Epidermis

• What type of epithelium is the dermis?

  Keratinized stratified squamous epithelium
• Melanocytes: pigment-producing cells
• Langerhan cells: Antigen-presenting cells
• Merkel cells: tactile epithelial cells
• What are the 3 less abundant cells in the epidermis?

  Melanocytes, Langerhan cells, and Merkel cells
• The function of the epidermis is to protect the body from HARMFUL INFLUENCES and against FLUID LOSS.
• The epidermis provides a PHYSICAL BARRIER against DERMAL and MECHANICAL insults like friction and against pathogens.
• Epidermis serves as a PERMEABILITY BARRIER against excessive loss or uptake of WATER
• Epidermis is NON-VASCULAR and receives nutrients by DIFFUSION from the DERMIS
• The thickness of the EPIDERMIS forms the basis for the differentiation between THICK SKIN and THIN SKIN
• Label:

  A) Palms and Soles

  B) All over the body

  C) 400-1400 um

  D) 75-150 um

  E) Present

  F) Absent

  G) Well-developed

  H) Poorly developed

  I) More

  J) Few

  K) Absent

  L) Present

  
• What is this?

  Thick skin

  
• What is this?

  Thin skin

  
• Stratum BASALE is a SINGLE LAYER of BASOPHILIC CUBOIDAL or COLUMNAR cells on the basement membrane at the dermal-epidermal junction.
• Stratum basale rest on the basement membrane via what?

  Hemidesmosomes
• What binds the cells of stratum basale together in the lateral and upper surface?

  desmosomes
• What is the deepest layer of the skin?

  Stratum basale
• Stratum basale has an INTENSE MITOTIC ACTIVITY
• What cells do stratum basale have?

  progenitor or precursor cells
• Thick skin has what thicker stratum?

  Spinosum
• Stratum spinosum has 4-6 layers of POLYHEDRAL CELLS which are actively synthesizing KERATINS
• Which stratum has cells appearing to form numerous cytoplasmic extension or "spines" which are DESMOSOMES?

  Stratum spinosum
• What is the thickest stratum of the epidermis?

  Spinosum
• Tonofibril: visible bundles of keratin that converge and terminate at the desmosomes
• Stratum spinosum: elements found are living keratinocytes, langerhan cells,and tonofibril
• Stratum granulosum: 3-5 layers of FLATTENED CELLS which are undergoing keratinization
• Granulosum: water-resistant layer
• Granulosum: transition between metabolically active cell layers and dead cell layers
• Granulosum contains what a LIPID-RICH Layer consisting of?

  Lamellar granules
• Stratum lucidum: 2-3 thin, TRANSLUSCENT layer of dead, flattened, anucleate keratinocytes
• Lucidum: barely visible layer
• Lucidum: only found in THICK SKIN
• Lucidium: tightly and dense packed cells
• Corneum: 15-20 layers of dead, anucleate, squamous keratinized cells
• Corneum: brick wall apperance
• Corneum: desquamation occurs in this layer