cutaneous histology and the basement membrane zone Flashcards by adam koraym

Epidermis

Stratified squamous epithelium

4 layers of epidermis

Extra layer on acral skin

Mainly composed of keratinocytes

typically .5-.1 mm thick

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Layers of the epidermis

Stratum corneum

Stratum lucidum (acral skin only

Stratum granulosum

Stratum spinosum

Stratum basale

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Stratum corneum

aka cornified layer or keratin layer

Comprised of anucleate corneocytes

Primary barrier of epidermis

Thicker at acral sites

No stratum corneum at mucosal site

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Stratum lucidum

Aka clear layer

Only seen on acral skin

Thin eosinophilic or clear band beneath stratum corneum

3-5 cell layers thick

May function to reduce friction

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Stratum granulosum

cells are flat
Filled with basophilic granules

Keratohyaline granules (Fillaggrin, involucrin, loricrin)

Odland bodies (lamellar grules, descharge ceramides and other fats into intercellular space)

Barrier, cell cohesion, hydrolytic enzymes

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Stratum spinosum

aka prickle or spinous layer, polygonal cells

Abundant eosinophilic cytoplasm

Oval vesicular nuclei, conspicuous nucleoli

5-10 cell layer thick

Progressively flatter toward surface, contains differentiating keratinocytes, contected by intercellular bridges

(Desmosomes, adherens junctions, tight junctions)

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Stratum basale

cuboidal or columnar cells
Single layer
perpindicular to dermis
more basophilic cytoplasm, dark large nuclei
Periapical cap of melanin

Connected by desmosomes

Connected to basement membrane by hemidesmosomes

Most mitotic activity

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Melanocytes

found in basal layer

Neural crest origin

No desmosomal attachements

Pale cytoplasm

1: 10 melanocyte:keratinocytes
1: 4 on cheek

Transfer pigment to keratinocytes

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Langerhans cells

Bone marrow-derived, dendritic antigen presenting cells

normally in epidermis in concentration simillar to melanocytes

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Merkel cells

found in basal layer of the epidermis, bulge of hair follicle,
oral mucosa

Not easily identified on H and E

Closely associated with sensory nerves, function as touch receptors

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Dermis

composed of papillary dermis and reticular dermis

Separated by superficial vascular plexus

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Papillary dermis

lies directly beneath the epidermis
Connects to epidermis via dermal papillae

Papillae contain capillaries

Fine vertically orientated collagen

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Meissner’s corpuscle

At dermal papilla of palms, soles, and lips

thick, lamellated capsule surrounding core of cells and nerve fibers

Sensory light touch receprots

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Reticular dermis

coarse thicker collagen fibers parallel to surface epithelium

Also contains sweat glands, lymph vessels, hair, blood vessels

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Fibroblasts

Thin, spindle shaped cells with elongate ovoid nuclei interspersed between collagen bundles

Synthesize collagen and elastin fibers and ground substance

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Elastic fibers

Not easily visible without special stains

horizontally oriented thicker fibers in reticular dermis

Vertically oriented and more fine fibrils in papillary dermis

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Pacinian corpuscle

At dermal subcutneous interface
Palms, soles, digits, genitalia, ligaments, joints

Lamellated in cross section
Encapsulated sensory receptors for deep pressure and vibration

Hair follicle

Infundibulum: Follicular orfice to entrance of sebaceous duct, normal keratinization

Isthmus: Sebaceous duct to insertion of erector pilli, trichilemmal keratinization (no granular layer), no inner root sheath

Lower portion: dermal papillae, matrix

inside the hair follicle

central cortex surrounded by cuticle

Inner root sheath surrounds the cuticle (supports hair fiber, degenerates at level of sebaceous gland)

Outer root segments: continuous with epidermis

sebaceous glands

Lobular lined with thin outer layer of basophilic germinative cells

Central bubbly clear cells filled with lipid

Nuclei scalloped

Duct lined with stratified squamous epithelium

Holocrine secretion

Eyelid (meibomian and wolf), vermillion oral mucosa (Fordyce), Tyson (penis), Montgomery (nipple)

