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Pharmaceutics > Biological Barriers > Flashcards

Biological Barriers Flashcards

1
Q

Hepatic Portal Vein Outline

A

All systemic blood vessels drain into hepatic portal vein for detoxification

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2
Q

Organ Usually targeted for absorption

A

Small intestines

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3
Q

Simple Def

A

Single layer of cells (absorption)

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4
Q

Stratified Def

A

Multiple layers of cells (protection)

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5
Q

Simple Squamous Def

A

Single, flattened, interlocking cells. Blood vessel lining and aveoli. Excellent permiability

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6
Q

Simple Columnar Def

A

Single, rectangular cells. Stomach, small intestine and upper respitory. Very good permiability

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7
Q

Stratified Squamous, non-keratinised

A

Multiple layers, flattened, nucleated cells. Buccal, sublingual, esophagus, vagina and cornea. Intermediate to very good permiability

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8
Q

Stratified Squamous Keratinised

A

Multi-layer, flattened, non-nucleated cells. Gums and skin. Poor permiability

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9
Q

Skin/Muscle/Adipose/Lung/ Intestinal Capillary Outline

A

continuous (don’t really have pores) cells with tight junctions ), 5nm in diameter

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10
Q

Hepatic Capillary Outline

A

Sinusoidal (large canals in tissue), open fenestrate (large gaps). 180nm wide

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11
Q

Connective Tissue Outline

A

Fenestrated (pores in vessels). 6-15 nm

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12
Q

Retinal/ Spinal Chord/ Enteric NS

A

Continuos, tight junctions (tightest). <1nm

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13
Q

Which are more permeable endothelia or epithelia

A

endothelia. Blood vessel walls begin with epithelial (extrinsic, less gaps) and move to endothelial (intrinsic, more gaps) cells. Permiability increases as you move away from lumen

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14
Q

Extrinsic Barrier of Intestinal Epithelium Outline

A

Mucus (gel hydrocarbon) produced by goblet cells. Traps gel of opposite charge and viscosity slows particle movement. Requires molecules to be lipophilic

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15
Q

What reduces mucus layers

A

Surfactant. Can result in opportunistic infection. Evaluate

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16
Q

Keratinised Def

A

Dense layer of protein. Reduces permiability

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17
Q

What regions of body have leakiest vessels

A

further away from skin the leakier the vessels. this prevents contamination of blood

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18
Q

Continuous Def

A

No gaps between cells. Low permiability

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19
Q

Fenestrated Def

A

Moderate gaps between cells. Moderate permiability

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20
Q

Sinusoidal Def

A

Large canal gaps between cells. Best permiability

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21
Q

Ways for substances to permiate cell barriers

A

Paracellular and Transcellular. Passive, active, endocytosis and carrier mediated. Moves from apical to basolateral side

22
Q

Paracellular Movement Def

A

Diffusion of substances between gaps in cells

23
Q

Transcellular Movement Def

A

Passive or active transport. Substances move through cell independently or with the help of proteins (efflux carriers and unflux carriers)

24
Q

Where can drugs act in relation to cells

A

They might act outside cell (hydrophilic) or inside cells (lipophilic)

25
Q

Better Transcellular diffusion is associated with

A

Higher lipophilicity, lower molecular weight (particle size) and no charge

26
Q

Association between dproperties of barrier (k) and diffusion coefficent

A

The higher the diffusion constant = the higher the permiability of barrier

27
Q

Relationship between properties of membrane and surface area exposed

A

More surface area = higher permiability of barrier

28
Q

4 types of endocytosis

A

phagocytosis, receptor mediated cytosis, phingocytosis (vesicles engulf small particles from interstitial fluid)

29
Q

Rate of dissolution association with dissolution rate constant (k)

A

Faster dissolution = higher constant

30
Q

Rate of dissolution association with surface area

A

Higher surface area = faster dissolution rate

31
Q

Relationship between Staurated solubility of drug (Cs) and dissolution rate

A

Higher saturated solubility = faster dissolution

32
Q

Relationhip between conc of drug already dissolved in solvent at given time (C) and rate of solution

A

Higher amount of drug dissolved = slower dissolution

33
Q

Molecular composition of epethilial barrier

A

Polar head (choline/phosphate/glycerol) and 2 non-polar tail (fatty acids)

34
Q

Dissolution rate constant association with Diffusivity

A

Higher dissusivity = higher dissolution rate constant

35
Q

association between dissolution rate constant and thickness of surrounding liquid (h)

A

Thicker liquid = smaller constant

36
Q

Association between dissolution rate constant and volume of solvent

A

The higher the solvent volume = the lower the constant

37
Q

Barriers and Log P

A

Different barriers have different log Ps. Eg rectal 0-5 and cornea 1-2

38
Q

Drug Transporters Outline

A

Can help facilitate active and passive transport. Apical and basolateral membranes have different transporters (ensure substances move in 1 direction). Transporters can be proteins on membrane and vesicles. Selective for what substrate they’re using

39
Q

Uniports Def

A

Carriers move substrate in 1 direction

40
Q

Symport Def

A

Carries 2 substances in 1 direction

41
Q

Antiport Def

A

Carries 2 substances in opposite directions

42
Q

Pept 1 Transporter Outline

A

Natural substrate: peptide. Drugs: ace inhibitor, lactam antibiotics and bestastin

43
Q

DMT-1 Outline

A

Substrate: Fe^2+ (heme iron)

44
Q

CNT 1 Transporter Outline

A

Natural substrate: amino acids. Drugs: zidovuldine and gemcitabine

45
Q

How does Fe3+ cross membrane and stay inside cell

A

Reduced to Fe2+. Taken up by DMT1

46
Q

Pinocytosis Def

A

Engulfment of molecules in extracellular fluid by membrane vesicles. Cells involves internalization despite metabolism needs of cell. Fat soulble vitamine (A, D, E and K)

47
Q

Receptor mediated endocytosis Outline

A

Receptors are on cell surface, receptors break off from membranes to form coated vesicles. Confirmational changes in membrane initiates process. Coating is lost and delivered to cell compartments. Receptors return to membrane. Eg insulin

48
Q

Tight Junction Def

A

Multiprotein complexes adjoin adjacent cells forming seals. Maintains cell polarity and barrier functions. Modulated by chemical signalling and/or exogenous ligands

49
Q

4 Protein Classes

A

Tight Junction (eg claudin), Tight junction associated proteins (eg ZO-1), scaffolding proteins and signalling proteins

50
Q

Relationship between perfusion, flow rate and distribution

A

High perfusion = high flow = fast distribution times = greater extent of absorption

51
Q

Efflux Pumps Def

A

Membrane transport proteins. Actively pump drugs out of cell in direction they’re absorbed, against conc gradient. Maintains low conc in cells

52
Q

Multidrug ressistance Transporters Outline

A

Pump structurally diverse drugs out of cell in ATP dependent fashion. Mainly cationic and lipophilic drugs (but substartes of all types). Expression increases at villi tips

Pharmaceutics (13 decks)

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