Circulation Flashcards
Systemic capillaries arteriolar ends
35mmHg
Sc Venous ends
10mmHg
Ave. Capillary pressure
17mmHg
Glomerular capillaries pressure
60mmHg
T/F
total blood flow through the lungs is the same as that in the systemic circulation because of the lower vascular resistance of the pulmonary blood vessels.
True
Ohm’s law in blood vessel
F = change in pressure/resistance
the total pulmonary vascular resistance is much higher than the systemic vascular resistance.
T/F
False. Lower
Decreased Radius of a Blood Vessel Markedly Increases Vascular Resistance.
True
portion slightly away from the wall has moved a small distance, and the portion in the center of the vessel has moved a long distance.
para-bolic profile for velocity of blood flow.”
the blood flows crosswise in the vessel and along the vessel, usually forming whorls in the blood, called eddy currents.
Turbulent flow
Turbulent flow due to
obstruction in a vessel,
when it makes a sharp turn, or
when it passes over a rough surface,
measure of the tendency for turbulence to occur
Reynolds’ number
turbulence will usually occur even in a straight, smooth vessel.
Reynolds’ number rises above approximately 2000
Pulmonary BP
25/8 mmHg
Pulmonary capillary pressure
16 mmHg
Thus, the conductance of the vessel increases in proportion to the
fourth power of the diameter, in accordance with the following formula:
Conductance = Diameter∝4
blood in the ring touching the wall of the vessel is barely flowing because of its adherence to the vascular endothelium
Poiseuille’s Law.
F →(π ∆Pr^4)/(8 η l)
viscosity of normal blood is about 4 times as great as the viscosity of water. T/F
False. 3
increase in arterial pressure not only increases the force that pushes blood through the vessels but also
initiates compensatory increases in vascular resistance within a few seconds through activation of the local control mechanism
ability of each tissue to adjust its vascular resistance and to maintain normal blood flow during changes in arterial pressure between approximately 70 and 175 mm Hg
blood flow autoregulation.
sympathetic nerve stimulation or vasoconstriction by hormones such as
norepineph rine, angiotensin II, vasopressin, or endothelin
Vascular distensibility Increase in volume/(Increase in pres × ssure Original volume)
fractional increase in volume for each millimeter of mercury rise in pressure
total quantity of blood that can be stored in a given portion of the circulation for each mm Hg pressure rise
compliance or capacitance
Vascular compliance=(Increase in volume / Increase in pressure)
the volume of blood injected causes immediate elastic distention of the vein, but then the smooth muscle fibers of the vein begin to “creep” to longer lengths, and their tensions correspondingly decrease.
stress-relaxation or Delayed compliance
T he difference between these two pressures, about 40 mm Hg
pulse pressure.
diameter of the aortic valve opening is reduced significantly, and the aortic pressure pulse is decreased significantly because of diminished blood flow outward
aortic valve stenosis
one half or more of the blood pumped into the aorta by the left ventricle flows immediately backward
allowing the diastolic pressure to fall very low before the next heartbeat.
patent ductus arteriosus
after each heartbeat, the blood that has just been pumped into the aorta flows immediately backward
As a result, the aortic pressure can fall all the way to zero between heartbeats
aortic regurgitation
there is an incisura in the aortic pulse contour because there is no aortic valve to close.
T/F
False. None
velocity of pressure pulse transmission in the aorta
3-5 m/sec
velocity of pressure pulse transmission in the large arterial branches,
7 to 10 m/sec
velocity of pressure pulse transmission in the small arteries
15 to 35 m/sec
the greater the compliance of each vascular segment, the slower the velocity, which explains
the slow transmission in the aorta and the much faster transmission in the much less compliant small distal arteries
cause of damping is twofold:
(1) resistance to blood movement in the vessels, and
2) compliance of the vessels.
Why?
resistance damps the pulsations because a small amount of blood must flow forward at the pulse wave front to distend the next segment
compliance damps the pulsations because the more compliant a vessel, the greater the quantity of blood required at the pulse wave
primarily responsible for this long-term regulation of arterial pressure; exhibit definitive changes with age, especially after the age of 50 years.
kidneys
The mean arterial pressure is therefore determined about
60 percent by the diastolic pressure and 40 percent by the systolic pressure.
pressure in the right atrium is called the
central venous pressure
factors that can increase this venous return and thereby increase the right atrial pressure are
1) increased blood volume
2) increased large vessel tone
3) dilation of the arterioles, which decreases the peripheral resistance
normal right atrial pressure
0 mm Hg,
normal right atrial pressure can increase to 20 to 30 mm Hg under very abnormal conditions, such as
1) serious heart failure or (2) after massive transfusion of blood
lower limit to the right atrial pressure
usually about −3 to −5 mm Hg below atmospheric pressure,
thus the pressure in the more peripheral small veins in a person lying down is usually
+4 to +6 mm Hg greater than the right atrial pressure.
