cutaneous histology and the basement membrane zone Flashcards
Epidermis
Stratified squamous epithelium
4 layers of epidermis
Extra layer on acral skin
Mainly composed of keratinocytes
typically .5-.1 mm thick
Layers of the epidermis
Stratum corneum
Stratum lucidum (acral skin only
Stratum granulosum
Stratum spinosum
Stratum basale
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
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
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
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)
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
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
Langerhans cells
Bone marrow-derived, dendritic antigen presenting cells
normally in epidermis in concentration simillar to melanocytes
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
Dermis
composed of papillary dermis and reticular dermis
Separated by superficial vascular plexus
Papillary dermis
lies directly beneath the epidermis
Connects to epidermis via dermal papillae
Papillae contain capillaries
Fine vertically orientated collagen
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
Reticular dermis
coarse thicker collagen fibers parallel to surface epithelium
Also contains sweat glands, lymph vessels, hair, blood vessels
Fibroblasts
Thin, spindle shaped cells with elongate ovoid nuclei interspersed between collagen bundles
Synthesize collagen and elastin fibers and ground substance
Elastic fibers
Not easily visible without special stains
horizontally oriented thicker fibers in reticular dermis
Vertically oriented and more fine fibrils in papillary dermis
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
