Lecture 3: Pulmonary Blood Flow Flashcards
Where does blood entering alveolar capillary come from?
Is this oxygenated or deoxygenated?
Right ventricle via pulmonary artery
deoxygenated
What is the function of an alveolar capillary?
Gas exchange
- get rid of the carbon dioxide
- receive oxygen from alveoli
Where does blood entering extra-alveolar capillary come from?
Is this oxygenated or deoxygenated?
Left ventricle via aorta
oxygenated
What is the function of an extra-alveolar capillary?
Provide nutrients to and remove waste from airways
How does blood from an extra-alveolar capillary return to the heart?
Pulmonary vein
-came from feeding the airways, so it has lower oxygen and mixes with newly oxygenated blood that exchanged with the alveoli
Basically blood that returns to heart is less oxygenated compared to the blood that literally just came from the alveoli because of this venous admixture
How do you calculate pulmonary blood pressure?
What is the normal PBP?
Pulmonary BP = Cardiac Output x Pulmonary Vascular Resistance
-25/15 mm Hg
Why is pulmonary vascular resistance so low?
High number of capillaries and reduced SNS control increases surface area and lowers PVR
During exercise, does PVR increase or decrease? Why?
Decreases since more pulmonary capillaries open up (thus increasing the surface area) to accommodate the need for more blood flow
In the apex of the lung, there is: \_\_\_\_ alveolar pressure \_\_\_\_ blood pressure \_\_\_\_ blood flow \_\_\_\_ size of alveoli
In the apex, there is: HIGH alveolar pressure LOW blood pressure LOW blood flow LARGE size of alveoli
In the base region of the lung, there is: \_\_\_\_ alveolar pressure \_\_\_\_ blood pressure \_\_\_\_ blood flow \_\_\_\_ size of alveoli
In the base region of the lung, there is: LOW alveolar pressure HIGH blood pressure HIGH blood flow SMALL size of alveoli
How does gravity and muscle activity affect blood flow?
Gravity pulls blood down = pooling in the LEs
Muscle activity = helps fight gravity pull and aid venous return by “pushing” blood up
What is the role of nitric oxide in regulation of pulmonary blood flow?
released from endothelium due to shear stress on vascular walls > smooth muscle relaxation and vasodilation increasing blood flow (as in slowing it down to increase gas exchange interactions)
What is the role of endothelin 1 and thromboxane A2 in regulation of pulmonary blood flow?
- vasoconstrictors that shunts blood away from diseased alveoli
- having these are indicators of increase in dead space (disease)
In the lungs, what forces are pushing fluid out of the capillaries into the alveoli?
- Pc (hydrostatic pressure of capillaries): push fluid out of capillaries
- Pt (hydrostatic pressure of tissue - unique in lungs): Negative pressure in lung tissue favors fluid pushed out of capillaries
πt (oncotic pressure of tissue): pulls water into alveoli
How does the starling forces result in a “wet” alveoli?
Net force = (Pc + Pt + Ot) - (Oc)
Forces pulling fluid out of the capillary overcome forces pulling fluid flowing into capillary, so net force favors leaking fluid unto alveoli
Why is a “wet” alveoli not good for oxygen diffusion?
How does the body compensate for this?
O2 is insoluble in H2O and cannot diffuse properly if alveoli is too wet
Lymphatics drain water in alveoli. If lymphatics are not functional, alveoli isn’t “drained” and impairs O2 exchange
What enzyme converts angiotensinogen to angiotensin 1?
Renin
Where is renin made?
jxtg cells of the kidneys
What converts angiotensin 1 to angiotensin 2?
ACE
Where is ACE found and what does it do?
What is a side-effect of ACE inhibitors?
Lungs and kidneys. Converts angiotensin I to angiotensin II and activates bradykinin.
bradykinin accumulation
What does angiotensin do?
Vasoconstrictor (increases BP)
Why do some people with high BP and are placed on ACE inhibitors develop a cough?
Accumulation of bradykinin
Lungs participate in the metabolism of what?
Arachidonic Acid Metabolites
- leukotrienes
- prostaglandins E2 and F2α
- thromboxane A2 (arachidonic acid metabolite)
At too low or too high lung volumes, what happens to PVR?
stretches capillaries causing compression, decrease in capillary radius > increase in PVR
What does Pulmonary HTN mean?
losing capillary network, so decreased gas exchange surface area > increased PVR > Pulmonary HTN
How does PVR compare with TPR ?
similar blood volume, lower blood pressure and total resistance compared to systemic circulation
