Skin Layers

Epidermis

• Stratum Corneum
  • Horny, Keratin Layer
• Stratum Lucidum
  • Seen with thick horny layer (palms & soles)
• Stratum Granulosum
  • Granular Layer
• Stratum Spinosum
  • Prickle, Spiny Layer
  • Langerhans Cells: Function as macrophage of the epidermis and process contact antigens
• Stratum Germinativum
  • Basal cell layer

• • Basal Cell Keratinocyte: only cell of the epidermis capable of division.
    • They divide and migrate upward.
    • Total turnover time is 28 days (14 days of migration and 14 days to be discarded)
  • Melanocyte: Produces malanin which is transferred to keratinocytes.
    • Melanin protects the skin from UV Radiation.
    • In whites, found mostly in basal cell layer.
    • In blacks, found throughout the epidermis.

Dermal-Epideramal Junction (Basement Membrane)

• Lamina Lucida
• Lamina Densa
• Sublamina Densa

Dermis

• Papillary Dermis: Immediately beneath epidermis.
  • Thin haphazardly arranged collage fibers, abundant ground substance, and delicate elastic fibers
• Reticular Dermis: extends to the subcutanous fat.
  • Coarse elastic fibers and thick collagen bundles arranged mostly parallel to skin surface

 

​

 

 

Skin Structures

Hair Follicle

• Hair growth proceeds through distinct phases
  • Anagen: prolonged growth
  • Catagen: short lived interphase
  • Telogen: final resting phase
• Cells of hair bulb produce hair shaft which is completely keratinized and has no living cells.
• Hair color is due to the amount and type of melanin.

Eccrine Glands

• Found in highest concentration on palms, soles, and axillae.
• Secretory coil located in dermis, transmits sweat directly to skin surface for cooling of body

Apocrine Glands

• Found primarily in axillae and anogenital regions and serves as a scent gland.
• derived from hair germ and opens directly into pilosebaceous follicle rather than skin surface.
• Become active at puberty

Sebaceous Glands

• Found on all body parts except palms and soles
• Produces oil (sebum) that is emptied into the hair follicle.
• Lubricates and protects the hair and skin

Arrectores Pilorum

• Smooth muscle attached to the base of the hair follicle
• Contract in response to cold or fright
• "goose bumps"

 

​Primary LesionsMacule:Circumscirbed, Flat (without elevation or depression), Nonpalpable change in skin color. <1 cm in diameter.e.g., freckle, petechiae​Patch:Similar to macule but > 1 cm Papule:Palpable, circumscribed, solid elevation,Less than 1 cm in diametere.g., elevated nevus​Wheal:Irregularly shapedElevated area or superficial localized edemavaries in sizeEdematous papulee.g., hive, mosquito bite​Nodule:Elevated solid massDeeper and firmer than papule1-2 cme.g., wart​Tumor:Solid mass that extends deep through subcutaneous tissuesimilar to Nodulelarger than 2 cme.g., epithelioma​Plaque:an elevation above the skin with a plateau-like surface. Vesicle:Circumscribed elevation of skinfilled with serous fluidless than 1cm.e.g., herpes simplex, chickenpox​Bulla:Similar to vesicle but > 1 cm. Pustule:Circumscribed elevation of skinSimilar to vesicle but filled with neutrophils and dead bacteria.Fluid is white or yellow (pus)Varies in sizee.g., acne, staphylococcal infection​ Secondary LesionsScale:an excess of horny material on the skinCrust:scab consisting of dried blood, serum, or pusErosion:Scooped out and shallow break.  No damage to the dermisFissure:linear form of an erosionUlcer:Deep lesion involving the dermisEschar:Dark colored, hard to remove crust on ulcer Shapes and Arrangements of LesionsAnnular:round lesion, ring-like.The rim is different from the centerLinear:long, thin lesion or smaller lesions in a long, thin line.Target or Iris:Concentric rings like an arches target.Imbricated:Target lesions with near form of an erosionSerpiginous:Snake-like.Partially circular and undulatingGeographic:Outline of a continent on a mapVegetating:Lesion has a surface that grows outward in uneven, fleshy tufts that feel soft.Verrucous:Wart-LikeTufts of protruding lesion are hyperkeratotic, not soft.Zosteriform:Conforming to the distribution of a nerve root.Polycyclic or Circinate:Annular lesions grow together, Parts of their cirlces form larger lesion.Grouped:Several similar lesions located in close proximity surrounded by a large area of normal skin Morphology of LesionsThe following aspects should be included in every description:SizeColorConsistency: Soft, Medium, FirmConfiguration: Shape or outline of lesionMargination: sharp or diffuseSurface Characteristics: Smooth or rough