External Respiration Flashcards
Where does external respiration occur? What does it consist of?
occurs at respiratory membrane
- sandwich of SSET surrounding loose irregular CT
- SSET contributed from Type I alveolar cells and capillary wall
capillary wall nucleus is opposite of basement membrane
anything that affects the tissue, especially increase loose irregular CT or fluid in alveoli, widens diffusion distance and decreases diffusion rate
What is Henry’s law?
when mixture of gas comes into content with liquid, each gas will dissolve in the liquid in proportion to its partial pressure
affects by temperature - decrease in T = increase of molecules in solution
- gas increases solubility in cold
Describe how the partial pressures of O2 and CO2 between the pulmonary capillary and alveolus drives gas exchange
PO2 in alveolus is 104 mmHg and 40 mmHg in pulmonary capillary
- diffuse down concentration gradient
PCO2 in alveolus is 40 mmHg and 45 mmHg in pulmonary capillary
- the gradient is less than O2, but diffuse at same rate bc CO2 is more soluble across membrane
What are the factors that affect external respiration?
partial pressure/solubility
respiratory membrane thickness
gas exchange surface area
ventilation-perfusion coupling
How does respiratory membrane thickness affect external respiration?
thicker the membrane, more distance/lower diffusion rate
- cannot decrease the size it already is
can thicken due to:
- pulmonary edema: adding fluid to alveoli increases diffusion due to having to pass through liquid, caused by pneumonia
- pulmonary fibrosis: increased amount of collagen/CT in respiratory membrane due to scarring of lung tissue
How does surface exchange are affect external respiration? What are some things that decrease SA?
surface exchange area - composed mostly of Type 1
- 1/2 size of tennis court
- increasing surface area increases gas exchange: when we take a breath in, we increase SA
decreases with emphysema (loss of alveolar walls) and blockage of alveoli (tumors, cystic fibrosis, inflammation)
How does ventilation-perfusion coupling in alveoli affect external respiration?
in lungs, if alveoli are not well ventilated, blood flow will be constricted and blood will be send to other alveoli with more O2
PO2 low - pulmonary arterioles constrict
PO2 high - pulmonary arterioles dilate
PCO2 low - bronchioles constrict
PCO3 high - bronchioles dilates
Why is oxygen dissolved in the blood important for O2 transport?
dissolved in plasma - contributes to partial pressure of O2 - 104 mmHg
1.5% of PO2 is dissolved in blood
as partial pressure of O2 increases, it drive more O2 into hemoglobin
- allows for more O2 to come from the alveoli
- driven until 100% saturation of hemoglobin
Describe the structure of hemoglobin
globin made of 4 polypeptide chains
- 2 alpha, 2 beta
- iron in center - donates 2 e- to O2
four molecules of O2 bind to each molecule of hemoglobin - oxyhemoglobin
What are the different affinities of each O2 with iron
each molecule binds with increased affinity
4th O2 > 3rd O2, 2nd O2, 1st O2
reverse for dissociation
fully saturated hemoglobin has 4 o2 bound
- heme is planar when oxygenated
What are factors that make it easier for hemoglobin and O2 to dissociate from each other?
increased temperature - increased O2 energy, doesnt want to stay bound to Fe
pH - decreased pH (increased [H+]) affects shape of hemoglobin and causes O2 not to fit
CO2 binds to protein part of hemoglobin (does not bind to Fe) and changes shape to prevent O2 from binding
all affected by exercise - makes O2/Fe dissociate faster so that more O2 can go to tissue
Describe the difference between deoxyhemoglobin and oxyhemoglobin
deoxyhemoglobin - taut or T form
- two AB dimers with constrained movement, has low O2 affinity
- dark red
oxyhemoglobin - Relaxed form
- O2 binding causes dimers to rupture and peptide chains have more movement
- higher affinity for O2
- bright red
In the oxygen association-dissociation curve, what are the X and Y axis
x axis - arteriole O2 - Partial pressure of O2 in blood (not bound to hemoglobin
Y - hemoglobin % saturation
100% hemoglobin saturation when plasma PO2 is 104 mmHg
In the oxygen dissociation curve, what causes it to shift left or right?
Right shift - requires higher O2 for same SaO2, enhanced unloading:
- increased temperature decreases affinity btw Fe and O2
- increased CO2 - need more O2 for tissue
- lowered pH - loss of affinity
Left shift - less O2 required for same SaO2, decreased unloading
- decreased temp, CO2
- increased pH
- fetal hemoglobin
How does 2,3-bisphosphogycerate, carbon monoxide, and hormones affect Fe/O2 affinity?
2,3-BPG - synthesized by erythrocytes
- increased BPG decreases affinity
- shift right for enhanced unloading
CO - 200-300X higher affinity for Hemoglobin
- increases HGB affinity for O2 - prevents O2 from dissociating
- blood leaves plasma but not hemoglobin - tissue starving for O2
- left shift
Hormones
- hormones increase RBC metabolism
- increase BPG synthesis
- enhances O2 unloading, shifts left
