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
oxygen diffusion gradient
- moves from alveoli to blood (98.5% saturated)
- PO2 in blood decreases bc mix w deoxy blood
- if PO2: move RBC> cap> tissue
gas exchange
inspired air:
(PO2 =160; PCO2 = 0.3)
Pulm Cap @ Venous:
(PO2 = 40; PCO2 = 45)
CO2 exit and O2 enter
expired air:
(PO2 = 104, PCO2 = 40) no net movement
pulmonary veins:
PO2 = 95; PCO2 = 40
due to mixing (after heart)
Interstitial fluid @ arteriole end:
(PO2 = 95; PCO2 = 45)
O2 enter and CO2 exits
(PO2 =40 (@rest 20 exercise); PCO2 = 45)
Tissue @ arteriole end:
(PO2 = 20; PCO2 = 46)
pulmonary arteries @ venous:
(PO2 = 40; POC2 = 45)
interstitial fluid: no net movement
hemoglobin and oxygen transport
- O2 transported by hemoglobin (98.5%) and plasma (1.7%)
oxygen-hemoglobin dissociation curve
describes the percentage of hemoglobin saturated with oxygen at any given PO2
- PO2 is 104mmHg when in lungs and is almost 100% saturated
- PO2 is 40mmHg in tissue and 85% saturated (drops after 40)
- lower the PO2 = more easily O2 leaves hemoglobin and it becomes less saturated
- 23% O2 released into tissue at rest
dissociation curve in exercise
-PO2 is low in exercise
- 73% of O2 released into tissues during exercise since there is less of it there (follow pp gradient)
- PO2 less than 40 will remove O2 from heme
Bohr Effect
As pH of blood declines, hemoglobin saturation of oxygen also declines
-decreased pH allows H to combine with hemoglobin, changing its shape so O2 can’t attach.
CO2 and temperature
- increase PCO2 = decrease pH (acidic) = more H ions
- carbonic anhydrase: CO2 + H20 = H + HCO3 (bicarbonate is pH buffer)
- increase temp: decrease O2 attach to hemoglobin (more exercise and increase temp = more O2 released)
Bisphosphoglycerate (BPG)
is released by RBC when they break glucose down for energy
- BPG bind to hemoglobin and kick off O2
shifting the curve
to right: Hb release O2 easier (at PO2 60, not 40)
- pH decrease, CO2 increase, temp increase, BPG increase
- increased O2 leave lungs to go to tissues due to exercise
