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24 Cards in this Set
- Front
- Back
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Fick's Law of Diffusion
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rate of diffusion= (D*A*deltaC)/ deltax
-D= diffusion coefficient - A= area - delta C= difference in concentration of ICF and ECF - delta x= distance |
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example of Fick's
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CO2 diffuses 20x better than O2 because of a higher diffusion coefficient:
hypoxia is more likely than hypercapnia (excess CO2) |
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permeability of membranes
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1. depends on size
2. almost impermeable to proteins: myoglobin and albumin |
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permeability of different organs
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1. lungs: increased permeability, interstitial [protein] almost the same as capillary blood
2. liver: very high permeability, high rate of synthesis and decomposition of proteins 3. brain: very low permeability: protection from toxic substances |
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filtration and resorption in capillary bed
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- permeable to H2O and solutes
- impermeable to proteins and cells - BP (and hydrostatic P) filters fluid and solutes to interstitium - oncotic P: created by blood proteins, causes resorption of fluid and solutes from interstitium into blood |
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P total in capillary bed
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= Pblood- Pinterst
= (Pblood- Poncotic blood)- (Phydros- Poncotic interst) - stronger force determines the direction and rate of transport: normally blood P is higher than interstitial side |
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P conditions in capillary bed
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- arterial side: high
- venous side: low -arterial and venous: constant oncotic - interstitial: very low hydrostatic and oncotic P, except in lung |
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interstitial P and fluid exchange
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- usually very low P
- little effect on fluid exchange/ net pressure, when compared to capillary P |
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net P at arterial side of capillary bed
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net filtration (into inters):
1. hydrostatic: cap 35, inters 0 2. oncotic: cap 26, inters 1 net P: (35-0)-(26-1)= 10 |
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net P at venous side of capillary bed
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net resorption (into blood):
1. hydrostatic: cap 16, inters 0 2. oncotic: cap 26, inters 1 net P: (16-0)- (26-1)= -9 |
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Total net P in systemic tissues
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-capillary P: hydro 18, oncotic 25
- inters P: hydro -7, oncotic 1 Starling: net P= hydro- oncotic = (18--7)- (25-1)= 1 - favors filtration: from capillaries into interstitium |
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Total net P in pulmonary tissues
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-capillary: hydro 12, onc 25
-inters: hydro -5, oncotic 18 Starling: net P= hydro- oncotic = (12--5)-(25-18)= 10 --> 10x higher than other tissues -high permeability to plasma proteins - ECF [protein] almost as high as in capillary blood |
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net pressure of lymphatic system
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causes continuous flow of water, solutes and proteins from capillaries into the interstitium
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accumulation in lymphatic system
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accumulation (water, solutes, and proteins) in the interstitium would be lethal within 24 hours
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lymphatic system
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maintains homeostasis by removing excess water, solutes, and proteins from the interstitium
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return of lymph
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1. from catchment area back to the RA, via thoracic duct or right lymphatic duct, to join the venous blood
2. through lymphatic vessels to the RV (subclavian v --> vena cava) |
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internal lymph nodes
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1. lymphocentrum lumbale
2. iliosacrale 3. inguinale profundum ( pigs) |
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collection of lymph
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- terminal end of lymph capillaries: cells not connected, overlapping
- overlapping cells act as valves between interstitium and lymph duct - terminals collect excessive fluid from interstitium: lymph - valves in subsequent vessels direct lymph towards heart |
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lymphatic vessels
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- edges of endothelial cells overlap:
1. valve effect 2. passage of high MW substances possible - valves prevent reverse flow and limit hydrostatic P |
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intrinsic lymphatic pumping
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-fluid strectches lymph vessels:
contraction of smooth m (P up to 50) |
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extrinsic lymphatic pump
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by compression:
1. contraction of mm 2. movements of body parts 3. arterial pulsations 4. compression of tissues from outside |
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lymphatic capillary pump
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-movements of surrounding tissues enlarge and fill capillaries
- capillary valves prevent reserve flow and direct lymph |
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factors which increased hydrostatic P in ECF
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1. increased capillary BP
2. decreased capillary oncotic P 3. increased capillary permeability 4. increased interstitial protein |
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purpose of lymph flow
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- high interstitial fluid:
1. increases the distance from capillaries to cells and causes transport problems 2. lymph flow increases steeply -transport capacity of lymph vessels is limited: when P rises to + values beyond 1 the lymph flow cannot increase/ remains at max |
