Overview of circulation- Exam 2

Question 1

Characteristics of pulmonary circulation

Answer 1

Systolic pulmonary artery pressure= 25 mm Hg

Pulmonary diastolic pressure= 8 mm Hg

Question 2

Functional parts of circulation

Answer 2

Arteries transport under high pressure
Arterioles control conduits
Capillaries gas and nutrients exchange
venules and veins used for storage

Question 3

Blood distribution in body

Answer 3

84% of blood in systemic circulation

16% of blood in pulmonary circulation

Question 4

84% of Blood distribution in systemic circulation

Answer 4

64% in veins
13% in arteries
7% in arterioles and capillaries

Question 5

What is the velocity of blood flow?

Answer 5

Volume of blood flow by area
V= F/A
Faster in arteries than veins
Very slow in capillaries due to gas and nutrients exchange

Question 6

Functional principles of circulatory system

Answer 6

Rate of blood flow controlled by tissue need
cardiac output controlled by sum of local tissue flow
A.P. regulation independent of cardiac output and local blood flow control

Question 7

Control of blood flow rate by tissue need

Answer 7

Micro vessels monitor tissue needs
Product accumulation acts directly on local blood vessels
local blood vessels dilate or constrict in response

Question 8

Control of cardiac output by local tissue flows

Answer 8

Heart responds to demand of tissues

Heart can enroll help of nerves signals to pump required amount of blood

Question 9

Factors determining blood flow

Answer 9

Pressure gradient
Resistance
F= Delta P/ Resistance
Cardiac output at rest = 5000 ml/min

Question 10

What are the types of flow

Answer 10

Laminar (streamline) flow

turbulent flow

Question 11

Characteristics of laminar flow

Answer 11

Blood flows @ steady rate and in streamlines

Blood vessels long and smooth

Question 12

Characteristics of turbulent flow

Answer 12

Non layered flow
Creates murmurs
Produce more resistance than laminar flow
Proportional to velocity of blood flow, vessel diameter and density
Inversely proportional to the viscosity of blood

Question 13

Blood viscosity

Answer 13

Property of blood to adhere to vessels walls and to each other
Based on number, shape and size of RBC
Blood more viscous than water (relative value=4.5)

Question 14

Blood density

Answer 14

Blood heavier than water (specific gravity=1.055)

Depends on proportion of components particularly RBC and its proteins

Question 15

What is Reynolds Number?

Answer 15

Measure of the tendency for turbulence to occur
Re=(velocity.diameter.density)/ viscosity
Re>200-400–>Turbulence will occur in some regions
Re> 2000—–> Turbulence will occur even in straight vessel

Question 16

What is Blood Pressure?

Answer 16

Force exerted by the blood against any unit area of the vessel wall.
measured with a mercury manometer or with electronic transducers

Question 17

What is Resistance?

Answer 17

Impediment to blood flow in a vessel
Indirectly calculated from measurements of blood flow and viscosity of blood
R=Pressure/(volume/time)

Question 18

Variables determining resistance

Answer 18

Vessels radius: most important variable
Blood viscosity
Vessel length

Question 19

Effects of resistance

Answer 19

Increase resistance—> Increase upstream pressure, Decrease of blood flow and downstream pressure

Decrease resistance—> Decrease upstream pressure, Increase blood flow and downstream pressure

Question 20

Values of resistance

Answer 20

Resistance of entire systemic circulation = 1PRU
Total peripheral resistance up to 4 PRU in strongly constricted vessels.
Total peripheral resistance as low as 0.2 PRU in greatly dilated vessels

Question 21

Resistance in the pulmonary system

Answer 21

Mean pulmonary arterial pressure= 16 mm Hg
Mean left atrial pressure=2 mm Hg
Resistance R=14/100= 0.14PRU

Question 22

What is conductance?

Answer 22

Measure of blood flow through a vessel for a given pressure difference.
Each tissue contribute to overall conductance
Exact reciprocal of resistance

Question 23

Arrangement of vessels

Answer 23

Arterioles, capillaries, venules and veins arranged in series
Parallel circuits formed supply blood throughout body

Question 24

Circulations arranged in parallel

Answer 24

Brains Gastrointestinal
kidney Skin
Muscle Coronary circulation

Question 25

Consequences of amputation

Answer 25

Removes parallel circuits
Reduction of total vascular conductance
Reduction of total blood flow
Increase total peripheral vascular resistance

Question 26

Determinant of blood viscosity

Answer 26

hematocrit
Anemia decreases viscosity
Polycythemia increases viscosity

Question 27

Blood flow autoregulation

Answer 27

Arterial pressure changes between 70-175 mm Hg

Vascular resistance adjustment and maintenance of normal blood flow done within AP parameters

Question 28

Characteristics of systemic circulation

Answer 28

Arterial pressure between 120-70 mm Hg (systolic-diastolic)
Arterial pressure drops to 0 at vena cava termination
Systemic capillary pressure from 35-10 mm Hg

Question 29

What are the causes of turbulent flow?

Answer 29

Blood flow is too great
Blood passes obstruction within the vessel
Blood makes sharp turn
Blood passes over rough surface