CAPILLARIES 1 : SOLUTE EXCHANGE Flashcards
What is the basic structure of a cell membrane
-2 layers of amphipathic phospholipids
-phosphate head is polar
-fatty acid tail non polar
-forms i layers In solution
Roles of cells membrane
-provides support and protection
-cell to cell recognition
-controls what enters and leave the cell
-regulates cell function
Describe passive transport
- movement of molecules down a gradient
-doesn’t require energy
-simple or facilitated
Describe active transport
-movement of molecules against a gradient
-requires ATP
Describe the endothelium
- blood vessel with the smallest diameter
-one cell thick
-semi permeable
What type of transport is solute exchange
Passive diffusion
Properties of passive diffusion
-do not require energy
-molecules move randomly
-move from area of high concentration to low
-good transport of lipid soluble solutes over short distances
Properties of the solute
-concentration gradient
-size of solute
-lipid solubility of solute
Properties of the membrane affecting transport
-membrane thickness/ composition
-aqueous pores in membrane
-carrier mediated transport
-active transport mechanisms
Describe continuous capillaries
-moderate permeability
-tight gaps between neighbouring cells
-continuous basement membrane
-blood brain Barrier
Found in muscles , skin , fat , connective tissue
Describe fenestrated capillaries
-High water permeability
-fenestration structures
-modest disruption tissues
-high water turnover
Describe discontinuous capillaries
-very large fenestration structures
-disrupted membrane
-when movement in cells is needed
Structural Properties of capillaries
-intercellular cleft 10-20nm wide
-caveolae & vesicles
-glycocalyx
What is glycocalyx
-structural property of capillaries
-covers endothelium
-negatively charged material
-blocks solute permeation
-blocks access to transport mechanisms
- highly regulated
What is permeability
Rate of solute transfer by diffusion across unit area of membrane per uni concentration difference
How does a porous membrane interfere with the diffusion of a lipid insoluble solute
-reduction in area for diffusion
-increased path length through membrane
-restricted diffusion pore produces hydrostatic issues
What is the glucose concentration in plasma
1g per litre
Total volume of plasma filtrate flowing to tissues per day
8 litres
Maximum filtration of glucose
8 g per day
Glucose consumption of a human adult
400g per day
What percentage of filtration transport only accounts for glucose transport
2%
What controls diffusion rate
-recruitment of capillaries ( dilation of arterioles leads to increased number of capillaries per fused which increases total surface area for diffusion )
-blood flow ( more blood more solutes )
-fall in interstitial concentration ( during metabolism more solute is used up therefore increasing concentration difference)
