Cutaneous histology and the Basement Membrane Zone Flashcards
What kind of tissue if the epidermis made of? How many layers are there? What kind of cells is it composed of?
- stratified squamous epithelium
- 4 layers of epidermis with and extra layer on acral skin
- main composed of keratinocytes
- .5-.1mm thick
Label these layers of skin please
What are the layers of the epidermis?
stratum corneum
stratum lucidum (acral skin only)
stratum granulosum
stratum spinosum
stratum basale
What are alternative names for stratum corneum? WHat kind of cells is it comprised of? What is its function? Where is it located?
- aka cornified layer or keratin layer
- comprised of anucleate corneocytes
- primary barrier of epidermis
- thicker at acral sites, no stratum corneum at mucosal site
What is another name for stratum lucidum? where is it seen? what cells are located there? how many layer is it? what is the function?
- aka clear layer
- only seen on scral skin
- thin eosinophilic (clear) band beneath stratum corneum
- may function to reduce friction
What kind of cells are in the stratum granulosum? what is its function?
- flat cells, filled with basophilic granules
- Keratohyaline granules:
- fillaggrin
- involucrin
- loricrin
- Odland bodies (laellar granules): discharge ceramied and other fats into the intercellular space
- Keratohyaline granules:
- Function: barrier, cell cohesion, hydrolytic enzymes
What is another name for the stratum spinosum? what kind of cells ar in it? How many layers is it?
- prickle or spinous layer
- polygonal cells
- abundant eosinophilic cytoplasm
- oval vesicular nuclei
- conspicuous nucleoli
- 5-10 cell layers thick
How does the appearance of the cells in the stratum spinosum change as you get closer to the surface? how are the cells connected?
progressively flatter towards surface
contains differntiating keratinocytes
connected by intercellular bridges (desmosomes, adherens junctions, tight junctions)
What kind of cells are in the stratum basale? How many layers? how are the cells connected?
- cuboidal or columnar cells
- single layer, perpendicular to dermis
- more basophilic cytoplasm, dark large nuclei
- periapical cap of melanin
- connected intercellularly by desmosomes, and to the basemen membrane by hemidesmosomes
- most mitotic activity
WHat is this layer? (with a star)
What cells are these?
- what layer?
- origin?
- characteristics
- function
Melanocytes!!!
- found in basal layer
- neural crest origin
- characteristics:
- no desmosomal attachments
- pale cytoplasm
- 1 melanocyte/10 keratinocytes (1/4 on cheek) **if you see melanocytes clustered you should be alarmed about cancer!
- function: transfer pigment to keratinocytes
What cells are these?
- where are they derived from?
- where are they found?
Langerhans cells
- bone marrow-derived, dendritic antigen presenting cells
- normally in epidermis in concentration similar to melanocytes
What cells are these?
Langerhans
What kind of cells are these?
- What layer of the epidermis are they found in?
- what are they closely associated with?
Merkel Cells!
- found in basal layer of epidermis
- bulge of hair follicles
- oral mucosa
- closely associated with sensory nerves: function as touch receptors
What is the dermis composed of? what are these separated by?
- composed of papillary dermis and reticular dermis
- separated by superficial vascular plexus
What layer is this? In what direction is the collagen oriented? Hw is ti connected to the epidermis
Papillary dermis
- lies directly beneath the epidermis
- connects to epidermis via dermal papillae
- papillae contain capillaries
- fine vertical oriented collagen
Where are Meissner’s corpuscles located and what is their function?
- At dermal papilla of palms, soles and lips
- thick lamellated capsule surrounding core of cells and nerve fibers
- sensory light touch receptors
What layer is this?
Reticular dermis
- coarse thicker collagen fibers parallel to surface epithelium
- also contains sweat glands, lymph vessels hair blood vessels
What are these cells? What is their function?
Fibroblasts!
- thin, spindle shaped cells with elongate ovoid nuclei interspersed bwtween collagen bundles
- synthesize collagen and elastin fibers and ground substance
WHat fibers are visible in the reticular dermis?
Elastic fibers!
- not easily visble without special stains
- horizontally oriented thickened fibers in reticular dermis
- vertically oriented and more fine fibrils in paipllary dermis
What is this image?
Pacinian corpuscle
Where are pacinian corpuscles found? how does thier structure relates to their funciton?
- at dermal-subcutaneous interface
- palms, soles, digits, genitalia, ligaments, joints
- ovid sahped, 1mm, lamellated in cross-section, encapsulated sensory receptors for deep pressure and vibration
What are the 3 parts of a hair follicle and what are their functions?
- Infundibulum
- follicular orifice to entrance of sebaceous glands, normalize keratinization
- isthmus
- sebaceous duct to insertion of arrector pili
- trichilemmal keratinization (no granular layer)
- no inner root
- Lower portion
- dermal papillae
- matrix
Name the layers of the hair follicle from most medial to most superficial
- central core
- cuticle
- Inner root sheath (Huxley’s layer, Henle’s layer)
- Outer root sheath-continuous with epidermis
- basment membrane
- fibrous sheath
What is the function of the IRS?
It surrounds the cuticle
supports hair fiber, degenerated at level of sebaceous gland. therefore there is no IRS above level of isthmus
What does a sebaceous gland look like on histology? what kind of secretion is it? the duct is lined with what kind of tissue?
