Venous circulation and lymph flow Flashcards
Comparing the vessel wall of an artery and a vein
- Smaller lumen of arteries
- radius – wall thickness ratio is different
- difference in the composition of connective tissue (elastic and collagenous fibers)
- difference in smooth muscle cell (SMC) coverage
- distensibility of veins is larger
- compliance of veins are larger
- venous valves
What is distensibility?
The capability of being distended or stretched under pressure
Compare Compliance of the vena cava and the aorta
Is the venous system a low or high pressure system?
The venous system is a low pressure system
Comparing the compliance of a vein and an artery (draw the graph)
Increased vascular tone decreases the compliance
-> How can this occur?
alpha1-dependent sympathetic stimulations
-> vasoconstriction
-> rigidity will be increased
-> compliance is lowered
Distribution of total blood volume in the venous system
What are the 5 organs with high venous blood storage capacity
- liver
- abdominal veins
- heart
- plexuses of the skin
- spleen
Which factor we need to increase for mobilization of blood from the venous system?
Increased sympathetic activity
Increased sympathetic activity- mobilization of blood from the venous system
-> What are the 2 ways to achieve this?
- exercise – blood volume in the gastrointestinal tract decreases; blood flow of the coronaries and skeletal muscle increases
- excessive bleeding
Venous pressure changes depend on the arterial pressure change
-> T/F?
F (No pulsatility beyond the capillaries)
What are the 3 factors influencing venous pressure changes
- Cardiac cycle – retrograde effect of the heart function
- Respiration
- Muscle contractions
Factors influencing venous pressure changes - respiration dependent changes-
=> How can inspiration and expiration affect intrathoracic pressure?
Inspiration – decreases the intrathoracic pressure
Expiration – reverses the process
Factors influencing venous pressure changes - foot veins
-> How does Muscle pump work?
rhytmic contraction of the muscles of the leg
Factors influencing venous pressure changes - foot veins
-> What is the function of the venous valves?
Maintaining the forward flow
what are the 2 components of central venous pressure (CVP) (anatomically)
Vena cava, right atrium
What is Central venous pressure (CVP)? (number)
0-2 Hgmm
Central venous pressure (CVP) is influenced by __
- inflow from the arterial side
- myogenic and neurogenic tone of postcapillary
- resistance vessels function of the right ventricule
What happen if central venous pressure (CVP) is increased?
Heart failure, increased volume, Valsalva maneuver (max. 20-30 Hgmm)
Symptoms of Valsalva maneuver (max. 20-30 Hgmm) ( a breathing method that may slow your heart when it’s beating too fast)
closed glottis, increased intrathoracic pressure
What happen if Central venous pressure (CVP) is decreased?
volume loss (min. (-3) – (-5) Hgmm)
What is mean systemic filling pressure (MSFP)?
the mean pressure that exists in the circulatory system when there is no blood motion.
Q = 0 ml/min
Give the number of mean systemic filling pressure (MSFP)?
7 Hgmm
Make a schematic diagram for The heart is restarted after the cardiac arrest
The effect of gravity on venous pressures
-> Pressures in the foot veins in a standing person
-> How can compensation occur?
Compensation
- α1-dependent increase of the vascular tone
- Low compliance at the high pressures
What is the venous pressure Outside the chest?
4-6 Hgmm