anatomy + physiology of vascular disease Flashcards
what are the 3 layers of a blood vessel
tunica interna; tunica media; tunica externa
what is the lumen
central blood-containing space surrounded by tunics
what are capillaries composed of?
endothelium with sparse basal lamina
components of tunica interna
endothelium; subendothelial layer; internal elastic lamina
why are valves important to consider in surgery
when using veins in bypasses, the valves must be facing the correct way
differences between veins and arteries
veins have a thinner tunica media, wider lumen and valves
where are elastic arteries located
near the heart - the aorta and its major branches
characteristics of elastic arteries (4)
large lumen to allow low resistance conduction of blood; contain elastin in all three tunics; withstand and smooth out large blood pressure fluctuations between systole and diastole; allows blood to flow fairly continuously through the body
what are muscular artieries
arteries distal to elastic arteries that deliver blood to body organs; active in vasoconstriction
characteristics of muscular arteries (2)
thick tunica media; more smooth muscle and less elastic tissue
role of arterioles (2)
lead to capillary beds; control flow into capillary beds vis vasodilation/contriction
veins characteristics (5)
formed when venules converge; composed of three tunics (thin interna + media, thick externa made of collagen and elastic networks); are capacitance vessels (blood reservoirs); have much lower blood pressure; have large diameter lumens to decrease flow resistance; have valves to prevent backflow
what are venous sinuses
specialised, flattened veins with extremely thin walls
what is blood flow
the actual volume of blood flowing through a vessel/organ/entire circulation in a given period (mL/min); equivalent to cardiac output if whole vascular system is considered
blood flow characteristics (2)
relatively constant at rest (5 mL/min); varies widely through individual organs according to immediate needs
blood flow/tissue perfusion is involved in… (4)
delivery of oxygen and nutrients/removal of waste from tissue cells; gas exchange in the lungs; absorption of nutrients from the digestive tract; urine formation by the kidneys
poiseuille’s law
ΔP = (8μLQ)/πr^4
what is blood pressure
force per unit area exerted on the wall of a blood vessel by its contained blood
what provides the driving force within the vascular system
differences in BP keeps blood moving from high to low pressure areas
main factors affecting blood pressure (3)
cardiac output; peripheral resistance; blood volume
blood pressure equation
CO x PR
why may older people be more at risk from bleeds (BP)
atherosclerosis decreases vessel flexibility; volume is depleted; certain medications (e.g. B-blockers)
blood flow/ blood pressure relationship
F ∝ ΔP
blood flow/ resistance relationship
F∝ 1/R; R is more important than ΔP in influencing BP
systolic pressure
pressure exerted on arterial walls during ventricular contraction
diastolic pressure
lowest level of arterial pressure during a ventricular cycle
pulse pressure
the difference between systolic and diastolic pressure
mean arterial pressure
pressure that propels the blood to tissues; diastolic pressure + 1/3 pulse pressure
average pressure gradient in venous system
20 mmHg (changes little); blood flow will be even if cut
factors aiding venous return (3)
respiratory pump (pressure change from breathing sucks blood towards the heart); muscular pump (contraction of skeletal muscles help push blood towards the heart); valves (prevent backflow)
what is autoregulation
automatic adjustment of blood flow to each tissue in proportion to its requirements at any given point in time
how is organ blood flow control
intrinsically controlled by modifying the diameter of local arterioles feeding its capillaries; MAP remains constant while local demands regulate the amount delivered to areas in need
what is an end organ
and organ with a singular blood supply
what is Amaurosis fugax
“fleeting vision”; temporary loss of vision in one or both eyes
different types of AAA (location)
supra renal; juxta renal; infra renal
what is an aneurysm
permanent, abnormal dilation of a BN to 150% of normal
what arterial diseases result in vessel blockage (3)
atherosclerosis; dissection; rarities
what arterial diseases result in expansions/burst
aneurysms (different cytokine released here than in athersclerosis)
what arterial diseases occur via travel through vessels
embolisms
areas commonly atherosclerosed (6)
carotid bifurcation; LAD; aortic bifurcation; common femoral; superficial femoral; aorta (distal to left subclavian)
common aneurysm areas (2)
abdominal aorta; popliteal arteries
what does decreased blood tissue perfusion result in?
vasodilation; collateral vessel formation; anaerobic metabolism; ischemia if compensatory mechs are unable to meet O2 demand
