Skin Histology

1
Chapter 5

• Skin Histology
• Epidermis
• J.F. Thompson, Ph.D.

2
The Architecture of the Skin

• 2 Principal portions
• Epidermis - epithelium
• Dermis areolar and dense irregular fibrous
  connective tissue
• Hypodermis
• beneath the dermis
• the subcutaneous layer next to
• adipose layer or
• muscle or
• bone

3
The Epidermis

• Stratified Squamous Epithelium
• 4 cell types
• Keratinocytes - 90
• filled with keratin (protein)
• waterproof barrier
• Melanocytes - 8
• produce melanin (pigment)
• pass melanin to keratinocytes
• Langerhans cells
• phagocytes (from immune system)
• easily damaged by UV light
• Merkel cells
• in deepest layer of hairless skin
• sensory transduction - touch

4
Keratinocytes and Melanocytes
5
Merkel Cells
6
Langerhans Cells
7
Epidermal Cell Layers

• Stratum basale
• A single layer of cuboidal/columnar cells
• Stem cells, melanocytes, Merkel cells
• Stem cells ? keratinocytes, mitosis pushes the
  other layers to the top
• Stratum spinosum
• 8 to 10 layers of closely packed cells
• Cell junctions - spot desmosomes
• Langerhans cells

8
Epidermal Cell Layers

• Stratum granulosum
• 3-5 layers of flattened, with keratohyaline
  granules
• beginning breakdown of nucleus, cell death
  initiated
• Stratum lucidum
• only in thick skin (palms, feet)
• 3-5 layers of clear, flat dead cells with keratin
• Stratum corneum
• 20-30 layers of flattened, dead, keratin-filled
  cells
• continuously shed and replaced
• 2-4 weeks for each cell to form and to move from
  the stratum basale to the surface

9
Thin Skin
10
Thin Skin

• Stratum Corneum
• Stratum Granulosum
• Stratum Spinosum
• Stratum Basale

11
Thick Skin
12
End Ch 5

• Skin Histology
• Epidermis