what plays the greatest role of all factors in determining the rate of blood flow through a vessel
DIAMETER OF BLOOD VESSEL
why is there actually a near equilibrium of reabsorption and filtration pressure by the venous and arterial ends of the capillary?
-More venule capillaries
-More surface area of venule capillaries (bigger)
-more permeable than the arterial capillaries.
fraction of filtered and reabsorbed fluid that flows into lymph to be returned to circulating blood
1/10th
the average imbalance of forces at the capillary membranes (net filtration) =
0.3 mmHg –> net filtration
how many mL per minute, not including kidneys, is the normal rate of net filtration in the entire body
2mL/min
average hydrostatic pressure along a systemic capillary
17.3 mmHg (one would think it’s 20mmHg bc of the diff between 30 and 10, but it’s bc of the increase in surface area of the venule capillaries
parabolic profile for velocity of blood flow, what is it and what causes it
velocity of fluid increases the further from the vessel wall it is. Caused by adherence of molecules to the vessel wall due to friction. the fluid in the middle moves rapidly because of the many layers of slipping molecules
what conditions increase tendency for turbelnce
-high velocity
-diameter of blood vessel
-density of blood
-inversely proportional to viscosity of blood
why do eddy currents increase friction
they are disorderly and increase the contact with vessel wall, adding to the friction tremedously
define blood pressure
the force exerted by the blood against any unit area of the vessel wall
1 mosm of solute can push a column of mercury ____
19.3 mm high
specific gravity of mercury is ____ times that of H20
13.6
1 mmHg = 1.36 cm of H20
blood flow changes rarely last more than a few hours in most tissues, even when increased levels of vasoconstrictors are sustained because:
autoregulatory mechanisms will eventually override most of the effects of vasoconstrictors to provide a blood flow that is appropriate for the needs of the tissue
why are veins more distensible than arteries
the walls of the arteries are thicker and far stronger than those of the veins
pulmonary arteries are more or less distensible than systemic arteries? why?
pulmonary arteries are 6X more distensible than systemic arteries bc they operate under pressure 1/6th those of the systemic arteries
compliance = ___ X ____
distensibility X volume
what’s more important, compliance or distensibility? why?
compliance. a highly distensible vessel with little volume in it may have less compliance than a much less distensible vessel that has a large compliance
3 main components of plasma colloid osmotic pressure
albumin : 21.8
globulins (immune cells): 6.0
fibrinogen: 0.2
Total: 28 mmHg in CV system
interstitial hydrostatic pressure
-3 mmHg (an outward pressure)
interstitial osmotic pressure
8mmHg
Why fluid doesn’t typically get pulled out from osmotic forces
plasma hydrostatic pressure in arteriole end of capillary
“blood pressure” : 30mmhg
what is the K(f) of the kidney
K(f) = filtration/NFP
K(f)= 12.5ml/min/mmHg
what substances contribute to the osmotic pressure within the interstitial fluid
proteoglycan filaments, collagen, hyaluronic acid
