Systemic Circulation Flashcards
Flow (Q) eqn
Q = v * A
= ∆P/R
v=linear velocity
A=cross sectional area
R=resistance
Resistance (R) eqn
R = 8ηl/πr^4
η = viscosity l = length r = radius
Cardiac Output eqn
CO = SV * HR
= (MAP - RAP)/TPR
SV = stroke vol HR = heart rate MAP = mean aortic pressure RAP = right atrial pressure TPR = total peripheral resistance
Stroke Vol eqn
SV = EDV-ESV
Artery Fxn:
Wall structure:
Fxn:
Passage from heart -> organs,
pressure reservoir,
recoil properties ∆ pulse flow to continuous flow
Wall Structure:
thick,
highly elastic,
large radii
Arteriole Fxn:
Wall structure:
Fxn: distribution of cardiac output, provide primary (highest) resistance, regulates blood flow to capillary beds, tonically active largest pressure drop happens here
Wall Structure:
highly muscular (smooth mm),
well-innervated,
small radii
Capillary Fxn:
Wall structure:
Fxn:
Exchange site,
determine ECF distribution b/w plasma/ISF
velocity lowest here
Wall Structure:
very thin,
large total cross-sectional area
Vein Fxn:
Wall structure:
Fxn:
Passage from organs -> heart,
blood reservoir
Wall Structure:
thinner than arteries,
highly distensible,
large radii
Compliance of BV is?
vol of blood a vessel can hold at certain pressure,
more compliant = holds more volume
C = V/P
Stressed Volume found in which vessels?
arteries
Unstressed Volume found in which vessels?
veins
Total blood vol =?
stressed vol + unstressed vol
Result of ↓ Vein Compliance
↓ Vein Vol:
blood moves from veins to arteries
Ѧ unstressed vol ↓ , stressed vol ↑
Result of ↑ Vein Compliance
↑ Vein Vol:
blood moves from arteries to veins
Ѧ unstressed vol ↑ , stressed vol ↓
Largest pressure drop in vessels occurs where?
arterioles to capillaries
Arteriosclerosis affects heart how?
narrows opening ->
↓ flow from LV to aorta ->
↓ SV (↓ blood into aorta) ->
↓ SP, PP, MAP
Plaque affects heart flow how?
walls become stiff ->
↓ compliance ->
larger P ∆
↓ cross sectional area ->
↑ velocity ->
↑ turbulence ->
can dislodge tissue fragments
Pressure drop between venules and veins is?
small
Hydrostatic pressure opposes what?
Return of blood to heart
Fxn of Venous Valves?
allows flow toward heart,
prevents backflow
Factors influencing venous return? (4)
1) mm activity/action of valves
2) sympathetic venous constriction
3) negative R atrial pressure
4) negative intra-thoracic pressure
Compliance is greater when?
pressure and volume are low
Compliance is lower when?
pressure and volume are high
Lower compliance affects ∆ in volume in response to a ∆ in pressure how?
∆ in volume is much greater at low compliance than at high compliance
Average pressure at beginning of systemic circulation?
93 mmHg (mean arterial pressure)
Pressure at end of system circulation?
0 mmHg
