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Skin > Epidermis and Dermis > Flashcards

Epidermis and Dermis Flashcards

1
Q

Layers of the epidermis (top to bottom)

A
  • Stratum corneum
  • Stratum lucidum (only in palmar and plantar skin)
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
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2
Q

Basal cell carcinoma

A
  • Most common CA, highest rates in caucasians
  • Risk factors: fair skin, UV light
  • Location is usually head/neck
  • Pearly papule forms, often bleeds
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3
Q

Melanoma Dx

A
  • ABCDE’s
  • Asymmetry of the spot
  • Border irregularity
  • Color variation/change
  • Diameter change
  • Evolution
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4
Q

SCC

A
  • 2 groups: aggressive or non-aggressive
  • Aggressive: prior radiation, thermal injury, chronic draining sinuses, chronic ulcers, immunosuppression
  • Non-aggressive: sun exposure
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5
Q

Dandruff

A

-Due to inflammation in the stratum granulosum/stratum corneum (superficial layers)

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6
Q

Skin collagen

A
  • Most skin collagen is type I (reticular dermis)
  • Type III around the papillary dermis
  • Type IV in basement membrane
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7
Q

Layers of the basement membrane zone (BMZ)

A
  • Separates epidermis from dermis
  • Basal keratinocytes
  • Lamina lucida (laminins)
  • Lamina densa (type IV collagen)
  • Sub-laminar densa fibrillar zone (anchoring fibrils, elastic/micro fibrils, type VII collagen)
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8
Q

Genetic epidermolysis bullous (EB) diseases

A
  • Genetic defects (mutations)
  • EB simplex (keratin 5 + 14), in epidermis (effects basal keratinocytes), leaves intra-epidermal blister
  • EB simplex w/ pyloric atresia or muscular dystronphy (plectin), intra-epidermal (effects basal keratinocytes)
  • Junctional EB (17 collagen, laminin, integrins), in lamina lucida (sub-epidermal)
  • Dystrophic (scarring) EB (type VII collagen, sub-epidermal lesions)
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9
Q

Bullous pemphigoid

A
  • Autoimmune against type XVII collagen (BP Ag 2), (pathogenic form)
  • Results in dysfunctional hemidesmosomes
  • Sub-epidermal lesion
  • Other forms (non-pathogenic, all in hemidesmosomes): plectin, BP Ag 1, alpha 6 and 4 integrin
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10
Q

Lamins

A
  • Helps type IV collagen (in lamina densa) bind to keratinocyte, binds to other macromoluecules and cells
  • Very adhesive, shaped like a cross
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11
Q

Type IV collagen

A
  • Highly sulfated domain
  • Helical and non-helical (flexible) domains
  • Globular carbohydrate domain
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12
Q

Proteoglycans

A
  • Protein core w/ glycosaminoglycans (GAGs) disaccharides coming off protein
  • can be heparan sulfate rich
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13
Q

Pemphigus

A
  • IgG against desmoglein 3 of desmosomes, keratinocytes disadhere to each other
  • Leaves intra-epidermal blister
  • Desmoglein 1 found in more superficial layers
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14
Q

EBA (Epidermolysis bullosa acquisita)

A
  • IgG against type VII collagen

- Leads to sub-epidermal blisters

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15
Q

Diseases summary for bullous

A
  • Abs against desmoglein 1 or 3 gives rise to pemphigus (intra-epidermis)
  • Mutations plectin and keratin gives rise to EB simplex (intra-epidermal)
  • Abs against type XVII (BP Ag, in HDs) gives rise to bollus pemphigoid (sub-epidermial)
  • Mutations in type 17, laminins, integrins in lamina lucida gives rise to junctional EB (sub-epidermal)
  • Abs against laminin 5 (332, lamina lucida) gives rise to MMP/CP (mucous membrane pemphigoid), sub-epidermal
  • Abs against type VII (anchoring fibril) gives rise to EBA (sub-epidermal)
  • Mutation in type 7 gives rise to dystrophic EB (sub-epidermal)
  • IgA Abs against epidermal transglutamase enz gives rise to DH (dermatitis herpetiformis), sub-epidermal lesions
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16
Q

Features to look for during skin examination

A
  • Distribution (site/extent of involvement, symmetrical, characteristic location)
  • Arrangement of multiple lesions (patterns)
  • Shape of individual lesion (diffuse vs demarcated)
  • Specific type of lesion
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17
Q

Describing lesions

A
  • Color
  • Consistency
  • Surface appearance (scaly, crusty, ect)
  • Anatomic components of skin affected
  • Type of lesion
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18
Q

Macule

A
  • Circumscribed, flat lesion that differs from surrounding skin by color
  • Can be any size or shape
  • Can be hypo or hyperpigmented, purport, or erythemetous/telangectasia (difference being redness goes away w/ pressure if erythemetous)
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19
Q

