principles of blood flow

Question 1

what is the trend of blood pressure as an individual ages?

Answer 1

sharp increase during early growth and subsequent rise after age 45

Question 2

what are the mean pressures in the large arteries, arterioles, capillaries, venules and veins?

Answer 2

large arteries 95, arterioles 60, capillaries 35-15, venules 15, veins 15-3

Question 3

is blood a newtonian fluid?

Answer 3

no

Question 4

what is the main change of blood pressure in the body?

Answer 4

cyclic periodic beating of the heart

Question 5

from what is the energy in the blood composed of?

Answer 5

static pressure, gravitational force and motion

Question 6

how to blood vessels accommodate pressure changes?

Answer 6

they change shape (elastic)

Question 7

describe flow through a series of tubes with different diameters? what property does this support?

Answer 7

constant flow throughout the tubes

conservation of mass- same amount of blood flows in as blood flows out in a given time

Question 8

define blood flow (Q).

Answer 8

the quantity of blood passing in a particular observation point in a given time interval

Question 9

describe blood flow in a parallel circuit.

Answer 9

volume flow is additive (Qt=Q1+Q2)

flow across any total cross sectional area is constant

Question 10

what two major vessels can be compared in the vascular system as being in series and having the same blood flow?

Answer 10

the aorta and the pulmonary artery

Question 11

describe a parallel circuit in the body and how it relates to flow in other vessels.

Answer 11

capillaries can be thought of as parallel circuits and their total blood flow is the same as the blood flow in the aorta

Question 12

what controls the rate of blood flow to a tissue? how is this accomplished?

Answer 12

the tissue need

accomplished by he adjustment of resistances located prior to the capillary beds

Question 13

what mainly controls cardiac output?

Answer 13

the sum of all local tissue flows

Question 14

id the arterial pressure regulated by local blood flow or cardiac output control?

Answer 14

no, arterial pressure has other means of regulation

Question 15

what is the main overall arrangement of vasculature? what are some exceptions?

Answer 15

overall arrangement is primarily a parallel circuit
splenic and mesenteric capillaries are in series with hepatic circulation and renal glomerular and tubular circulations are in series with each other

Question 16

how is hypoxia avoided in tissues?

Answer 16

flow of oxygen in the arteries to the tissues must be equal to or greater than the rate of oxygen consumption by the tissues

Question 17

what is mobilized during exercise to accomplish the necessary added profusion of tissues? Where does the added flow go?

Answer 17

venous reserve

the flow goes to the skin, muscles and heart while maintaining flow to the brain

Question 18

what is the flow of oxygen in arteries?

Answer 18

flow of O2=cardiac output x arterial O2 content

Question 19

define the velocity of a fluid. how is it different from flow?

Answer 19

the rate of displacement of a particle of fluid with respect to time. flow is the rate of displacement of a volume of fluid (distance per hour instead of volume per hour)

Question 20

what is the equation for volume in a cylindrical tube. under what conditions is the flow past successive cross sections equal?

Answer 20

Q=A (cross sectional area) x v (velocity)

the fluid must be incompressible and the tube must be rigid

Question 21

what is the equation for cross sectional area of a cylinder?

Answer 21

A=pi x r^2

Question 22

what is the velocity of a particle?

Answer 22

v=change in distance/change in time

v=Q/A

Question 23

if the flow of a fluid is constant and v=Q/A, then what must be true of two different cross sectional areas in the same circuit?

Answer 23

v1 x A1=v2 x A2

Question 24

how does linear velocity relate to cross sectional area?

Answer 24

velocity is inversely related to cross sectional area

Question 25

what is the Q of the aorta?

Answer 25

5L/min

Question 26

what is the ratio of velocity of the aorta to the velocity in the capillaries?

Answer 26

510:1

Question 27

what is the equation for transit time of a blood cell between two points in the system?

Answer 27

t=l/v (length/velocity) | t-V/Q (volume/flow)

Question 28

how long does it take for a red blood cell to travel through a capillary bed?

Answer 28

1 second

Question 29

what is the total circulation time for one bass through the systemic and pulmonary circulation?

Answer 29

one minute

Question 30

when is the approximation for circulating blood in a steady flow of incompressible fluids in rigid, straight cylindrical tubes acceptable?

Answer 30

for all but the smaller vessels

Question 31

what assumptions are not always true of flow when talking about blood?

Answer 31

that the flow is laminar with no slippage at the wall and that the viscosity is constant across the diameter of the vessel

Question 32

define viscosity. when does it effect fluid flow?

Answer 32

how much a fluid resists shear forces | affects flow when there are changes in velocity

Question 33

what is a at the vessel surfaces in contact with blood?

Answer 33

a boundary layer.

Question 34

what is another equation for flow using pressure and resistance? where does resistance to flow come from?

Answer 34

Q= pressure difference/resistance | resistance comes from the walls of the vessel and the viscosity of the blood

Question 35

why is pressure from the heart propagated throughout the circulatory system?

Answer 35

because the blood is incompressible and continuous

Question 36

blood viscosity and resistance from vessel walls are what type of forces?

Answer 36

frictional forces

Question 37

what variables of flow does Poiseuille's law relate?

Answer 37

pressure difference, radius of the vessel, viscosity and length of the tube

Question 38

how is resistance related to radius and area?

Answer 38

resistance is inversely related to the radius to the fourth power resistance is inversely related to the square of the cross sectional area

Question 39

what vessels mainly determine the resistance to the flow of the blood?

Answer 39

the arterioles

Question 40

how does the sympathetic nervous system control blood flow?

Answer 40

receptors are stimulated that cause vasoconstriction of vascular smooth muscle. This increases the flow greatly

Question 41

besides vessel radius, what affects resistance to flow? what variable has an inverse relationship to this variable?

Answer 41

viscosity temperature is inversely related to viscosity (colder temperatures increase blood viscosity and decrease blood flow)

Question 42

what equation can help you measure pressure drop along a length of blood vessel? what conditions increase pressure drop in blood vessels?

Answer 42

Poiseuille's law | decreased radius, increased viscosity and increased lenth of the vessels

Question 43

where in the vasculature is blood pressure decreased more slowly and where more rapidly?

Answer 43

slowly: large arteries and veins rapidly: small arterioles and capillaries

Question 44

what is the total resistance for blood vessels in series?

Answer 44

Rt=R1+R2+R3...

Question 45

what is the total resistance for blood vessels in parallel?

Answer 45

1/Rt=1/R1+1/R2+1/R3...

Question 46

how are branches in a parallel network correlated to the total resistance? what is the implication of this for capillaries?

Answer 46

more branches in a parallel network decreases the total resistance the overall resistance for a capillary bed may be very low even though the resistance in each capillary is relatively high