DD 03-03-14 08-09am Clinical Dermatology-Terminology and Functions - Dunnick Flashcards
Skin - key factos
Skin is the largest organ
– Weight 4 kg
– Covers 2 square meters of surface area
Skin diseases are common!
– 8.5% diagnoses in Family Practice Clinics
– 30% Pediatric Conditions
Significant economic burden in treating skin disease & skin disease causing loss of days worked.
Function of the skin
- Decoration/Beauty
- Barrier– Physical, LIght, Immunologic
- Vitamin D synthesis
- Water Homeostasis
- Thermoregulation
- Insulation/Calorie Reservoir
- Touch/Sensation
Structure/Cells Involved in Skin’s Function as a Physical Barrier
Epidermis, Keratinocytes
Structure/Cells Involved in Skin’s Function as a Light Barrier
Epidermis: Melanocyte
Structure/Cells Involved in Skin’s Function as a Immunologic Barrier
Epidermis: Langerhans cells
Structure/Cells Involved in Skin’s Function in Vitamin D synthesis
Epidermis: Keratinocytes
Structure/Cells Involved in Skin’s Function in Water homeostasis
Epidermis: Keratinocytes
Adnexa: Eccrine glands
Structure/Cells Involved in Skin’s Function in Grasp
Adnexa: Nails
Structure/Cells Involved in Skin’s Function in Lubrication of the Skin
Adnexa: Sebaceous glands
Structure/Cells Involved in Skin’s Function in Phermones/ Body Odor
Adnexa: Apocrine glands
Structure/Cells Involved in Skin’s Function in Thermoregulation
Adnexa: Eccrine glands
Dermis: Blood vessels
Structure/Cells Involved in Skin’s Function in Strength & Elasticity
Dermis: Fibroblast (Produces collagen and elastin)
Structure/Cells Involved in Skin’s Function in Sensation
Dermis: Nerves
Structure/Cells Involved in Skin’s Function in Insulation
Subcutaneous Fat
Structure/Cells Involved in Skin’s Function as a Calorie Reserve
Subcutaneous Fat
Fitzpatrick Skin Type I
Hair - Red/Blond Eyes - Blue/Green Skin - White Freckles - +++ Sunburn - Always Tan - 0
Fitzpatrick Skin Type II
Hair - Blond/Brown Eyes - Light to Medium Skin - Fair Freckles - ++ Sunburn - Easily Tan - Minimally
Fitzpatrick Skin Type III
Hair - Brown Eyes - Medium to Dark Skin - Light Brown Freckles - + Sunburn - Initially Tan - Gradually
Fitzpatrick Skin Type IV
Hair - Medium to Dark Eyes - Dark Skin - Moderate Brown Freckles - 0 Sunburn - Minimally Tan - Tans Well
Fitzpatrick Skin Type V
Hair - Dark Eyes - Dark Skin - Dark Brown Freckles - 0 Sunburn - Rarely Tan - Dark Tan
Fitzpatrick Skin Type VI
Hair - Dark Eyes - Dark Skin - Black Freckles - 0 Sunburn - Never Tan - Always Tan
Components of the skin
Epidermis
Dermis
Adnexal structures
Subcutaneous Fat
Epidermis
a stratified squamous epithelial layer
Dermis
An underlying CT layer, which includes:
- papillary layer (loose CT) immediately under epidermis
- deeper reticular layer (dense CT)
Adnexal structures
- Apocrine glands
- Eccrine glands
- Hair
- Nails
- Sebaceous glands
Subcutaneous Fat
Composed of adipocytes
Regional variation of skin
Thick skin is hairless & found on the palms / soles
Vitamin D Synthesis
- 7-dehydrocholesterol converted to cholecalciferol (Vitamin D3) in skin by UVB
- Cholicalciferol (Vitamin D3) & Ergocalciferol (Vitamin D2) can both be ingested & absorbed through intestines.
- Vit D2 & D3 then converted to calcidiol (25-hydroxy Vitamin D) by liver.
- 1,25-dihydroxy-Vitamin D (calcitriol) is active form & is synthesized by kidneys.
