Pulmonary blood flow Flashcards
where do alveolar capillaries recieve blood from?
what is its oxygen and CO2 content?
how does its blood return to heart?
? blood gas in vein?
function?
from right ventricle thru pulmonary artery
low O2/ high CO2
pulmonary vein
high PaO2/ low PaCO2
gas exchange in alveoli
where do extra-alveolar capillaries recieve blood from?
what is their gas content?
where do they deilver blood?
how does its blood return to heart?
function?
blood gas in vein?
left ventricle thru aorta
high O2/ low CO2
to tissue of lungs
pulmonary veins (venous admixutre)- reduces O2 content of pulmonary veins and increases CO2
provides nutrients to and removes waste from airways
low PaO2/ high PaCo2
what is the equation for pulmonary blood pressure?
PBP= CO* PVR
PVR= pulmonry vascular resistance
how was PVR compare to the rest of the body?
way lower because the same amount of blood that comes from heart (CO= 5L/mon) has to go to lungs that has way lower blood pressure (25/15 vs 120/80 in body)
(think about equation if this doesnt make sense)
what things is PVR determined by?
- high number of capillaries
- how many capillaries open at given moment
- lung volume- at low or very high volumes resistance increases because of the stretch or compression of caps (diameter decreases)
** sympathetic tone has way less influence than the bronchial branch (vasoconstriction)
how does PVR respond to exercise?
PVR drops because more pulmonary capillaries open to accomodate increased CO
what lung dieases lead to an increase in resistance?
COPD, interstitial lung disease, sleep disorderd breathing—> all lead to caps being destroyed and increase in resistance
how does the PVR normal value, BP, and BV compare to that TPR?
lower
lower
equal
when someone locks their knees, why is it they pass out?
gravity pulls their blood to their legs—>
their skeletal muscles cant pump the blood back up to thorax—>
causing less blood returns to heart (and then brain)
what are the blood flow, alveoli size and blood pressure in the apex of lung?
little blood flow
expanded- high alveolar pressure
reduced- above level of heart
what are the blood flow, alveoli size and blood pressure in the middle of lung?
normal
average
a little higher- at level of heart?
what are the blood flow, alveoli size and blood pressure in base of lung?
lots of blood
smaller- low alveolar pressure
higher-below heart
what is the role of nitric oxide?
made by endothelium when sheer forces—> causes smooth muscle relaxation/vasodilation—> plays big role in normal pulmonary blood flow by slowing down blood to get more ox to tissues and dont damage capillaries?
what are some chemical modulators of blood flow that arent normally present (unless in disease)?
what do they (msybe) play role in?
endothelin 1- vasocontrictor made in lungs
thromboxane A2- ditto
pulmonary arterial hypertension and left-sded heart dysfunction
why do we want to keep the alveoli “dry”?
O2 is not very water soluble—> if caps leaked water into alveoli it would impair O2 to get into blood
what controls how much fluid moves from caps to lung?
Starling forces–> two main components:
- hydrostatic pressures of the caps and tissues
- oncotic pressures of caps and tissues
what direction does cap hydorstatic pressure (Pc) send blood in the lung?
push fluid into alveoli
what direction does tissue hydrostatic pressure (Pt) send blood in the body?
pushes fluid into cap in the rest of body
what direction does Pt want to send blood in the lung?
from cap into alveolus
due to negative hydrostatic pressure in tissues as a result of same forces causing negatvie IPP (chest wall wanting to expand and lungs wanting to shrink… increase in IP volume)
what direction does cap oncotic pressue (πc) move blood?
pulls water into cap
what direction does blood flow in tissue oncotic pressure (πt) in alveoli?
pulls water into alveolus
what are all of the forces moving water from cap to alveolus? which is greatest?
Pc, πt, Pt
Pc is the greatest
what are the forces moving water from alveolus to cap?
only πc
what is the equation for the sum of forces of fluid movement in lungs?
what is result?
(Pc+πt+Pt)- πc
Starling forces favor fluid filtatration along lenght of pulmonary cap and and move fluid into alveoli
