Chapter 18

Question 1

Hemodynamics

Answer 1

is the study of blood moving through the circulatory system

Question 2

Flow, also called volume flow rate

Answer 2

-indicates the volume of blood moving during a particular time
-Answers the question how much?
-Units are liters/min, ml/s or any volume over time

Question 3

Velocity

Answer 3

-indicates the speed or swiftness of a fluid
-Answers the question how fast and in what direction
-Units are cm/s, m/min or any distance over time

Question 4

Flow, there are 3 forms

Answer 4

Pulsatile
Phasic
Steady

Question 5

Pulsatile flow

Answer 5

-occurs when blood moves with a variable velocity
-Blood accelerates and decelerates from cardiac contraction
- typically in arterial circulation

Question 6

Phasic flow

Answer 6

-occurs when blood moves with a variable velocity
-Blood accelerates and decelerates from respiration
-often in venous circulation

Question 7

Steady flow

Answer 7

-occurs when a fluid moves at a constant speed or velocity
-present in the venous circulation when individuals stop breathing for a moment

Question 8

Laminar flow

Answer 8

-flow streamlines are aligned and parallel
-Characterized by layers of blood that travel at individual speeds

Question 9

Plug flow

Answer 9

all of the layers travel at the same velocity

Question 10

Parabolic

Answer 10

velocity is highest in the center and gradually decreases to its minimum at the vessel wall
-flow has a bullet-shaped profile

Question 11

Turbulent flow

Answer 11

chaotic flow patterns in many different directions at many speeds

Question 12

Eddy currents (vortex)

Answer 12

may appear as small swirling, rotational patterns

Question 13

a murmur or a bruit

Answer 13

Sound associated with turbulent flow
- can be heard on auscultation with a stethoscope

Question 14

critical Reynolds Number

Answer 14

number of > 2000

Question 15

Energy Gradient

Answer 15

from high energy to low energy

Question 16

pressure gradient

Answer 16

blood moving from high to low pressure

Question 17

Kinetic energy

Answer 17

objects with greater mass and speed move more swiftly

Question 18

Gravitational energy

Answer 18

objects move more swiftly from high to low gravitation

Question 19

As blood flows through the circulation, energy is lost in 3 ways

Answer 19

Viscous loss
Frictional loss
Inertial loss

Question 20

Viscous loss

Answer 20

Viscosity describes the thickness of a fluid, and more energy is lost with the movement of high viscosity fluids
-units of Poise [pwahz]

Question 21

Frictional Energy Loss

Answer 21

occur when flow energy is converted to heat as one object rubs against another

Question 22

Inertial Energy Loss

Answer 22

Refers to the tendency of a fluid to resist changes in its velocity

Question 23

In the circulatory system inertial energy loss happens during 3 events:

Answer 23

Pulsatile flow
Phasic flow
Velocity changes

Question 24

Stenosis

Answer 24

Is a narrowing in the lumen of a vessel and has these effects on blood flow

Question 25

Resistance increases with

Answer 25

Increase in tube length
Increase in viscosity
Decrease in tube diameter

Question 26

Ohms Law

Answer 26

The movement of fluid through a tube and the movement of electricity through a wire are similar

Question 27

Venous Hemodynamics

Answer 27

Veins are thin and collapsible, low resistance vessels

Question 28

Hydrostatic Pressure

Answer 28

Pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level
-Measured in mmHg

Question 29

Hydrostatic Pressure and Blood Pressure

Answer 29

Blood pressure is only accurate if taken at heart level as it is not affected by hydrostatic pressure

Question 30

Hydrostatic pressure in the standing person is estimated at:

Answer 30

100 mmHg at the ankle
75 mmHg at the knee
50 mmHg at the waist
-30 mmHg at the top of the head

Question 31

Respiration has a profound effect on venous flow for 2 reasons

Answer 31

1. Venous system is low pressure
2. Muscles responsible for respiration alter pressures in the thorax and abdomen

Question 32

Inspiration

Answer 32

-The diaphragm moves downward, and thoracic cavity expands, abdominal cavity compresses
-Thoracic pressure decreases, abdominal pressure increases
-Flow into the thoracic cavity and to the heart increases
-Flow from the legs into the abdominal cavity decreases