Papule

A
  • Small (less than .5cm), solid, circumscribed elevated lesion
  • Localized hyperplasia of dermis or epidermis, or localized cellular infiltrates in the dermis or metabolic deposits can give papules
  • Papules may be acuminate (pointed), umbilicated (dome-shaped w/ central dimple), or flat-topped
20
Q

Nodules

A
  • A palpable, solid, circumscribed, elevated lesion
  • Larger than .5cm
  • Can be epidermal, epidermal-dermal, dermal, dermal-subdermal, subcutaneous
21
Q

Vesicles and bulla

A
  • Vesicle is a circumscribed, elevated lesion that contains fluid
  • A vesicle with a diameter greater than .5cm is a bulla
  • Vesicles w/ purulent material are pustules
  • Vesicles and bulla arise from cleavage at various levels of the skin
  • Cleavage just beneath the stratum corneum produces subcorneal vesicle
  • Cleavage within epidermis produces intraepidermal vesicle
  • Cleavage at or below dermal-epidermal interface produces sub epidermal vesicle
22
Q

Plaques

A
  • A mesa-like elevation that occupies a relatively large surface area
  • Often formed by a confluence of papules
23
Q

Wheals

A
  • A rounded or domed papule or plaque that usually disappears within hours
  • Epidermis is not affected; there is no scaling
  • The borders are sharp but not stable, and tend to move around
  • Hives (urticaria) are result of edema in the upper portion of the dermis
24
Q

Erosions

A
  • Loss of most superficial epithelial layer (part of the epidermis)
  • Excoriations are erosions left by scratching
  • Erosions heal w/out scarring
25
Q

Ulcers

A
  • Loss of entire epidermis and portion of dermis as well

- Heals with scarring

26
Q

Crusts

A
  • Serum, blood, or purulent material dries on skin

- Usually are encrusted exudates, characteristic of injury and pyogenic infection

27
Q

Scaling (desquamation)

A
  • Abnormal shedding or accumulation of stratum corneum in flakes
  • Can form densely adherent mass as seen in SCC
28
Q

Layers of the skin

A
  • Epidermis, basement membrane zone, dermis (hypodermis is not considered part of the skin)
  • Integument is skin plus appendages (glands, hair follicles, nails)
  • Epidermis and dermis form irregular ridges w/ each other
  • Arterio-venous shunt (anastomoses) is called glomus body. Resides in dermis and regulates body temp (most abundant in hands/feet)
29
Q

Epidermis cell types

A
  • Superficial, avascular layer of predominantly kerationcytes (keratin-producing stratified squamous epithelium)
  • Also contains melanocytes (on stratum basale, produces melanin), langerhans cells (APC dendritic cells in stratum spinosum), and merkel cells (sensory transducers in stratum basale)
  • Neural crest (melanocytes), ectodermal (merkel cells and keratinocytes) and mesodermal origin (langerhans cells)
30
Q

Stratum basale

A
  • Single layer, deepest layer. Contain columnar/cuboidal keratinocytes and are attached to basal lamina by hemidesmosomes
  • Contains basal (stem) cells that proliferate and move to higher layers (origin of psoriasis)
  • This layer contains Merkel cells and melanocytes
31
Q

Stratum spinosum

A
  • A layer a few keratinocytes thick (prickle cells, make abundant keratin filaments) and attached to adjacent cells by desmosomes
  • Keratins are bundles of intermediate filaments-> tonofilaments-> tonofibrils
  • Keratinocytes in the deeper layer of stratum spinosum can divide (source of SCC)
  • Contain lamellar bodies (membrane-coating granules) in the higher part of the stratum spinosum and form impermeable lipid sheets
  • Contains langerhans cells
  • Site of warts (verrucae), marked epidermal hyperplasia due to HPV
  • Malphagian layer = stratum spinosum + stratum basale
32
Q

Stratum granulosum

A
  • Most superficial layer w/ nuclei, a few layers of flattened keratinocytes
  • Keratinocytes contain keratohyalin granules (non-membrane-coating cystine and histidine rich protein)
  • Also contain bundles of keratin filaments (tonofibrils w/ filaggrin protein) and lamellar bodies
  • PM of keratinocytes have cornfield envelope (filament proteins inside and lamellar bodies outside)
33
Q

Stratus lucidum

A
  • Clear, homogenous layer of dead cells
  • Contain no nuclei but contain eleidin (transformation product of keratohyalin)
  • Only found on palmar and plantar skin
34
Q

Stratum corneum

A
  • Most superficial layer, consisting of flattened dead 14-sided polygonal keratinocytes (scale-like)
  • shedding of stratum corneum is desquamation
35
Q

