Dynamics of blood and lymph flow

Question 1

What are Bernoulli’s Principles?

Answer 1

1. sum of kinetic energy of flow+ pressure energy is constant
2. energy is lost in overcoming resistance is irreversible
3. the pressure drop in conversion of potential to kinetic energy is reversible
4. greater velocity of flow in a vessel, lower lateral pressure distending its walls
5. when a vessel is narrowed, the velocity of flow in the narrowed portion increases and in the distended portion pressure decreases

Question 2

How do the veins in the head respond to standing?

Answer 2

Veins tend to collapse
Superior sagittal sinus may be -10mmHg (10mmHg less than heart)
Magnitude of negative pressure is proportionate to negative distance
Dural sinuses have rigid walls and cannot collapse (pressure in them when standing/sitting is subatmospheric)
Dural sinus pressure not always negative-> depends on position

Question 3

What is normal CVP at right atrium?

Answer 3

4.6mmHg

Fluctuates with respiration and heart action

Question 4

What are the causes of high CVP

Answer 4

Anything that puts strain on the right heart
A rapid fluid bolus
Pulmonary embolism
Tension pneumothorax
Cor pulmonale

Question 5

When is the pressure in the subclavian vein above atmospheric pressure?

Answer 5

As it crosses 1st rib when lying down

Question 6

What is the venous pressure in the ankle when standing?

Answer 6

85-90mmHg

Higher than standing than walking because walking causes blood to get pumped back to the heart

Question 7

What are the features of venous pressures of veins in the feet?

Answer 7

1. Venous pressure increases on standing
2. Diminishes on exercise
3. In subjects with incompetence and valves of deep veins, remains elevated in exercise
4. Always diminishes on elevation of the legs