pulmonary capillary flow
- increase ventilation or cap flow = blood flow increase
- shunted blood: blood not fully oxygenated (from bronchioles or caps around alveoli)
- Regional distribution of blood: determined by gravity and also by alveolar PO2 (partial pressure of oxygen)
carbon dioxide diffusion gradient
-Moves from tissue into tissue caps
-From pulmonary caps into alveoli
