Lab Lecture: Accessory Organs of the Epidermis

Introduction

• Focus on accessory organs: nails, hairs, and glands.
• Importance of identifying structures for the lab exam.

Nails

• Derived from the stratum corneum:
  • Most superficial layer of the epidermis.
• Key Structures:
  • Nail body (Nail plate): Visible part, except the free edge.
  • Free edge: Unattached end of the nail.
  • Lanula: White portion due to thicker stratum basale.
  • Nail folds: Lateral borders.
  • Nail grooves: Where nail meets the folds.
  • Nail root: Hidden under living tissue.
  • Nail matrix: Surrounds nail root, responsible for growth.
  • Cuticles:
    • Eponychium: Above the nail.
    • Hyponychium: Below the free edge, both made of thickened corneum.

Hair

• Regions (Zones):
  • Hair bulb: Deepest part, contains hair matrix.
  • Hair root: Between bulb and exposed part.
  • Hair shaft: Exposed portion, made of dead keratinocytes.
• Structures within hair root:
  • Medulla: Innermost layer.
  • Cortex: Middle layer, contains cells.
  • Cuticle: Outer layer.
• Associated with:
  • Hair papilla: Contains blood vessels and nerves.
  • Erector pili muscle: Involuntary control, triggers with temperature or stress.

Glands

Sweat Glands (Sudoriferous)

• Merocrine-Eccrine Glands:
  • Secrete mostly water via exocytosis.
  • Found in both thin and thick skin, abundant in forehead, palms, soles.
  • Simple cuboidal structure.
• Apocrine Glands:
  • Larger, secrete lipids and proteins.
  • Found in axillary, pubic, and anal regions (thin skin).
  • Activated during puberty, associated with body odor.
  • Modified forms:
    • Ceruminous glands: Secrete earwax (cerumen).
    • Mammary glands: Secrete breast milk.

Oil Glands (Holocrine/Sebaceous)

• Secrete sebum:
  • Lubricates hair and skin.
  • Usually associated with hair follicles.
  • Activated by puberty hormones, potential cause of acne.

Conclusion

• Review the hit list for all structures to identify.
• Check lab model recordings for visual aid.
• Reach out with questions.