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PM3A > (PM3A) Skin > Flashcards

(PM3A) Skin Flashcards

1
Q

What is the largest organ in the body?

A

The skin

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2
Q

How much of the human body mass does the skin comprise, as a percentage?

A

15%

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3
Q

How much water is lost through the skin everyday?

Give your answer as a volume.

A

Approximately 500mL

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4
Q

Name some key functions of the skin.

A
  • Thermal insulation (from the fatty layer)
  • Cutaneous sensation
  • Metabolic functions
  • Blood reservoir
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5
Q

How much of the body’s overall blood volume does the skin hold?

A

Approximately 5%

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6
Q

What is the integumentary system?

A

(1) A system which protects the body from damage

(2) It includes:
- Skin
- Sweat glands
- Oil glands
- Hairs
- Nails

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7
Q

What are the main layers of the skin?

A

(1) Epidermis
(2) Dermis
(3) Subcutaneous Tissue

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8
Q

What components of the skin comprise the epidermis?

A

(1) Stratum corneum
(2) Granular cell layer
(3) Spinous cell layer
(4) Basal cell layer

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9
Q

What components of the skin comprise the dermis?

A

(1) Sebaceous gland
(2) Erector pili muscle
(3) Sweat gland
(4) Nerves
(5) Hair follicle
(6) Collagen fibres
(7) Elastin fibres

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10
Q

What components of the skin comprise the subcutaneous tissue?

A

(1) Artery
(2) Vein
(3) Adipose tissue (fat)

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11
Q

Where does the stratum corneum thicken?

A

Load bearing areas

i.e. soles/ palms

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12
Q

What differs in the skin in load bearing areas?

A

The stratum corneum thickens

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13
Q

What happens when the stratum corneum is damaged?

A

(1) Damaged skin barrier
(2) Eczema

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14
Q

What happens when the stratum spinosa (spinous cell layer) goes wrong?

A

Spinous cell carcinoma

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15
Q

What happens when the stratum basale (basal cell layer) goes wrong?

A

(1) Hyper-proliferation (psoriasis)

(2) Basal cell carcinoma

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16
Q

How often does skin replace itself?

A

Every 28 days

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17
Q

How long does it take for the stratum basale to form the stratum corneum?

A

Approximately 14 days

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18
Q

What types of cell are within the epidermis?

A

(1) Keratinocytes
(2) Melanocytes
(3) Merkel cells
(4) Langerhan’s cells

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19
Q

What is a keratinocyte?

A

Cell within the epidermis

Produces keratin, a fibrous protein

Gives rise to protective properties

Produced in stratum basale layer

Dead, keratin-filled scale-like structures

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20
Q

Where are keratinocytes produced?

A

In the stratum basale layer

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21
Q

Where is keratin production increased in the body?

A

Areas with regular friction

e.g. palms and feet

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22
Q

What is a melanocyte?

A

Cell within the epidermis

Synthesises melanin - a pigment

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23
Q

What happens to the melanin produced by melanocytes?

A

Taken up by keratinocytes

Forms a pigment shield to protect nucleus from UV radiation

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24
Q

(1) Which cell produces melanin?

(2) Which layer is this in?

A

(1) Melanocyte

(2) Epidermis

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25
Q

What is a Merkel cell?

A

A sensory receptor for touch

Low-abundance cell

Have disc-like sensory nerve endings

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26
Q

Where are Merkel cells found?

A

In the epidermis of the skin

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27
Q

What is a Langerhan’s cell?

A

Dendritic cells which are produced in the bone marrow

Process microbial antigens

Become antigen-presenting cells (APCs)

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28
Q

Where are Langerhan’s cells found?

A

Epidermis of the skin

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29
Q

What is the largest component of the skin?

A

Dermis

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30
Q

What comprises the dermis?

A

Fibrous connective tissue

Richly supplied with nerve fibres, blood vessels, and lymphatic vessels

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31
Q

How many layers comprise the dermis?

A

Two

(1) Papillary
(2) Reticular

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32
Q

What is the papillary layer?

A

Layer within the skin (dermis)

Thin superficial layer

Produces structures like nipples and ridges, e.g. finger prints

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33
Q

Which layer of the skin gives rise to finger prints?

A

Papillary layer of the dermis

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34
Q

What is the reticular layer?

A

Dense + irregular connective tissue

Comprises 80% of the dermis thickness

Provides strength and resilience

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35
Q

Name 5 appendages of the skin.

A

(1) Hair
(2) Hair follicles
(3) Sweat glands
(4) Oil (sebaceous) glands
(5) Nails

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36
Q

How many types of sweat gland are there?

A

Two

(1) Eccrine
(2) Apocrine

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37
Q

Give another name for sudoriferous glands.

