Integumentary System

• Functions of body membranes


  • Cover body surfaces
  • Line body cavities
  • Form protective sheets around organs
• Types of body membranes

  • Epithelial membranes
  • Connective tissue membranes
• Epithelial membranes


  • Cutaneous membranes
  • Mucous membranes
  • Serous membranes
• Epithelial membranes


  Simple organs that contain an epithelial tissue layer and a connective tissue layer
• Cutaneous membrane


  Dry membrane that is the outermost protective boundary of the body, composed of epidermis and dermis
• Mucous membranes


  Moist membranes that line all body cavities open to the exterior, adapted for absorption or secretion
• Serous membranes


  Line open body cavities that are closed to the exterior, occur in pairs with a visceral and parietal layer, composed of simple squamous epithelium and areolar connective tissue
• Synovial membranes


  Loose areolar connective tissue that lines fibrous capsules surrounding joints, bursae, and tendon sheaths, secretes lubricating fluid
• Components of the integumentary system

  • Skin (cutaneous membrane)
  • Skin appendages
  • Sweat glands
  • Oil glands
  • Hair
  • Nails
• Functions of the integumentary system

  • Insulate and cushion deeper body organs
  • Protect from mechanical, chemical, thermal, UV, and microbial damage
  • Aid in body heat loss or retention
  • Aid in excretion of urea and uric acid
  • Synthesize vitamin D
• Epidermis


  Outer layer of the skin, composed of stratified squamous epithelium with keratinocytes that produce keratin
• Layers of the epidermis

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum (thick skin only)
  • Stratum corneum
• Melanin


  Pigment produced by melanocytes in the stratum basale, determines skin color
• Epidermal dendritic cells


  Alert and activate immune cells to threats
• Merkel cells


  Associated with sensory nerve endings, serve as touch receptors
• Dermis


  Connective tissue layer underlying the epidermis, contains two layers: papillary and reticular
• Papillary layer


  Upper dermal region with projections (dermal papillae) that indent the epidermis, contain capillary loops and receptors
• Reticular layer


  Deepest skin layer, contains blood vessels, sweat and oil glands, and deep pressure receptors
• Pigments that contribute to skin color

  • Melanin
  • Carotene
  • Hemoglobin
• Skin color variations


  • Redness (erythema)
  • Pallor (blanching)
  • Jaundice (yellow cast)
  • Bruises (black and blue marks)
• Skin appendages


  • Cutaneous glands
  • Sebaceous glands
  • Sweat glands
  • Hair
  • Hair follicles
  • Nails
• Sebaceous glands


  Produce sebum (oil) to make skin soft and moist, prevent hair from becoming brittle, and kill bacteria
• Types of sweat glands

  • Eccrine glands
  • Apocrine glands
• Eccrine glands


  Open to sweat pores on the skin surface, produce acidic sweat for body temperature regulation
• Apocrine glands


  Ducts empty into hair follicles in the armpit and genitals, release sweat with fatty acids and proteins, play a minimal role in body temperature regulation
• Hair


  Produced by hair follicles, root is embedded in the dermis
• Sebaceous gland


  • Eccrine gland
  • Sweat pore
  • Hair in hair follicle
  • Sebaceous gland duct
• Photomicrograph


  Microscopic image
• Dermal connective tissue


  Tissue in the dermis layer of skin
• Secretory cells


  Cells that produce and secrete substances
• Appendages of the Skin

  • Sweat (sudoriferous) glands
  • Hair
• Sweat (sudoriferous) glands


  Produce sweat
• Sweat glands are widely distributed in the skin
• Types of sudoriferous glands

  • Eccrine glands
  • Apocrine glands
• Eccrine glands


  • Open via duct to sweat pores on the skin's surface
  • Produce acidic sweat containing water, salts, vitamin C, traces of metabolic waste
  • Function in body temperature regulation
• Photomicrograph of a sectioned eccrine gland

  • Sebaceous gland
  • Secretory cells
  • Eccrine gland
  • Sweat pore
  • Eccrine gland duct
  • Dermal connective tissue
• Apocrine glands


  • Ducts empty into hair follicles in the armpit and genitals
  • Begin to function at puberty
  • Release sweat that also contains fatty acids and proteins (milky or yellowish color)
  • Play a minimal role in body temperature regulation
• Hair


  • Produced by hair follicle
  • Root is enclosed in the follicle
  • Shaft projects from the surface of the scalp or skin
  • Consists of hard keratinized epithelial cells
  • Melanocytes provide pigment for hair color
  • Hair grows in the matrix of the hair bulb in stratum basale
• Structure of a hair root and follicle

  • Hair root
  • Hair shaft
  • Arrector pili muscle
  • Hair follicle
  • Hair bulb
  • Sebaceous gland
• Hair anatomy


  • Central medulla
  • Cortex surrounds medulla
  • Cuticle on outside of cortex
  • Most heavily keratinized region of the hair