Cells of the Epidermis
Keratinocytes
Melanocytes
Langerhans cells
Keratinocytes
- Form barrier layer
- Synthesize keratin (major intracellular fibrous protein of skin)
- Involved in defined cycle of proliferation, differentiation, & apoptosis
Melanocytes - defition / source / location
- Pigment producing cells arising from neural crest
- Located primarily in basal layer of epidermis, in hair follicles
- Reside in basal layer of epidermis in 1:10 ratio (melanocyte:keratinocyte)
Melanocytes - action
- Synthesize melanin (tyrosin-derived pigment)
- Melanin is packaged in granules (melanosomes)
- These granules are transferred from melanocytes to keratinocytes via dendritic processes
- Ea/ melanocyte supplies melanin to ~30 nearby keratinocytes
- Melanin in basal keratinocytes protects DNA from UV damage
Langerhans cells
= Dendritic cells in epidermis derived from bone marrow stem cell
- Found in small numbers in all epidermal layers
- Participate in cell-mediated immune reactions by processing & presenting antigens (circulate back and forth between skin & lymph nodes)
Skin color variation
NOT due to the number of melanocytes in the skin
DUE TO:
- The type of melanin produced:
- The distribution melanosomes
Types of melanin produce
Eumelanin: black to brown pigment
Pheomelanin: yellow to red-brown pigment
Distribution of melanosomes in skin
Light Skin:
- melanosomes distributed in clusters above nucleus
Dark Skin:
- melanosomes distributed individually throughout cytoplasm
Life cycle of Keratinocytes
- Epidermis is continually renewed by mitosis of keratinocytes in the basal layer & by shedding of dead keratinocytes from the surface
- Process typically takes 28 days
- The layered nature of the epidermis (5 layers) is an expression of this developmental sequence
Layers of the Epidermis
- Stratum basalis (germinativum) = Basal cell Layer
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Stratum basalis (germinativum) = Basal cell Layer
- deepest layer of epidermis
- Consists of a single layer of columnar or cuboidal cells (keratinocytes)
- Basal keratinocytes are the stem cells of the epidermis (source of new keratinocytes & thus a site of intense proliferation)
Cell attachments in Basal Cell Layer of Epidermis
Hemidesmosomes:
- attach basal cells are firmly to basal lamina of dermal epidermal junction
Desmosomes:
- attach keratinocytes to each other
Tonofilaments:
- protein structures (keratin filaments) that insert into dense plaques of desmosomes on cytoplasmic side of plasma membrane
Stratum spinosum ;ayer of Epidermis
- Has a “prickly” or spiny appearance due to desmosome attachments between cells
- Intercellular adhesion depends upon tonofilament-desmosome interaction in the distribution of stress
- Synthesis of involucrin & membrane coating granules begins in this layer
Stratum granulosum layer of Epidermis
- Cells of this layer contain different types of granules
- Keratohyalin granules contain Profilaggrin (filaggrin precursor).
- -> Filaggrin cross-links keratin tonofilaments & is important in barrier function of skin
- Filaggrin is mutated in dry skin conditions including ichthyosis & atopic dermatitis
Stratum lucidum layer of Epidermis
- Under light microscope, a thin, light staining band seen only in thick skin
- Cells of this layer no longer have nuclei or organelles
Stratum corneum layer of Epidermis
- Outermost layers of epidermis
- Keratinocytes have lost their nuclei & organelles and entire cell is filled with keratin
- Desmosomes still connect tightly packed adjacent cells
Layers of the Dermis
Papillary Layer
Reticular Layer
Papillary Layer
- site of attachment to epidermis & necessary to its development / differentiation
- contains capillary network (blood supply for epidermis)
- pathway for defense cells
- contains Meissner’s corpuscles which sense touch
Reticular Layer
- contains extensive collagen & elastic fibers that provide strength & flexibility
- houses (along w/hypodermis) epidermal derivatives such as glands & hairs, and plays major role in their development & functioning
- pathway for major blood vessels arranged specifically to facilitate thermoregulation
- site of nerve tracts & major sensory receptors
- Pacinian corpuscles sense vibration, pressure & touch
Encapsulated touch receptors
In dermis
Include:
- Meissner’s corpuscles
- Pacinian corpuscles
Meissner’s corpuscles
- detect delicate touch
- most commonly found in dermal papillae of thick skin
- consist of Schwann cells & sensory nerve terminals wrapped by fibroblasts & collagen
Pacinian corpuscles
= rapidly adapting receptors that detect changes in deep pressure (vibrations)
- found in dermis of both thin & thick skin
= large structures resembling an onion
- concentric layers are composed of flattened CT-like cells interspersed w/ intercellular fluid & collagen
- single sensory nerve fibers terminates w/in this structure
Adnexal Structures of the Skin
Apocrine sweat glands Eccrine sweat glands Hair Nails Sebaceous glands
Apocrine sweat glands
- Specialized sweat glands located in axillary, pubic & perianal regions
- -> produce milky, viscid, carb-rich secretion that is initially odorless
- -> subsequent bacterial action leads to a characteristic axillary body odor
