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59 Cards in this Set
- Front
- Back
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The role of lymphatics
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Regulate Interstitial Volume
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Is the role of the capillaries regulation of BF or exchange?
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Exchange.
Capillaries are a single layer of endothelium. Have no smooth muscle like arterioles or precapillaries. They DO NOT regulate BF. They are a resistor - they slow down blood flow to allow exchange to occur. |
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The opening b/n two endothelial cells
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Intracellular Junctions
Clefts Pores |
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How do small water soluble ions, Glucose, and water get across the capillary barrier?
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They must go through the intracellular junctions/ pores via filtration.
(not lipid soluble). Not really a problem though. they easily cross and equillibrate. |
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How do lipid soluble substances (O2, CO2) get across capillary barriers?
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Easily cross the endothelial cell membranes via diffusion.
Do not have to travel through the intracellular junctions/ pore. |
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How is the Blood brain barrier different in terms of it's capillary barrier?
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LIPID SOLUBLE ONLY
It's intracellular junctions/ pores are so small that even Glucose and water cannot passively filter through. Glucose, and all other water soluble things, must be actively transported across. |
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How do LARGE molecules like albumen, proteins get cross the capillary barrier?
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Too big to pass through the intracellular junctions/ pores.
ENDOCYTOSIS - which is super slow. |
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Do the endothelial cells of capillaries have contractile proteins myosin and actin?
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YES
When they contract they will cause the clefts to get BIGGER. Pulls the endothelial cells apart. |
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How do capillaries become leaky?
Why doesn't this increase blood flow to the vasculature? |
Actin and myosin proteins in the endothelial cells contract to make the intracellular junction bigger. (due to histamine)
(This does not affect the diameter of the capillaries, it only makes their pores bigger). This is why they still don't regulate blood flow. |
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Filtration
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Movement of fluid out of the capillary into the interstitial space.
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Absorption
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Movement of fluid into the capillary from the interstitial space
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Under normal condition, hydrostatic pressure favors
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Filtration into the interstitium.
(Hydrostatic pressure in the vasculature is higher than hydrostatic pressure in the intersitium). |
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Under normal conditions, Colloid osmotic pressure (oncotic) pressure in the vasculature favors..
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Absorption of fluid into the capillaries from the intersititium.
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Hydrostatic pressure
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the pressure exerted by the height of a fluid in a column or by the pressure head on the fluid.
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Hydrostatic pressure in the interstitium favors
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Absorption of fluid back into the capillaries.
(never happens). |
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In most areas of the body, hydrostatic interstitial pressure is....
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NEGATIVE, ie Subatmospheric.
Therefore....it is literally sucking fluid out of the capillaries via filtration. Filtration pressure (Pc - Pi) is LARGE. |
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Will a strong myogenic response (VC of arterioles due to increased HP) counteract increased venous and capillary hydrostatic pressure?
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NO!!
Increased pressure will cause arterioles to VASOCONSTRICT. TO maintain wall tension. WHY? To try and reduce capillary pressure by decreasing flow. BUT, ITS NEVER ENOUGH. Will not work when venous pressure is high. |
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Flow is directly regulated by...
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The arterioles.
Gatekeepers of flow. |
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Venous pressure has a direct effect on...
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CAPILLARY HYDROSTATIC PRESSURE.
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How will increased capillary HYDROSTATIC pressure effect the arterioles?
Why? |
MYOGENIC CHANGES (INTRINSIC)
Increased pressure will cause arterioles to VASOCONSTRICT. TO maintain wall tension. WHY? To try and reduce capillary pressure by decreasing flow. BUT, ITS NEVER ENOUGH. Will not work when venous pressure is high. |
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Oncotic pressure in the _____ is greater than the _________.
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Oncotic pressure in the capillary is greater than the interstitium.
PROMOTES CAPILLARY ABSORPTION. |
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Oncotic force
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The osmotic force drawing water in.
Created by albumen and plasma proteins. |
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What creates oncotic pressure in the plasma?
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Albumens.
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Absorption = _____ - _______.
