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.