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25 Cards in this Set

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What does Fick's Law state about diffusion of small, water-soluable substances across a capillary wall?
The law states that the rate (ease) and direction of diffusion depends on both the permeability and the concentration gradient.
What is an A-V Shunt?
An ateriovenous anastomoses, which is a vessel that runs from an arteriole to a venule, bypassing the capillary bed.
Name 3 reasons that capillaries are good exchange vessels
1. Capillary walls are very thin at only one cell thickness
2. Capillary walls are porous
3. Blood flow is relatively slow (because there are millions of them)
According to the Starling Hypothesis, the exchange of water and solutes between capillaries and the interstitial tissue space rely on the balance of what factors?
1. Capillary hydrostatic pressure
2. Interstitial hydrostatic pressure
3. Capillary oncotic pressure
4. Interstitial oncotic pressure
5. the capillary permeability
What is oncotic pressure?
The osmotic pressure due to the presence of colloids (non-diffusable substances) in solution.
Define filtration
When fluid leaves the capillary because the net net hydrostatic pressure is greater than the net oncotic pressure
Define reabsorption
When fluids enters the capillary because the net hydrostatic pressure is lower than the net oncotic pressure.
What is the purpose of the lymphatic system?
To recapture fluid and plasma proteins that have leaked from vessels into the interstitial space, in order to filter them and return back into the blood circulation via a vein.
Define edema
the accumulation of excess fluid in the interstitial spaces. This is due to a shift in one of the factors of Starling's hypothesis.
Name three mechanisms that cause edema
1. a hydrostatic pressure gradient
2. a colloid-osmotic pressure gradient
3. increased capillary permeability
Name a cause of increased capillary permeability based edema
histamine release (allergic reaction)
Name a cause of increased hydrostatic pressure edema
pulmonary edema from left-sided heart failure, systemic edema from right-sided heart failure
Name a cause of decreased oncotic pressure edema
hypo-proteinemia associated with malnutrition, severe burns,
Name some alternative reasons for edema
lymphatic obstruction or atresia (narrowing), immobilization, increased endothelial permeability to proteins
High Altitude Pulmonary Edema
Not completely understood:
Lower atmospheric pressure with reduced oxygen concentration. Pulmonary arteriole vasoconstriction occurs, with increased capillary permeability. The edema that accumulates is very proteinaceous.
systolic pressure (SP)
the peak (highest) arterial pressure in the cardiac cycle
diastolic pressure (DP)
the lowest arterial pressure in the cardiac cycle
Mean Arterial Blood Pressure (MABP) calculation
DP + 1/3(SP - DP)
dicrotic notch
in the recording of the arterial pressure, indicates the closure of the aortic valve and the end of ventricular systole
pulse pressure (PP)
the difference between systolic and diastolic pressures
SP - DP
Blood pressure reporting (manual)
is written SP/DP such as 120/90
Physical attributes of systolic pressure
the blood flow into the arteries during systolic contraction is higher than the flow out of the arteries (into the arterioles), which causes an increase in arterial volume and pressure.
Physical attributes of diastolic pressure
the result of aortic/arterial vessel wall recoil.
During diastole, the elastic recoil of the arterial walls provides the driving force to propel blood out the arteries
What happens when the aorta is stiff or has reduced elasticity?
during systole the aorta does not expand at all, so the systolic pressure is increased (same volume in a smaller space).
during diastole, there is less recoil in the aorta, so the diastolic pressure is reduced.
What are general cardio/circulatory factors that will affect blood pressure?
stroke volume, heart rate, total peripheral resistance, compliance of the blood vessels