Integumentary system

• Bluish skin color associated with hypoxia is one sign of heart failure and other disorders
• The integumentary system helps maintain a constant body temperature, protects the body, and provides sensory information about the surrounding environment
• The skin is also known as the cutaneous membrane
• The integumentary system is composed of the skin, hair, oil and sweat glands, nails, and sensory receptors
• The subcutaneous layer contains nerve endings sensitive to pressure
• The dermis is a deeper and thicker layer composed of connective tissue (dense irregular connective tissue) and is vascular
• The skin ranges in thickness from 0.5 mm on the eyelids to 4.0 mm on the heels
• Many people spend a great deal of time and money to restore their skin to a more normal or youthful appearance
• The subcutaneous layer (hypodermis) is deep to the dermis, consists of areolar and adipose connective tissues, and serves as a storage depot for fat
• The epidermis is a superficial and thinner layer composed of epithelial tissue and is avascular
• The skin is vulnerable to damage from trauma, sunlight, microbes, and pollutants in the environment, but its protective features ward off such damage
• Abnormal skin eruptions or rashes

  • chickenpox
  • cold sores
  • measles
• Changes in skin color may indicate homeostatic imbalances in the body
• Dermatology is the medical specialty that deals with the structure, function, and disorders of the integumentary system
• The integumentary system includes the skin, hair, oil and sweat glands, nails, and sensory receptors
• Tactile epithelial cells


  Function in the sensation of touch
• Subcutaneous layer


  Serves as a storage depot for fat and contains large blood vessels that supply the skin
• Cells of the Epidermis

  • Keratinocytes, Melanocytes, Intraepidermal macrophages, Tactile epithelial cells
• Melanocytes


  Produce the pigment melanin, which contributes to skin color and absorbs damaging ultraviolet (UV) light
• Epidermis

  Composed of keratinized stratified squamous epithelium
• Keratinocytes


  Produce the protein keratin, which protects the skin and underlying tissues from abrasions, heat, microbes, and chemicals
• Intraepidermal macrophages


  Participate in immune responses against microbes invading the skin
• Nerve endings in the skin

  • Lamellated corpuscles or Pacinian corpuscles sensitive to pressure
• Several distinct layers of keratinocytes in various stages of development form the epidermis
• Intraepidermal macrophages' role in the immune response


  Help other cells of the immune system recognize and destroy invading microbes
• The fingertips, palms, and soles have thick skin
• Keratinocytes in stratum basale


  Characteristics include large nuclei, cytoplasm with ribosomes, Golgi complex, mitochondria, rough endoplasmic reticulum, and keratin intermediate filaments
• Intraepidermal macrophages and projections of melanocytes are present in the stratum spinosum
• Tactile disc or Merkel disc


  Structure involved in detecting touch sensations
• Melanocytes and tactile epithelial cells with their associated tactile discs are scattered among the keratinocytes of the basal layer
• Layers of thin skin

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Thin stratum corneum
• Stratum basale is the deepest layer of the epidermis
• Tonofilaments


  Form the tough protein keratin in the epidermal layers, protect deeper layers from injury, attach to desmosomes and hemidesmosomes
• Stratum granulosum


  Consists of three to five layers of flattened keratinocytes undergoing apoptosis
• Stratum spinosum


  Consists of numerous keratinocytes arranged in 8 to 10 layers, cells become somewhat flattened, produce coarser bundles of keratin intermediate filaments, provide strength and flexibility to the skin
• Layers of thick skin

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Thick stratum corneum
• Lipid-rich secretion


  • Deposited in the spaces between cells of stratum granulosum, stratum lucidum, and stratum corneum
  • Acts as a water-repellent sealant, retarding loss and entry of water and foreign materials
• Stratum corneum


  Consists of 25 to 30 layers of flattened dead keratinocytes, provides protection from injury and microbial invasion
• Stratum granulosum


  Located about the middle of the epidermis, consists of three to five layers of flattened keratinocytes undergoing apoptosis
• Keratohyalin


  Assembles keratin intermediate filaments into keratin