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Dermatology > Structure and function of skin > Flashcards

Structure and function of skin Flashcards

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1
Q

What are the 2 layers of skin?

A

Epidermis - striatified squamous epithelium

Dermis - connective tissue

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2
Q

What is the embryological origin of the epidermis?

A

Ectoderm cells form a single layer periderm

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3
Q

What is the embryological origin of the dermis?

A

Formed from the mesoderm below the endoderm

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4
Q

What is the embryological origin of melanocytes?

A

Pigment producing cells from the neural crest

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5
Q

What are blaschko’s lines?

A

Developmental growth pattern of skin that doesn’t follow vessels, nerves or lymphatics

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6
Q

What is an epidermal nevus?

A

A benign harmatomatous growth following a linear arrangement that follows the lines of Blaschko

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7
Q

What are the appendages of the skin?

A

Nails
Hair
Glands
Mucosae

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8
Q

How is skin able to move so freely?

A

The dermis sits on the sub-cutis which is a rolling sheet of fat alowing movement

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9
Q

What is a sebaceous gland?

A

A small gland in the skin which secretes a lubricating oily matter into the hair follicles to lubricate the skin and hair

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10
Q

What cell type is the epidermis made up of

A

Keratinocytes

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11
Q

How many layers make up the epidermis?

A

4 layers

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12
Q

What other cells are situated within the epidermis?

A

Melanocytes
Langerhans
Merkel

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13
Q

What are the 4 layers of the epiderm?

A

Basal layer (ectoderm)
Prickle cell layer
Granular layer
Keratin layer

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14
Q

What is an apocrine gland?

A

Present in armpits, groin and are around nipples

Scent glands that secrete an odor

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15
Q

What regulates epidermal turnover?

A

Growth factors
Cell death
Hormones

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16
Q

What conditions can arise due to a loss of control in epidermal turnover?

A 
Skin cancer (malignant) 
Psoriasis (benign)
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17
Q

Why is psoriasis red in appearance?

A

Blood vessels move closer to the surface of the skin

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18
Q

How many days does it take a keratinocyte to move from the basal cell layer to the keratin layer?

A

28 days

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19
Q

What are the characteristics of the basal layer?

A

One cell thick
Small cuboidal
Intermediate filaments (keratin)
Highly metabolically active

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20
Q

What are the characteristics of the prickle cell layer?

A

Larger polyhedral cells
Lots of desmosomes
Intermediate filaments connect to desmosomes

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21
Q

What are the characteristics of the granular cell layer?

A 
2/3 layers of flat cells 
Contain large keratohyalin granules 
Odland bodies 
High lipid content
Origin of cornified envelope
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22
Q

What do the keratohyalin granules contain?

A

Filaggrin and involucrin

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23
Q

What is a corneocyte?

A

Lipids and proteins from the burst granular cell

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24
Q

What are the characteristics of the keratin layer?

A

Made up of corneocytes, keratin and filaggrin

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25
Q

What does filaggrin do?

A

Attracts and traps water creating not only a tight waterproof barrier but providing moisture to the skin (without you get eczema)

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26
Q

What is the cornified envelope?

A

Sheath made from protein and lipids

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27
Q

Where are there mucosal membranes?

A

Eyes, mouth, nose, genito-urinary and GI tracts

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28
Q

What are some specialisations in the oral mucosa?

A

Keratanised in hard palate to deal with pressure

Tonge papillae

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29
Q

What are some specalisations in the ocular mucosa?

A

Lacrimal glands
Eye lashes
Sebaceous glands

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30
Q

What is the embryological origin of melanocytes?

A

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

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31
Q

What do melanocytes produce?

A

Pigment producing dendritic cells

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32
Q

What organelles do melanocytes contain?

A

Melanosomes

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33
Q

What is the function of melanosomes?

A

Convert tyrosine to melanin pigment

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34
Q

What are the different types of epidermal cells?

A

Keratinocytes
Melanocytes
Langerhans
Merkel cells

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35
Q

What embryological structure is dermis derived from?

A

Mesoderm

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36
Q

What embryological structure is epidermis derived from?

A

Ectoderm

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37
Q

What is the function of melanin?

A

Absorbs light (natural density filter)

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38
Q

What happens to full melanosomes?

A

They are transferred to adjacent keratinocytes via dendrites to form a protective cap over the nucleus

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39
Q

What is the pathogenesis of vitiiligo?

A

The melanocytes are attacked by T cells

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40
Q

What is the pathogenesis of albinism?

