Introduction to Wound Healing

What is Skin?

diagram of skin

  • A barrier between internal organs and the external environment
  • The body’s largest organ contributing to one sixth of the total body weight
  • A sensory organ for pain, temperature, and touch
  • A protective barrier against disease-causing organisms

 

Structure and Function of the Skin

structure of the skin diagram

A. Structure

Epidermis

  • The outmost/top layer of the skin
  • Has an average thickness of 0.1mm
  • Avascular (no blood vessels)
  • Divided into five sublayers/strata: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum germinativum (stratum basale)
  • Contains four distinct layers of cells:
    1. Keratinocytes - Most abundant; Produces keratin which provides mechanical and physical protection as well as producing enzymes and antibiotics that detoxify chemicals that are harmful to the skin
    2. Melanocytes - Produce melanin which imparts color to skin and hair
    3. Merkel Cells - Play a role in transmission of sensory messages
    4. Langerhan Cells – These cells police the outer body surface to take up foreign proteins (antigens) that invade the epidermis; They can travel to a nearby lymphnode where they present the antigens to a type of immune cell called Killer T lymphocyte.
  • The external layer is almost completely replaced every three to four weeks

Dermis

  • Immediately below the epidermis
  • Largest portion of the skin
  • Composed of two layers:
    1. Papillary
      – Lies directly below the epidermis and contains fibroblasts that form collagen (a component of connective tissue)
    2. Reticular
      – Lies beneath the papillary layer and produces collagen and elastin
  • Provides tensile strength, mechanical support and protection to the underlying muscles, bones, and organs
  • Made up of blood and lymph vessels, nerves, sweat and sebaceous glands and hair roots
  • Often referred to as true skin

Hypodermis/Subcutaneous

  • Innermost layer of the skin
  • Composed of fat, blood vessels, and connective tissue
  • Anchors to deep tissue
  • Regulates body and skin temperature
  • Stores energy in the form of fat

B.  Function

  • Facilitates perception of environment – pain, pressure, touch, and temperature
  • Provides a barrier against friction, chemicals, heat/cold, pressure, radiation, and microorganisms
  • Plays a role in fluid balance, thermal regulation, and facilitates in Vitamin D synthesis

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The content and images on the Wound Care Site are intended for Health Professionals and may be disturbing to some.
Last Updated July 20, 2009 | © 2007, LHSC, London Ontario Canada