- lobular: lined with thin outer layer on basophilic germinative cells
- central bubbley
- Vicerative clear cells filled with lipid
- nuclei “scalloped”
- duct lined with stratified squamous epithelium
- holocrine secretion
what are sebaceous glands called in the
eyelid
vermillion/oral mucosae
penis
nipple
eyelid- Meibomian and wolf
vermillion, oral mucosae-fordcye
penis-tyson
nipple-montgomery
what does an apocrine gland look like on histology? where are they fond and describe their activity
- coiled secretory portion, in lower reticular dermis or subcutaneous fat
- single layer of columnar secretory cells with round nuclei
- straight ducts open into hari folliclesabove level of sebacous glands
- rarely opens into epidermal surafce
- found in axillae, anogenital area, external ear canal, eyelid (Moll’s), areola
- inactive until puberty
what surrounds apocri glands? describe the difference in lumen between aporine and eccrine
surrounded by layer of myoepithelial cells
lumen may be larger than in eccrine tissue
What is decapitation secretion?
apical portion of glandular cells are “pinched off” into the lumen
where are eccrine glands located?
what are the 3 parts?
- present everywhere except vermillon of lips, glans, labia minors, nail beds, inner prepuce
- greatest on palms, soles, axillae, forehead
- 3 parts
- spiraled intraepidermal potions (acrosyringium)
- intradermal duct (straight and coiled portions)
- coiled secretory portion
What is the intraepidermal spiraled portion of the eccrine gland also called?
acrosyringium or epidermal sweat duct unit
empties directly into epidermal surface
WHat is the intradermal straight portion of the eccrine gland?
two layers of small cuboidal cells
what is the coiled secretory potion of the eccrine gland?
one distinct layer of secretory cells
layer of myoepithelial cells
lies in lower reticular dermis
surrounded by thick basement membrane
What are lymphatics?
they are thin-walled vessels lined by attenuated epithelium
have multiple valves
usually collapsed and difficult to detect in dermis unless there is an obstruction
How is subcutaneous fat arranged?
- arranged in lobules, separated by vascular septa
- dissolved in routine processing and a large single globule of lipis displaces the nucleus and cytoplasm
What kind of hairs are present on the scalp?
- many large terminal hairs
- hair bulbs extend into subcutaneous fat
WHat is the dermis like on the trunk?
dermis is thick
broad parallel fascicles of collagen in reticular dermis
what is the dermis like on the eyelid/how do you know you are looking at the skin of the eyelid?
small hair follicles, skeletal muscle present
How do you know you are looking at tissues of the nose?
conspicuous sebaceous glands
often drain directly onto the skin surface
How do I know I am looking at the ear?
thin epithleium like in the eyelid, small villous hair follicle, dermis is small and thin, adipose, then cartilage
What is acral skin
palms and sole
thick compact strateum corneum
prominent rete ridge pattern
stratum lucidum present
WHat is different about mucosal tissue?
No granular layer (or stratum corneum)
keratinocytes are pale due to glycogen content
Patients with acquired, autoimmune blistering diseases have ___________
circulating autoantibodies directed against specific autoantigens in skin
autoantigens represent important structural proteins in eidermal basement membrane. some of these structural proteins are mutated in patients with inherited blistering diseases
WHat are the parts of the basment membrane zone BMZ structure?
Hemidesmosomes
lamina lucida
lamina densa
sublamina densa
What is this image showing?
Hemidesmosome
What is this image showing?
Desmosome
WHat are the 2 antigens in a hemidesmosome?
- BP 230 (Bullous Pemphigoid Antigen 1)
- belonds to plakin family or proteins
- cytoplasmis localization
- organization of the cytoskeleton architecture
- BP 180 (Bullous Pemphigoid Anitgen 2)
- aka type XVII collagen
- transmembrane protein conencting basal keratinocytes through CP 230 to the cytoskeleton and through lamin 332to dermal collagen VII
What is the lamina lucida?
- It is immediately underlying hemidesmosomes is a thin structre known as the lamina lucida
- may actually be artifact of tissue preparation and dehydration
- one of the major components is BP 180
What is the lamina densa
- composed of mostly type IV collagen (most abundant collagenous glycoproteins of teh BMZ) and laminins
- comprises more than half of its mass
- key laminin is 332
- binds to hemidesmosomal protein integrin a6B4 on the basal keratinocytes
- binds type VII collagen in the dermis
- provides adhesions between these 2 structures
WHat makes up the sublamina densa?
- type VII collagen
- large protein composed of 3 identical a chains
- form anchoring fibrils
- necessary to maintain epidermal-dermal cohesion,
- binds to both type I and type IV collagens
What are the 3 lab tests for autoimmune bullous disorders?
DIF, IIF, ELISA
Direct immunofluorescence=tissue bound IgG
Indirect Immunofluorescence=circulating IgG
What is direct immunofluorescence?
- heps detect molecules such as immunoglobulins and complement (C3) within biopsy specimens
- skin samples from perilesional skin
- fluorescein-conjugated antibodies against human immunoglobins or complement are used to detect deposits of immunoreactant in the patient’s skin
WHat is indirect immunofluorescence (IIF)
- Indirect immunofluorescence detects circulatin antibodies against BMZ in the patients serum
- patient serum applied to a foreign substrate such as normal human skin
- circulatin antibodies from the sera bind to the BMZ antigen in the substrate
- in the 2nd step anitbody antigen complex is detected by fluorescein-conjugated antibody
What is Bullous Pemphigoid?
- most common autoimmune bullous dermatosis
- primarily seen in the elderly
- tense blisters with serous or rarely even hemorrhagic content appear in phases
- extremely stable-the oof of the blister consists of the entire epidermis
- antibodies to BP antigen 1(BP230) and BP antigen 2 (BP180)
- DIF shows linear deposits of IgG and C3 along the BMZ
How can you detect Bullous Pemphigoid?
- IIF shows linear staining of the epidermal side of salt-split skin
- the BP 180 and BP230 ELISA show positive results correlating ith the disease activity
- BP has a better prognosis than pemphigus vulgaris
- less severe cases can be treated with high potency steroids
- oral steroids and other immunosuppresants are used or severe disease with caution due to potential side effects in the elderly population