Other cells in epidermis

A
  • Melanocyte: branching cells that synthesize melanin in melanosomes (contain tyrosinase, which is UV sensitive). Melanin protects against UV radiation
  • Extensions of melanocytes project to stratum spinosum and melanin is transferred (cytocrine secretion) to keratinocytes
  • Langerhans cells: dendritic cells that contain birbeck granules (paddle-shaped) and facilitate immune response via APC capabilities
  • Merkel cells: oval, clear cells near areas of vascularization and richly innervated tissue
  • nucleus is irregular and cell contains NTs to relay afferent signals. function as sensory mechanoreceptors (touch)
  • Contain desmosomes and keratin
36
Q

Dermis

A
  • Mesoderm-derived composed of DIrCT and contains many T1 collagen and elastic fibers
  • Has 2 layers: dermal papillary layer forms dermal papillae which interdigitates w/ epidermis
  • Dermal papillary layer contains capillary loops and meissner’s corpuscles (fine-touch receptors)
  • Dermal reticular layer is major portion of the dermis and is composed of dense bundles of collagen and elastic fibers
  • Also contains paccinian (pressure receptors) and ruffini (encapsulated mechanoreceptors) corpuscles, as well as krause’s end-bulbs (cold and pressure receptors)
37
Q

Defects of the dermis

A
  • Epidermolysis bullosa is blister formation following minor trauma due to defects in the intermediate filaments and anchoring fibrils that attach dermis to epidermis
  • Keloids: swelling in the skin due to excess collagen deposition resulting in large scar
38
Q

Eccrine sweat gland

A
  • Coiled, simple tubular gland in skin throughout body except lips and external genitalia. Consists of secretory unit and duct
  • Secretory unit is subcutaneous and in dermis, composed of dark cells (line lumen and contain mucinoglycoprotein secretory granules), clear cells (underlie dark cells and extend canaliculi to lumen to secrete), and myoepithelial cells (scattered beneath clear cells to contract and aid in gland expression)
  • Duct is lined by stratified cuboidal epithelial cells (contain keratin) and have predominant terminal web
  • Secretory unit passes through interpapillary peg to reach epidermis
39
Q

Apocrine sweat gland

A
  • Large specialized glands in the axilla, areola, perianal region and external auditory canal (ceruminous, or wax, glands)
  • Cytoplasm does not become part of the secretion, uses merocrine (eccrine) secretion
  • Stimulated by hormones
  • Usually located near hair follicle
40
Q

Sebaceous gland

A
  • Branched, holocrine, acinar glands w/ a short duct emptying sebum (oily secretion of degenerating epithelial cells) into hair follicle
  • Found almost everywhere (except palms and soles) but mostly on face, forehead, and scalp
  • Inflamed, obstructed sebaceous gland is acne
41
Q

Hair follicle 1

A
  • Invagination of the epidermis extending deep into dermis. Forms keratinized hair
  • Hair bulb is the lower part of the hair, from out to in: medulla-> cortex-> cuticle
  • Hair bulb arises from dermal papilla, which receives melanin from melanocytes and blood from capillary network (with nerves)
  • Hair shaft: contains the same components of the bulb (minus papilla), extends out of the skin (keratinized epidermis)
42
Q

Hair follicle 2

A
  • Internal root sheath surrounds hair, composed of cuticle, huxley’s layer and henle’s layer (from in to out) is keratinized epidermis
  • External root sheath is a direct continuation of stratum basal and spinosum + BMZ
  • Glassy membrane in a non-cellular layer that is a thickening of the basement membrane and separates the hair from the surrounding dermal sheath
  • bulge areas provides insertion point of arrector pili. has stem cells (bulge cells) that have high proliferative capacity and are multipotent. can regenerate hair follicles, sebaceous gland, and epidermis
  • Bulge cells AKA transit amplifying cells (TAC)
43
Q

Arrector pili muscle

A
  • Smooth muscle attaching at oblique angle to dermal sheath at bulge area
  • Passes under sebaceous gland, through reticular layer of dermis and attaches to papillary layer of dermis
  • Contraction raises hair (goose-bumps)
44
Q

Nails

A
  • Keratinized plates on a bed of epidermis, covered by cuticle at proximal end (stratum corneum)
  • cuticle overlies crescent-shaped white lunula
  • At the distal end they are underlain by hyponychium (stratum corneum)
  • Grow as a result of mitoses in the matrix of the nail root
45
Q

Thick vs thin skin

A
  • Thick: prominent stratum corneum, developed stratum granulosum, has stratum lucidum, on palms and soles, no hair follicles, sebaceous glands, or arrector pili muscles
  • Thin: small stratum corneum, thin or no stratum granulosum, no stratum lucid, found on other parts of the body, contains hair follicles, sebaceous glands, and arrector pili muscles

Skin (14 decks)

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