A

Genetic partial loss of pigement production

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41
Q

What is nelson’s syndrome?

A

Melanin stimulating hormone is produced in excess by the pituitary causing hyperpigmentation

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42
Q

What is a malignant melanoma?

A

A tumour of the melanocyte cell line

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43
Q

What embryological structure do langerhans cells arise from?

A

Mesenchymal origin - bone marrow

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44
Q

Where are langerhans cells found in the epidermis?

A

Prickle cell level in the epidermis
Dermis
Lymph nodes

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45
Q

What is the function of langerhans cells?

A

Antigen presenting cells

Pick up antigens in skin and circulate to lymph nodes via lymphatic system

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46
Q

Where are merkel cells found?

A

In the basal layer between keratinocytes and nerve fibers

47
Q

What is the function of merkel cells?

A

Mechanoreceptors essential for light touch sensation

48
Q

Where does the pilosebaceous unit originate from?

A

Grows out of the basal layer with an adjacent sebaceous gland

49
Q

How is hair pigmented?

A

Via melanocytes above the dermal papilla

50
Q

What are the phases of growth for hair?

A 
Anagen = growing
Catagen = involuting
Telogen = resting
51
Q

What are the different types of hair follicles?

A

Lanugo (in utero)
Vellus
Terminal

52
Q

What can cause hirsutism?

A

Polycystic ovaries - too much testosterone

53
Q

What causes alopecia areata?

A

Autoimmune hair loss as hair follicle cells are attacked by T lymphocytes

54
Q

How do nails grow?

A

Stem cells in basal layer but instead of becoming prickle cells they enter a different differentiation program and start to form flat cells that produce keratin

55
Q

Where does nail growth start?

A

Nail matrix

56
Q

What is the dermo-epidermal junction?

A

Inferface between epidermis and dermis

57
Q

What is the function of the dermo-epidermal junction?

A

Support, anchorag, adhesion, growth and differentiation of basal cells
Semi-permable membrane acts as a barrier and filter

58
Q

What makes up the dermo-epidermal junction?

A

Lamina lucida
Lamina densa
Sub-lamina densa zone

59
Q

What is bullous` pemphigoig?

A

An autoimmune skin disease, involving the formation of blisters at the space between the epidermis and dermis skin layers. It is a type II hypersensitivity reaction, with the formation of anti-hemidesmosome antibodies

60
Q

What is epidermolysis bullosa?

A

A group of genetic conditions that result in easy blistering of the skin and mucous membranes. Blisters occur with minor trauma or friction and are painful

61
Q

What cells make up the dermis?

A

Mainly ground substance

Fibroblasts, macrophages, mast cells, langerhans cells, lymphocytes

62
Q

What do fibroblasts produce?

A

Collagen and elastin

63
Q

What is present in ground substance?

A

Glycosaminoglycans

64
Q

Why is there a greater blood supply than needed for the skin?

A

Thermoregulatory processes

65
Q

How do the blood vessles form in the skin?

A

Horizontal plexuses

66
Q

What blood vessels supply the hair follicle?

A

Deep vascular plexus

67
Q

What blood vessels supply the epidermis?

A

Papillary dermis

68
Q

What is angiomia?

A

Overgrowth of blood vessles

Benign

69
Q

What nerves are present in the skin?

A

Somatic sensory (dermatomes):
Free nerve endings
Autonomic nerve supply - blood vessels, nerves and glands

70
Q

What are the special receptors present in the skin?

A

Pacinial corpuscle

Meissners corpuscle

71
Q

What nerve supply do the sebaceous glands have?

A

Autonomic supply

72
Q

What do the pacinal corpsucle detect?

A

Deep pressure - found deep in the dermis

73
Q

What do meissner’s corpscule detect?

A

Touch and vibration

74
Q

What do pacinial corpuscles look like histologically?

A

Onion rings

75
Q

What is a neurofibromatosis?

A

Overgrowth of nerve endings causing multiple tumours

Linked to underlying CNS tumours

76
Q

What are the 3 different types of skin glands?

A

Sebaceous
Apocrine
Eccrine

77
Q

What do sebaceous glands produce?

A

Sebum - squalene, wax esters, TG and FFA

78
Q

What is the function of sebaceous glands?

A

Control moisture loss

Protect from funal infections

79
Q

What is the treatment for acne vulgaris?

A

Topical retinoids
Antibiotics
Roaccutane

80
Q

What and where are the apocrine sweat glands?

