Cardiovascular System - Vascular Function and Hemodynamics Flashcards
two closed systems of conduits
- pulmonary vessels
2. systemic vessels
main classes of blood vessels (3)
- arteries
- capillaries
- veins
where do arteries carry blood?
away from heart
what do capillaries do?
connect arteries with veins
where do veins carry blood?
to the heart
classification of arteries
- aorta
- arteries
- arterioles
aorta
largest artery of systemic circulation
arteries
medium and small arteries branching off aorta
arterioles
smallest branches of arteries
structure of systemic arteries (3 main layers)
- tunica intima
- tunica media
- tunica externa
tunica intima
epithelium, basement membrane, and elastic fibers
tunica media
smooth muscle
tunica externa
connective, elastic, and collagenous fibers
function of aorta and its branches
- elastic vessels
- receive blood directly from heart (oxygenated)
- blood volume is under high pressure (stressed volume)
function of arterioles
- resistance vessels (extensive development of smooth muscle)
- site of highest resistance to blood flow
- regulate blood flow and pressure
- innervated by sympathetic adrenergic nerve fibers
structure of capillaries
- smallest and most numerous blood vessels
- thin-walled structures lined with a single layer of endothelial cells surrounded by a basal lamina
function of capillaries/ perfusion
- nutrients, gases, water, and solute are exchanged
- not all capillaries are perfused with blood at all times
- selective perfusion of capillary beds depending on the metabolic needs of the tissues
internal respiration (capillary bed)
- gas exchange between blood and tissues
exchange vessels in capillary bed (3)
terminal arterioles, capillaries, and venules
classification of veins (3)
- venules
- small and medium veins
- vena cava (superior and inferior)
structure of veins
- thin-walled
- same three layers as arteries (smooth muscle, elastic muscle, and connective tissues)
function of veins (systemic circulation)
- carry blood toward the heart (deoxygenated)
- large capacitance (hold >60% of total blood volume)
- blood volume under low pressure (unstressed volume)
vessels in pulmonary circulation
- arteries
- capillaries
- veins
veins in pulmonary circulation
- transport oxygenated blood from the lungs to the left atrium of the heart
(2 pulmonary veins for each lung)
capillaries in pulmonary circulation
- gases, water, and solute exchanged between the blood and the alveolar gas
- external respiration (gas exchange between blood and air)
arteries in pulmonary circulation
- carry deoxygenated blood from right ventricle to the lungs
- lower pressure and vascular resistance
stroke volume (SV)
amount of blood pumped from a ventricle each time the ventricle contracts
cardiac output (CO)
- volume of blood pumped by a ventricle in 1 minute
- CO = SV * heart beats per minute
circuit through the cardiovascular system
- oxygenated blood fills left ventricle
- blood is ejected from left ventricle to aorta
- cardiac output is distributed among various organs
- blood flow from the organs is collected in the veins
- venous return to the right atrium
- mixed venous blood fills the right ventricle
- blood is ejected from the right ventricle into the pulmonary artery
- blood flow from the lungs is returned to the heart via the pulmonary veins
main functions of the vascular system (4)
- transforms pulsatile output of the heart to a more continuous flow (arteries)
- distributes the CO to the tissue based on tissue needs (arterioles)
- exchanges materials with the tissues (capillaries)
- provides a volume reservoir (veins)
physical principles of blood flow
- steady-state flow
- elasticity of vessels
- velocity in vessels
- steady-state flow in tubes
blood flow through a blood vessel is determined by:
- pressure difference between the two ends of the vessels
2. resistance of the vessel to blood flow
compliance (elasticity) in veins vs arteries
compliance of veins is much greater than compliance of arteries
capacitance definition
/ old vs young arteries
- ability to distend, hold a volume of blood at a given pressure
- old arteries must have higher pressure than young arteries to hold same volume
branching of systemic circulatory system
highest to lowest velocity of vessels
aorta –> capillaries –> vena cava
assumptions for poiseuille’s flow (6)
- fluid is Newtonian
- flow is laminar
- no “slippage” at walls
- tube is cylindrical with circular cross section, // walls
- walls of tube are rigid
- tube is long compared to the entrance length
entrance effects in establishing poiseuille’s flow
“plug flow” to laminar flow!
slowly reaches a parabolic velocity profile
arterial pulse pressure
- ejection of blood into the arterial tree cause the arterial pressure pulse
- pulse depends on stroke volume and arterial compliance
relationship between pulse pressure and stroke volume
- larger SV causes larger pulse pressure
- same stroke volume at higher Pa causes larger pulse pressure
effect of compliance on pulse pressure
same stroke volume at lower compliance causes a larger pulse pressure
pressures in the systemic circulation (4)
- diastolic pressure
- systolic pressure
- pulse pressure
- mean pressure
diastolic pressure in systemic circulation
- lowest arterial pressure measured during a cardiac cycle
- pressure in artery during ventricular relaxation when no blood is being ejected from the LV
systolic pressure in systemic circulation
- highest arterial pressure measured during a cardiac cycle
- pressure in the artery after blood has been ejected from the LV during systole
pulse pressure
difference between systolic and diastolic pressures
mean pressure
average pressure in a complete cardiac cycle
estimation of blood pressure by sphygmomanometry
- fast decline in cuff pressure may miss the first Korotkoff sound
- 1st Korotkoff sound is where cuff pressure is just lower than systolic pressure
- disappearance of Korotkoff sound represents point where cuff pressure just lower than diastolic pressure
pressure in systemic circulation
highest to lowest
- left ventricle –> aorta –> arteries –> arterioles –> capillaries –> venules –> veins –> vena cava –> right atrium
pressure in pulmonary circulation (highest to lowest)
right ventricle –> pulmonary artery –> arteries –> arterioles –> capillaries –> venules –> pulmonary veins –> left atrium
