Transcript Skin (Integument)

Skin (Integument)
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Heaviest single organ in the body (16% BW)
Thin skin
Thick skin (smooth and hairless hand and palms)
Consists of three major regions
– Epidermis – outermost superficial region
– Dermis – middle region
– Hypodermis – deepest region
Basic Histology P360-370
Cells of the Epidermis
• Keratinocytes – produce the fibrous protein keratin
• Melanocytes – cells with cytoplasmic extensions
produce the brown pigment melanin
• Langerhans’ cells –star shaped epidermal macrophages
that help to activate the immune system
• Merkel cells – function as touch receptors in
association with sensory nerve endings
EPIDERMIS: Cell types II
dead
Keratinocytes
principal cell
Melanocyte
alive
to make & transfer pigment
Langerhans APC cell migrates to node for immunity
Merkel cell
sensory receptor
Nerve cell represented by
its axon
Layers of epidermis
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Stratum basale/germinativum (“basal or “forming” layer)
– One layer thick mitotic cells
– 10-25% melanocytes with processes into next layer
– Merkel cells with sensory neurons
Stratum spinosum (“prickly” layer)
– Cells appear spiny due to numerous desmosomes
– Many Langerhans cells
Stratum granulosum (“grainy” layer)
– Cells flatten
– Organelles/nuclei begin to disintegrate
– Keratin precursor granules begin to form
– Lamellated granules with water-proof lipid form and will be spewed out between cells
Stratum corneum (“horny” layer)
– Cells are dead—too far from underlying capillaries to live
– 20-30 cells thick up to ¾ of dermal thickness
– Keratin, thickened membranes and glycolipids between cells provide “overcoat” for
body to protect against water loss and other possible “assaults” on body
Layers of the Epidermis: Stratum Basale
(Basal Layer)
• Deepest epidermal layer firmly attached to the
dermis
• Consists of a single row of columnar or cuboidal
cells the youngest Keratinocytes
Layers of the Epidermis
Epidermis
• Stratified squamous
epithelium
• Contains no blood
vessels/avascular
• 4 types of cells
• 5 distinct strata (layers)
of cells
Layers of the Dermis
Papillary
Reticular
Layers of the Dermis: Papillary
Layer
• Papillary layer
– Thin areolar connective tissue with collagen and
elastic fibers
– Its superior surface contains peglike projections
called dermal papillae.
– Separated from the germinal layer by basal lamina
– Dermal papillae contain capillary loops, Meissner’s
corpuscles, and free nerve endings
Hypodermis
• Subcutaneous layer deep to the skin
• Composed of adipose and areolar
connective tissue
Histopathologic terms for
abnormalities of the epidermis
• Acanthosis- thickening of the spinous layer of the
epidermis due to hyperplasia of keratinocytes
• Atrophy- thinning of the epidermis (also a clinical
term)
• Dyskeratosis- Premature keratinization of
single cells within the epidermis and adnexal
epithelium
• Necrosis
• Acantholysis- loss of connection between
keratinocytes
• Spongiosis- intercellular edema of epidermis
or adnexa, may culminate in intraepidermal
vesicles
• Scale, crust - keratinous material on the skin surface
(scale), plasma with white and\or red blood cells
(crust), or both (scale-crust)- also clinical
• Erosion- interference in the continuity of the
epidermis, heals without a scar-also clinical
• Ulcer- interference in the continuity of the skin
including epidermis and dermis. Following healing
there is a residual scar- also clinical
Premalignant lesions
• Actinic keratosis
• Bowen's disease
Actinic keratosis
• Aetiology :
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Exposure to ionising radiation
Chronic exposure to sun
Hydrocarbons
Arsenicals
• Clinical features:
– Usually less than 1 cm in diameter
– Tan-brown or red coloured
– Have a rough, sandpaper like consistency.
• Microscopy:
– Cytological atypia is seen in the lower-most layers
of the epidermis
– May be associated with hyperplasia of basal cells
BOWEN DISEASE
BOWEN DISEASE
(Carcinoma in situ)
• Squamous cell carcinoma that have not
invaded through basement membrane of the
dermoepidermal junction
• Microscopy:
– Characterized by cells with atypical nuclei
(enlarged and hyperchromatic) at all levels of the
epidermis.