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Absorption = sigma * [OPc - OPif]
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Oncotic pressure favors
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absorption in the capillaries.
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Oncotic pressure is directly related to ______
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Oncotic pressure is directly related to the ALBUMEN concentration in the blood plasma.
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Albumen is produced in the
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LIVER.
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An osmotic force can be caused by...
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anything that does not filter into the interstitium
Dextran Albumen etc |
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As Fluid is filtered out, capillary hydrostatic pressure
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decreases.
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As fluid is filtered out capillary oncotic pressure
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increases
(less diluted with water). |
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In most capillaries, hydrostatic pressure and oncotic pressure will
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equilibrate....there will be a net fluid movement of ZERO.
This promotes adequate exchange without causing edema or dehydration. (This does NOT happen in the kidneys...filtration is constant). |
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In what organ tissues do Oncotic pressure and hydrostatic pressure in the capillaries NOT EQUILIBRATE?
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The kidneys.
.....Hydrostatic pressure is larger so that you can PEE STUFF OUT. |
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Reflection Coefficient (sigma)
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Tells how well you are maintaining osmolarity of the vasculature.
1 = Perfect (all proteins get reflected off the membrane back into the capillary) 0 = Awful (NO proteins get reflected, they all cross). Describes the fraction of plasma and interstitial oncotic pressures that are transmitted across the capillary wall. If proteins are too large to cross the capillary wall, then there is 100% reflection and sigma is 1.0 (HIGH ONCOTIC PRESSURE) If ALL proteins easily cross, then there is a 0% reflection and sigma is 0. (NO ONCOTIC PRESSURE). |
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Sigma (Reflection Coefficient) impacts the ______ component of fluid flux.
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Sigma (Reflection Coefficient) impacts the absorptive component of fluid flux.
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Net Fluid Movement (Jv)=
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Net fluid movement = Filtration - Absorption
=Kf *(HPc - HPif) -- Sigma*(OPc - OPif) (STARLINGS EQUATION) Positive # - Net Filtration Zero - No net movement Negative # = ABSORPTION KNOW!!!!!!! |
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The higher the sigma, the _____ the oncotic capillary force.
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The higher the sigma, the greater the oncotic capillary force.
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Effective osmole has a sigma of
Ineffective osmole as a sigma of |
1.0.
0 |
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Filtration Coefficient (Kf)
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Index of the capacity of a membrane to transport water. Tells you HOW MUCH DOES WATER FLUX??
Takes into account: ---> # of Pores ---> Pore Size ---> # of Perfused Capillaries (determined by precapillary sphincters). Fluid Flux (Jv) is directly proportional to the filtration coeffiecient. |
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If sigma = 1.0
absorption value... |
will not change
sigma (OPc - OPif) Absorption will equal the difference in oncotic pressure. |
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Overall fluid flux (Jv) is directly proportional to the _______ ________.
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Fluid flux (Jv) is directly proportional to the filtration coefficient (Kf).
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Contractile proteins in capillary endothelial cells will increase ___________ and decrease _______.
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Contractile proteins in capillary endothelial cells will increase Filtration Coefficient (Kf) and decrease Reflection Coefficient (sigma).
(contractile proteins pull the fenestrations apart and make the poors BIGGER). Bigger pores increase filtration coefficient and decrease reflection. |
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Bigger capillary pores will increase ______ and decrease _______.
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Increase Filtration Coefficient (Kf)
Decrease Reflection Coefficient (sigma). |
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Filtration = _____ - ______.
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Filtration = Kf * [HPc - HPif]
Favors filtration into the interstitium. |
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Starling's Equation
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Net fluid movement = Filtration - Absorption
Jv = Kf *(HPc - HPif) -- Sigma*(OPc - OPif) |
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Pores/ Fenestra of Lymphatic System are very
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LARGE
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What can filter into the lymphatic system?
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EVERYTHING.
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What do Lymphatics Do?
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Regulate interstitial Fluid Volume.
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What is the most important factor influencing the rate of Lymph Flow?
