Lecture 12 Flashcards
Where is the majority of the blood in the body found?
The systemic venous system
How much of the bodies total blood does the venous system hold?
64%
How much blood, on average, is found in a 70kg human?
5L
Why does the body store excess blood that is not needed?
In the case of injury where blood is lost, the body can continue to survive
What are the capacitance vessels
Veins
What is the vessel type of the arterial system?
High pressure, low volume
What is the vessel type of the venous system?
Low pressure, high volume
What is compliance?
The extent to which a vessel allows deformation in response to an applied force
Why are the arterials low compliance?
The walls are thick and heavily composed of smooth muscle tissue making them very rigid
Why are the veins high compliance?
The walls are thin and heavily composed of elastin making them very bendy
What is the compliance formula?
Compliance = V / P
What is venoconstriction
The contraction of veins
What is the ‘survival’ value of veins?
Loss of arterial blood due to arterial puncture can be life-threatening. Veins undergo venoconstriction in order to pump the extra blood out of the veins and into the arterial system
What is venous pooling
The collection of blood in the legs and feet
What causes venous pooling
Gravity
What counteracts venous pooling?
Venous valves and skeletal muscle
How does skeletal muscle counteract venous pooling
Skeletal muscle can alter its tensile state therefore muscle tone acts to stiffen the veins and contraction of them increases venous return to the heart
How do venous valves counteract venous pooling
Venous valves ensure a unidirectional flow of venous blood towards the heart
What is starling’s law of the heart?
The more stretched muscle fibres are before a contraction, the stronger the contraction will be
What does starling’s law mean for the heart?
The more blood pumped in before atrial contraction, the more stretch the sarcomeres will undergo and therefore the stronger the contraction will be
