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Dermatology > The Structure of the Skin > Flashcards

The Structure of the Skin Flashcards

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Dermatology Board Prep flashcards
1
Q

What kind of epithelium is the epidermis?

A

Stratified cellular epithelium

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2
Q

Describe the foetal development of the skin?

A

Ectoderm cells form single layer periderm, gradual increase in the layers of cells, periderm casts off

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3
Q

What is the dermis formed from?

A

Mesoderm below ectoderm

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4
Q

What is present at 4 weeks foetal skin development?

A

PBD
Periderm
Basal layer
Dermis

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5
Q

What is present at 16 weeks of foetal skin development?

A 
KGPBD
Keratin Layer
Granular Layer
Prickle Cell layer
Basal Layer
Dermis
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6
Q

What is present at 26 weeks foetal skin development?

A

Skin and all appendages

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7
Q

What are Blaschko’s lines?

A

Developmental growth pattern of the skin, not following vessels, nerves or lymphatics

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8
Q

What do blaschko’s lines tell you?

A

Developmental problems of the skins

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9
Q

What are the skin appendages?

A

Nails
Hair
Glands
Mucosae

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10
Q

Describe the demis

A

Connective tissue, less cellular, situated on a rolling sheet of fatty subcutaneous tissue

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11
Q

Where does the skin permanently divide?

A

Epidermal cell layer

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12
Q

Describe the skin of the hand

A

Dynamic- formation of calluses

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13
Q

Describe the skin of the abdomen

A 
Thin epidermis
Lots of dermis
Hair follicles
Glands
Subcutaenous fat
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14
Q

Describe the skin of the scalp

A

Hair follicles and sebaceous glands

Errector pilli muscles

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15
Q

What controls the regulation of epidermal turnover?

A

Growth Factors
Cell Death
Hormones

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16
Q

What conditions show a loss of control of epidermal turnover?

A

Psoriasis

Skin cancer

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17
Q

Why does skin appear white in psoriasis?

A

Thickened keratin does not slough off

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18
Q

Why does skin appear red in psoriasis?

A

Variations in the skin thickness, blood vessels go al the way to the top of the skin

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19
Q

How long does it take for a cell to travel from the basement membrane to the top?

A

28 days

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20
Q

How thick is the basal layer?

A

One cell thick

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21
Q

Describe the cells of the basal layer

A

Small and cuboidal

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22
Q

What is found in abundance in the basal layer?

A

Intermediate filaments (keratin)

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23
Q

What is the function of the basal layer?

A

Highly metabolically active

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24
Q

Describe the cells of the Prickle Cell layer

A

Larger polyhedral cells

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25
Q

What is found in abundance in the prickle cell layer?

A

Desmosomes

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26
Q

What is the function of desmosomes in the prickle cell layer?

A

Connected by intermediate filaments, connect and disconnect to organise cells on their way up

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27
Q

How thick is the granular layer?

A

2-3 layers of flatter cells

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28
Q

What is found in the granular layer?

A
  • Large keratohyalin granules containing structural filaggrin and involucrin proteins
  • Odland bodies (lamellar bodies)
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29
Q

What is the granular layer the origin of?

A

Cornified envelope

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30
Q

What is the important processes of the granular layer?

A

Nuclei are lost, and cells filled to the brim with proteins.
The cells then burst and the granules are released, chopped open, lipids and proteins kit together and form a cornified envolope

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31
Q

What does the keratin layer consist of?

A

Corneocytes; overlapping non-nucleated cell remnants

80% keratin and filaggrin

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32
Q

What is the promise of lamellar granules in the keratin layer?

A

Release lipid

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33
Q

How does the skin maintain its waterproof barrier?

A

Tiny amino acids bind water molecules and retain water in the skin if you dont have filaggrin you get dry skin

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34
Q

What is HPV?

A

Infection of keratinocytes which causes warts

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35
Q

Describe the masticatory mucosa

A

Keratinised to deal with friction/pressure

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36
Q

Describe the lining mucosa

A

non-keratinised

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37
Q

Describe the specialised mucosa

A

tongue papillar- taste

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38
Q

Describe the ocular mucosa

A

lacrimal glands, eye lasher, sebaceous glands

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39
Q

What is 95% of the epidermis?

A

Keratinocytes

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40
Q

Describe the migration of melanocytes

A

Migrate from neural crest to the epidermis in the first 3 months of foetal development

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41
Q

What are melanocytes

A

Pigment producing dendritic cells

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42
Q

What do melanocytes do?

