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84 Cards in this Set
- Front
- Back
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Velocity of blood flow through a given vascular segment varies with... |
...the total cross sectional area of that segment |
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As the sum of the cross sectional area increases... |
...velocity of blood flow often decreases |
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The total cross sectional area of vessel segments increases from... |
...aorta to the capillaries |
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The total cross sectional area of vessel segments decreases from... |
...capillaries to the aorta |
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The velocity of blood flow decreases from... |
...aorta to the capillaries |
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The velocity of blood flow increases from... |
...capillaries to the vena cavas |
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What does the low blood velocity in the capillaries maximize? |
The low blood velocity maximizes the amount of time available for transcapillary exchange |
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In consecutive vascular segments the mean blood pressure... |
...decreases |
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Mean blood pressure is highest... |
...in the aorta |
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Mean blood pressure reaches its lowest values in... |
...the vena cavas |
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The greatest decrease in mean blood pressure occurs in... |
...arterioles |
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Despite the greatest drop in mean blood pressure occurs in the arterioles, it does not have the lowest blood pressure because... |
...they are the vessels with the greatest amount of resistance |
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What are present in the walls of the arteries that prevents the the mean blood pressure from dropping to 0? |
Elastic fibers |
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As blood travels through the capillaries... |
...blood pressure slowly decreases |
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Where is the skeletal muscle pump present? |
In medium size veins |
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How does the skeletal muscle pump function? |
When skeletal muscles contract, they shorten up and bulge out, squeezing the vein and increasing the blood pressure, thus moving blood in the veins. |
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When the skeletal muscle pumps blood... |
...the valve closest to the heart opens, while the valve furthest from the heart stays closed. |
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When do varicose veins occur? |
When the valves in veins become stretched and do not close properly |
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At any instant, most blood volume is contained where? |
In the peripheral veins surrounding organs |
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What are the 3 layers of tissue that are found in every blood vessel? |
1. Tunica interna, 2. tunica media, and 3. tunica externa |
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What do veins lack, but arteries have? |
Elastic lamina |
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What causes arteries to be to be resistant and round? |
The internal and external elastic lamina found in the tunica interna and tunica media, respectively. |
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Why don't veins hold a definitive shape? |
Because they lack elastic lamina |
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What kinds of vessels are veins? |
Capacitance (storage) vessels (i.e. they store blood) |
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Where does nutrient and waste exchange between the tissues take place? |
In the capillaries |
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What allows for substances to easily diffuse across a capillary? |
A 1 cell layer thick endothelium |
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What is a basement membrane? |
A thin layer of connective tissue that surrounds a capillary |
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What characterizes a continuous capillary? |
Very small spaces between endothelial cells and a complete basement membrane |
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Where are continuous capillaries found? |
In nervous tissue, skeletal muscle tissue, and adipose tissue |
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What characterizes a fenestrated capillary? |
There are large pores in the wall of the endothelium and a complete basement membrane |
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What do the pores of a fenestrated capillary allow for? |
Increased ease of movement of substances across the membrane |
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Where are fenestrated capillaries found? |
In endocrine glands, the kidneys, and the digestive tract (particularly the small intestine) |
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What characterizes a discontinuous capillary? |
Wide gaps in the endothelium and an incomplete basement membrane |
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Where are discontinuous capillaries found? |
In the liver and the spleen |
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What is the movement of water and dissolved solutes from the blood, across the capillary membrane, to the interstitial space? |
Filtration |
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Where does the greatest amount of filtration take place in the capillary? |
At the arterial end of the capillary |
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What is the movement of water and dissolved solutes from the interstitial space, across the capillary membrane, back into the blood? |
Reabsorption |
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Where does the greatest amount of reabsorption take place in the capillary? |
At the venous end of the capillary |
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What are the two kinds of pressures involved in filtration and reabsorption? |
1. Hydrostatic pressures and 2. osmotic pressures |
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What is hydrostatic pressure defined as? |
Pressure that fluid is exerting on the walls of a vessel |
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What is osmotic pressure defined as? |
The strength by which a solution draws in water across a membrane |
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As the concentration of solution increases... |
...osmotic pressure increases |
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What is Intercapillary Hydrostatic Pressure? |
