LESSON 18 - venous return and the pulmonary circulation Flashcards
describe venous circulation :
a conduit return blood to the right side of the heart from the periphery
describe the type of blood veins circulate :
veins return oxygenated blood to the heart but deoxygenated blood in rest of the body
how many reservoirs for blood volume ?
5
what are the 5 reservoirs for blood volume ?
- pulmonary
- veins
- heart
- arteries
- arterioles, capillaries
what % of “reservoir” for blood volume is in the pulmonary ?
9%
what % of “reservoir” for blood volume is in the veins ?
64%
what % of “reservoir” for blood volume is in the arterioles & capillaries ?
7%
what % of “reservoir” for blood volume is in the arteries ?
13%
what % of “reservoir” for blood volume is in the heart ?
7%
what is venous return (VR) ?
volume of blood that returns from the veins to the ratio each minute
FILL IN THE BLANK
“venous return = rate of blood return from the ____ to the _____ “
veins to the atrium
describe the venous return and cardiac output closed loop :
right ventricle … pulmonary … left ventricle … systemic …
where within the closed loop do we see VR (venous return) ?
systemic to right ventricle
where within the closed loop do we see CO (cardiac output) ?
right ventricle to pulmonary and left ventricle to systemic
FILL IN THE BLANK
venous return = _________ = _________
right ventricle output = left ventricle output
TRUE OR FALSE
all pumps have to be operated at the same speed
TRUE
why must all pumps have to be operated at the same speed ?
to sustain that high level of cardiac output
during exercise, an increase in venous return = ?
increase right ventricle and left ventricle filling
how does venous return increase ?
during exercise (think of cardiac output)
what is the formula for venous return (VR) ?
VR = ΔP / TVR
what is TVR ?
resistance in the large veins and vena cave
what is ΔP ?
pressure differential
what is P venous (peripheral venous pressure) ?
pressure in the peripheral veins draining tissues
which part of the venous return system is the highest point of pressure ?
the beginning of the system
which parts of the circulatory system are a high pressure system and high resistance ?
- left ventricle
-arteries - arterioles
which parts of the circulatory system are a low pressure system and low resistance ?
- venules
- veins
between arteries and veins which have more smoother muscles ?
arteries
within the circulatory system which are the exchange vessels ?
capillaries
do we see low or high resistance in the venous circulation ?
low resistance
describe the anatomy of veins :
- thinner walls
- lack of smooth muscle
- lack of sympathetic tone
- more compliant
describe the anatomy of arteries :
- thicker walls
- lots of smooth muscle
- more elasticity
- easier to return to original state
between veins and arteries which are more compliant ?
veins
what does compliant mean ?
the ability of a blood vessel to adjust the blood pressure and increase the volume of blood that it can hold
between veins and arteries which are more likely to blow open ?
venis
between veins and arteries which have a higher resistance ?
arteries
does venous return have any effect on stroke volume ?
no
why do we see increasing preload ?
to facilitate the rise in venous return
what is preload ?
the volume of blood received by the heart during (EDV)
what does an increase in venous return mean for preload ?
increase in preload
what is after load ?
how much blood is left in the left ventricle
TRUE OR FALSE
“the preload is the highest amount getting ready for contraction”
TRUE
what are the effects of posture on venous pressure ?
when standing from supine, gravitational forced “pull” venous blood to the lower limbs
FILL IN THE BLANK
“due to the high compliance of veins around ____ mL of blood can redistribute to peripheral veins”
500mL
“ever felt light headed when standing” is an example of what topic ?
effect of posture on venous pressure
what is adema ?
buildup in blood volume
does gravity pull blood volume up or down ?
down (ex. survivor challenge)
if you’re standing up for too long and feel light headed, what do we do to get rid of that gravitational force and to make the blood flow better ?
laying down
is an increase in venous return necessary to increase cardiac output ?
yes, an increase in venous return is necessary to increase cardiac output
an increase in what three things leads to an increase in cardiac output
- venous return
- EDV
- stroke volume
how do venous blood flow in one direction ?
valves (prevent back flow, help continuously bring blood, etc)
where do veins in the systemic system direct blood ?
direct blood to right atrium
describe the valves in veins :
- thin
- membranous flap-like valves
- spaced at short intervals within veins
what is the purpose of having valves ?
permit one way blood flow back to heart
describe the pressure of blood in the large veins :
pressure of blood in the large veins is very low (difficult to return blood to heart)
what are vessels within nucleus well tethered to ?
surrounding tissues (transmission of forces)
when in the upright posture, gravity oppose what type of flow of blood and from where ?
gravity opposes the upward flow of blood from the lower body
what are required to help increase venous return (veins/valves) ?
active mechanisms
describe a skeletal muscle pump :
the mechanism whereby skeletal muscles aid the return of blood to the heart by compressing embedded veins
what happens during exercise if there were no muscle pump ?
high flow of blood through muscle would lead to pooling in compliant vasculature
what do muscle pumps prevent ?
pooling by maintaining a low volume of blood volume within muscle veins and displacing it back to heart
what does tethering cause with skeletal muscle pump ?
causes negative venous pressure which “sucks” blood through muscle above what could be provided by left ventricle force alone
describe veins during muscle contraction :
- muscles shorten
- muscle pushes veins (massage like)
- helps blood flow
describe veins during muscle relaxation :
- muscles are not being pushed
- generates forward pressure that shoots blood upwards towards the heart
muscle lengthening
what is the respiratory muscle pump ?
consists of abdominal and thoracic structures that are important in the expansion and contraction of the lungs
what does decent of diaphragm during inspiration do to intra-abdominal pressure and pressure gradient between the thorax and abdomen (causing translation of blood centrally)
increase intra-abdominal pressure and increase in pressure gradient between thorax and abdomen
during inspiration how does the diaphragm move ?
moves down
during expiration how does the diaphragm move ?
moves up
when does inspiration decrease intrathoratic pressure and increase pressure gradient ?
between the RA and system venous circuit (outside thoracic cavity)
when the thoracic cavity decreases what does it mean for blood ?
increase in blood
what happens to thoracic pressure of abdomen and thoracic cavity when you push diaphragm down ?
increase thoracic pressure of abdomen and thoracic cavity
what is driving pressure ?
the difference between plateau pressure and positive end-expiratory pressure
TRUE OR FALSE ?
the right and left heart both circulate the same volume of blood at the same frequency
TRUE
@ rest what is the L/min ?
5
with low resistance circulation; pressure generated by RV is much less or much more than the left ?
much less
@ severe exercise what is the L/min ?
20+
describe the relationship of the Q LV vs Q RV on a graph :
- always the exact same
- growing exponentially together
describe the relationship of systemic arterial vs pulmonary arterial pressure on a graph :
significantly more pressure is generated on the L side (systemic) over the R side (pulmonary)
describe the relationship of systemic peripheral vs pulmonary vascular resistance on a graph :
systemic starts super high and eventually falls way down while pulmonary maintains pretty low down
what does greater aerobic fitness mean for resistance ?
less resistance in the pulmonary vasculature
