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Dermatology > Structure & function > Flashcards

Structure & function Flashcards

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Dermatology Board Prep flashcards
1
Q

What is the largest vital organ in the body?

A

The skin

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2
Q

Systemic disease can manifest on the skin. T/F

A

True

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3
Q

The skin can be divided into two layers. What are these?

A

Epidermis and dermis

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4
Q

What are the embrological origins of the epidermis, dermis and melanocytes?

A

Epidermis - ectoderm. Dermis - mesoderm. Melanocytes - migrate from neural crest.

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5
Q

How developed is the skin during gastrulation? (7-10 days)

A

There is cellular organisation into the germ layers

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6
Q

How long does complete skin development take?

A

26 weeks gestation

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7
Q

Describe the embryological development of the skin

A
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8
Q

What name is given to the patten in which skin develops? What structures do they follow?

A

Blaschko’s lines. They don’t follow any structures

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9
Q

What are appendages? (in relation to the skin)

A

Nails, hair, glands, mucosae

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10
Q

What are the epidermal cell layers (from top to bottom)?

A

Keratin, granular, prickle cell and basal

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11
Q

From which epidermal cell layer do new cells differentiate?

A

Basal layer

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12
Q

There are marked differences between the epithelium at different sites of the body (e.g between the sole of the foot and the armpit). T/F

A

True

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13
Q

Epithelial cell turnover is regulated by which factors?

A

Growth factors, hormones and cell death

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14
Q

How long does it take for a keratinocyte to migrate from the basement membrane to the keratin layer?

A

28

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15
Q

Describe the features of the basal layer

A

Small cuboidal cells forming a single layer. Possesses lots of intermediate filamints of keratin. The most metabolically active layer of the epidermis

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16
Q

Describe the features of the prickle cell layer

A

Large polyhedral cells connected by many desmosomes and possessing lots of intermediate filaments.

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17
Q

What happens when epithelial desmosomes are burst (intraepithelial blistering)? How might this occur?

A

Water escapes giving the skin a wet and glistening appearance. This may happen during inflammation where there is increased water.

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18
Q

Describe the features of the granular layer

A

Two/three layers of flatter cells possessing odland (lamellar) bodies and keratohyalin granules (containing filggrin & involucrin). High lipid content. One of it’s functions is to remove the nuclei from keratinocytes

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19
Q

What do we call keratinocytes which have lost their nuclei?

A

Corneocytes

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20
Q

Describe the features of the keratin layer

A

Mostly an insoluble cornified envelope consisting of mostly ketain and filaggrin. Also possesses lamellar granules which release lipid. Acts as a waterproof barrier

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21
Q

What virus can cause warts? Which does the virus do to the cells?

A

Human papilloma virus. It causes over proliferation of keratinocytes.

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22
Q

Are mucosal surfaces typically affected by skin disease?

A

They can be. Most commonly seen in severe skin disease

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23
Q

What is the most common epidermal cell?

A

Keratinocytes

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24
Q

What are melanocytes

A

Pigment producing dendritic cells

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25
Q

Where are melanocytes found?

A

Basally & suprabasally

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26
Q

What is the function of melanocytes? Describe this process

A

Converts tyrosine to melanin. The melanin is transferred from melanocytes to keratinocytes via dendrites. The melanin forms a protective “cap” over the DNA of the cells, to protect from UV radiation.

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27
Q

From which organelle do melanocytes originate?

A

golgi apparatus

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28
Q

What is vitiligo?

A

an autoimmune disease which causes the depigmentation of areas of skin (due to loss of melanocytes)

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29
Q

What is albinism?

A

a genetic condition which results in loss of pigmentation in the skin

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30
Q

What is Nelson’s syndrome?

A

hyperpigmentation of the skin due to an overactive thyroid producing more melanin stimulating hormone

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31
Q

Where do Langerhans cells originate?

A

bone marrow (like many other immune cells)

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32
Q

Where are Langerhan’s cells found?

A

suprabasally in the epidermis, dermis, lymph nodes

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33
Q

What is the function of langerhan’s cells?

A

They are immune cells involved in antigen presentation

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34
Q

What special feature do Langerhan’s cells possess?

A

Birbeck granules/racket organelles

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35
Q

What is the function of Merkel cells?

A

Mechanoreceptors

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36
Q

Where are Merkel cells found?

