Pressure and Flow in Arteries Flashcards
What is the main method used for measurement of arterial pressure?
Auscultation of Korotkoff sounds using sphygmomanometer and stethoscope
What is the function of elastic arteries?
Act as a pressure reservoir to dampen down pressure variations (prevents pressure getting too high in systole and too low in diastole)
What is the pressure wave affected by?
Stroke volume
Velocity of ejection
Elasticity of arteries
Total peripheral resistance
What is the ‘normal’ arterial pressure?
120/80 mmHg
What happens to arterial pressure with age?
It increases as blood vessels lose elasticity
What happens to pressure in blood vessels moving from the arteries all the way through to the veins?
Decreases
Between which two types of vessels is the decrease in pressure the greatest?
Arteries and arterioles
Moving into these resistance vessels the area increases dramatically as the diameter of the vessels decreases, this increase in area means that pressure decreases dramatically too
What is the systemic filling pressure?
The pressure of blood exiting the circulatory system - created by the arterioles and pushes blood into the veins
What is the pressure drop through the arteries?
95 to 90 mmHg
What is the pressure drop through the arterioles?
90 to 40mmHg
What is the pressure drop through the veins?
20 to 5 mmHg
What is the pressure in the pulmonary circulation in comparison the to the pressure in the systemic circulation?
1/5th of systemic
What is the main determinant of blood velocity?
Total cross-sectional area - higher it is the lower the velocity is
Fastest in aorta and slowest in capillaries
Why do external influences affect flow in veins?
They are distensible and collapsible
Is the pressure in the veins high or low?
Low
Does gravity affect the driving pressure from arteries to veins?
No
What does gravity cause in the veins of the legs and why?
Venous distension - Gravity causes increase in pressure in lower limbs and as the veins cannot cape with increased pressure, the expand and absorb the velocity of the blood
How does the distension in the veins on the legs affect the mean arterial pressure?
Decrease in venous return -> EDV -> decrease preload-> decrease SV -> decrease CO -> decrease MAP
What is orthostatic (postural) hypotension?
Decrease in BP when standing due to gravity
What can jugular (venous) collapse in the neck be used to estimate?
Central venous pressure
What sound is heart when cuff pressure is just less than systolic pressue?
Tapping - blood flow through for short time
What sound is heard when cuff pressure is between diastolic and systolic pressure?
Thumping - blood flows through for longer time
What sound is heard when cuff pressure is the same as diastolic pressure?
Muffled
What sounds id heard when cuff pressure is above systolic or below diastolic pressure?
Nothing - flow is laminar