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Interstitial Fluid Volume/ Pressure
Direct Relationship with lymph flow. -drive fluid into and through the lymph. -makes sense because Lymph's job is to regulate interstiital fluid volume. |
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How does CHF cause edema?
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Increase blood volume/ venous pressure causes
INCREASED HYDROSTATIC PRESSURE IN THE CAPILLARY BEDS Causes increased filtration. |
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Vasomotion
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When the smooth muscle of lymphatic cells shows SPONTANEOUS CONTRACTIONS that occur at regular intervals.
This also helps drive lymph flow back into the circulaton. |
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What are all the factors that affect Lymph Flow?
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1) Interstitial Fluid Pressure (most important)
2) Vasomotion of lymph smooth muscle 3) Compressive Forces in the tissues |
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Edema
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Accumulation of fluid in the interstitial space.
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How does Liver Disease cause edema?
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Liver can't make albumen. Decreased albumen in the blood.
DECREASED ONCOTIC PRESSURE IN THE CAPILLARY BEDS. Less Absorption. Fluid stays in interstital space. |
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Nephrotic/ Nephritic Syndrome
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Syndrome of loss of albumen in the kidneys.
Causes Edema due to decreased oncotic pressure in the capillary beds. |
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How can an ankle sprain cause edema?
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INCREAESED CAPILLARY PERMEABILITY
Release of autacoids like Histamine Bradykinin Cytokines (TNF alpha) all cause contraction of capillary fenestrae, making them BIGGER and more leaky. |
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Four Causes of Edema
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1) HYDROSTATIC PRESSURE IN THE CAPILLARY
--->Promotes Filtration, which overwhelms oncotic and lymph drainage ----> Caused by 1) Increased Venous Pressure, 2) Decreased Arteriole Resistance (VD) to increase flow, and 3) Increased BV (CHF). 2) DECREASED CAPILLARY ONCOTIC PRESSURE ---->Caused By: Albumen deficiency. Liver Disease. Nephrotic Syndrome. Nephritic Syndrome. (Loss of albumen in the urine.). Malnutrition. 3) CHANGE PERMEABILITY (Kf and Sigma) ----->Make Kf go UP and sigma go DOWN. -----> Increased filtration, less reflection. Lose proteins into interstitial space. -----> Caused by Histamine, Bradykinin, and Cytokines (TNF alpha) that all cause contraction of actin/ myosin proteins on the capillary endothelium, causing increased pore size. -----> Examples: Sprained ankle 4) BLOCKED LYMPHATIC SYSTEM -----> Elephantitis (a worm blocks the lymphatics). Breast removal - remove the lymphatics. |
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What determines Hydrostatic Pressure in the capillaries?
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Increased capillary HP pressure will cause filtration and is .....
1) DIRECTLY RELATED TO FLOW (Q) greater the flow, greater the pressure. ARTERIOLES are the gatekeeper of flow. ----->Arteriole VC - decreased Cap. flow, decreased HP/ filtration. ----> Arteriole VD - increased Cap. flow, increased HP/ filtration. 2) DIRECTLY RELATED TO BLOOD VOLUME ----->Volume and pressure are DIRECTLY related. ------> Increase BV, increase HP, increase Filtration ------> Decrease BV, decrease HP, decrease Filtration 3) DIRECTLY RELATED TO VENOUS PRESSURE ----> Increased VP, Blood BACKS UP. Increased Capillary Pressure--> Increased filtration. (Arterioles will myogenically vasoconstrict here but not enough to reduce capillary pressure/ filtration). ----> Decreased VP, Decreased CP. Decreased Filtration |
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If sigma = 0
Absorption value |
will be zero.
Absorption = sigma* (HPc - HPif). There will be no absorption. This happens in bowman's space. |
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Characteristics of the Lymphatic System
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* LARGE PORES in the terminal lymphatic.
* Little anchoring filaments are on the terminal lymphatic. * Has VALVES in the collecting lymphatics * Larger vessels have SMOOTH MUSCLE: contract to propel the lymph-->"VASOMOTION" *Contents empty into subclavian vein, ie return to the general circulation |
