Hemodynamics (Exam 1) Flashcards
1
Q
Blood Vessels: Flow of blood, tunics (3)
A
- Arteries > Arterioles > Capillaries > Venules > Veins
- Three tunics:
- Tunica interna (intima) - simple squamous (endothelium)
- very thin
- Tunica media - smooth muscle and elastic fibers - vasoconstriction/vasodilation
- much thicker in arteries than in veins
- Tunica externa - elastic and collagen fibers
- Tunica interna (intima) - simple squamous (endothelium)
2
Q
Arteries: Overview
A
- Vasoconstriction/vasodilation
- Elastic arteries (Pressure reservoir)
- closest to heart
- Elastic fibers
- closest to heart
- Muscular arteries (Distributing arteries)
- More smooth muscle = more control
- Anastomosis
- 2 or more arteries to tissues
- Collateral circulation
3
Q
Capillaries: definition (2 words), function
A
- Single layer of endothelium and basement membrane
- Exchange vessels
- Microcirculation = flow from arterioles > capillaries > veins
- Capillary bed = 10-100 capillary network (precapillary sphincters control flow
4
Q
Blood Distribution: Percentages
A
- Blood reservoirs = systemic veins and venules (64%)
- Blood can be diverted if needed (venoconstriction)
- Remainder:
- 13% = systemic arteries/arterioles
- 9% = pulmonary blood vessels
- 7% = heart
- 7% = systemic caps.
5
Q
Capillary Exchange: definition, methods (3)
A
- Movement of substances between blood and interstitial fluid
- Accomplished by:
- Simple diffusion - passive transport through fenestrations or endothelial cells
- Transcytosis - useful for large, lipid-insoluble substances
- Bulk flow
6
Q
Bulk Flow: definition and functions
A
- Movement of large numbers of substance at faster rate
- Regulates relative volumes of blood and interstitial fluid
- Pressure driven
- Filtration and Reabsorption
7
Q
Filtration: definition and causes
A
- Bulk flow from capillaries into interstitial fluid
- Promoted by:
- Blood hydrostatic pressure (BHP) (Interstitial fluid hydrostatic pressure (IFHP) negligible)
- Fluid pushing out from walls of capillaries. Higher BHP = more fluid expelled
- Interstitial fluid osmotic pressure (IFOP)
- osmotic pressure - draw fluid into area
- Blood hydrostatic pressure (BHP) (Interstitial fluid hydrostatic pressure (IFHP) negligible)
8
Q
Reabsorption: denition and causes
A
- Bulk flow from interstitial to capillaries
- Promoted by:
- Blood colloid osmotic pressure (BCOP) - caused by plasma proteins
- main factor in reabsorption
- Again, IFHP close to zero
- Blood colloid osmotic pressure (BCOP) - caused by plasma proteins
9
Q
Starling’s Law of the Capillaries
A
- Near equilibrium of filtration and reabsorption volumes
- Net filtration pressure
- NFP = (BHP+IFOP) - (BCOP + IFHP)
- (BHP+IFOP) = Filtration
- (BCOP+IFHP) = Reabsorption
- +NFP = net filtration (arterial end)
- -NFP = net reabsorption (venous end)
- NFP = (BHP+IFOP) - (BCOP + IFHP)
10
Q
Edema: Defintion and causes (3)
A
- Filtration >> Reabsorption
- Due to:
- Increased capillary BP (high BHP)
- Increased capillary permeability
- Decreased concentration of plasma proteins (low BCOP)
11
Q
Blood flow: definition and causes (3)
A
- Volume of blood in tissue over time (mL/min)
- Influenced by:
- Cardiac output (HR and SV)
- Pressure difference between areas (Pressure gradient)
- gradient = high to low
- Resistance in vessels
- increase = less blood flow
12
Q
Blood Pressure: definition, characterisitics, equations (MAP and Pulse Pressure)
A
- Hydrostatic pressure exerted by blood on vessel walls
- Systolic BP = highest arterial pressure during systole
- Diastolic BP = lowest arterial pressure during diastole
- Decreases w/ distance
- MAP = diastolic + 1/3 (systolic-diastolic)
- Mean Arterial Pressure
- Pulse pressure = systolic-diastolic
13
Q
Resistance: Equation (MAP = ___), causes of increase (3)
A
- MAP = CO x R
- Higher R = higher BP
- R increases with:
- Smaller lumen (vasoconstriction)
- Blood viscosity (mostly increased RBCs)
- Length of vessel
14
Q
Venous Return: Causes
A
- Caused by pressure from left ventricle
- Decreased by increased pressure in right side of heart
- Also due to:
- Skeletal muscle pump
- Respiratory pump (abdominal cavity pressure goes up, thoracic cavity pressure goes down )
15
Q
Velocity of blood flow: Overview
A
- Inversely proportional to total cross-sectional area
- Branching causes cross-sectional area to increase
- BP can increase velocity
19
Q
Circulatory Pathways
A
- Systemic - aorta > body tissues > vena cavae
- Pulmonary - pulm. Arteries > lungs > pulm. veins
- Hepatic portal - venous blood from GI organs to liver
