chapter 14- Exam 2 Flashcards
what does the circulatory system do
Transporting nutrients to the tissues
Transporting waste products away from the tissues
Transporting hormones
what are the arterial walls like and what do they do
they have strong walls and transport blood under high pressure
what are the arterioles wall like and what do they do
have muscular walls that can completely relax/dilate altering blood flow in each tissue in response to its needs
what controls blood into the capillaries
arterioles
what do the capillaires do
exchange fluid, nutrients, electrolytes, hormones, and other substances between the blood and the interstitial fluid
what are the capillary walls like and what do they do
walls are very thin with numerous minute capillary pores permeable to water and other small molecular substances
what are the venules
venules receive blood from capillaries and gradually become progressively larger veins to transport blood back to the heart and serve as a major reservoir of blood
what is the venous systems walls like
Because the pressure in the venous system is very low, the venous walls are thin, but muscular enough to contract or expand and act as a controllable reservoir
what happens to the volume of blood in a closed system
the fixed volume of blood in various areas change with demand
what percent of the entire blood volume is in the systemic circulation
84%
how does the 84% of the blood volume in the systemic circulation get divided up
64- in veins 13 in arteres 7 -systemic arterioles + caps 7 in the heart 9 in pulmonary circulation
what have a larger cross sectional area
veins or arteries
veins
what are the cross sectional areas of the systemic system
Aorta = 2.5 Small Arterioles = 20 Arterioles =40 Capillaries= 2500 Venules =250 Small Veins =80 Venae Cavae =8
what is hemodynamics
the physical factors that govern blood flow
what is similar to Ohms law in electricity
flow of fluid is proportional to the drive force (pressure) through a resistance
what is velocity of BF
is the speed at which blood flows in the circulation (mm/sec)
what happens to the velocity with the fixed volume of blood
Velocity of blood flow is inversely proportional to the vascular cross-sectional area
what is the equation of the velocity of blood flow
velocity or BF= BF/ cross sectional area
what are the units of flow
cm^3/ min
**1 ml = 1 cm^3
what are the units of velocity
cm/ min
what are the units of cross secitonal area
cm^2
at rest with a relatively constant flow what are the velocity
Aorta 33cm/sec
> Arterioles
> Small veins
> Capillaries 0.3 cm/sec
what is flow equal too
velocity x Area
how do you keep flow constant
as area decreases ( means velocity increases )
what is pressure equal
force/ area
where is high pressure found
in the arterial tree
where is low pressure
in the venous side of the circulation
what happens with large pressures in the arteriolar capillary jx
it willldrop across
how is blood flow controlled to tissues
blood flow is controlled in relation to tissue needs
how is Q controlled to tissues
Q is mainly controlled by local tissue flow
how is arterial pressure control to tissue
arterial pressure is controlled independent of either local blood flow control or Q control
when tissue is active what will happen to blood flow
it can increase as much as 20 to 30 times the resting level
how can Q increase
the heart cant increase Q greater than 4 to 7 time resting level
– 5 L/min at rest to 35 L/min in high level athletes So not possible to increase blood flow everywhere in the body.
what do the microvessel do
they continuously monitor tissue needs, dilating or constricting, to control local blood flow precisely to that level required for the tissue activity.
what are some other things that help the vessels in controlling blood flow
Central nervous system and hormones provide additional help in controlling tissue blood flow.
how is Q controlled
mainly controlled by the sum of all local tissue flow
—For example: Exercise → ↑ VR → ↑ Cardiac Output
—CO increases to meet the increasing needs of increasing metabolic tissue
how is arterial pressure controlled
this is controlled independent of either local blood flow control or cardiac output control
go to slide 17
read about the arterial pressure and how the body handled it
what does Q =
change in Pressure over resistance
what is flow
through a blood vessel is determined by Q
- the pressure difference between the two ends of the vessels ( arterial - venous )
2 resistance of the vessel
what is blood flow
quantity of blood that passes a given point in the circulation in a given period of time
what is unit of blood flow
usually expressed as milliliters (ml) or Liters (L) per minute
what is Q
Overall flow in the circulation of an adult ~5 liters/min
what is laminar flow
Blood usually flows in streamline fashion with each layer of blood remaining the same distance from the wall, this type of flow is called laminar flow
what happens with laminar flow occurs
the velocity of blood in the center of the vessel is greater than (2x greater) that toward the outer edge creating a parabolic profile
what are some causes of turbulent blood flow
- High velocities
- Sharp turns in the circulation
- Rough surfaces in the circulation
- Rapid narrowing of blood vessels
what will you hear with laminar flow
is it silent
what will you hear with turbulent flow
it tends to cause vascular murmurs
why are murmurs important
they help with diagnosing vessel stenosis, vessel shunt, and cardiac valvular lesions
what is reynolds number
a dimensionless quantity used to predict flow patterns
what is the reynolds number equation
ssel diameter D x mean velocity v x density ρ divided by viscosity η
when does turbulence occur
- With a large diameter and rapid flow
- High Velocity
- Sudden change in vessel diameter
what is blood pressure
Blood pressure is the force exerted by the blood against any unit area of vessel wall
what is resistnace
Resistance is the impediment to blood flow in a vessel
Δ P = mmHg
Q ml/min
*** read bottom of slide 29 and 32
what is conductances
Conductance is a measure of the blood flow through a vessel for a given pressure difference
***its ml/min per mmHg
what is conductance sensitive to
change in diameter of vessels
== The conductance of a vessel increases in proportion to
the fourth power of the radius
what is poiseuillie law
look at slide 35 for equaiton
