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Flashcards in Clin Phys Week 9 E Deck (39):
1

What are the 3 layers of arterial and venous walls? Briefly describe each

Tunica interna (intima) - endothelial layer that lines the lumen of all vessels

Tunica media - smooth muscle the elastic fibre layer, regulated by sympathetic nervous system (controls vasoconstriction and vasodilation)

Tunica externa - contains collagen fibres protect and reinforce the vessels

2

What is the lumen?

Central blood-containing space surrounded by tunics

3

What are capillaries composed of?

Endothelium with a sparse basal lamina

4

What is blood flow?

The actual volume of blood flowing through a vessel, organ, or the entire circulation (tissue) in a given period of time. (equivalent to CO) (ml/min)

5

Define perfusion

Rate of blood flow per given mass of tissue (ml/min/g)

6

What is blood flow velocity?

A measurement of the rate of which blood flows through a particular vessel (cm/min)

7

What is laminar flow? What causes it?

When blood flows in streamlines. Caused by the outside layers in contact with the wall adhering and the inner layers slipping over each other

8

What causes turbulent blood flow?

This occurs when blood is passing an obstruction, makes a sharp turn or increases in velocity

9

What does Q represent in terms of the hydrodynamics of fluid flow?

Q = flow

10

What does P represent in terms of the hydrodynamics of fluid flow?

Difference in pressure

11

What does R represent in terms of the hydrodynamics of fluid flow?

Resistance to pressure

12

What is the equation for fluid flow according to hydrodynamics?

Q = P/R

13

What is the formula Q = P2-P1 = P? Describe what it means.

Flow = Pressure 2 (pressure at the start of the vessel) - Pressure 1 (pressure at the end of the vessel) = Difference of pressure

 

It means the pressure difference between 2 end of the vessel creates flow along pressure gradient

14

What does SPR mean?

Systemic peripheral resistance

15

What does TPR mean?

Total peripheral resistance

16

What are the 4 main factors that impact resistance?

  • Amount of fluid in the system (CO)
  • Blood viscosity
  • Vessel length
  • Vessel diameter

17

How does vessel length impact resistance?

The longer the vessel the greater the resistance

18

How does the amount of fluid in the system (CO) impact resistance?

The more fluid in the system, the greater the resistance

19

What resistance factors remain relatively constant?

Blood viscosity - stickiness of the blood

Blood vessel length

20

What does TR = 1/R1 + 1/R2 + 1/R3 mean?

It means the total resistance of the system is the sum of the reciprocals of the individual resistances.

21

By how much does resistance vary with vessel radius?

The resistance varies inversely with the fourth power of vessel radius. e.g. If the radius is doubled, the resistance is 1/16 as much

22

What blood vessels does the sympathetic nervous system act on?

Small arteries

Arterioles

Venules

Veins

23

What is the rate of flow through the system at rest normally? (assuming CO is 6l/min)

100ml/sec

24

What is vascular compliance? What is the formula for it?

The total quantity of blood able to be stored in a given portion of the circulation for each mmHg rise. vascular compliance = increase in volume = increase in pressure

25

How much more vascular compliance do systemic veins have compared to its corresponding artery?

24 times

26

What is systemic blood pressure measured in?

mmHg

27

What is systems blood pressure?

The force exerted by blood against any unit area of blood vessel wall.

28

Where is systemic pressure highest?

The aorta

29

What is the systemic blood pressure in the right atrium?

0 mmHg

30

Where does the steepest change in systemic blood pressure occur?

In the arterioles

31

What is systolic pressure?

Pressure exerted on arterial walls during ventricular contraction

32

What is diastolic pressure?

The lowest level of arterial pressure during a ventricular cycle

33

What is pulse pressure?

The difference between systolic and diastolic pressure

34

What is mean arterial pressure? What is its formula?

The average pressure through each cycle of the heart beat

 

MAP = CO x TPR

35

What values does the capillary blood pressure range between?

20-40mmHg

36

What factors increased venous return?

Increased blood volume

Increased large vessel tone

Dilation of the arterioles

37

What is the venous pressure at the feet when a person is standing? (approx)

90mmHg

38

What factors aid venous return?

Respiratory pump - pressure changes created during breathing suck blood towards the heart by squeezing local veinsMuscular pump - contraction of muscles push blood towards heart

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