Human Phys 4.2 Flashcards
What is a normal right atrial pressure?
0 mmHg
What is the lower limit of right atrial pressure?
-3 to -5 mmHg (pressure of chest cavity)
When can right atrial pressure increase to 20-30 mmHg?
Under abnormal conditions (HF or massive blood transfusion)
What is the regulation of right arterial pressure?
Ability of the heart to pump blood out of the right side and into the lungs
Tendency for blood flow from the periphery into the right atrium
What are factors that increase right atrial pressure?
Hypervolemia
Factors that decrease CO
Heart failure
Increase in large vessel tone
Dilation of arterioles
How does an increase in large vessel tone occur?
Sympathetic activation causes increased peripheral venous pressure and decreases venous compliance
What are factors that decrease right atrial pressure?
Hypovolemia
Deep inhalation
What is the pressure when veins are distended?
Almost zero
What may increase venous pressure?
Compression of veins at certain anatomical locations
What does the higher venous pressure relative to right atrial pressure drive?
Venous return into the right atrium
Jugular vein distention
When right atrial pressure rises above 0 mmHg and blood begins to back up into the large veins
What does a right atrial pressure or 4-6 mmHg cause?
Corresponding increase in peripheral venous pressure (heart failure)
What is the normal abdominal cavity pressure?
6 mmHg
What are reasons that abdominal cavity pressure can rise to 15-30 mmHg?
Pregnancy
Tumors
Abdominal obesity
Excessive fluid
Hydrostatic pressure
Pressure exerted by a fluid at equilibrium at a given point due to gravity
What is the role of venous valves?
Valves that prevent blood from moving backwards
How does the muscle pump work relative to blood flow?
Muscle contraction helps push blood from one vein compartment to the next
When does varicose veins happen?
When the valves of veins become incompetent or destroyed due to being overstretched because of excessive venous pressure
What does stretching of veins increase?
CSA but the valves do not increase in size and no longer close completely
This leads to increase venous pressure and eventually the valves will fail resulting in varicose veins
How do venous ulcers form?
Increase in venous pressure leads to increase leakage of fluid out of the capillaries and constant edema in the legs
What does the edema prevent in venous ulcers?
Adequate diffusion of nutrients to muscle and skin cells