Blood pressure within the capillary |
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What is intercapillary hydrostatic pressure also known as? |
Blood hydrostatic pressure |
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As blood travels from the arterial end to the venous end, blood pressure... |
...decreases (35 mmHg -> 15 mmHg) |
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What process does intercapillary hydrostatic pressure contribute to? |
Filtration |
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What is Interstitial (fluid) Hydrostatic Pressure? |
Fluid pressure outside of the capillary |
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What process does interstitial (fluid) hydrostatic pressure contribute to? |
Reabsorption |
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In order to have osmotic pressure... |
...solutes must be present (blood and hemolymph) |
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What contributes to plasma osmotic pressure (POP)? |
Proteins within the blood |
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What process does plasma osomtic pressure contribute to? |
Reabsorption |
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Why is interstitial (fluid) osmotic pressure (IOP) less than plasma osmotic pressure (POP)? |
There are not as many large solutes present in the interstitial space |
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What process doe interstitial osmotic pressure contribute to? |
Filtration |
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What is the sum of filtration pressures equal to? |
Intercapillary hydrostatic pressure + Interstitial osmotic pressure |
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What is the sum of reabsorption pressures? |
Plasma osmotic pressure + Interstitial hydrostatic pressure |
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When the sum of filtration pressures > the sum of reabsorption pressures... |
...filtration occurs |
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When the sum of filtration pressures < the sum of reabsorption pressures... |
...reabsorption occurs |
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When the sum of filtration pressures = the sum of reabsorption pressures... |
...there is no net movement |
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What is edema? |
A situation in which bodily tissues contain an excessive amount of hemolymph between cells, causing swelling. |
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What are some causes of edema? |
Systemic hypertension, trauma to the tissue, a decrease in [plasma protein], and poor lymphatic drainage |
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If blood pressure is high enough, there may be more filtration down the length of the capillary, therefore... |
...there is an increase in intercapillary hydrostatic pressure |
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Trauma in the tissue causes the release of many chemicals, one such is histamine. What does histamine do? |
It causes vasodilation and increases vascular permeability. Therefore, proteins move out of blood and into interstitial space, decreasing reabsorption. |
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What happens when there is a decrease in [plasma proteins]? |
There is a decrease in plasma osmotic pressure. Therefore, there is a decrease in reabsorption. |
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What two factors contribute to mean arterial blood pressure? |
Total peripheral resistance and cardiac output |
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What is total peripheral resistance? |
The impedious (resistance) to blood flow |
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What is cardiac output? |
It is equal to stroke volume |
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What are some factors that can influence total peripheral resistance? |
Blood viscosity, length of blood vessels, and vascular diameter |
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An increase in blood viscosity... |
...results in an increase in total peripheral resistance, which increases mean arterial blood pressure |
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A decrease in blood viscosity... |
...results in a decrease in total peripheral resistance, which decreases mean arterial blood pressure |
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What can increase blood viscosity? |
Polycythemia |
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An increase in the length of a blood vessel... |
...results in an increase in total peripheral resistance, which increases mean arterial blood pressure |
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A decrease in the length of a blood vessel... |
...results in a decrease in total peripheral resistance, which decreases mean arterial blood pressure |
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An increase in vascular diameter... |
...results in a decrease in total peripheral resistance, which decreases mean arterial blood pressure |
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A decrease in vascular diameter... |
...results in an increase in total peripheral resistance, which increases mean arterial blood pressure |
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What is the vasomotor center? |
A group of neurons within the medulla oblongata that influences vasodiameter |
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What connects the vasomotor center to blood vessels? |
Sympathetic nerve fibers |
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An increase in the frequency of action potentials... |
...results in vasoconstriction, which increases blood pressure |
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A decrease in the frequency of action potentials... |
...results in vasodilation, which decreases blood pressure |
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What is the function of barroreceptors? |
To monitor tension on vessel walls caused by blood pressure |
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When blood pressure changes, what is the response of the barroreceptors? |
The propagate action potentials up to the vasomotor center telling it to constrict or dilate vessels |
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What is microcirculation? |
Circulation through the capillary bed |
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In order to regulate blood flow through the capillary... |
...the pre-capillary sphincter must relax or contract |
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When the pre-capillary sphincter is relaxed... |
...there is blood flow through the capillary bed |
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When the pre-capillary sphincter is contracted... |
...there is no blood flow through the capillary bed |
