RT 211 | LECTURE 3

• Layers of the Skin:

  • Epidermis:
  • Horny layer (stratum corneum)
  • Clear or translucent layer (stratum lucidum)
  • Granular layer (stratum granulosum)
  • Prickle cell layer (stratum spinosum)
  • Germinal or basal layer (stratum germinativum)
  • Dermis:
  • Papillary layer (stratum papillare)
  • Reticular layer (stratum reticulare)
• Epidermis:

  • Outer layer
  • Also known as squamous due to flat and scaly superficial cells
• Layers of Epidermis:

  • Horny layer:
  • Composed of degenerated cells without cellular structure
  • Translucent or clear layer:
  • Consists of cells without nuclei and cellular outlines
  • Granular layer:
  • Contains flattened cells with granules
  • Prickle cell layer:
  • Consists of many-sided cells
  • Germinal or basal cell layer:
  • Columnar cells at the deepest part of the epidermis
  • Contains a pigment determining skin darkness
• Dermis:

  • Composed of loose (areolar) connective tissue with fibrous bands and elastic tissue fibers
  • Papillary layer:
  • Elevated surface with hollows
  • Reticular layer:
  • Forms an interlacing network
  • Contains blood vessels and nerves
• Appendages of the Skin:

  • Nails
  • Hair
  • Sebaceous glands
  • Sweat or sudoriferous glands
  • Ceruminous glands
• Nail:

  • Stratum lucidum thickens to form a protective covering
  • Nail root: covered by skin fold
  • Body of the nail: exposed part with lunula close to the root
  • Eponychium: outer epidermis layer at the base
• Hair:

  • Modification of the epidermis
  • Hair follicle: canal opening on the skin surface
  • Root of a hair: part below the skin level in a follicle
  • Bulb: inner enlarged end of each hair root
• Sebaceous Gland:

  • Small glands beside hair follicles
  • Secretes oily substance (sebum) for lubrication
• Sweat or Sudoriferous Glands:

  • Simple tubelike glands with a single canal and coiled secreting part
  • Secrete watery solution with sodium chloride and waste products
• Ceruminous Glands:

  • Modified sweat glands in the external ear
  • Secrete wax into the external auditory meatus
• Subcutaneous Tissue:

  • Areolar connective tissue layer between skin and deeper structures
• Functions of the Skin:

  • Protective covering
  • Excretes water and waste products
  • Regulates body temperature
  • Contains sensory receptors transmitting sensations to the brain
• Secreting Glands:

  • Extract raw materials and manufacture secretions
  • Endocrine Glands
  • Exocrine Glands
• Classification of Exocrine Glands:

  • Simple tubular gland
  • Branched tubular gland
  • Simple saccular or alveolar gland
  • Branched saccular or alveolar gland
  • Combined tubualveolar gland