A

Axillae and perinuem
Androgen dependent
Produce oily fluid that has an odor after bacterial decomposition

81
Q

What and where are eccrine sweat glands?

A

Whole skin surface

Cool by evaporation, moisten palms

82
Q

What is the nerve supply to eccrine glands?

A

Sympathetic nerve supply

83
Q

What is the function and consequence of failure of the barrier of skin?

A

Fluid loss leads to dehydration
Protein loss leads to hypoalbuminaemia
Infection

84
Q

What is the function and consequence of failure of the thermoregulation of skin?

A

Heat loss leads to hypothermia

85
Q

What is the function and consequence of failure of the immune defence of skin?

A

Spread of infection

86
Q

What is the function and consequence of failure of the metabolic function of skin?

A

Disordered thyroxine metabolism

87
Q

What is the function and consequence of failure of the communication function of skin?

A

Inability to display healthy skin is a stigma

88
Q

What is the function and consequence of failure of the sensation of skin?

A

Pain sensation working lead to pain

89
Q

What is an example of a barrier failure disease?

A

Steroid-sulphatasae deficiency X-linked ichythosis
Not normal lipid distribution in keratin layer
Cumulative irritant hand dermatitis

90
Q

What does the skin aid metabolism of?

A

Vitamin D

Thyroid hormone

91
Q

What is a disease example when the skin’s immune defence is inadequate?

A

Crusted scabies

Tuberculoid leprosy

92
Q

What is a granuloma?

A

Specialized macrophages (anitchov cells) around a core of fibrinoid collaged necrosis. Aschoff cells are interspersed between other cells while lymphocytes make up the outer layer

93
Q

What is eczema herpeticum?

A

Disseminated herpes simpex virus infection

94
Q

What is the definition of stigma?

A

Situation of an individual who is disqualified from full social acceptance

95
Q

What is a ruffini ending?

A

Slowly adapting mechanoreceptor responsible for the sensation of the stretch of your skin, sustained pressure on skin and perception of heat

96
Q

What is a hair follicle?

A

An invagination of the epidermis

97
Q

What is contained within the central medulla?

A

Soft heratin

98
Q

What is contained within the outer cortex?

A

Hard keratin

99
Q

What is the papilla?

A

Contains multiple vascular channels

100
Q

What does the matrix region contain?

A

Keratin producing cells

101
Q

What is the hypochium?

A

Secures the free nail edge

102
Q

What is seen histologically in acute dermatitis?

A

Intra-epidermal vesicles containing white cells and cell debris
Intracellular oedema called spongiosis

103
Q

What is seen histologically in psoriasis?

A

Parakeratosis
Micro-abscesses
Elongated rete pegs

104
Q

What is seen histologically in normal skin from the sole of the foot?

A

Thick keratin layer
Prominent granular layer
Irregular DEJ
Eccrine sweat gland duct

105
Q

What is seen histologically in bullous pemphigoid?

A

Fluid filled bulla with eosinophils

106
Q

What it toxic epidermal necrolysis?

A

Drug induced, keratinocyte death resulting in epidermal detachement at the DEJ

107
Q

What are the 3 stages to wound healing?

A

Inflammation
Proliferation and tissue remodelling
Tissue remodelling

108
Q

What occurs during the inflammation phase of wound healing?

A

Platelets form the initial clot and release inflammatory mediators
Leucocytes debride the wound bed by phagocytosing bacteria and scavenging cellular debris
Inflammation gradually decreases as keratinocyte proliferation and new tissue formation becomes predominant

109
Q

What occurs during the proliferation and tissue remoddeling phase of wound healing?

A

Cells divide to re-epithelialise the wound surface
Granulation tissue formation is stimulated
Fibroblasts lay down matrix and contract the wound (fibroplasia)
Endothelial cells develop into new blood vessels (angiogenesis)
New tissue formed

110
Q

What occurs during the tissue remoddeling phase of wound healing?

A

New tissue converted to mature scar tissue

Fibroblasts lay down collagen to improve strength of scar and restore normal dermal matrix

111
Q

What is primary intention wound healing?

A

Acute wound closed by approximating wound edges

112
Q

What is secondary intention wound healing?

A

An acute wound is left to heal on its own

113
Q

What should you consider in delayed wound healing?

A 
Infection
Poor arterial blood supply
Poor nutrition
Impaired venous return 
Repeated traume 
Systemic disease - diabetes, anaemia

Dermatology (24 decks)

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