lect 23- Pulmonary circulation Flashcards
what is the circulation for high pressure, low flow
thoracic aorta–> bronchial arteries–> trachea, bronchial tree, adventitia, CT
what is the circulation for low pressure, high flow
pulmonary artery and branches–> alveoli
what is the value for the pulmonary arterial pressure
24/9 mm Hg
what is the value for mean pulmonary arterial pressure
15 mm Hg
what is the pressure gradient in pulmonary system
7 mm Hg
what is the mean pressure in the left atrium
2 mm Hg
what happens to pulmonary circulation if there is a failure in the life side of the heart
increases blood volume as much as 100%
increases blood pressure
mild systemic effect because systemic blood volume is 9 times that of the pulmonary system
what is “dirty blood”
blood coming from the lung parenchyma and life side of the heart (it bypasses the pulmonary capillaries)
what happens when oxygen concentration in alveoli is 70& or more below normal
adjacent blood vessels constrict
caused by unknown vasoconstrictor that is possibly released by alveolar epithelial cells
describe zone 1 of the lungs
no blood flow; local alveolar cap. pressure never rises higher than alveolar air pressure
describe zone 2 of the lungs
intermittent blood flow (only during systole)
describe zone 3 of the lungs
continuous blood flow
how is blood flow normally distributed into the zones
apices have zone 2 flow
lower areas have zone 3 flow
what happens to the zones in the lungs during exercise
convert apices from zone 2 to zone 3 flow
what leads to general circulation when a person stands up
the fact that the pulmonary veins are a blood reservoir, increasing pulmonary blood volume by up to 400 ml
what results from obstructing blood supply to one normal lung
blood flow through other lung is doubled
because of passive dilation of pulmonary vessels, the pulmonary pressure in the other lung is only slightly increased
what agents constrict pulmonary arterioles
norepinephrine
epinephrine
angiotensin II
some prostaglandins
what agents dilate pulmonary arterioles
isoproterenol
acetylcholine
what agents constrict pulmonary venules
serotonin
histamine
E. coli endotoxin
what does sympathetic vasoconstrictor nerve fibers do
outflow from cervical sympathetic ganglia
decrease pulmonary blood flow by as much as 30%
mobilize blood from pulmonary reserve
what happens to blood from through the lungs during exercse
it increases 4X to 7X
number of open capillaries increases up to 3X
distends all capillaries and increases flow rate up to 2X
increase in pulmonary arterial pressure
why is it important that pulmonary arterial pressure rises little even during max exercise
it conserves energy of right side of heart
prevents significant rise in pulmonary capillary pressure
what happens during left heart failure
blood begins to dam up in left atrium
left atrial pressure rises from 1-5 mm Hg to 40-50 mm Hg
when is pulmonary edema likely to occur
when left atrial pressure rises above 25-30 mm Hg
how does colloid osmotic pressure in pulmonary interstitial tissue compare to that in peripheral tissue
in pulmonary interstitial tissues it is about 2X as high
how is alveolar epithelium ruptured
by any positive pressure in the interstitial spaces greater than alveolar air pressure
what is the total outward force for capillaries (pulmonary interstitial forces)
29
what is the mean filtration pressure
28
how can excess fluid in the lung capillary be carried away
pulmonary lymphathics
what are the most common causes of pulmonary edema
left-sided heart failure or mitral valve disease
damage to pulmonary blood capillary membranes (infections, breathing noxious substances)
at what pressure will lungs usually collapse
-4 mm Hg
what is pleural effusion
edema of the pleural cavity
what are causes of pleural effusion
blockage of lymphathic drainage form pleural cavity
cardiac failure
considerably reduced plasma colloid osmotic pressure
infection/inflammation
what does hypoxia do to pulmonary arteries
increases the pressure in them, possibly because of the release of prostaglandin
what is the result of bronchial obstruction
constriction of vessels supplying the poorly ventilated alveoli
what does reduction of blood flow to a portion of the lung do to alveolar PCO2
lowers alveolar PCO2, resulting in a constriction of the bronchi supplying that portion of the lung