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Skin cancer
types
 basal cell carcinoma
 squamous cell carcinoma
 malignant melanoma
 secondary skin cancers
• Basal cell carcinoma
– From stratum basale
– Least malignant - 99% full cure
• Squamous cell carcinoma
– From stratum spinosum
– Prognosis is good if removed early
• Melanoma
– Melanocyte cancer
– Highly metastatic
– Resistant to chemotherapy
• ABCD Rule
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Asymmetry
Border irregularity
Color: several present
Diameter: greater than 6 mm
Squamous cell carcinoma
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Exposure to sunlight
Industrial carcinogens (tars and oils)
Chronic ulcers and osteomyelitis
Old burn scars
Ingestion of arsenicals
Ionising radiation
Tobacco and betel nut chewing in oral cavity
Patients with xeroderma pigmentosum
SQUAMOUS CELL CARCINOMA
Basal cell carcinoma (Rodent ulcer)
• Slow growing tumors that rarely metastasize
• Aetiology:
– Chronic sun exposure
– Immunosuppression
– Patients with inherited defects in DNA(xeroderma pigmentosum)
• Clinical features:
– Lesions appear as pearly papules often containing prominent dilated
subepidermal blood vessels (telangiectasias)
– Advanced lesions may ulcerate,and extensive local invasion of bone or facial
sinuses may occur (rodent ulcers).
• Site: occurs on hairy skin, the most common location being face, usually
above a line from the lobe of ear to the corner of mouth.
– The tumour enlarges in size by burrowing and by destroying the tissues locally
like a rodent and hence the name ‘rodent ulcer’
What is this?
NODULAR BCC
SUPEFICIAL BCC
• Microscopy :
– Malignant Cells are seen arising from basal layer of
epidermis and extending into dermis
– Arranged as cords and islands
– Composed of cells with basophilic hyperchromatic
nuclei
– Stroma is mucinous with many fibroblasts and
lymphocytes
– Malignant cells at the periphery of the islands are
arranged radially with their long their long axis parallel
to each other (palisading)
– The islands of tumor cells are seperated from the
surrounding stroma by clefts (due to shinkage of
epithelial tumor nests).
Melanocytic lesions of the skin
Benign and Malignant
Disorders of pigmentetion
• Vitiligo
– Is a common diorder charecterised by partial or
complete loss of pigment producing melanocytes.
• Melasma
– Mask like zone of facial hyperpigmentatiom
Melanocytic nevi
• Localized benign abnormality (malformation or
neoplasia) of the melanocytic system
• Usually acquired
• Most nevi develop during the second and third
decades
• Variable number- 20-30
• Distribution- more common in skin of head, neck,
trunk
• Exposure to UV light is an exacerbating factor for the
development of nevi
Common melanocytic nevi
• Junctional nevus- only epidermal component, flat or
slightly elevated, non hairy, light brown
• Compound nevus- both epidermal and dermal
components, slightly elevated or dome-shaped
• Intradermal nevus- only dermal component, flat or
dome-shaped, often hairy
Congenital nevi
Dysplastic nevi
• Dysplastic nevus syndrome- genetically
determined syndrome in families prone to
develop melanomas
• Clinically- atypical, >5mm, irregular, variegated
• Appear in adolescence, continue to appear in
adult life
• Architectural and cytologic atypia
Dysplastic nevi and melanoma
• Individuals with dysplastic nevi have an
increased risk of melanoma
• Familial dysplastic nevi and history of
melanoma- risk of melanoma approaching
100% by age 75y
Malignant melanoma
• Increasing incidence- 3-8% per year
Malignant melanomarisk factors
• Solar radiation is the major cause of MM in
light-pigmented populations
• Most melanomas arise in intermittently sunexposed areas (males- trunk, upper back;
females- lower legs, upper back)
• In whites- higher rates in the less pigmented