Chapter 6 Lecture

Chapter Overview

  • Focus on the integumentary system, its components, and functions.

Icebreaker Questions

  • Functions of the skin?
  • Identify structures that help accomplish skin functions.
  • How does the human body repair damaged skin?

Layers of the Skin

Learning Objectives (6.1.1 - 6.1.13)

  • Understanding the anatomy and functions of the skin and its layers.

Components of the Integumentary System

  • The integumentary system comprises:
    • The skin
    • Hair
    • Nails
    • Associated exocrine glands

Skin Layers

  • The skin consists of three main layers:
    • Epidermis
    • Dermis
    • Hypodermis (Subcutaneous layer)
  • Fascia connects the skin to underlying muscles.

Surgical Anatomy

Think, Pair, Share Activity 1

  • Order of skin layers cut during abdominal surgery:
    1. Epidermis
    2. Dermis
    3. Hypodermis
    4. Fascia

Epidermis

  • The most superficial layer of the skin.
  • Composed of keratinized stratified squamous epithelium.
  • Avascular (lacks blood vessels).
  • Contains four to five layers, depending on the site:
    • Thick skin (five layers)—found on palms and soles.
    • Thin skin (four layers)—found elsewhere.

Layers of the Epidermis

  • Thick skin has one extra layer.
  • Cells migrate from the deepest to the superficial layer.
  • Mature cells are termed keratinocytes.
  • Keratin grants toughness and water resistance.
Layers (Superficial to Deep)
  1. Stratum corneum
  2. Stratum granulosum
  3. Stratum spinosum
  4. Stratum basale

Knowledge Check Activity 1

Question
  • Identify which layer is absent in thin skin:
    • Stratum corneum
    • Stratum lucidum
    • Stratum basale
    • Stratum granulosum
    • Stratum spinosum
Answer
  • Stratum lucidum (B) is absent in thin skin.

Stratum Basale

  • Deepest of the epidermal layers.
  • Single layer of actively dividing cells that replace upper layers.
Additional Cells in Stratum Basale:
  • Merkel cells: Sensory receptors for touch.
  • Melanocytes: Produce melanin, protecting from UV radiation.

Stratum Spinosum

  • Comprises eight to ten layers of keratinocytes.
  • Cells shaped like footballs; pointed ends appear spiny.
  • Contains Langerhans cells for immune defense.
  • Cells move towards the stratum granulosum.

Stratum Granulosum

  • Cells flatten and accumulate keratin, giving it a granular appearance.
  • Melanin may diffuse into this layer.
  • Cells begin to die in the most superficial regions.

Stratum Lucidum

  • Present only in thick skin (palms and soles).
  • Formed of tightly packed dead keratinocytes.
  • Contains eleidin, a protein functioning as a water barrier.

Stratum Corneum

  • Most superficial layer; 15 to 30 layers of dead keratinocytes.
  • Cells are shed due to mechanical forces.
  • Deep layers migrate to replenish the corneum.

Dermis

  • Composed of connective tissue.
  • Forms projections into the epidermis.
  • Contains:
    • Blood vessels
    • Hair follicles
    • Glands
  • Supports the epidermis with nutrients, strength, and elasticity.

Layers of the Dermis

  • Two layers of the dermis:
    • Papillary Layer:
    • More superficial, made of loose areolar connective tissue.
    • Dermal papillae project into epidermis.
    • Contains blood vessels, nerve fibers, tactile corpuscles (Meissner’s).
    • Reticular Layer:
    • Deeper and thicker, composed of dense irregular connective tissue.
    • Contains hair follicles, blood vessels, and nerves.
    • Contains Pacinian corpuscles that sense deep pressure.

Hypodermis

  • Also called the subcutaneous layer.
  • Extends to the dermis.
  • Composed of adipose and loose areolar connective tissue.
  • Provides insulation and cushioning.
  • Highly vascularized.

Think, Pair, Share Activity 2

  • If a cut bleeds, identify cut layers.
Answer
  • The epidermis and dermis have been