Flashcards in Hemodynamics Deck (40)
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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
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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
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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
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Causes of Edema
Poor venous return
Kidney failure
Histamine makes capillaries more permeable
Obstructed lymphatic drainage
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