A

Basally - between keratinocytes and nerve fibres

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37
Q

Merkel cell tumours are usuallu benign.T/F

A

False - they are rare malignant tumours with an extremely high mortality rate (caused by a virus)

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38
Q

Hair follicles are also known as what?

A

Pilosebacous units

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39
Q

What cells control our hair pigmentation?

A

Melanocytes (only those located above the dermal papilla)

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40
Q

List the components of a pilosebacious unit

A

Hair shaft, medulla, cortex, external and internal root sheath, papilla of hair follicle, matrix, arrector pilli muscle, sebaceous gland

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41
Q

What is hair composed of?

A

Specialised keratins

42
Q

List the phases of hair growth and what occurs during each phase.

A

Anagen (growing), Catagen (involuting) and Telogen (resting)

43
Q

What are the different types of hair?

A

Lanugo (in utero), vellus (fine, downy skin hair) and terminal (pubic, underarm, head hair)

44
Q

What is the time scale for each of the phases of hair growth?

A

Anagen - several years

Catagen - 3/4 weeks

Telogen - everyday shedding occurs (50-100 hairs)

45
Q

When may hair loss in humans be asynchronus? How will the hair appear when it first grows back?

A

Under times of huge stress or hormonal changes (e.g pregnancy). It will first appear white/grey until pigment is added

46
Q

What is virilisation? What causes this?

A

The apperance of typically male features (e.g facial hair) on a female. Excess androgen.

47
Q

What is alopecia areata?

A

Autoimmune hair loss

48
Q

Nails are more biochemically similar to hair than to bone. T/F

A

True

49
Q

What are nails made of?

A

Specialised keratins

50
Q

Name some parts of the nail

A

Lunula, cuticle, nail plate, hyponychium, nail bed, nail matrix

51
Q

What are the two main causes of a nail which appears crumbly?

A

Fungal infection

Small repeated traumas & so poor differentiation over a period of time (e.g handball players)

52
Q

Damage to the stem cells in the nail matrix may cause unusual nail growth permenantly. T/F

A

True

53
Q

What are some of the functions of the dermo-epidermal junction?

A

Support, anchorage, adhesion, growth & differentiation of epidermal cells

54
Q

What type of barrier is the dermo-epidermal junction?

A

Semi-permeable membrane

55
Q

Name the two sections that the dermo-epidermal junction is divided into

A

lamina lucida & lamina densa

56
Q

Define (and give an example of ) inherited and autoimmune conditions of the dermo-epidermal junction

A

Inherited - mutations in the proteins of the dermo-epidermal junction resulting in skin fragility (e.g epidermolysis bullosa)

Autoimmune - antibodies formed against proteins in the dermo-epidermal junction (e.g dermatitis herpetiformis)

57
Q

What are the symptoms of epidermolysis bullosa? What may occur in severe conditions?

A

Skin blistering, tearing, inability to be touched or held due to skin fragility. Epidermolysis bullosa dystropica of the hands.

58
Q

What is bullous pemphigoid? Which test may diagnose it?

A

An autoimmune blistering disorder due to defects of skin tethering (i.e problems within the dermo-epidermal junction). Immunofluorescent histology

59
Q

List the components of the dermis

A

Cells (fibroblasts, macrophages, mast cells, langerhan’s cells), fibres (collagen, elastin), ground substance, blood vessels, lymphatics & nerves

60
Q

What is the function of fibroblasts in the dermis?

A

Secretion of collagen

61
Q

What is ground substance composed of?

A

Mucopolysaccharides, glycosaminoglycans

62
Q

What are the two main extrinsic factors which contribute to photo aging? What happens to give the apperance of aged skin?

A

UV light & smoking. Less well formed collagen fibres, less elastin (solaris elastosis) and less nutrients being directed to the dermis

63
Q

What is the function of horizontal plexuses?

A

They connect deep and superficial vessels

64
Q

What is angioma? What is a haemangioma?

A

They are basically interchangeable terms used to describe a benign tumour of the blood vessels

65
Q

What is another name for an angioma? What are the main problems with angiomas?

A

Port wine stains. They may sometimes bleed or look unsightly

66
Q

What is the characteristic histology of an angioma?

A

dilated vascular spaces

67
Q

What things may cause chronic lymphoedema?

A

Reccurent infection causing permenant damage to the lymphatics

Lymph node blockage

68
Q

What are the functions of pacinian and meissners corpuscles respectively?

