Skin & Soft Tissue: Anatomy & Physiology

Anatomy

Skin Layers

  • Epidermis
  • Dermis
  • Subcutaneous Fascia (Hypodermis)

Epidermis

  • Layers: Mn
    • Stratum Corneum – Thickest & Outermost Layer
    • Stratum Lucidum – Present Only in Thicker Skin (Palms & Soles)
    • Stratum Granulosum
    • Stratum Spinosum
    • Stratum Basale (Stratum Germinativum)
    • Basement Membrane
  • Cell Types:
    • Keratinocytes
      • Primary Cell Type of the Epidermis
      • Originate in the Basal Layer
      • Produce Keratin & Secrete Lipids to Form a Water Barrier
    • Melanocytes
      • Derived from Neural Crest Cells
      • Produce Melanin & Transfer it to Keratinocytes
      • Skin Tone is Based on Melanin Production
        • Melanocyte Density is Generally Similar
    • Langerhans Cells
      • Dendritic Cells (Antigen Presenting Cells)
    • Merkel Cells
      • Sensory Receptors for Light Touch
      • Highest Density in Fingertips

Dermis

  • Layers:
    • Papillary Layer – Outermost Layer Just Deep to the Basement Membrane
      • Made of Loose Connective Tissue with Loosely-Packed Collagen
      • Dermal Papillae – Extensions into the Epidermis that Form Papillary Ridges (Fingerprints)
    • Reticular Layer – Deeper Layer
      • Made of Dense Connective Tissue with Densely-Packed Collagen (Provides Strength
      • Tensile Strength Provided by Type I Collagen
  • Sensory Nerves:
    • Pacinian Corpuscle: Sense Deep Pressure
    • Meissner Corpuscle: Tactile/Low-Frequency Stimulation
    • Ruffini Corpuscle/Ending: Sense Sustained Pressure & Warmth
    • Krause End-Bulbs: Sense Cold
  • Sweat Glands:
    • Eccrine Sweat Glands
      • Distribution: Everywhere but Highest in Palms/Soles
      • Secretion: Aqueous Fluid for Cooling
      • Secrete Directly onto the Skin
    • Apocrine Sweat Glands
      • Distribution: Axilla, Groin, Gluteal & Inframammary Folds
      • Secretion: Cloudy Thick Sweat Mn
      • Secrete into the Pilary Canal of Hair Follicles
      • Inactive Prior to Puberty
  • Langer’s Lines – Topological Cleavage Lines that Define Tension
    • Correspond to Collagen Alignment in the Reticular Dermis
    • Often Used in Making Surgical Incisions

Subcutaneous Tissue (Hypodermis)

  • Primarily Used for Fat Storage (Adipocytes)
  • Also Contains Nerves, Blood Vessels & Lymphatics

Layers of the Epidermis 1

Layers of the Dermis 2

Contents of the Dermis 3

Langer’s Lines 4

Mnemonics

Layers of the Epidermis

  • “Come, Let’s Get Sun Burned”
    • Corneum
    • Lucidum
    • Granulosum
    • Spinosum
    • Basale

Apocrine vs Eccrine Sweat Glands

  • Dirty Apes (APE-ocrine) Stink

References

  1. Haggstrom M. Wikimedia Commons. (License: CC BY-SA-3.0)
  2. OpenStax College. Wikimedia Commons. (License: CC BY-3.0)
  3. Blaus B. Wikimedia Commons. (License: CC BY-3.0)
  4. Goran Tek-en. Wikimedia Commons. (License: CC BY-SA-4.0)