A

Sweat glands

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38
Q

What is an eccrine sweat gland?

A

Simple + coiled gland

Regulated by sympathetic autonomic nervous system

Prevents over-heating of the body

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39
Q

What is an apocrine sweat gland

A

Larger than eccrine sweat glands

Empty into hair follicles

Secretions contain sweat + fatty substances + proteins

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40
Q

How is odour produced on the skin?

A

Mixture of sweat, fatty substances, and proteins, with bacteria

Decomposes and produces odour

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41
Q

Describe the secretion pattern of an apocrine sweat gland.

A

Periodic

In bursts

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42
Q

Give another name for an oil gland.

A

Sebaceous gland

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43
Q

Where are oil/ sebaceous glands found?

A

All over the body

NOT palms or soles of feet

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44
Q

What do oil/ sebaceous glands produce?

A

Sebum

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45
Q

(1) What is the role of sebum?

(2) Where is it produced?

A

(1) Soften and lubricate skin and hair + bactericidal properties

(2) Oil/ sebaceous glands

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46
Q

How are oil/ sebaceous glands regulated?

A

Hormonal control

via androgens

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47
Q

What improves ease of administration through a nail?

A

Damage to nail - e.g. psoriasis

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48
Q

Define transdermal, as an administration route.

A

Through the skin

For systemic effect

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49
Q

Define local, as an administration route.

A

Effect close to site of administration

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50
Q

Define topical, as an administration route.

A

Effect on skin

Usually epidermis

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51
Q

What defines penetration in transdermal delivery?

A

Drug enters the skin

Passes through the stratum corneum

52
Q

What defines permeation in transdermal delivery?

A

Drug passing THROUGH the skin

Systemic/ local

53
Q

How can first pass hepatic metabolism be avoided by using the skin as a delivery route?

A

Transdermal delivery avoids first pass hepatic metabolism

54
Q

(1) Does skin affect bioavailability?

(2) Why/ why not?

A

(1) Yes, it can do

(2) Skin is metabolically active

55
Q

What mainly affects transdermal delivery?

A

Stratum corneum

56
Q

What is the shunt route?

A

Permeation of a drug through hair follicles and sweat ducts

57
Q

What is steady state permeation?

A

Permeation predominantly through the stratum corneum

58
Q

How many cells thick is the stratum corneum?

A

Approximately 20 cells thick

59
Q

Which gland are hair follicles mostly associated with?

A

Oil/ sebaceous glands

60
Q

What is an example of a specialised apocrine gland?

A

Milk gland

61
Q

What is the ‘brick and mortar’ model?

A

A model used to describe the structure of keratinocytes in the stratum corneum

62
Q

Define transcellular route.

A

Through the cells

Usually through keratinocytes in the stratum corneum

63
Q

Define intercellular route.

A

Around the cells

Usually around keratinocytes in the stratum corneum

64
Q

What is the most common rate-limiting structure in transdermal delivery?

A

Multiple lipid bilayers

65
Q

How many routes for micro-permeation are there in transdermal delivery?

A

Two

(1) Transcellular
(2) Intercellular

66
Q

What are/ is the micro-permeation route(s)?

A

(1) Transcellular
(2) Intercellular

67
Q

What is the most common lipid in the human stratum corneum?

A

Ceramides

Comprise approximately 41% of all lipids in stratum corneum

68
Q

Give an example of an amphiphilic lipid.

A

Ceramide

Found in stratum corneum

69
Q

How are crystalline areas formed in the stratum corneum?

A

Lipids (such as ceramides) packing closely together

70
Q

(1) What is the role of a penetration enhancer?

(2) How does it achieve this?

A

(1) Increase transdermal delivery + drugs given transdermally

(2) Disrupts the crystalline areas formed by lipids in the stratum corneum

71
Q

Where are crystalline areas found in the skin?

A

Stratum corneum

In the epidermis

72
Q

What is the most common micro-permeation route?

A

Intercellular > Transcellular

73
Q

When are shunt routes most often used in transdermal delivery?

A

For faster penetration (immediate effect)

For drugs which are unable to cross the lipid barrier

74
Q

What is a permeant?

A

The molecule moving through/ into the skin

75
Q

What is flux?

A

The rate of permeant moving through the skin

Measured in joules (J)

76
Q

What is the permeability coefficient?

A

Speed of permeant transport

Kp

77
Q

What does the unit Kp refer to?

A

Permeability coefficient

78
Q

What are the units of Kp?

A

cm/hour

79
Q

What is the diffusion coefficient?

A

Fundamental property of the permeant in a particular membrane

D

80
Q

What is the diffusion coefficient symbol?

A

D

81
Q

What does the symbol D refer to, with regard to skin.

A

Diffusion coefficient

82
Q

What is the unit for diffusion coefficient (D)?

