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Integumentary System Overview

Mar 7, 2025

The Integumentary System Overview

Structure of the Skin (Integument)

  • Composed of two main layers:
    • Epidermis: The outermost superficial region.
    • Dermis: Lies beneath the epidermis, primarily made of fibrous connective tissue.
  • Hypodermis (Superficial Fascia):
    • Subcutaneous layer situated deep to the skin.
    • Not a part of the skin, but shares some functions.
    • Mainly composed of adipose tissue, providing shock absorption and insulation.

Epidermis Details

  • Type of Epithelium:
    • Keratinized stratified squamous epithelium.
  • Layers of the Epidermis:
    • Stratum basale
    • Stratum spinosum
    • Stratum granulosum
    • Stratum lucidum (present only in thick skin)
    • Stratum corneum
  • Cell Types in Epidermis:
    • Keratinocytes
    • Melanocytes
    • Dendritic (Langerhans) cells
    • Tactile (Merkel) cells

Dermis Overview

  • Composition:
    • Strong, flexible connective tissue.
    • Contains fibroblasts, macrophages, occasionally mast cells, and white blood cells.
  • Functions:
    • Matrix fibers bind the body together.
    • Houses nerve fibers, blood, lymphatic vessels, epidermal hair follicles, oil and sweat glands.
  • Layers:
    • Papillary layer
    • Reticular layer

Skin Color

  • Pigments Influencing Skin Color:
    • Melanin (the only pigment synthesized in the skin)
    • Carotene
    • Hemoglobin

Skin Appendages

  • Types:
    • Hairs and hair follicles
    • Nails
    • Sweat glands
    • Sebaceous (oil) glands

Sweat Glands

  • Also known as sudoriferous glands.
  • Located all over skin except nipples and parts of external genitalia (~3 million per person).
  • Types:
    • Eccrine (Merocrine) Sweat Glands:
      • Most numerous, especially on palms, soles, and forehead.
      • Ducts lead to pores, involved in thermoregulation.
      • Sweat is 99% water with salts, vitamin C, antibodies, dermcidin, and wastes.
    • Apocrine Sweat Glands:
      • Found in axillary and anogenital areas.
      • Produce sweat mixed with fatty substances and proteins, leading to body odor.
      • Begin functioning at puberty, potentially acting as sexual scent glands.
    • Modified Apocrine Glands:
      • Ceruminous glands (secrete earwax)
      • Mammary glands (secrete milk)

Sebaceous (Oil) Glands

  • Widely distributed, but not in thick skin of palms and soles.
  • Develop from hair follicles, secreting into them.
  • Remain relatively inactive until puberty and are stimulated by hormones.
  • Produce sebum, an oily secretion that softens hair and skin.

Functions of the Integumentary System

  • Protection
  • Body temperature regulation
  • Cutaneous sensation
  • Metabolic functions
  • Blood reservoir
  • Excretion

Skin Cancer

  • Most skin tumors are benign and non-metastatic.
  • Risk Factors:
    • UV radiation overexposure
    • Frequent skin irritation
    • Some lotions contain DNA-repairing enzymes.
  • Types of Skin Cancer:
    • Basal cell carcinoma
    • Squamous cell carcinoma
    • Melanoma

Melanoma

  • Cancer of melanocytes, most dangerous type.
  • Highly metastatic and resistant to chemotherapy.
  • Treatment involves surgical excision and immunotherapy.
  • ABCD Rule for Detection:
    • A: Asymmetry
    • B: Border irregularity
    • C: Color variation
    • D: Diameter > 6 mm

Burns

  • Causes: Heat, electricity, radiation, and certain chemicals.
  • Effects: Protein denaturation and cell death.
  • Immediate Threat: Dehydration and electrolyte imbalance, leading to renal shutdown and shock.
  • Evaluation:
    • Rule of nines used to estimate fluid loss.
  • Classification by Severity:
    • Partial-thickness burns:
      • First degree: Epidermal damage only.
      • Second degree: Damage extends to upper dermis.
    • Full-thickness burns:
      • Third degree: Involves entire skin thickness, requires grafting.
  • Treatment:
    • Debridement, antibiotics, temporary coverings, and skin grafts.