Functions of Arteries/Veins Flashcards
(27 cards)
differential “reservoir” functions of arteries and veins
Arteries
- thick, highly elastic walls
- pressure reservoir
- high in elastin
Veins
- thin walled
- highly distensible
- blood reservoir
ability to accommodate volume when filling pressure increases
compliance
another word for compliance
distensibility
formula for compliance
C = ΔV/ΔP
ability to recoil to original size; inversely related to compliance
elastance
The greater the amount of elastic tissue:
- the lower the compliance
- the greater the elastance
Which is more compliant? arteries or veins
veins
How do arteries serve as a pressure reservoir during systole and diastole?
Systole: The ejected blood stretches the elastic large arteries, increasing wall tension and pressure. Some of this energy in momentarily stored, allowing the vessels to function as a pressure reservoir.
Diastole: Elastic recoil of larger arteries propels blood into the remainder of the circulatory system, enduring the continuous flow of blood during both systole and diastole.
pulse pressure
systolic - diastolic
systolic vs diastolic blood pressure
Systolic: ventricle ejects blood into the arteries –> arterial blood pressure increases to ~ 120 mmHg
Diastolic: arterial elastic recoil –> arterial blood pressure decreases to 80 mmHg and the cardiac cycle repeats itself
mean arterial pressure
1/3 pulse pressure + diastolic pressure
40% systolic pressure + 60% diastolic pressure
*weighted toward diastole because more time is spent in diastole than in systole during the cardiac cycle
Determinant of PP:
PP = SV / C
- directly proportional to SV
- indirectly proportional to compliance
hardening of the arteries
atherosclerosis
*leads to decreased arterial compliance
narrowing of the aortic valve
aortic stenosis
*leads to decreased SV
needed to measure pulse
palpation of convenient artery where pulse can be detected (radial carotid)
needed to measure BP
auscultation of large artery
art of listening to the heart
auscultation
How to listen to the heart:
- stethoscope placed on antecubital artery
- inflatable cuff placed around the upper arm near the brachial artery
- measure pressure with a sphygmomanometer/cuff
- inflate cuff over 120 mmHg (~180 mmHg)
- no sound when the artery is occluded
- deflate cuff slowly
- as pressure nears systole (120 mmHg), artery opens and Korotkoff sounds (knocking) in heard due to turbulence
- when pressure reaches diastolic level (80 mmHg), artery remains open but knocking sound disappears
- return to laminar flow
effect of age on arterial pressure
increased mean, systolic, and pulse pressures due to decreased compliance with age (arteriosclerosis = hardening of arteries)
How does gravity influence blood pressure?
The heart is a zero reference zone because it pumps the blood.
Below the heart = fluid pressure adds to the pressure generated
Above the heart = fluid pressure subtracts from the pressure generated
*There is a 1 mmHg pressure change for every 13.6 mm distance away from the heart
help pump blood upwards towards the heart against gravity (in the legs)
venous valves
How does the venous pump work standing vs walking?
Standing: venous blood pools in the legs due to gravity (pressure increases to ~80 mmHg)
Walking: muscle contraction compresses veins and causes one-way movement of blood to the heart via venous valves (pressure drops because hydrostatic column disrupted)
enlarged, swollen, twisted veins often caused by damaged or faulty valves
varicose veins
risk factors for varicose vein development
obesity, extending standing, family history, pregnancy
