skin layers

The integument: the cover

Consists of:

• Epidermis (superficial)

• Epithelial tissues

• Dermis (deep to epidermis)

• Fibrous connective tissues

• Hypodermis / Subcutaneous
  tissue / Superficial fascia (deep to dermis)

• Adipose connective tissue

• Several accessory structures & appendages

• Hair, nails, glands, etc...

Epidermis: Superficial Layers of Skin

Keratinized Stratified Squamous Epithelium

Cells of the Epidermis

• Keratinocytes (majority of cells)
  Makes keratin
  Desmosomes

• Melanocytes (deep within epidermis)

• Makes melanin
  Protection from UV damage

• Dendritic (langerhans) cells

• Macrophages (WBCs) - immunity

• Tactile (merkel) cells

• Sensory touch receptors

Stratum basale (deepest)

• Single row, actively mitotic cells
  25-45 days journey to surface = death!
  Melanocytes present

stratum spinosum

Several layers of cells in a web-like series of filaments
Melanocytes & dendritic cells present

Stratum granulosum

• 4-6 cell layer where cells
  appearance changes = flattening!
  Keratinization begins

Stratum lucidum

• Only present in thick skin

• Thin & translucent

• Flat, dead keratinocytes

Stratum corneum (superficial)

20-30 rows, flat, dead keratinized "cells"

Protection & barrier

Dermis: Deep, Double Layer

Connective tissues: Areolar, Dense Irregular

Papillary Layer (20% of dermis)

• Areolar connective tissue

• Collagen & elastic fibers, BVs

• Allows WBCs to work

• Superficial projections

  -Contain Meissner's corpuscles

(touch receptors)

• Contain free nerve endings

(pain receptors)

Ridges in thick skin

Enhance grip

Fingerprints

Reticular Layer (80% of dermis)

• Dense irregular connective tissue

• Elastic fibers = recoil

• Collagen fibers = strength, bind water & create
  cleavage lines

• Incisions parallel heal faster

Flexure lines

Visible dermal creases at/near joints

Striae (stretch marks)

Dermal tears

Blisters

Fluid-filled pocket b/w epidermis & dermis

Autoimmune blistering disorders include bullous pemphigoid & pemphigoid gestationis (rare)