Obedece a la existencia de factores que operan sobre regiones u órganos perturbando alguna de las fuerzas que componen la ley de starling. Transcript of Edema. Edema. Tipos: Circunscrito Generalizado Definición Incremento clínicamente Alteración de las fuerzas de Starling. – Daño capilar. Edema Agudo Pulmonar No Cardiogénico (EAPnC): también denominado de capilar pulmonar, que ocasionará desequilibrio en las fuerzas de Starling, esto.
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Los botones se encuentran debajo. En la piel de dedos nariz labios y orejas, reg temp. De musc liso de arteriolas, cambia el flujo cap. Entre endotelio cap y liq int. Contribuyen a det la permeabilidad de los caps. Influyen en el crec. Pueen idferenciarse y convertirse en nuevas cel endot o cel musc lisas.
Uniones estrechas membranas celulas se fusionan Otros tienen conductos llamados fenestraciones que atraviesan toda la cel. Clasificacion de acuerdo a permeab al agua.
In some organs, precapillary sphincters a circular band of smooth muscle at entrance to capillary can regulate the number of perfused capillaries. Dif mas imp y pinocitosis menos imp. En el caso de la pared capilar el flujo se puede expresar como: Pero si tras la picadura de una abeja. He named these plasmalemmal vesicles and they are now more commonly referred to as caveolae Fig. The majority of caveolae are found connected to the luminal and abluminal plasma membranes by means of stomata that are generally closed by thin diaphragms.
Little is known about the composition of these diaphragms other than that they contain a unique protein, PV—1, and likely sulfated proteoglycans . Palade postulated that caveolae shuttled across capillary endothelium carrying cargoes of plasma fluid and proteins and this was subsequently demonstrated experimentally with tracers reviewed in . Thus it seemed that the large pores postulated by physiologists were not pores at all but shuttling caveolae and that transport of large molecules across capillaries was anything but passive.
Endothelial permeability is regulated in part by the dynamic opening and closure of cell-cell adherens junctions AJs. Endogenous pathways that increase vascular permeability affect the function and organization of VE-cadherin and other proteins at AJs in diverse ways.
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For instance, several factors, including vascular endothelial growth factor VEGFinduce the tyrosine phosphorylation of VE-cadherin, which accompanies an increase in vascular permeability and leukocyte diapedesis; in addition, the internalization and cleavage of VE-cadherin can cause AJs to be dismantled. Bulk Flow Convection Poros y perforaciones fenestraciones Bulk flow of fluid and electrolytes occurs through “pores” and intercellular clefts d,e,f in preceding figure This mechanism of exchange is particularly important in renal glomerular capillaries; however, it occurs to variable extent in nearly all tissues.
Therefore, changes in pressure driving forces either hydrostatic or osmotic and in the size of “pores” or intercellular clefts will alter exchange. Contraction of capillary endothelial cells by substances such as histamine and bradykinin increases intercellular pore size and greatly augments fluid and electrolyte movement by increasing the capillary filtration constant. There is some evidence that vesicles can fuse together creating pores across endothelial cells c in preceding figure.
Vesicular Transport Vesicular transport is involved in the translocation of macromolecules across capillary endothelium b in preceding figure. Active Transport Some molecules e. Las hendiduras ocupan 0.
Microcirculación y circulación linfática
The movement or flux of a molecule is directly related to its diffusion constant across the barrier, the surface area available for diffusion, and the concentration gradient across the barrier. In the case of O2 diffusing from the exchange vessels into edemaa tissue, increasing the partial pressure of oxygen pO2 in the plasma, or increasing the surface area for exchange i. Starping convectivo de agua arrastre por solvente: Otro mec es por transcitosis. Pero en el caso de prot peq too inflluye la carga.
Las prot cargadas neg el flujo es menor que las neutras. Vesiculaes furezas 50 a dw. Algunas de las macromolec transportadas pueden ser procesadas por la cel. No es dde ferry que carga y descarga. Acute vascular hyperpermeability AVH A rapid increase in vascular permeability occurs when the microvasculature is exposed acutely to any of a number of vascular permeabilizing factors, e. Some of these agents e. Not only is the quantity of extravasated fluid greatly increased above that found in BVP but its composition staeling greatly changed.
As already noted, the fluid passing from the sgarling into normal tissues under basal conditions is a plasma filtrate, i. However, the fluid that extravasates in AVH is rich in plasma proteins, approaching the levels found in plasma, eddma is referred to as an exudate. Among the plasma proteins that extravasate are fibrinogen and various members of the blood clotting cascadMore recently, a structure was discovered in venular endothelium, the vesiculo-vacuolar organelle VVOthat offers an alternative, trans-endothelial cell route for plasma extravasation in response to permeability factors [44—48].