What happens when When the right atrial pressure rises above its normal value of 0 mm Hg,
blood begins to back up in the large veins.
pressure in the abdominal cavity of a recumbent person normally averages about +6 mm Hg, but it can rise to +15 to +30 mm Hg as a result of
pregnancy, large tumors, abdominal obesity, or excessive fluid
in an adult who is standing absolutely still, the pressure in the veins of the feet is about
+90 mm Hg simply because of the gravitational weight of the blood in the veins between the heart and the feet
In the arm veins, the pressure at the level of the top rib is usually about
+6 mm Hg
+35 mm Hg pressure in the veins of the hand. Y?
gravitational difference between the level of the rib and the hand is +29 mm Hg, this gravitational pressure is added to the +6 mm Hg pressure caused by compression of the vein
negative pressure can exist in the dural sinuses of the head t/f
True
if the sagittal sinus is opened during surgery,
air can be sucked immediately into the venous system; the air may even pass downward to cause air embolism
it is efficient enough that under ordinary circumstances the venous pressure in the feet of a walking adult remains less than +20 mm Hg.
venous pump” or “muscle pump,
reservoirs and the volume they provide
100 milliliters
several hundred milliliters
as much as 300 milliliters
50 to 100 mil-liliters of blood;
another 100 to 200 milliliters when the pulmonary pressures decrease to low values.
spleen, As much as 50 milliliters of concentrated red blood cells can be released into the circulation, raising the hematocrit 1 to 2 percent.
liver, the sinuses of which can release several hundred milliliters of blood into the remainder of the circulation;
the large abdominal veins,
venous plexus beneath the skin, which also can contribute several hundred milliliters.
heart and the lungs, although not parts of the systemic venous reservoir system
peripheral circulation of the entire body has about
500 to 700 square meters
generally have internal diameters of only 10 to 15 micrometers
arterioles
total thickness of the capillary wall is only about
0.5 micrometer
The internal diameter of the capillary is — barely large enough for red blood cells and other blood cells to squeeze through.
4 to 9 micrometers,
most important factor affecting the degree of opening and closing of the metarterioles and precapillary sphincters that has been found thus far
is the concentration of oxygen in the tissues.
results from thermal motion of the water molecules and dissolved substances in the fluid,
Diffusion
lipid-insoluble substances that can go only through the pores.
sodium ions and glucose
Water
Cl
the rate at which water molecules diffuse through the capillary membrane is about 80 times as great as the rate at which plasma itself flows linearly along the capillary
True
width of the capillary intercellular cleft-pores,
Pores. The width of the capillary intercellular cleft-pores, 6 to 7 nanometers, is about 20 times the diameter of the water molecule
The capillaries in various tissues have extreme differences in their permeabilities
True
proportional to the concentration difference of the substance b
net” rate of diffusion
concentration of oxygen in capillary blood is normally greater than in the interstitial fluid
Determine Fluid Movement Through the Capillary Membrane.
Hydrostatic and Colloid Osmotic Forces
force f luid outward through the capillary membrane.
tends to cause osmosis of fluid outward through the capillary membrane.
capillary pressure
interstitial fluid colloid osmotic pressure
force fluid inward through the capillary membrane
cause osmosis of fluid inward through the capillary membrane.
interstitial fluid pressure interstitial fluid pressure
capillary plasma colloid osmotic pressure
If the sum of the Starling forces is postive, there will be a net fluid absorption from the interstitial spaces into the capillaries.
T/F
False. Negative
direct micropipette cannulation of the capillaries, which has given an average mean capillary pressure of
about 25 mm Hg in some tissues such as the skeletal muscle and the gut,
has given a capillary pressure averaging about 17 mm Hg in these tissues.
indirect functional measurement of the capillary pressure,
the “functional” capillary pressure in this tissue is measured to be about 17 mm Hg.
Isogravimetric Method for Indirectly Mea suring “Functional” Capillary Pressure
The colloid osmotic pressure of normal human plasma averages about 28 mm Hg
19 mm of this pressure is caused by molecular effects of the dissolved protein and 9 mm is caused by the
Donnan effect
extra osmotic pressure caused by sodium, potassium, and the other cations held in the plasma by the proteins.
Donnan effect
the pressures in the arterial and venous capillaries are averaged to calculate mean functional capillary pressure for the entire length of the capillary. This mean functional capillary pressure calcu-lates to be
17.3 mm Hg.
fluid that must be returned to the circulation through the lymphatics.
net filtration,
The normal rate of net filtration in the entire body, not including the kidneys, is only about 2 ml/min
whole body capillary filtration coefficient.
net filtration rate of 6.67 ml/min of fluid per mm Hg for the entire body
any factor that increases interstitial fluid pressure also increases lymph flow
Decreased plasma colloid osmotic pressure
Elevated capillary hydrostatic pressure. interstitial fluid colloid osmotic pressure,, permeability of the capillaries
any external factor that intermittently compresses the lymph vessel also can cause pumping.
Contraction of surrounding skeletal muscles • Movement of the parts of the body • Pulsations of arteries adjacent to the lymphatics • Compression of the tissues by objects outside the body
two primary factors that determine lymph flow are
the interstitial fluid pressure and (2) the activity of the lymphatic pump
When the tissues lose their negative pressure, fluid accumulates in the spaces and the condition known as
edema occurs.
