Mammalian Blood system Flashcards
Structure & function of veins
Wide lumen with little elastic or muscle tissue, contain valves to prevent backflow. Carry blood to the heart at a low pressure.
Structure & function of arteries
Thick and muscular walls, elastic tissue to stretch and recoil as heart beats - maintaining pressure
Divide into arterioles which can restrict and relax to control blood flow
Structure & function of capillaries
Walls one cell thick - branches of arterioles. Create beds around organs and tissues. Narrow diameter which gives large surface area to volume ratio. Narrow lumen reducing flow rate so more time for diffusion. Permeable walls
What is tissue fluid?
Fluid that surrounds cells in tissues, made from small molecules that leave the blood plasma e.g. water and dissolved substances
How is tissue fluid formed?
1 - Near arteriole end, hydrostatic pressure is high
2 - Difference in hydrostatic pressure causes fluid to move out of capillary along pressure gradient, proteins remain in the plasma
3 - As fluid leaves, water potential decreases
4 - Water moves back into venule end of capillary by osmosis
5 - Excess tissue fluid collects in lymph vessel and eventually returned back to circulatory system
What do cords in the heart do?
Attach the AV valves to ventricles to stop them from being forced up into atria when ventricles contract
How do valves work?
If higher pressure behind it, it opens and vice versa
When does aortic pressure rise and fall?
Rises as ventricles contract because blood forced into aorta. Gradually falls because of wall elasticity, creating recoil
When does ventricular pressure rise and fall?
Low at first, but gradually increases as ventricles fill with blood and atria contract. When left AV valve closes and ventricles contract pressure rises.
When does atrial pressure rise and fall?
Always quite low because thin walls of atria don’t create lots of force. Highest when atria contract, but drops when AV valve closes.
When does ventricular volume rise and fall?
Rises as atria contract, falls when blood forced into aorta
What happens in the Diastole?
Both atria and ventricles relaxed. Atria fills with blood, so pressure opens AV valves
What happens in the atrial systole?
Muscle of atrial wall contracts, forcing out remaining blood they contain into verticles. Ventricles relaxed.
What happens in the ventricular systole?
Ventricles contract. Increases the blood pressure in ventricles, AV valves shut. Pressure increases till semi-lunar valves open.
Cardiac output =
heart rate * stroke volume