- begin to function in puberty
- have ducts which empty into hair follicles just above sebaceous glands
Eccrine sweat glands
- Traditional sweat glands distributed over most of the body
- Not found in lips, under nails or on glans penis, glans clitoris, or labia minora
- -> Watery, enzyme-rich secretion
- initially isotonic
- becomes hypotonic as Na+ reabsorbed by ducts
- Important for thermoregulation
Hair
- Develop in utero w/ downgrowth of epidermis forming a pilosebaceous unit
- Hair itself consists of central medulla of soft keratin + cortex & cuticle of hard keratin
- Hair growth is intermittent (growth period of 2-3 years followed by rest period of several months)
- Pigment comes from melanocytes at base of hair
- W/contraction of arrector pili muscle (smooth muscle), hairs stand on end (“goose bumps”)
Sebaceous glands
- Oil glands which secrete sebum (complex mixture of lipids)
- develop along w/ hair follicles & empty their secretion into upper 1/3 of hair follicles
- development accelerated at puberty
Types of Primary Skin Lesions
Macule < Patch Papule < Nodule < Tumor Plaque Scale Wheal Vesicle < Bulla Pustule Atrophy < Erosion < Ulceration
Macule
- Circumscribed change in skin color that is flush w/ surrounding skin
- Lesion is <1.0 cm in diameter (smaller than patch)
Examples:
Solar lentigo
Traumatic purpura
Patch
- Circumscribed change in skin color that is flush w/ surrounding skin
- Lesion is ≥1.0 cm in diameter (bigger than macule)
Examples:
Café au lait spot
Vitiligo
Papule
= A solid or cystic elevation
- <1.0 cm in diameter (smaller than nodule & tumor)
Examples:
Acne
Eruptive xanthoma
Nodule
= A solid or cystic elevation
- > 1.0 cm but <2.0 cm in diameter (larger than papule, smaller than tumor)
- Example: Dermato-fibroma
Tumor
- A solid or cystic elevation
- > 2.0 cm in diameter (larger than papule/nodule)
- Example: Follicular cyst
Plaque
- An elevated lesion that is >1.0 cm in diameter
- Example: Psoriasis
Scale
= Desiccated, thin plates of cornified epidermal cells that form flakes on the skin surface
- Example: Ichthyosis
Wheal
= Circumscribed, flat-topped, firm elevation of skin with a well-demarcated and palpable margin
- Example: Urticaria
Vesicle
= Circumscribed, elevated lesion containing clear serous or hemorrhagic fluid
= <1 cm in diameter (smaller than bulla)
Examples:
- Contact dermatitis
- Herpes simplex
Bulla
= Circumscribed, elevated lesion containing clear serous or hemorrhagic fluid
= >2 cm in diameter (larger than vesicle)
- Example: Bullous pemphigoid
Pustule
= A vesicle containing purulent exudate
- Example: Folliculitis
Atrophy
= A depression from the surface of the skin with underlying loss of epidermal or dermal substance (less severe loss than erosions & ulcerations)
- Example: Lichen sclerosis et atrophicus
Erosion
= A depression from the surface of the skin with a loss of all or part of the epidermis (more severe loss than atrophy, less severe than ulcerations)
- Example: Burn
= Can be a secondary lesion
- Example: Ruptured bulla
Ulceration
- A depression from the surface of the skin with a loss of the entire epidermis and at least some of the dermis (more severe loss than atrophy & erosion)
- Example: Ecthyma
Secondary Lesions result from…
- external forces such as scratching, picking, infection or healing of primary lesions
Types of Secondary Lesions
Lichenification
Scar
Fissure
Crust
Lichenification
= Dry, leathery thickening of the skin with exaggerated skin markings
- EX: Chronic eczema
Scar
= An elevated or depressed area of fibrosis of the dermis or subcutaneous tissue resulting from an antecedent destructive process
- EX: Healing wound
Fissure
= A deep linear split in the skin extending through the epidermis
- EX: Traumatized eczema
Crust
= Dried exudates of serum, blood, sebum, or purulent material on the surface of the skin
- EX: Acute and/or secondarily infected eczema
Disease caused by Skin chronically exposed to sunlight (face, neck, hands, arms)
Actinic keratosis
Basal cell carcinoma
Squamous cell carcinoma
Skin disease in central chest, shoulders, & earlobes
Keloids
Skin disease in extensor arms and legs, intragluteal cleft, umbilicus
Psoriasis
Skin disease in antecubital fossa, popliteal fossa
Atopic dermatitis
Skin disease in anterior surface of lower legs
Palpable purpura
Pretibial myxedema
Necrobiosis lipoidica diabeticorum
Erythema nodosum
Skin disease in axilla & inguinal areas
Hidradenitis suppurativa
Skin disease in posterior neck & back
Folliculitis
Skin disease in web spaces of toes & sides of feet
Tinea pedis
Skin disease in web spaces of fingers & wrists
Scabies
Skin disease in palms & soles
Secondary syphilis
Erythema multiforme
Skin disease with Clustered arrangement
Herpes simplex
Skin disease with Grouped arrangement
Lichen planus
Granuloma annulare
Skin disease with Linear arrangement
Allergic contact dermatitis
Skin disease with Zosteriform arrangement
Herpes zoster
Skin disease with Annular arrangement w/out scale
Urticaria Hansen disease (leprosy)
Skin diseases with Annular arrangement with scale
Dermatophytosis
Pityriasis rosea
Skin diseases with Coalescing arrangment
Psoriasis
Drug hypersensitivity eruption
Viral exanthema
Urticaria
