intergumentary

• Integumentary system

  The skin and its accessory structures

  
• The skin


  • Largest organ of the body
  • Protective shield against heat, light, injury, and infection
  • Regulates body temperature
  • Stores water and fat
  • Sensory organ
  • Prevents water loss
  • Prevents entry of bacteria
  • Acts as a barrier between the organism and its environment
  • Helps to make vitamin D when exposed to the sun
  • Comprises 15% of the total adult body weight
  • Thickness ranges from 0.5mm at its thinnest part (eyelids) to 4mm at its thickest part (palms of the hands and soles of the feet)
• Epidermis


  • Composed of keratinized stratified squamous epithelium
  • Contains four principal types of cells: keratinocytes, melanocytes, Langerhans cells, and Merkel cells
• Keratinocytes


  • About 90% of epidermal cells
  • Arranged in four or five layers
  • Produce the protein keratin
  • Produce lamellar granules which release a water-repellent sealant
• Melanocytes


  • About 8% of epidermal cells
  • Produce the pigment melanin
  • Melanin contributes to skin color and absorbs damaging ultraviolet (UV) light
  • Particularly susceptible to damage by UV light
• Langerhans cells


  • Arise from red bone marrow and migrate to the epidermis
  • Help other cells of the immune system recognize and destroy invading microbes
• Merkel cells


  • Least numerous of the epidermal cells
  • Located in the deepest layer of the epidermis
  • Contact the flattened process of a sensory neuron (nerve cell), a structure called a Merkel (tactile) disc
• Layers of thin skin

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Thin stratum corneum
• Layers of thick skin

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Thick stratum corneum
• Dermis


  • Composed of a strong connective tissue containing collagen and elastic fibers
  • Contains blood vessels, nerves, glands, and hair follicles
• Regions of the dermis

  • Papillary region
  • Reticular region
• Papillary region


  • Makes up about one-fifth of the thickness of the total layer
  • Consists of areolar connective tissue containing thin collagen and fine elastic fibers
  • Contains capillary loops and tactile receptors called Meissner corpuscles or corpuscles of touch
• Reticular region


  • Attached to the subcutaneous layer
  • Consists of dense irregular connective tissue containing fibroblasts, bundles of collagen, and some coarse elastic fibers
  • Provides the skin with strength, extensibility, and elasticity

  
• Hypodermis


  • Deep to the dermis, but not part of the skin
  • Consists of areolar and adipose tissues
  • Fibers that extend from the dermis anchor the skin to the subcutaneous layer
  • Serves as a storage depot for fat and contains large blood vessels and pacinian corpuscles sensitive to pressure
• Functions of the integumentary system

  • Thermoregulation
  • Storage of blood
  • Protection
  • Cutaneous sensations
  • Excretion and absorption
  • Synthesis of vitamin D
• Thermoregulation


  1. Liberating sweat at skin surface

  2. Adjusting flow of blood in dermis
• Skin's role in protection

  • Keratin protects underlying tissues
  • Lipids released by lamellar granules inhibit evaporation of water and entry of water
  • Sebum from sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals
  • Acidic pH of perspiration retards growth of some microbes
  • Melanin helps shield against damaging effects of ultraviolet light
  • Langerhans cells and macrophages carry out protective immunological functions
• Cutaneous sensations


  • Tactile sensations - touch, pressure, vibration, tickling
  • Thermal sensations - warmth and coolness
  • Pain - indication of impending or actual tissue damage
  • Wide variety of nerve endings and receptors distributed throughout the skin
• Skin's role in excretion and absorption

  • Normally has a small role in excretion and absorption
  • About 400 mL of water evaporates through it daily
  • A sedentary person loses an additional 200 mL per day as sweat
  • Absorption of water-soluble substances is negligible, but certain lipid-soluble materials do penetrate the skin
• Accessory structures of the skin

  • Hair
  • Nail
  • Sweat glands
  • Sebaceous glands
• Hair growth phases

  1. Anagen

  2. Catagen

  3. Telogen

  
• Sweat glands


  • Also known as sudoriferous glands
  • Produce sweat to cool the body
  • Types: Merocrine, Eccrine, Apocrine
• Sebaceous glands


  • A type of oil gland that helps to lubricate and waterproof the skin and hair
  • Generate and secrete sebum
  • Components: Basal cell, Undifferentiated sebocytes, Differentiated sebocytes, Sebum
• Skin pathologies

  • Basal cell carcinoma
  • Squamous cell carcinoma
  • Melanoma
  • Eczema
  • Acne
  • Burns
  • Scars and keloids
  • Bedsores
  • Stretchmarks
  • Calluses
• Basal cell carcinoma


  • A form of cancer that affects the mitotically active stem cells in the stratum basale of the epidermis
  • The most common of all cancers that occur in the United States
  • Frequently found on the head, neck, arms, and back
• Squamous cell carcinoma


  • A cancer that affects the keratinocytes of the stratum spinosum
  • Presents as lesions commonly found on the scalp, ears, and hands
  • The second most common skin cancer and is more aggressive than basal cell carcinoma
• Melanoma


  • A cancer characterized by the uncontrolled growth of melanocytes
  • The most fatal of all skin cancers
  • Identified by ABCDE: Asymmetry, Borders, Color, Diameter, Elevated
• Eczema


  An allergic reaction that manifests as dry, itchy patches of skin that resemble rashes, may be accompanied by swelling, flaking, and bleeding
• Acne


  • A skin disturbance that typically occurs on areas of the skin that are rich in sebaceous glands (face and back)
  • Most common along with the onset of puberty due to associated hormonal changes, but can also occur in infants and continue into adulthood
• Burns


  • Skin damage by intense heat, radiation, electricity, or chemicals
  • Classified by severity: First-degree, Second-degree, Third-degree, Fourth-degree
  • Rule of Nines associates specific anatomical areas with a percentage that is a factor of nine
• Scars and keloids

  • Scar - collagen-rich skin formed after wound healing that differs from normal skin
  • Keloid - a raised or hypertrophic scar that is a result of an overproduction of scar tissue
• Bedsores


  • Also called decubitus ulcers
  • Caused by constant, long-term, unrelieved pressure on certain body parts, reducing blood flow and leading to tissue death
  • Most common in elderly patients who have debilitating conditions that cause them to be immobile
• Stretchmarks


  Results when the dermis is stretched beyond its limits of elasticity, as the skin stretches to accommodate the excess pressure
• Calluses


  • Occur because the basal stem cells in the stratum basale are triggered to divide more often to increase the thickness of the skin at the point of abrasion
  • CORN - a specialized form of callus that forms from abrasions on the skin that result from an elliptical-type motion