A

convert tyrosine to melanin

  • eumelanin (brown or black)
  • phaeomelanin (red, yellow)
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43
Q

What is the protective function of the melanocytes?

A

Melanosomes form a protective cap over the nucleus, protecting the nuclear DNA in basal cells

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44
Q

What stimulates melanin production?

A

Signal given out by the pineal gland

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45
Q

Describe vitiligo?

A

Melanocytes are attacked by T cells

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46
Q

What happens in albinism?

A

Genetic partial loss of pigment production

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47
Q

What happens in nelsons syndrome?

A

Melanin stimulation hormone is produced in excess by the pituitary

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48
Q

What is malignant melanoma?

A

Tumour of the melanocyte cell line

49
Q

What are langerhans cells?

A

Suprabasal cells of mesenchymal origin.

Found in the prickle cell layer.

50
Q

What is the roll of langerhans cells?

A

Antigen presenting cells

Pick up antigens in skin and circulate to lymph nodes

51
Q

What is a birbeck granule?

A

Specific to langerhans cells, don’t know what they do. Look like maracas

52
Q

What is a Merkel cell?

A

Basal cell between keratinocytes and nerve fibres

53
Q

What is the function of merkel cells?

A

Mechnoreceptors, direct extension of the brain

54
Q

What is a pilosebaceous unit?

A

Epidermal component plus dermal papilla

55
Q

What is found in a pilosebacous unit?

A

Specialised keratins, adjacent sebaceous gland

56
Q

What causes hair pigmentation?

A

Melanocytes above the dermal papilla

57
Q

What happens in acne vulgaris?

A

bacteria in the hair shaft feed on the complex lipids and create small free fatty acids which can diffuse into the skin and act as a pro inflammatory signal, therefore the red boils can be treated with antibiotics to slow bacteria or by starving them by using retinoids which block the formation of sebum (mix of ceramide in sebaceous glands)

58
Q

Describe the embryological phases of hair growth

A 
Anagen= 3-7 years
Catagen = 3-4 weeks
Telogen= 50-100 per day
59
Q

What influences telogen?

A

Changes in hormone profiles, thyroxine and androgens

- Langulo (in utero), villus, terminal

60
Q

Why does hair fall out in chemotherapy?

A

All hair goes into the telogen phase

61
Q

What causes hair growth in PCOS?

A

High male sex hormones cause hair growth in areas with the receptor

62
Q

What is alopecia areata?

A

Hair follicle cells are attacked by T lymphocytes

63
Q

What are nails made of?

A

Specialised keratins

64
Q

What is the nail matrix?

A

Zone of stem cells- exquisitely sensitive / root similar to hair bulb

65
Q

What is the growth rate of nails?

A

0.1mm per day
fingers>toes
summer>winter

66
Q

What is the dermo-epidermal junction?

A

interface between dermis and epidermis

67
Q

What is the function of the dermo-epidermal junction?

A

> Support, anchorage, adhesion, growth and differentiation of basal cells

> Semi-permeable membrane acting as barrier and filter

> helps with diffusion of blood to the epidermis

68
Q

What is bullous pemphigoid?

A

Antibody forms against the junction structures

69
Q

What is seen in epidermolysis bullosa?

A

Hands are fused, knitting deformities

70
Q

What is ground substance?

A

Ground Substance; proteins, hyalouronic acid, glucosaminoglycans

Found in the dermis

71
Q

What cells are found in the dermis?

A

Mainly fibroblasts (make collagen and elastin), macrophages, mast cells, lymphocytes, langerhans cells

72
Q

What other than cells and ground substance is found in the dermis?

A 
Fibres- collagen and elastin
Muscles
Blood vessels
Lymphatics
nerves
73
Q

What is photoaging?

A

Loss of collagen and lack of elastin.

Telomere shortening.

74
Q

What is important in elastin fibre destruction of ageing process?

A

UV light and smoking

75
Q

What is an angioma?

A

Malformation of blood vessels, cause is unclear

76
Q

Describe lymphatic vessels

A

Sub-epidermal meshed netoworks.

Smaller non-contractile vessels-> larger contractile lymphatic trunks

77
Q

What is the function of lymphatic vessels?

A

continuous draining of plasma proteins, extravasated cells and excess interstitial fluid

78
Q

What is the immune function of lymphatic vessels?

