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Dermatology > Structure and function of the skin > Flashcards

Structure and function of the skin Flashcards

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1
Q

What is the epidermis made of?

A

Stratified squamous epithelium

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2
Q

What is the dermis made of?

A

Connective tissue

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3
Q

Where is the epidermis derived from embryologically?

A

Ectoderm

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4
Q

Where is the dermis derived from embryologically?

A

Mesoderm

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5
Q

Where do melanocytes migrate from embryologically?

A

Neural crest

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6
Q

What are Blaschko’s lines?

A

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

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7
Q

What is 95% of the epidermis made of?

A

Keratinocytes

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8
Q

What are the 4 layers of the epidermis?

A

Basal layer, prickle cell layer, granular layer, keratin layer

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9
Q

How long does it take keratinocytes to travel from the basement membrane to the top layer of skin?

A

28 days

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10
Q

How thick is the basal layer? What cell type is it?

A

1-3 cells thick, small cuboidal

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11
Q

Describe the prickle cell (spinous) layer

A

Larger than basal cells, polyhedral cells, composed of keratinocytes, lots of desmosomes, intermediate filaments connect to desmosomes

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12
Q

Describe the granular layer

A

Composed of flattened cells containing the darkly staining keratohyalin granules, Odland bodies, high lipid content, cell nuclei lost

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13
Q

Describe the keratin layer (horny layer/ stratum corneum)

A

Corneocytes (flattened dead enucleate keratinocytes), tight waterproof barrier, lamellar granules release lipid

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14
Q

What is Nelson’s syndrome?

A

Excess α-MSH production in the pituitary, person appears darker than they should

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15
Q

Where do Langerhans cells orginate from?

A

Mesenchyme, bone marrow

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16
Q

Where are Langerhans cells found?

A

Prickle cell layer of epidermis, dermis, lymph nodes

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17
Q

What type of cell is the Langerhan cell? What MHC type do they have?

A 
Antigen presenting cell (presents to T cells), dendritic cell (like the melanocyte)
MHC class II antigens
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18
Q

What are Merkel cells and where are they found?

A

Non-dendritic cells, lying in or near the basal layer and are the same size as keratinocytes
Mechanoreceptors
Found in normal epidermis between keratinocytes & nerve fibres
Sparse desmosomes connect these cells to neighbouring keratinocytes
Concentrated in localised thickenings of the epidermis near hair follicles

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19
Q

What is merkel cell cancer caused by? What is the mortality rate like?

A

Viral infection, rare

High mortality

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20
Q

What is a pilosebaceous unit?

A

A hair follicle and its associated sebaceous glands

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21
Q

What causes hair pigment?

A

Melanocytes in the hair bulb

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22
Q

Which muscles are responsible for the erection of hairs that causes goosebumps?

A

Arrector pili muscles

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23
Q

Which 3 layers of skin are present at 4 weeks foetal development?

A

Periderm
Basal layer
Dermis (corium)

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24
Q

At which stage of foetal development do we see the 4 layers of epidermis + dermis?

25
What are arrector pili muscles supplied by?
Adrenergic nerves
26
What are the 3 phases of hair growth? How long does each stage last on the scalp?
Anagen (growing) - 3-7 yrs Catagen (involuting) - 3-4 weeks Telogen (resting) - 3 months, each day 50-100 hairs
27
When are lanugo hairs shed?
About 1 month before birth
28
Which hairs replace lanugo hairs?
Vellus hairs
29
Define hirsutism
Male pattern hair growth in a woman
30
Define virilisation
Development of male physical characteristics (e.g. muscle bulk, body hair, deep voice) in a female or precociously in a boy Typicall due to excess androgen production
31
Which type of hair loss is associated with autoimmune diseases?
Alopecia areata
32
Nail growth rate
0.1 mm per day | From matrix to free edge is ~6 months
33
What effect might psoriasis have on nail growth rate?
Increases it
34
Another name for dermo-epidermal junction
Basement membrane
35
2 layers of the dermo-epidermal junction
Lamina lucida & lamina densa
36
How is the DEJ connected to the dermis and epidermis?
To the epidermis by hemidesmosomes from basal cells to lamina lucida Anchoring filaments connect hemidesmosomes to lamina densa To the dermis by anchoring fibrils from lamina densa to dermis
37
Autoantibodies to proteins in DEJ can cause which diseases of the DEJ?
Pemphigus, pemphigoid, dermatitis herpetiformis
38
Inherited diseases of the DEJ
Epidermolysis bullosa simplex (EBS) | Dystrophic epidermolysis bullosa (EBD)
39
Positive immunofluorescence suggest which DEJ disease?
Bullous pemphigoid
40
Components of the dermis
Cells - mainly fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells Fibres – collagen, elastin Ground substance Blood vessels, lymphatics, nerves
41
Why is collagen important?
Tensile strength
42
Purpose of fibroblasts
Synthesise connective tissue matrix of dermis | Secrete collagen
43
Functions of ground substance
It binds water, allowing nutrients, hormones and waste products to pass through the dermis It acts as a lubricant between the collagen and elastic fibre networks during skin movement Allows the dermis to act as a shock absorber
44
Purpose of blood vessels in skin
Regulate body temperature
45
Deep plexus arterioles supply...
Sweat glands & hair papillae
46
Define angioma & haemangioma
``` Angioma = an abnormal growth produced by the dilatation or new formation of blood vessels Haemangioma = a benign tumour of blood vessels, often forming a red birthmark ```
47
What do Pacinian & Meissner's corpuscles sense?
Pacinian - pressure | Meissner's - vibration
48
Where are apocrine sweat glands found?
Axilla & perineum
49
Which of the 3 glands found in skin does not open into a hair follicle?
Eccrine
50
Where are eccrine glands found?
Whole skin surface (inc. palms, soles) | Especially axillae
51
Purpose of eccrine sweat glands?
Regulating body temperature | Moisten palms / soles to aid grip
52
What do eccrine glands secrete?
Water, electrolytes, lactate, urea, ammonia
53
Antimicrobial peptides found on the skin
Defensins and cathelcidins
54
Wavelength of light used to make vitamin D
290 to 320 nm UV
55
Layer of the skin that scabies affects
Keratin layer
56
Who does crusted scabies affect?
Immunosuppressed
57
Cause of eczema herpeticum
HSV
58
Difference between discoid lupus and systemic lupus
Discoid affects just the skin & doesn't go internal | Systemic affects systems of the body

Dermatology (10 decks)

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