A

cm^2/hour

83
Q

What is responsible for the driving force for diffusion?

A

Concentration gradient

84
Q

How is flux calculated?

A

flux = Kp x concentration

Flux = aD/γh

85
Q

What is the most accurate calculation for finding ‘flux’?

A

Flux = aD/γh

a = thermodynamic activity of the permeant in its vehicle
D = diffusion coefficient
γ = activity in the membrane
h = membrane (stratum corneum) thickness

86
Q

What is a Franz cell used for?

A

Measuring diffusion for a delivery

87
Q

What temperature must a Franz cell be kept at?

A

32ºC

88
Q

Up to how long can a patch be used for to continually deliver a drug?

A

7 days

89
Q

What is a lag phase in transdermal delivery?

A

The initial delay whilst an equilibrium is found across the membrane

90
Q

Describe the order of a patch delivered drug.

A

Zero order

Until 10% of drug activity is lost
OR
>10% is present in receiver solution

91
Q

Describe the gradient of a patch delivered drug.

A

Pseudo-steady state flux

92
Q

What is described as the ‘driver’ for drug delivery?

A

Thermodynamic activity

93
Q

What molecular weight is ideal for transdermal delivery?

A

300-500Da

94
Q

What log P is ideal for transdermal delivery?

A

1-~3.5

95
Q

What aqueous solubility is ideal for transdermal delivery?

A

> 100 mg/mL

96
Q

What is the average patch size?

A

Approximately 10-25cm^2

97
Q

How can estimation of drug flux be beneficial?

A

When deciding if a drug is appropriate for transdermal delivery

98
Q

For which skin type are lotions preferred?

A

Normal-dry

99
Q

For which skin type are creams preferred?

A

Dry

100
Q

For which skin type are gels preferred?

A

Normal-oily

101
Q

What formulations are preferred for a thick, scaly lesion?

A

Fatty, i.e. ointments/ pastes

102
Q

What formulations are preferred for a wet, weeping lesion?

A

Aqueous based, e.g. cream, lotion, gel

103
Q

What is the typical bioavailability for topical products (e.g. gels/ creams)?

A

1-3% bioavailability

104
Q

What is the typical bioavailability for patches (e.g. fentanyl/ buprenorphine)?

A

30-70%

105
Q

What is a suspension?

A

A saturated solution

106
Q

What is occlusion?

A

Closing up/ blocking off

107
Q

What is an enhancer?

A

A drug which reversibly interacts with skin to increase drug flux

108
Q

How does an enhancer achieve its function?

A

Disrupts intercellular lipid structure in stratum corneum

109
Q

What is the Hawthorne effect?

A

Patients modifying their behaviour in response to knowing they are being observed

e.g. falsifying reported adherence

110
Q

How does the permeability of neonatal skin compare to that of adults?

A

It is more permeable

111
Q

What does DIA mean?

A

Drug in adhesive

112
Q

What is at the centre of a liposome?

A

Hydrophilic core

113
Q

What can the hydrophilic core of a liposome be used for?

A

Trapping hydrophilic materials

114
Q

What can the membrane of a liposome be used for?

A

Trapping lipophilic materials

115
Q

What is iontophoresis?

A

A device used to drive a drug molecule into the skin

116
Q

When is iontophoresis used?

A

To drive molecules into the skin

Often used for neutral molecules

117
Q

What is iontophoresis currently approved for in the UK?

A

Hyperhidrosis

118
Q

What are some proposed limitations to the method of iontophoresis?

A

Damage to drug stability

Changes in charge/ pH to drug

119
Q

What is a microneedle used for?

A

To penetrate the stratum corneum, but not the pain receptors

120
Q

What materials can be used to produce a microneedle?

A

(1) Carbon
(2) Silicon
(3) Polymeres

121
Q

Which type of molecule may be able to be delivered using microneedles, as a revolutionary method?

A

Biologics/ biomacromolecules

i.e. insulin, vaccines, antibodies, hormones

122
Q

How can microneedles be used to detect presence of skin conditions?

A

Coating microneedle tips in specific antibodies, to recognise presence of specific antigens

123
Q

What is epidermolysis bullosa?

A

Skin condition causing insufficient anchoring of the epidermis to the dermis

This makes the skin fragile

124
Q

(1) What gene mutation causes epidermolysis bullosa?

(2) Why?

A

(1) Laminin beta-3 (LAMB3)

(2) LAMB3 codes for an epidermal anchoring protein

125
Q

What does epidermolysis bullosa cause?

A

Ulceration/ blistering due to epidermal fragmentation or detachment from the dermis

126
Q

What does epidermolysis bullosa lead to over time?

A

Skin cancers

It is incurable

PM3A (36 decks)

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