3.3.4.1 Mass Transportin Animals - Circulation Flashcards
(17 cards)
Circulation - pulmonary circulation
- deoxygenated blood is pumped from the right ventricle of heart to the lungs, where it is oxygenated - returns to the left atrium - the pulmonary circulation
Systemic circulation
- oxygenated blood is pumped from the left ventricle to the body, where it unloads o2 - then returns to the right atrium
Coronary, pulmonary, renal arteries role
Coronary A = supply the cardiac muscle with oxygenated blood
Pulmonary A = veins transport blood to and from the lungs
Renal A and veins = transport blood to and from the kidneys.
Aorta and vena cava role
Aorta = transports blood from the heart to the body
Vena cava = retunes blood from the body to the heart
Atrial systole (contraction)
- higher pressure in atria than ventricles
- blood moves into the ventricles
- increase ventricular volume, decrease atrial vol
- artrioventricular valves open, semi-lunar valves closed
Ventricular systole (contraction)
- higher pressure in ventricles than atria / arteries
- blood moves into the arteries
- increase arterial volume, decrease ventricular vol.
- atrioventricular valves close, semi-lunar valves open.
Ventricular diastole (relaxation)
- higher pressure in atria / arteries than ventricles
- blood flows away in the arteries
- blood flows in the atria (venous return) and then into ventricles
- increase atrial & ventricular volumes, decrease arterial vol.
- semi-lunar valves close, artrioventricular valves open
Arteries - function
- Transport blood under highest pressures, from heart to organs
- Accommodate variations in pressure
- Prevent pressure from falling too quickly
How to arteries achieve their function
- thick elastic tissue layer: stretch to accommodate high pressure & recoil to maintain pressure
- narrow lumen to resist flow & maintain pressure + control flow of blood
Arterioles - function
- transport blood under high pressures, from arteries to capillaries
- change diameter to control pressure changes & flow of blood to different tissues
How to arterioles achieve their function
- thick muscle tissue layer: contract and relax to control changes in rate of flow
- narrow lumen to maintain pressure
- elastic tissue layer: can stretch & recoil to maintain + accommodate pressure pressure
Veins - function
- transport blood under lowest pressures, from organs to heart
- maintain pressure so that blood is retuned to the heart
How do veins achieve their function
- thin elastic and muscle tissue layer: some ability to contract to maintain pressure
- wide lumen to reduce resistance to flow
- pocket valves: close to prevent the backwards flow of blood
Capillaries - structure
- single layer of squamous (flattered) endothelial cell
- basement membrane of connective tissue
- narrow (approx. the same diameter as one RBC)
How capillary structure relates to function
- reduces diffusion distance for rapid diffusion
- many capillaries in a network, branch between cells to further minimise diffusion distance
- reduced velocity of blood flow due to narrow vessels - more time for exchange
Formation of tissue fluid
- in capillaries the hydrostatic pressure is higher at the arterial end
- this pushes fluid out of the capillary
- it is opposed by the water potential of the blood, which is lower than that of the tissue fluid & the hydrostatic pressure of the tissue fluid.
- overall fluid is forced OUT from the capillary by ultrafiltration
Return of tissue fluid
- further along the capillary, at the venous end, the hydrostatic pressure falls
- formation of the tissue fluid reduces the water potential of the blood slightly, because the plasma proteins cannot cross the basement membrane, but the vol of water has decreased.
- so fluid moves INTO the capillary, but some tissue fluid drains into the lymphatic system