Apocrine gland

coiled secretory portion

located in lower reticular dermis subcutaneous fat

Straight duct opens into hair follicle above level of sebaceous gland

Rarely opens onto epidermal surface

found in axillae, anogentital area, external ear canal, eyelid (Moll’s), areola

Inactive until puberty

Apocrine gland histology

single layer of columnar secretory cells with round nuclei

Surrounded by layer of myoepithelial cells

lumen may be larger than in eccrine tissue

Decapitation secretion: apical portion of glandular cells are pinched off into the lumen

Eccrine gland

present everywhere except vermillion of lips, glans, labia minora, nail beds, inner prepuce

Greatest on palms, soles, axillae, forehead
Spiraled intraepidermal portion (acrosyringium)
Intradermal duct (straight and coiled portion)
Coiled secretory portion

Intraepidermal spiraled portion of the eccrine gland

AKa acrosyringium or epidermal sweat duct unit

Empties directly onto epidermal surface

intradermal straight portion of the eccrine gland

two layers of small cuboidal cells

colloid secretory portion of the eccrine gland

coiled secretory portion: one distinct layer of secretory cells, layer of myoepithelial cells lies in lower reticular dermis Surrounded by thick basement membrane

Lymphatics

thin walled vessels lined by attenuated epithelium Have multiple valves Usually collapsed and difficult to detect in dermis Seen in obstruction

Subcutaneous fat

arranged in lobules, separated by vascular fibrous septa Fat is dissolved by routine processing large single globule of lipid that displaces nucleus and cytoplasm

Scalp

many large terminal hairs, hair bulbs extends into subQ fat

Trunk

dermis is very thick Broad parallel fascicles of collagen in reticular dermis

Nose

Conspicuous sebaceous glands Often drain directly onto the skin surface

Basement membrane Zone

area between epidermis and dermis Dermo-epidermal adhesion Regulation (cell differentiation, motility, transmission of extracellular signals)

Layers of the BMZ

Hemidesmosomes Lamina lucida Lamina densa Sublamina densa

hemidesmosomes are compromised of

``` BP 230 (Bullous pemphoid Ag 1): Belongs to the plakin family of proteins, located in cytoplasm of keratinocyte, organizes the cytoskeleton architecture ``` ``` BP180 (Bullous pemphoid Ag2): AKA type 17 collagen Transmembrane protein (connects basal keratincocytes thru BP230 to the cytoskeleton and dermal collagen 7 ```

Lamina lucida

immediately underlying hemidesmosomes is a thin structure known as the lamina lucida may actually be an artifact of tissue prep and dehydration one of the major component is BP180

Lamina densa

Type 4 collagen and laminins The key BMZ laminin is laminin 332 (binds to hemidesmosomal protrein integrin on the basal keratinocytes) Also binds to type 7 collagen in the dermis Provides adhesion between these 2 structures

Sublamina densa

Type VII collagen Large protein composed of 3 identical alpha chains Form anchoring fibrils Necessary to maintain epidermal dermal cohesion Binds to both type 1 and 4 collagen

Direct immunofluorescence (DIF)

helps detect molecules (Igs and C3) within biopsy The skin Fluorescein-conjugeteed Ab against human Ig or complement are used to detect deposits of immunoreactant in the patient skin

Indirect immunifluorescense

detects circulating Ab against BMS in pt serum PT serum applied to foreight substrate (normal human skin) The circulating antibodies from the sera bind Ab - Ag complex detected

Bullous pemphigoid (BP)

Most common autoimmune bullous dermatosis Seen in elderly Tense blisters with serous/hemorrhagic content- very stable, roof is the entire dermis Antibodies to BP Ag (Bp230) and BP Ag 2 (BP 180) Cause subepidermal blisters DIF shows linear deposits of IgG and C3 along the BMZ IIF shows linear stain on the epidermal side of salt split skin The BP 180 and BP230 ELISA show positive results correlating with the disease activity BP better than PV, less sever cases can be treated with steroids