Pathophys/Path Flashcards
Layers of skin?
- Epidermis
- Dermis
- Subcutis
Cells in Epidermis?
Keratinocytes
Melanocytes
Langerhans cells
Markel cells
Cells in Dermis?
Fibroblasts Collagen Elastic Blood Vessels Nerve Endings
Cells in Subcutis?
Fat
Blood Vessels
Fibrous Septae
Epidermis
- Primarily barrier function, protection, wound healing
- Barrier-structure and organization
- Wound healing-must be able to “fix” itself
- Self-renewing, sheds every 28 days
- Cells grow from stem cells in basal layer and terminally differentiate as the move up
- Apoptosis normally low in epidermis (can increase)
- 4 Layers
4 layers of Epidermis?`
1) basal
2) spinous
3) granular
4) stratum
Basal Layer
- In epidermis
- Source of stem cells
- Division starts here
- Basal cells adhear to dermis (BM zone) through HEMIDESMOSOMES
Spinous Layer
- In epidermis
- Cells stop dividing/start terminal differentiation
- Develop lipid (lamellar granules) important to barrier function
- “spiny” due to visible DESMOSOMES with which one KC adheres to another
Granular Cell Layer
- In epidermis
- Intracellular keratohyline granules synthesized (including profilaggrin)
- Lipids in lamellar granules secreted into intercellular space to form water barrier to keep water in skin
Stratum Corneum
- In epidermis
- Nuclei and organelles degenerate, cells flatten
- Profilaggrin processed into filaggrin (help keep water in cells)
- Keratins (structural cytoskeletal proteins) combine with filaggrin into macrofibrils that help create protective layer
Brick and mortar?
Stratum corneum
Brick- flattened keratinocytes filled with keratin and filaggrin
Mortar- lipid mixture surrounding keratinocytes providing water barrier
Keratins
- In epidermis
-major fibrous structural proteins in hair/nails
-over 40+
-combine to form INTERMEDIATE FILAMENTS
(pairs differ by location in body)
-mechanically stabilize cell against physical stress
-have large amounts of sulfur-containing amino acid cysteine
Melanocytes
- In epidermis
- Pigment-producing cells
- Derived from neural crest; migrate during embryonic development
- “live” along basal cell with about 1 per 10 keratinocytes
- transfer pigment to surrounding keratinocytes
Langerhans Cells
- Dendritic cells in mid-epidermis
- Major immune players in skin
- Recognize abnormal antigen: take up, process, present to lymphocytes in regional lymph nodes
- Important in allergic rxns, tumor surveillance
Merkel Cells
- In epidermis (basal layer)
- touch sensation
- develop in malignant tumors
Dermis
- Support Layer
- Thickness Varies by site (1-4mm)
- Blood vessels/lymphatics, nerves, sweat/oil glands, hair follicles
Fibroblasts
- In Dermis (main cell)
- Mesenchymal origin
- Responsible for synthesis and degradation of connective tissue proteins (collagen, elastin, glycosminoglycans)
- Injury to skin triggers mitosis of fibroblasts
- Responsible for wound healing/scar formatin
Mast Cells
- In Dermis
- Part of immune system
- Specialized tissue cells rich in histamine and heparin granules
- Release their granules when triggered by injury or when bind to IgE Ab during allergic rxn
- Histamine and other mediators important in allergic rxns and wound healing “wheal & flare”
Hair Follicle
- Extend through dermis into subcutis
- Each has associated sebaceous (oil) glands
Pilosebaceous unit
- Hair follicle
- Sebaceous (oil) gland
- Apocrine sweat glands (in axilla and anogenital skin)
- Arrector pili muscle (goose bumps)
Eccrine Sweat Glands
- “true”
- present throughout body
- open directly on skin (no hair follicle)
- function to regulate temp by evaporative cooling of sweat
Subcutis
Fat layer that separates dermis from underlying fascia, muscle, organ
Serves as: Insulation, Energy, Protection from injury
Sun Damage
Hurts Keratinocytes, failure to “delete” (apoptosis)
damaged cells can result in skin cancer
Filaggrin Defect
Atopic dermatitis (barrier defects)
Epidermolysis Bullosa Simplex
Genetic mutations in Keratin 5/14
-blister
Melanocytic Tumors
1) Nevus: benign
2) Melanoma: malignant
Functions of Skin
1) barrier
2) immune recognition/surveillance
3) damage repair
4) thermoregulation
5) photoprotection
6) communication
Barrier Function
-regulate water loss, protection from mechanical/chemical/microbial insults
If defective: dehydration, infection, injury of skin (ulcers), inflammation
Immune Regulation of Skin
Innate and adaptive
-can be involved and injured by immune function
Defective: infection, cancer, autoimmune/inflammation, allergic rxns
Autoimmune Bullous Diseases
- disorders of epidermal adhesion or cohesion mediated by autoantibodies to skin adhesion molecules
- characterized by erosions or blisters in skin (mucosa)
Pemphigus Vulgaris Ab?
Anti-Desmosome Abs
Bullous Pemphigoid Ab?
Anti-Hemidesmosome Abs
Repair Injury
Wound healing, repair DNA or apoptosis
Defective: chronic skin ulcers, infection, cancer
Xeroderma Pigmentosa
skin cancer in childhood
Thermoregulation
-constant temp, insulation from fat and hair, control heat loss through sweat/changes in dense microvasculature
Defection: bad for health/confort, hypo/hyperthermia
Hypohiseoric Ectodermal Dysplasia
Genetic mutation in EDAR gene (ectodyplasin A receptor)
- protein critical for proper interaction b/w developing ectoderm and mesoderm
- abnormal hair follicels, sweat glands, teeth
- can’t regulate temp: over heat
Raynauds’ Phenomenon
- Chronic episodic attacks of digital ischemia
- Provoked by cold
- Painful, can ulcerate
- Can be associated with underlying autoimmune disease
Circulation Abnormalities
-diseases that injure blood vessels
-results in cutaneous necrosis/ulveration
Ex: Small vessel vasculitis
Skin Communication
touch, hot/cold, mechanoreceptors
Dysfunction: itch, dysesthetic pain/burning, hyperesthesia (sensitive skin), pain
Ex: Neuropathic ulcers, Trigeminal Trophic Syndrome
Photoprotection of skin
-epidermis has dark pigment (melanin), helps prevent against UV radiation
Dysfunction: cancer, burning
Ex: albinism