VVOs are grape-like clusters comprised of hundreds of uncoated, cytoplasmic vesicles and vacuoles that together form an organelle that traverses venular endothelial cytoplasm from lumen to albumen Figs.
Y recargar CO2 urea etc. Otra posibilidada en transcitosis. F principal filtrac Pi se aproxima a O. Pero como la viscosidad y el espesor de la pared son constantes k entonces se puede expresar como: La Lp depende de el area superficial y la conductancia. A high value indicates a highly water permeable capillary. A low value indicates a low capillary permeability. The filtration coefficient is the product of these two components: The glomerular capillaries are naturally very leaky as this is necessary for their function; they have a high filtration coefficient.
Capillary filtration coefficient is a critical determinant of fluid flux across the microvascular wall. Changes in capillary filtration coefficient have been stwrling in a number of disease processes. Measurement is typically made by venous occlusion plethysmography using either the upper or lower limb, but a variety of measurement protocols have been used and the importance of the site of measurement remains unclear.
In both studies capillary filtration coefficient was significantly fueraas when measured at the forearm than at the calf group A: Isovolumetric venous pressure the maximum pressure starlimg which there is neither net filtration nor absorption at the microvascular wall was similar in upper and lower limbs in both groups of subjects. We conclude that limb capillary filtration coefficient is dependent on the site of measurement.
Caution is required when comparing fuerrzas recorded at different sites even if corrected for the volume of soft tissue under study. Grupo A Forearm 6. Because both hydrostatic and oncotic forces are normally expressed in units of mmHg.
The net driving force NDF for fluid movement is the net pressure gradient determined by the sum of the individual hydrostatic and oncotic pressures. The permeability is usually referred to as the filtration constant KFand is determined by the physical properties of the barrier i. For example, fenestrated capillaries have a higher KF than continuous capillaries.
Furthermore, substances such as histamine, which are released in response to tissue injury or inflammation, increase KF. The surface area A is related to the length, diameter, and number of capillaries available syarling exchange.
The surface area is dynamic in vascular beds such as skeletal muscle where the number of perfused starllng increase several-fold during exercise. If this is positive, filtration occurs, and if negative, reabsorption occurs.
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The Starling equation reads as follows: By convention, outward force is defined as positive, and inward force is defined as negative. The solution to the equation is known as the net filtration or net fluid movement Jv. If positive, fluid will tend to leave the capillary filtration.
If negative, fluid will tend to enter the capillary absorption. This equation has a number of important physiologic implications, especially when pathologic processes grossly alter one or more of the variables.
In essence the equation says that the net filtration Jv is proportional to the net driving force. The first four variables in the list above are the forces that contribute to the net driving force. Reflection coefficient The reflection coefficient is often thought of as a correction factor. The idea is that the difference in oncotic pressures contributes to the net driving force because most capillaries in the body are fairly impermeable to the large molecular weight proteins.
The term ultrafiltration is usually used to refer to this situation where the large molecules are retained by a semipermeable membrane but water and low molecular weight solutes can pass through the membrane. Many body capillaries do have a small permeability to proteins such as albumins.
This small protein leakage has two important effects: Both these effects decrease the contribution of the oncotic pressure gradient to the net driving force. It can have a value from 0 up to 1.
Glomerular capillaries have a reflection coefficient close to 1 as normally no protein crosses into the glomerular filtrate. In contrast, hepatic sinusoids have a low reflection coefficient as they are quite permeable to protein. This is advantageous because albumin is produced in hepatocytes and can relatively freely pass from these cells into the blood in the sinusoids.
The predominant pathway for albumin and other proteins to enter the circulation is via the lymph. Si persiste vasoc predomina la abs a lo largo del tiempo porque va aumentando Ponc int se va equilibrando Quemaduras o toxinas puede modificar la permeab y porlo tanto el coef de filtrac. Depending upon the organ, the pressure may drop statling the length of the capillary axial pressure gradient by mmHg. The axial gradient favors filtration at the arteriolar end where PC is greatest and reabsorption at the venular end of the capillary where PC is the lowest.
An increase in either arterial or venous pressure will increase capillary pressure; however, a given change in PA is only about one-fifth as effective in changing PC as the same absolute change in PV.
Because venous resistance is relatively low, changes in PV are readily transmitted back to the capillary, and conversely, because arterial resistance is relatively high, changes in PA are poorly transmitted downstream to the eedma. Furthermore, PC is increased by precapillary vasodilation particularly by arteriolar dilation ; precapillary vasoconstriction decreases PC.
Venous constriction increases PC, whereas venous dilation decreases PC. P corriente arriba 2. P corriente abajo 3. Esto ocurre solamente si R es igual, pero no es igual. Pc tiende a seguir P corriente abajo Pv.