Year 12 - Mass transport in humans Flashcards
Describe the function of valves in the heart/veins/arteries
Prevent backflow ensuring unidirectional flow of blood
Describe the function of the coronary arteries
Deliver oxygenated blood and glucose to the heart muscle cells
Explain how the heart muscle and valves maintain a one-way flow of blood from atrium to artery.
Atrium contracts increasing pressure.
Atrium higher pressure than ventricle = Atrioventricular valves open
Blood passes to ventricle down pressure gradient.
Ventricle fills and contracts increasing pressure.
Ventricle higher pressure than atrium = Atrioventricular valve closes
AV valve prevents backflow.
Ventricle higher pressure than aorta/pulmonary artery = semilunar valve opens
Blood passes to aorta down pressure gradient
Aorta/pulmonary artery higher pressure than ventricle = semilunar valve closes
SL valve prevents backflow.
Name the key arteries, chambers, valves and veins in order describing the pathway a red blood cell takes when going from:
Heart to lungs to heart to kidneys to heart
In the human circulatory system.
Right atrium ———-> right ventricles ——–>pulmonary artery -> lungs -> pulmonary veins -> left atrium ———> left ventricle ——-> aorta -> renal artery -> kidney -> renal vein -> vena cava -> right atrium
What blood vessel has the lowest pressure?
Vena Cava
Describe how the structure of a capillary is related to its function.
Endothelium one cell thick so short diffusion pathway
Narrow lumen so reduces rate of flow making more time for diffusion
Pores between cells to increase rate of diffusion
Contrast the structure of a vein and artery
Artery has narrow lumen whereas vein has wider lumen
Artery has thicker wall whereas vein has thinner wall
Artery has more muscle whereas vein has less muscle
Artery has more elastic tissue whereas vein has less elastic tissue
Artery has no valves whereas veins have valves
Explain how the structures of the walls of arteries and arterioles are related to their functions
Elastic tissue stretches when ventricle contracts then recoils maintaining pressure by smoothing out flow of blood
(smooth) Muscle contracts to constrict and decrease diameter of lumen (vasoconstriction)
so, Changes flow = decrease in flow
Endothelium is smooth so reduces friction
Describe how to change blood flow to muscles
Muscles in arterioles relax causing vasodilation (widening lumen of blood vessel) to increase blood flow (ie during exercise)
Muscles in arterioles contract causing vasoconstriction (decreasing diameter of lumen of blood vessel) to decrease blood flow.
Describe how the structure of an artery is related to its function
Elastic tissue to allow stretching and recoiling to smooth out flow of blood
Elastic tissue stretches just after ventricles contract so high pressure
Elastic tissue recoils when ventricles relax so low pressure.
Muscles for contraction
Thick wall withstands pressure stopping bursting.
Smooth endothelium to reduce friction
Semi-lunar valve to prevent backflow
Explain how blood in a vein is returned to the heart
Muscles around veins contract pressing on the walls and squeezing blood through valves.
Valves prevent backflow to ensure unidirectional flow towards heart
Wide lumen so little resistance.
Heart contracts to pump blood through arteries into veins to move blood further.
Heart during diastole causes less pressure than veins so draws blood from veins into atrium.
Explain how tissue fluid is formed and how it may be returned to the circulatory system.
High hydrostatic pressure at arterial end of capillary
Water passes out through fenestrations
Plasma protein remains in capillary
This lowers water potential
Water moves back into capillary at venous end down its water potential gradient by osmosis
Lymph system collects excess tissue fluid and returns to blood (by lymphatic vessels joining to vena cava)
