Human Bio Exam #2

• Integumentary system

  Consists of skin and accessory structures: hair, glands, and nails
• Appearance of the integumentary system

  Can indicate physiological imbalances in the body
• Imbalances in the body


  Show changes in the skin (color, texture)
• Functions of the integumentary system

  • Protection
  • Sensation
  • Vitamin D production
  • Temperature regulation
  • Excretion
• Protection


  The skin provides protection against abrasion and ultraviolet light
• Sensation


  The integumentary system has sensory receptors that can detect heat, cold, touch, pressure, and pain
• Vitamin D production


  When exposed to ultraviolet light, the skin produces a molecule that can be transformed into vitamin D
• Temperature regulation


  The amount of blood flow beneath the skin's surface and the activity of sweat glands in the skin both help regulate body temperature
• Excretion


  Small amounts of waste products are lost through the skin and in gland secretions
• Skin


  Made up of two major tissue layers: the epidermis and the dermis
• Epidermis


  The most superficial layer of skin, a layer of epithelial tissue that rests on the dermis
• Dermis


  A layer of dense connective tissue under the epidermis
• Subcutaneous tissue


  A layer of connective tissue that connects the skin to underlying bone/muscle, not part of the skin
• Epidermis


  • Prevents water loss and resists abrasion
  • Keratinized stratified squamous epithelium
• Layers of the epidermis

  • Stratum corneum (most superficial)
  • Intermediate strata
  • Stratum basale (sitting on BM)
• Stratum corneum


  The most superficial stratum of the epidermis, consists of dead squamous cells filled with keratin
• Stratum basale


  Cells of the deepest strata perform mitosis, pushing older cells to the surface to slough off
• Problems with the epidermis

  • Dandruff
  • Callus
  • Corn
• Dermis


  • Composed of dense collagenous connective tissue
  • Containing fibroblasts, adipocytes, and macrophages
  • Nerves, hair follicles, smooth muscles, glands, and lymphatic vessels extend into the dermis
• Factors that determine skin color

  • Pigments in the skin
  • Blood circulating through the skin
  • Thickness of the stratum corneum
• Melanin


  Group of pigments responsible for skin, hair, and eye color (brown and black), provides protection against UV light
• Melanocytes


  Cells that produce melanin in the epidermis
• Exposure to ultraviolet light

  Stimulates melanocytes to increase melanin production, resulting in a suntan
• Albinism


  A single mutation can prevent the production of melanin and cause it
• Carotene


  Yellow pigment found in plants, high consumption can make the skin look very yellow
• Blood color


  Contributes to skin color, a decrease in blood flow can make the skin appear pale, and a decrease in blood oxygen level can produce a bluish color (cyanosis)
• Subcutaneous tissue


  Loose connective tissue that attaches the skin to underlying bone and muscle and supplies it with blood vessels and nerves, contains about half the body's stored lipids
• Hair


  Each hair arises from a hair follicle, an invagination of the epidermis that extends into the dermis
• Hair growth cycle


  1. Growth stage

  2. Resting stage

  3. New hair formation and old hair falling out
• Arrector pili muscle


  Smooth muscle cells attached to hair follicles that can contract and cause the hair to become perpendicular to the skin's surface (goosebumps)
• Major glands of the skin

  • Sebaceous glands
  • Sweat glands
• Sebaceous glands


  Connected to hair follicles, produce sebum to lubricate hair and skin
• Eccrine sweat glands


  Located in almost every part of the skin, produce secretion (sweat) for thermal regulation
• Apocrine sweat glands


  Simple, coiled, tubular glands that produce a thick secretion rich in organic substances, open into hair follicles in the armpits and genitalia
• Functions of the integumentary system in protection

  • Reduction in body water loss
  • Barrier against microorganisms and foreign substances
  • Protection against abrasion
  • UV light absorption by melanin
  • Hair insulation
  • Hair, eyebrows, eyelashes, and nails provide additional protection
• Sensory receptors


  Associated with the skin, can detect pain, heat, cold, and pressure
• Vitamin D production


  UV light causes skin to produce precursor molecule, converted in liver and kidneys to active vitamin D
• Temperature regulation - too hot

  Blood vessels in dermis dilate to dissipate heat, sweat glands secrete to enable evaporative cooling
• Temperature regulation - too cold

  Dermal blood vessels constrict to conserve heat, sweat glands stop secreting
• Excretion


  Integumentary system plays a minor role, removing small amounts of waste products like urea, uric acid, and ammonia through sweat