A
  • surveillance by circulating lymphocytes and Langerhans cells
  • channelling of micro-organisms / toxins
79
Q

What is the cause of chronic lymphoedema?

A

Obesity causes lack of muscle pump and accumulation of fluid

80
Q

What are the consequences of lymphoedema?

A

Fragile skin can break and any time, causing ulcers

Cellulitis- bacterial infection of the lymphatics

81
Q

What are pacinian receptors?

A

Pressure receptors

82
Q

What are meissners corpuscles?

A

Vibration receptors

83
Q

What do autonomic nerves supple?

A

Blood vessels, nerves and glands

84
Q

What is neurofibromatosis?

A

Overgrowth of nerves

85
Q

What is a blackhead?

A

Open comedone

86
Q

What is a whitehead?

A

Closed comedone

87
Q

What is a sebaceous gland?

A

Holocrine secretion opening into a pillary canal

88
Q

Where are sebaceous glands located?

A

largest on face and chest

89
Q

What are sebaceous glands sensitive to?

A

Hormones

90
Q

What do sebaceous produce?

A

Sebum, Squalene, wax esters, TG and FFA

91
Q

What are the functions of sebaceous glands?

A

Control moisture loss, protection from fungal infection

92
Q

What do apocrine glands develop as?

A

Part of the pilosebaceous unit

93
Q

Where are apocrine glands found?

A

Axillae and perineum

94
Q

What are apocrine glands dependant on?

A

Androgens

95
Q

What do apocrine glands produce?

A

Produce oily fluid odour after bacterial decomposition

96
Q

Where are eccrine glands found?

A

Whole skin surface; palms, soles, and axillae in particular

97
Q

What stimulates eccrine glands?

A

Sympathetic cholinergic nerve supply- mental, thermal and gustatory stimulation

98
Q

What are the functions of eccrine glands?

A

Cooling by evaporation

Moisten palms and soles to aid grip

99
Q

How much to eccrine glands secrete per day?

A

can be >10L per day

100
Q

What is acute skin failure?

A

Toxic epidermal necrolysis

101
Q

What is the most common trigger for TEN?

A

Drugs; paracetamol, echinacea

102
Q

What happens if the skin fails all over the body?

A
  • Pain
  • Infection
  • Water balance (renal failure)
  • thermoregulation
  • protein loss (albumin and keratin) -> water loss into tissues and oedema everywhere
103
Q

What is proven to extend the life of TEN patients?

A

Keeping them warm

104
Q

What is erythroderma?

A

Red skin- covering 80-90% of the body

105
Q

What is the most common causes of erythronderma?

A

T cell lymphoma
Dermatitis
Psoriasis

106
Q

What is the epidermis a physical barrier to?

A

Friction, mechanical trauma

UV radiation

107
Q

What is the epidermis a Chemical barrier to?

A

Irritants, allergens, toxins

108
Q

What is the epidermis a pathogenic barrier to?

A

Bacteria, viruses, fungi

109
Q

What is steroid-sulphatase deficiency X-linked ichthyosis?

A

No normal lipids in the lipid layer

Loss of barrier function

110
Q

What can cause a syndrome like steroid-sulphatase deficiency X-linked ichthyosis?

A

HMG-CoA reductase inhibitors

111
Q

What is dermatitis?

A

Inflammation of the skin

112
Q

What is type 4 hypersensitivity?

A

Contact allergy (remember it doesn’t happen on first exposure)

113
Q

Which wavelength penetrates deepest into skin?

A

Longer the wavelength, deeper the penetration ; radio waves, visible light, UVA, UVB

114
Q

The shorter the wavelength the …. the energy of the …..

A

higher

photon

115
Q

What is the ratio of melanocytes to keratinocytes in the skin?

A

1:10

116
Q

Describe vitamin D metabolism in the skin?

A

Converted in skin at 290 to 320 nm UV in the stratum granulosum and spinous granulousm

117
Q

Describe the thyroid metabolism in the skin

A

Converts T4 -> T3

80% conversation occurs in peripheral tissues; such as the skin

118
Q

Describe eczema herpeticum

A

People with eczema are prone to infections like herpes simplex 1

119
Q

What is scabies?

A

infection of the mites on the skin surface, in crusted scabies there are million son mites; this is caused by an immunosuppression

Dermatology (15 decks)

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