Intro to Dermatology Flashcards
Functions of the Skin
- Decoration/Beauty
- Barrier –> physical, light, immunologic
- Vitamin D synthesis
- Water Homeostasis
- Thermoregulation
- Insulation/Calorie Reservoir
- Touch/Sensation
Fitzpatrick Skin Types
Types I - VI
Factors in: hair color, eye color, skin color, freckles, how easily you sunburn, and if you tan
Fitzpatrick Type I
Red/blond hair
Blue/green eyes
White skin
+++ Freckles
Always sunburn
Don’t tan
Fitzpatrick Type II
Blond/brown hair
Light to medium eyes
Fair skin
++ Freckles
Easily sunburn
Minimally tan
Fitzpatrick Type III
Brown hair
Medium to dark eyes
Light brown skin
+ Freckles
Initially sunburn
Gradually tan
Fitzpatrick Type IV
Medium to dark hair
Dark eyes
Moderate brown skin
0 freckles
Minimally sunburn
Tans well
Fitzpatrick Type V
Dark hair
Dark eyes
Dark brown skin
0 freckles
Rarely sunburn
Dark tan
Fitzpatrick Type VI
Dark hair
Dark eyes
Black skin
0 freckles
Never sunburn
Always tan
Components of the Skin
- Epidermis
- Dermis
- Adnexal Structures
- Subcutaneous fat
Cells of the epidermis
Keratinocytes
Melanocytes
Langerhans cells
Keratinocytes
Form barrier layer; synthesize keratin; involved in defined cycle of proliferation, differentiation, and apoptosis
Melanocytes
Pigment producing cells; arise from neural crest
Located primarily in basal layer of epidermis in hair follicles
Synthesize melanin, which protects DNA from UV damage
Melanin is packaged in melanosomes (granules)
Langerhans cells
Dendritic cells found in small numbers in all epidermal layers
Where do we get variation in skin color?
- Type of melanin produced
- Eumelanin: black to brown pigment
- Pheomelanin: yellow to red-brown pigment
- Distribution of melanosomes
- Light Skin: melanosomes distributed in clusters above the nucleus
- Dark Skin: melanosomes distributed individually throughout the cytoplasm
What DOES NOT influence skin color variation?
of melanocytes in skin
How frequently does your skin renew?
~ every 28 days
Layers of epidermis
- stratum basalis (germinativum) = Basal cell Layer
- stratum spinosum
- stratum granulosum
- stratum granulosum
- stratum corneum
Stratum basalis
Consists of a single layer of columnar or cuboidal cells (keratinocytes)
• Basal keratinocytes are the stem cells of the epidermis
- Hemidesmosomes: attach basal cells are firmly to the basal lamina of the dermal-epidermal junction
- Desmosomes: attach keratinocytes to each other
- Tonofilaments: protein structures (keratin filaments) that insert into the dense plaques of desmosomes on the cytoplasmic side of the plasma membrane
Stratum spinosum
Has a “prickly” or spiny appearance due to desmosome attachments between cells
- intercellular adhesion depends upon the tonofilament-desmosome interaction in the distribution of stress
- synthesis of involucrin and membrane coating granules begins in this layer
Stratum granulosum
Keratohyalin granules contain Profilaggrin (filaggrin precursor). Filaggrin cross-links keratin tonofilaments and is important in the barrier function of the skin.
Stratum lucidum
under the light microscope, a thin, light staining band seen only in thick skin
• cells of this layer no longer have nuclei or organelles
Stratum corneum
- the outermost layers of epidermis
- keratinocytes have lost their nuclei and organelles and the entire cell is filled with keratin
- desmosomes still connect tightly packed adjacent cells
Layers of Dermis
- Papillary layer
- Reticular layer
Papillary layer of dermis
Site of attachment to epidermis and necessary to its development and differentiation
- contains capillary network that is blood supply for epidermis
- pathway for defense cells
- contains Meissner’s corpuscles which sense touch
Reticular layer of dermis
- contains extensive collagen and elastic fibers that provide strength and flexibility
- houses (along with hypodermis) epidermal derivatives such as glands and hairs and plays a major role in their development and functioning
- pathway for major blood vessels arranged specifically to facilitate thermoregulation
- site of nerve tracts and major sensory receptors
- Pacinian corpuscles sense vibration, pressure and touch
Meissner’s corpuscles
- detect delicate touch
- are most commonly found in the dermal papillae of thick skin
- consist of Schwann cells and sensory nerve terminals wrapped by fibroblasts and collagen
Pacinian corpuscles
- are rapidly adapting receptors that detect changes in deep pressure (vibrations)
- are found in the dermis of both thin and thick skin
- large structures resembling an onion
- the concentric layers are composed of flattened connective tissue like cells interspersed with intercellular fluid and collagen
- a single sensory nerve fiber terminates within this structure
Adnexal structures of skin
- Apocrine sweat glands
- Eccrine sweat glands
- Hair
- Nails
- Sebaceous glands
Apocrine sweat glands
- Specialized sweat glands located in the axillary, pubic and perianal regions
- produce a milky, viscid, carbohydrate-rich secretion
- 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 the lips, under the nails or on the glans penis, glans clitoris, or labia minora
- Watery, enzyme-rich secretion
- Important for thermoregulation (cooling)
Hair
- Develop in utero with down growth of the epidermis forming a pilosebaceous unit
- The hair itself consists of a central medulla of soft keratin, and a cortex and cuticle of hard keratin.
- Hair growth is intermittent; a growth period of 2 to 3 years is followed by a rest period of several months.
- Pigment comes from melanocytes at the base of the hair
Sebaceous glands
- Oil glands which secrete sebum, a complex mixture of lipids
- develop along with hair follicles and empty their secretion into the upper one-third of hair follicles
- development accelerated at puberty
