blood vessels & heart Flashcards
artery
has a muscular thick wall which withstands pressure
it’s endothelium is present but folded which allows it to stretch
its narrow and maintains high pressure
its elastic and can stretch and recoil
no valves apart from aorta and PA
high pressure drops when the ventricles relax but stay high to do elastic recoil of walls
pressure decreases with distance from heart as there is resistance to blood flow due to friction with the larger surface area of walls and dissipation of energy in elastic recoil
thick wall resist pressure . thick layer of elastic tissue stretches with high pressure then recoils maintaining pressure pushing the blood further. smooth out flow
narrow lumen maintain pressure thick muscle prevents rupture
veins
wall is thin . present and not folded endothelium the lumen is wide and reduces resistance larger volume
elastic content is low and the valves prevent backflow
pressure is low which means low flow rate
thin walls as pressure is low . walls are squeezed by skeletal muscle and breathing movements to push blood
wide lumen to fit large volume of blood and lower resistance.
valves ensure no black flow
capillaries
small diameter but many: no cell is far from a capillary so short diffusion distance for respiratory gasses . takes blood close to cells. the friction of blood with the walls and large surface area lowers pressure and slows blood which enhances exchange
thin walls one cell think endothelium layer , maximum transport.
narrow lumen: blood just fits in the capillaries so reduces diffusion distance to haemoglobin in the red blood cells.
capillary pores allow some substances to leak out through the wall this then further reduces pressure
arterioles constriction
muscular muscles can contract, it constricts to reduce blood flow and when muscles relax they dilate and increases blood flow
explain how tissue fluid is formed
hydrostatic pressure of blood is high at the arterial end due to contraction of the left ventricle
water and small soluble molecules forced out of capillary eg amino acids
this reduces the volume and therefore the pressure of the capillary
plasma proteins and large molecules remain
this lowers the water potential of the blood
water moves back into the venous end of capillary through osmosis
lymph system collects excess tissue fluid which returns to the blood
high blood pressure
increase in hydrostatic pressure at the article end
more
how does protein deficiency result in odema
Less plasma protein in blood
Water pot blood isn’t lowered enough
Water p gradient isn’t high
And so less water moved back into capillary by osmosis at the venule end
How do blocked lymph vessels lead to oedema
Excess tissue fluid is built up as its unable to be taken in by lymph vessels
explain 4 ways in which the structure of the aorta is related to its function
elastic tissue allows stretching and smooths out blood flow
it stretches when the ventricle contracts
thick walls withstand pressure
smooth endothelium layer reduces friction
semilunar valves prevent back flow
how is the highest blood pressure produced in the left ventricle
stronger contractions due to thickness of the muscle
describe the role of the coronary artery
the heart is make up of cardiac muscle and it has its own blood supply from the coronary arteries
why are the ventricles thicker
made up of thicker muscle than atria because blood needs to be pumped further away and so a high pressure needs to be generated by more muscle
why’s the left side of the heart thicker
because blood needs to be pumped to all the body systems so higher pressure is needed
higher pressure on the right side would force more fluid out at the capillaries which would impair gas exchange
the rise and fall in blood pressure in the aorta is greater than in the small arteries . suggest why
the aorta is close to the heart where the pressure is the highest due to the contraction of the left ventricle
the aorta has elastic tissue so can stretch and recoil
what factor limits the minimum internal diameter of the lumen of a capillary
the diameter of the blood cells
the thickness of the aorta
wall changes all the time during the cardiac cycle
explain why
aorta walls stretch because the ventricle contracts
pressure increases and then recoils when the ventricle relaxes
when the pressure falls . this memorials smooth flow
what does contraction of the aorta walls do
increases pressure
how do the tendens help maintain blood flow in one direction
the valves close due to high blood pressure form behind
the tendens ensure that the valves don’t invert and blood doesn’t flow back
Describe the movement of blood from the kidney to the lungs
The red blood cell travels form the renal vein to the vena cava to the right atrium. The blood is then pumped to the right ventricle and then to the pulmonary artery into the lungs
The pressure in the left ventricle has increased however the blood flow into the aorta hasn’t started , why is this?
This is because the semi lunar valves must be closed because the pressure is higher in the Aorta
Explain the small increase in pressure in the rate of blood flow in the aorta
Elastic recoil of the aorta tissue smooths out the blood flow and maintains blood rate
