33. Pulmonary circulation. Special circulation Flashcards
Venous blood from the whole body passes through what circulation
Pulmonary circulation
What are some characteristics of the pulmonary vessels compared w the systemic vessels
Short, wide highly distensible
Thinner walls
Lesser smooth muscle
Pulmonary arterioles has 1/5 of the pressure as systemic
Pressure in Pulmonary artery is lower than in aorta
How deos this affect stroke volume of right ventricle compared w left
EQUAL stroke volume
What is pulmonary arterial pressure in systole compared w aorta
25 mmHg in p.a
125 mmHg aorta
Does pulmonary capillaries form tissue fluid
No
Pressure too low (6-7mmHg)
Pulmonary Blood vessels have high compliance
What does this mean
Blood passing through them can change but does this not significantly change the pressure
Compare the blood flow through the apices of the lung to the base of lung
Much less blood flow to apices than bases
For regulation, what are pulmonary vessels strongly dependent on the changes on
alveolar pO2 and pCo2
What happens in an area of low pO2 but high pCO2
Arteriolar resistance increases
Therefore reduces blood flow
Blood is redirected to areas where ventilation is better and gas exchange is improved
WHch organ constantly needs a rich supply of blood
brain
Compared to total oxygen supply, how uch of it is consumes by brain
20%
What happens when interruption of 10-12 mins of O2 supplied to brain
Structural changes in neurons
Brain cant survive
What type of regualtion is very well expressed in cerebral bloood
Autoregulation
Eveen w/o the changes in carotid artery pressure, cerebral blood flow is still constant
Does neural and sympathetic incluences affect cerebral blood flow
Not really
What are the main regulators of cerebral blood flow
pCO2, pO2 blood pH
When is blood flow increased to an area in the brain
When cerebral activity is increased
Total blood flow not altered tho
When can cerebrl vessels becomes compressed and impair blood flow to brain
When increased production/ decreased outflow of cerebral spinal fluid causes increase in intracranial pressure
Corornary blood flow is about how much of the cardiac output
5%
What advantageous abt the heart capillary network
10 times denser than skeletal muscle so east to transport substances
What do cardiomyocytes contain to allow them to have a high affinity for oxygen
myoglobin
CAn the heart function in hypoxic conditions
no, very limited anaerobic capacity
WHy during systole, the blood flow to the left ventricle is reduced
Due to compression on coronary vessels by the ventricular muscle
receives most of its blood flow at diastole
when pO2 decreases and pCO2 increases- hypoxemia, how can you increase coronary blood flow
adenosine, Nitric oxide, lactate, H2CO3 are vasodilators that dilate the coronary vessels
Changes in cutaneous blood flow is due to what
thermoregualtion
What is the cardiac output for cutaneous blood flow ( temperature in comfort zone)
5%
What are the 2 types of resistance vessels in the skin
arterioles
arterio-venous anastomoses
Aretrio-venous anastomoses: what nerves are tey controlled by? WHere are they found?
What activates their refelx mechanism
Only under sympathetic control - ( cutaneous vessels have no parasymoathetic control)
Skin of palms, soles,pinna, nose, lips
Thermoreceptors
What happens when artertio-venous anastomoses constrict/ open
constrict: Blood flows through capillary networks with large surface area, allows heat loss
Open: blood bypasses capillary network and flows directly in venous vessels. doesnt allow heat loss
What is the blood flow throug the digestivesystem
20-25% of Cardiac output
Which parts of digestive system is best supplied with blood flow
muscosa of digestive tube and upper compartments
What happens in fasting condtions compared to feeding
fasting: capillary pressure favours filtration
Feed: Splanchnic capillaries reabsorb, they dilate
What innervation regulates digestive organs
sympathetic
arterioles has lots of a-adrenergic receptors that causes vasocontriction and decreases splanchnic blood flwo
