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Flashcards in Hemodynamics Deck (40):
1

Pressure generated is a result of...

Ventricle contraction

2

Veins

Lower blood pressure tan arteries
Accommodate increased volume
Steady flow, opposite branching patters than arteries
Blood reservoirs

3

Venules

Small veins collecting blood from capillaries

4

Venous Sinuses

No smooth muscle

5

Varicose Veins

Twisted, dilated, superficial veins
Caused by leaky venous valves
Allow back flow and pooling of blood
Deeper veins not susceptible because of surrounding muscles

6

Portal System

Blood flows through two consecutive capillary networks before returning to the heart
Example: hepatic portal system between liver and intestines

7

Anastomoses

Points where two blood vessels merge

8

Arteriovenous Shunt

Artery flows directly into vein
Shunt changes direction of blood flow
Used to decrease heat loss in the cold

9

Venous Anastomosis

Most common blockage
Less serious
Alternative drainage of organs

10

Arterial Anastomosis

Collateral circulation (coronary)

11

Blood Distribution

60% of blood volume at rest is in systemic veins and venules
15% of blood volume is in arteries and arterioles

12

Venous Constriction

Constriction of veins during increased muscular activity or during hemorrhage
Increased Venoconstriction = Increased Preload, Stroke Volume, and Cardiac Output

13

Capillary Exchange

Only occurs across capillary walls between blood and surrounding tissues

14

Three Routes of Capillary Exchange

Intercellular clefts
Fenestrations
Through cytoplasm

15

Mechanisms Involved in Capillary Exchange

Diffusion
Transcytosis
Filtration and reabsorption

16

Filtration

Blood pressure drives fluid out of capillary
High on arterial end, low on venous end

17

Reabsorption

Colloid osmotic pressure draws fluid into capillary
Same on both ends
Results from plasma proteins

18

Oncotic Pressure

Net colloid osmotic pressure

19

Dynamics of Capillary Exchange

Provides tissue with nutrients

20

Net Filtration

At arterial end of capillaries is about 20l/day

21

Net Reabsorption

At venous end of capillaries is about 17l/day

22

Starling's Law of the Capillaries

Volume of the fluid and solutes reabsorbed is almost as large as the volume filtered

23

Net Filtration Pressure

Determines whether fluids leave or enter capillaries

24

Net Outward Pressure

10 mm Hg at arterial end

25

Net Inward Pressure

9 mm Hg at venous end

26

Edema

An abnormal increase in interstitial fluid if filtration exceeds reabsorption
Not noticeable until 30% above normal

27

Result of Excess Filtration

Increased blood pressure
Increased permeability of capillaries allows plasma proteins to escape

28

Result of Inadequate Reabsorption

Decreased concentration of plasma proteins lowers blood colloid osmotic pressure
Inadequate synthesis or loss from liver disease, burns, malnutrition, or kidney disease

29

Causes of Edema

Poor venous return
Kidney failure
Histamine makes capillaries more permeable
Obstructed lymphatic drainage

30

Consequences of Edema

Circulatory shock
Tissue necrosis
Pulmonary edema
Cerebral edema

31

Vasoconstriction

Sympathetic stimulation of arterial alpha receptors
Decreases diameter
Increases blood pressure

32

Vasodilation

Sympathetic stimulation of beta receptors
Increases diameter
Promotes blood flow

33

Factors Affecting Circulation

Pressure differences that drive the blood flow
Resistance to flow
Venous return

34

Blood Flow

Amount of blood flowing through a vessel in a given time (ml/min)

35

Perfusion

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

36

Hemodynamics

Physical principles of blood flow based on pressure and resistance

37

Flow Equation

DeltaP/R

38

Resistance Equation

1/r^4

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Blood Flow Equation

r^4

40

Only Possible Immediate Change to Blood Flow

Change in radius