Venous Hemodynamics

Most blood is in the veins about ____

2/3rds

Venous Hemodynamics is ____ and not much changes seen within it during the cardiac cycle

steady

veins have ____ walls, thus ____ compliance

thinner, higher

Blood leaves _____ —> ______ —> _____

capillaries, venules, veins

veins are ____ vessels than capillaries. Resistance to flow is _____.

larger, low

What kind of resistance to flow are in veins?

low

Pressure in venules is low (__ mmHg) but higher than the pressure in right atrium (__ mmHg)

15 mmHg, 0-8 mmHg

At the capillary bed: vessel diameter ____

decreases

At the capillary bed: numbers of vessels ____

increases

At the capillary bed: ____ slows down so the capillaries exchange ____ and _____.

velocity, nutrients, oxygen

Venous return to heart: several mechanisms must exist: Pressure gradient must be present. A pressure difference between ____ and ____

venules, heart

Venous return to heart: several mechanisms must exist: During inspiration the lungs fill with air which causes a drop in _____ (____ pressure) in the chest cavity which forces blood to rush into the chest (heart) again; pressure _____ exists.

pressure, negative, gradient

Venous return to heart: several mechanisms must exist: presence of valves allows flow to be directed to the ____.

heart

presence of valves prevents _______ of blood (reflux), thus it forces blood in one direction towards the ____.

backflow, heart

Venous return to heart: several mechanisms must exist: When calf muscles contract, they force blood into _____ towards the heart

veins

Normally, in the calf, there are _____ ______ where blood is stored; when calf is contracted, it forces the blood to flow from the _____ to the veins

soleal sinuses, sinuses

The difference between intrinsic (intravascular) and extrinsic pressures surrounding the vessel

transmural pressure

You may have noticed that at times veins have circular appearances as well as oval appearances. What does this mean?

It is due to transmural pressure

Think when a patient is lying supine, you will notice that the vein has an oval or elliptical shape. Why?

Transmural pressure is low due to extrinsic pressure exceeding the intrinsic pressure

What happens when a patient is standing up? Transmural pressure becomes _____, hydrostatic pressure ____, vein becomes ____ or ____

high, increases, circular or round

Venous blood flow is affected by:

patients position and respiration

Supine position: _____ _____ between veins and heart is significant → blood flows to ____ atrium

pressure gradient, right

Patient standing: gravity acts on blood in the form of _______ ______ (weight of the column of blood from a specific reference point)

hydrostatic pressure

Patient standing: ____ is the reference point (HP is __)

heart, 0

Patient standing: below heart, HP _____ as the _____ increases from the heart

increases, distance

Patient Standing: ___ HP is located at more ___ parts of the body (feet and ankles)

high, distal

Patient standing: ____ _____ is the reason venous stasis ulcers are found in the ____, not thighs

HP, ankles

HP Equaiton

HP= density x gravity x height

Anything below heart (height), HP will be ______. Arm below heart, veins ____

positive, dilate

If the height is above the heart, HP is _____. Arm above head, veins _____

negative, collapse