lecture 12 - venous blood flow Flashcards
What percentage of blood is found in the systemic veins?
64%
What is compliance in terms of blood vessels?
The ability to allow deformation in response to an applied force
Do veins have low or high compliance?
High
Do arteries have low or high compliance?
Low compliance due to their thick, rigid walls
What is the equation for vessel compliance?
Compliance = ΔV/ΔP (change in volume/change in pressure)
What is the ‘survival value’ of veins?
They can store the body’s excess blood via venous pooling in case it is needed
Why does venous pooling occur?
Veins have a high vascular compliance, meaning that blood tends to accumulate/pool in them
Is arterial or venous volume greater?
Venous
In what position is venous volume uniform throughout the body?
Supine
When orthostatic, how is venous volume distributed?
Volume below the heart increases, with pooling in the lower limbs, while volume above the heart decreases
How do venous valves counteract pooling?
They create a discontinuous column that provides a more even distribution of weight, preventing all the blood from pooling at the bottom of the veins due to gravity
How does muscle tone influence venous pooling?
Contracting muscles helped to contract veins to propel blood back to the heart. High muscle tones helps to force valves open and closed, preventing leaky valves.
What is Starling’s Law of the Heart?
Law states that the more stretched muscle fibres are before a contraction, the stronger the contraction will be. (for cardiomyocytes).
How does ventricular volume increase the strength of cardiac contractions?
The ventricles are filled under pressure so that the muscle fibres stretch, allow a greater area for muscle fibre/sarcomere contraction. Increased volume creates a more forceful systolic contraction
