Pulmonary and blood flow

Question 1

Information about the Alveolar capillaries

Answer 1

Receive blood from the right Ventricle

Blood has a low O2/high CO2 content

are involved in the exchange of O2 and CO2 between the blood and the air

MIllions of alveolar capillaries make it so the alveoli are effectively a sheet of capillaries

Question 2

What are the Extra-alveolar capillaries

Answer 2

also called the Bronchiole capillaries

recieve blood from the left ventricle

have a high O2/low CO2 content

Deliver oxygen and CO2 to the tissues of the lungs that are not alveoli

return to the heart in the pulmonary veins (venous admixture)

• reduces the PaO2 of the arterial blood by a few mmHg
• increases the PaCO2 to a small degree

Question 3

what is the equation of the pulmonary vascular resistance

Answer 3

PBP = CO x PVR

PBP= Pulmonary blood pressure
CO = Cardiac output (same as arterial side)
PVR = resistance to blood flow through the lungs (how hard is it to pump blood through the lungs)

Question 4

what is the difference between the PVR and the TPR and what affect does it have on the too circulations

Answer 4

PVR is much smaller than TPR

the puulmonary vascular resistance is much lower than we see in the rest of the body

therefore the pulmonary BP is 25/15 mmHg vs the systemetic BP of 120/80 mmHg

Question 5

How is the Pulmonary Vascular resistance determined

Answer 5

high number of capillaries

How many are open at any given moment in time (perfectly normal to not be using all your lungs at rest)

Much less sympathetic tone/vasoconstricting forces

lung volume, at low or very high volumes the resistance increases a little because the stretch of the tissue compresses the capillaries

Question 6

what happens to the PVR during excersise

Answer 6

During excersise the PVR will drop as more pulmonary capillaries open up to accommodate the increased cardiac output

dont want too much pressure in lungs

Question 7

what can cause pulmonary hypertension

Answer 7

COPD

Interstitial lung disease

sleep-disordered breathing

Question 8

to account for gravity, what differences are in the apex of the lung??

Answer 8

at the Apex of the lung, the blood pressure is reduced because it is slightly above the level of the heart

PA > Pa> PV

larger alveoli and the blood flow is less

Question 9

to account for gravity, what differences are in the middle of the lung??

Answer 9

In the middle, the blood pressure is a little higher because we are at the level of the heart

the alveoli are average size

blood flow is normal

Pa>PA>PV

Question 10

to account for gravity, what differences are in the base of the lung??

Answer 10

At the base, the blood pressure is high because we are below the level of the heart

the alveoli are smaller

the blood flow is greater than in any other region

Pa>PV>PA

Question 11

what are the three chemical modulators of Pulmonary blood flow, what do they do, and when are they active

Answer 11

Nitric oxide

• made by endothelium
• causes smooth relaxation and vasodilation
• significant role in normal pulmonary blood flow

Endothelin 1

• made in lungs
• Vasoconstrictor
• pathological conditions

Thromboxane A2

• found in the pulmonary vasculature under wrong conditions
• vasoconstrictor

Question 12

how do we keep the alveoli dry, to allow for optimal gas diffusion of O2

Answer 12

since O2 does not dissolve well in water we need to get rid of this in the alveoli to allow for good transportation

the lymphatics are important for removing filtered fluid from the capillary

Question 13

what are the forces that contribute to the movement of fluid in and out of the capillary into the lung

Answer 13

into the lung:
Capillary Hydrostatic pressure (Pc)
interstitial oncotic pressure (ni)
Interstitial hydrostatic pressure (Pc)
-this is due to the negative pressure created by the chest wall and the lung)

into the capillary:
capillary oncotic pressure (nc)

net usually favors filtration from the capillary

Question 14

what can lead to pulmonary edema

Answer 14

CHF

Question 15

Metabolic functions of the lung significance of an inhibitor

Answer 15

Renin is an enzyme that conversts angiotensinogen protein to angiotensin 1 (weak vasoconstrictor)

in the lung, Angiotensin 1 is converted to more active angiotensin 2 by ACE (angiotensin converting enzyme)

ACE also inactivates bradykinin, therefore if an individual is on ACE inhibitors they can develop a cough do to the accumulation of bradykinin

metabolism of arachidonic acid metabolites

• leukotrienes and prostaglandins/thromboxane A2 are produced by immune system activation in the lungs
• Prostoglandin E2 and F2alpha are almost completely removed from circulation in the lungs as are leukotrienes