A

Pacinian - pressure

Meissner - vibration

69
Q

Give an example of a disease which affects the nerve fibres in the skin

A

Neurofibromatosis

70
Q

What is hyperhydrosis?

A

Abnormal excess sweating

71
Q

Where are sebaceous glands found?

A

Mostly on the skin, scalp and chest but found all over the body apart from the soles of the feet & palms of the hands

72
Q

What are the main functions of sebaceous glands? When do they become active?

A

Prevention of moisture loss/moisturation of the skin & protection against bacterial/fungal infections. Post-puberty

73
Q

What do sebaceous glands produce? What is this composed of?

A

Sebum - squalene, wax esters, triglycerides & free fatty acids

74
Q

What causes/contributes to acne? When is it usually triggered?

A

increased sebum, blocked sebaceous ducts & bacteria. During puberty

75
Q

Where are apocrine sweat glands found?

A

Armpits and perineum

76
Q

What is the function of apocrine sweat glands?

A

Androgen dependent scent glands

77
Q

Where are eccrine sweat glands found?

A

The whole skin surface but particularly the palms and soles and armpits

78
Q

What stimulates eccrine sweat glands?

A

Mental state, temperature and gustatory sensations

79
Q

What are the functions of eccrine sweat glands?

A

cooling by evaporation and moistens palms & soles to increase grip

80
Q

What is erythroderma?

A

Erythema on over 80% of the body

81
Q

What is toxic epidermal necrolysis?

A

A severe skin reaction, usually triggered by drugs, which causes the epidermis to lift from the dermis

82
Q

What are the conseqeunces of skin failure and how does this occur?

A

Dehydration - fluid loss

Hypoalbuminaemia - protein loss

Infection - loss of barrier protection

Hypothermia - heat loss

Spread of infection - loss of immune defense

Disordered thyroxine metabolism

Stigma - psychological impact

Pain - sensation not lost with skin

83
Q

What does the skin barrier protect against?

A

Trauma, UV radiation, irritants, toxins, allergens & pathogens

84
Q

What is icthyosis? Give an example of what causes it

A

Scaly skin due to abnormal keratin layer. Steroid-sulphatase deficiency/X-linked

85
Q

What is the typical pattern of irritant hand dermatitis caused by hand washing?

A

Most severe on finger tips or in between fingers

86
Q

The skin is involved in thyroid hormone AND vitamin D metabolism. T/F

A

True

87
Q

How is vitamin D stored in the liver and kidney respectively?

A

Liver: hydroxycholecalciferol

Kidney: 1,25 - dihydroxycholecalciferol

88
Q

Where do humans get vitamin D from?

A

Oily food in the diet & UV light

89
Q

What proportion of thyroid hormone metabolism occurs in the thyroid gland? Where does the rest occur? What is it that gets metabolised?

A

20%. Peripheral tissues e.g the skin. Thyroxine (T4) is converted to Triiodothryonine (T3)

90
Q

What receptors in the skin allow it to detect body temperature? What are the changes that modify body temperature?

A

Thermoreceptors.

Blood vessel constriction/relaxation, behavioural, sweating, hair arrector muscles, shivering, etc

91
Q

How is tissue lost due to frostbite?

A

Strong vasoconstriction cuts off the blood supply to tissue causing it to die

92
Q

Give an example of a non-specific immune response involving the skin

A

Scratching to remove a parasite

93
Q

Crusted scabies only occur in patients with weakened immune systems and represent a strong immune response to few mites. T/F

A

False - there will be many mites in a patient with crusted scabies (and no itch!)

94
Q

What is Hansen’s disease?

A

Leprosy (i.e a chronic granulomatous infection)

95
Q

What is eczema herpiticum?

A

Eczema infected with herpes simplex virus

96
Q

What are the communication functions of the skin?

A

Important visually, for giving off scent and in sociosexual behaviour

97
Q

Acne vulgaris is associated with unemployment. T/F

A

True

98
Q

What are the different types of nerve receptors within the skin?

A
99
Q

What are neuropathic ulcers? Give two examples of diseases which might lead to the formation of these ulcers

A

Ulcers that form due to a loss of nerve sensation preventing the patient from feeling/noticing ulceration of the skin. Diabetes and leprosy

100
Q
A

Dermatology (26 decks)

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