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Flashcards in Peripheral Vascular system Deck (31)
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1
Q

What are some factors that affects diffusion?

A
  1. conc. diff
  2. Surface area for exchange
  3. distance of diffusion
  4. perm of capillary wall to substance
2
Q

What some other factor besides diffusion that affects fluid movement?

A

Pores
Hydrostatic pressure- fluid pushed
Osmotic pressure - water attracted

3
Q

What is starling hypothesis?

A

Describes the relationship between opposing hydrostatic and oncotic forces on net bulk flow
- either filtration or resorption
Net flow= K[(Pc-Pi)-(Pie(c)-Pie(i))]
also (Pplasma-Pif)-(Pieplasma-Pieif)

4
Q

What is Pc?

A

Hydrostatic pressure of intracapillary fluid

5
Q

Whta is pie(c)?

A

Oncotic pressure of intracapillary fluid

6
Q

What are Pi and Pie(i)?

A

Same quantities for interstitial fluid

7
Q

What is K?

A

Constant expressing how readily fluid can move across capillaries

8
Q

What is filtration and what is its starling flow?

A

Net movement of solutes and fluid out into the interstitial fluid
- Positive net pressure gradient

9
Q

What is reabsorption and what is its starling flow?

A

Net movement of solutes and fluid into the capillary from IF

- Negative net pressure gradient

10
Q

Where does filtration and reabsorption happen?

A

Arteriole

Venule- oncotic pressure usually doesn’t change

11
Q

What is an exception to the oncotic pressure rule? How does it work?

A

Release of histamine

-Increase cap perm and protein leak into IF (lowers oncotic pressure)

12
Q

What is the role of the lymphatic system?

A

Keeping IF protein conc. low

  • Very porous
  • Collects particles and moves to LN where particles are removed and fluid is returned to venous system
13
Q

What is the resistance across vessels in series?

A

Total resistance is sum of individual resistances

  • Rs=R1+R2+R3
  • pressure with highest R will have greatest impact of pressure and flow
14
Q

How does one compare vessels in parallel?

A

Resistance of vessels in parallel is not determined by diameter by total cross sectional area of all capillaries
1/Rp= 1/R1+1/R2+1/R3

If all the same Rp=Rx/n

15
Q

What is the relationship between flow and flow rate?

A

Since vessels have diff total cross sectional area and thus diff resistance something must change to keep flow (Liters/Min) the same
- Flow velocity changes (mm/sec)

16
Q

What the purpose of the peripheral venous system?

A

Serve as a reservoir (60%) blood here

- secondary is central venous system

17
Q

What consists of the central venous system?

A

Great veins of thorax and right atrium

18
Q

When peripheral veins constrict what happens?

A

Blood is displaced and enters central system

  • raises venous volume, pressure and cardiac filling
  • thus more in and more out (starling)
19
Q

Where does blood pressure decrease the most?

A

Pulsatile nature disappears across arterioles

about 25 mmHg in Caps

20
Q

What is the pressure in the central venous system?

A

0 mmHg

21
Q

What compensates for increased resistance in arterioles? Why?

A

Pressure drop Q= ^P/R

  • flow must remain the same
  • arterioles have increase resistance and to keep flow the same pressure drop must do so to compensate
22
Q

What determines the resistance of organs?

A

Typically arterioles since greatest resistance

- lumen diameter is regulated to adjust resistance

23
Q

What is total peripheral resistance?

A

Overall resistance to flow through the entire systemic circulation
- organs are in parallel

24
Q

What are 2 ways to decrease resistance TPR?

A
  1. Add another organ system

2. Decrease resistance in any organ

25
Q

What is compliancy?

A

How much pressure in response to volume change
C=^V/^P
- Large shifts in blood into/out of PVS has only small changes in pressure

26
Q

What counters blood pooling?

A

Active venous constriction

27
Q

What is the purpose of the elastic properties of arteries?

A
  1. Convert pulsatile flow coming from heart into smooth steady flow before entering vascular bed]
  2. Store pressure energy during expansion to push blood through the periphery
28
Q

What is mean arterial pressure?

A

Average effect pressure that drives the blood through the systemic organs

Pa=Co*TPR

also Pa=2/3Pd+1/3Ps
Pd+1/3(Ps-Pd)

29
Q

how does one calculate the arterial pulse pressure?

A

Systolic minus diastolic

Pp=Ps-Pd

30
Q

What determines arterial pulse pressure?

A

Stroke volume and Compliance

Pp=SV/Ca

31
Q

Does atrerial pulse pressure change with aging?

A

Yes

  • increase volume
  • decrease Ca
  • leads to increase in pulse pressure and mean arterial pressure