part 2

• Integumentary system

  Consists of the skin and accessory structures, such as hair, glands, and nails
• Integument

  Covering
• The integumentary system is one of the most familiar systems of the body to everyone because it covers the outside of the body and is easily observed
• Major functions of the integumentary system

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

  It provides protection against abrasion and ultraviolet light, prevents microorganisms from entering the body, and reduces water loss (preventing dehydration)
• Sensation

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

  When skin is exposed to ultraviolet light, the skin produces a molecule that can be transformed into Vitamin D, an important regulator of Calcium homeostasis
• 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 and subcutaneous tissues

  • Epidermis
  • Dermis
  • Subcutaneous
• Epidermis

  The most superficial layer of the skin, prevents water loss and resists abrasion
• Dermis

  A layer of dense connective tissue where the epidermis rests, responsible for most of the skin's structural strength
• Subcutaneous

  A layer of connective tissue that connects the skin to underlying muscle or bone, not part of the skin
• Two major tissue layers of the skin

  • Epidermis
  • Dermis
• Epidermis

  A stratified squamous epithelium, where mitosis produces cells in the skin's deepest layer that push older cells to the surface to slough off
• Keratinization

  A process where cells change shape and chemical composition when skin moves, becoming filled with keratin which makes them more rigid and durable
• Strata (distinct layers) in the epidermis

  • Stratum basale
  • Stratum corneum
• Stratum basale

  The deepest stratum, consisting of cuboidal and columnar cells that undergo mitotic cell division about every 19 days
• Stratum corneum

  The most superficial stratum of the epidermis, consisting of dead squamous cells filled with keratin and coated/surrounded by lipids, acting as a waterproofing material
• Dermis

  Composed of dense collagenous connective tissue containing fibroblasts, adipocytes, macrophages, as well as nerves, hair, follicles, smooth muscles, glands, and lymphatic vessels
• Collagen and elastic fiber

  Responsible for the structural strength of the dermis
• Collagen

  Oriented in different directions, can resist stretch and produce cleavage lines or tension lines, most resistant to stretch
• An incision made across the cleavage lines produces scar tissue
• If skin is overstretched, the dermis can be damaged, leaving lines that are visible through the epidermis called stretch marks
• Dermal papillae

  Projections on the upper part of the dermis that extend through the dermis, containing many blood vessels that supply the overlying epidermis with nutrients, remove waste products, and help regulate body temperature
• In the palms of the hands, soles of the feet and the tips of the digits, the dermal papillae are arranged in parallel, curving ridges that shape the overlying epidermis into fingerprints and footprints, increasing friction and improving the grip of the hand
• Types of injections

  • Intradermal (ID)
  • Subcutaneous (SQ)
  • Intramuscular (IM)
• Intradermal (ID) injection

  Administered by drawing the skin taut and inserting a small needle at a shallow angle into the dermis, e.g. tuberculin skin test
• Subcutaneous (SQ) injection

  Achieved by pinching the skin to form a tent and inserting a short needle in the adipose tissue of the subcutaneous, e.g. insulin injection
• Intramuscular (IM) injection

  Accomplished by inserting a long needle at a 90-degree angle in the skin into the muscle deep to the subcutaneous tissue, e.g. some vaccines and antibiotics
• Factors that determine skin color

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

  A group of pigments primarily responsible for the skin, hair, and eye color, providing protection against ultraviolet light from the sun
• Melanocytes

  Irregularly shaped cells with many long processes that extend between epithelial cells of the deep part of the epidermis, producing melanosomes (pigment granules)
• Although many genes are responsible for skin color, a single mutation can prevent the production of melanin
• Conditions related to melanin production

  • Albinism
  • Increased melanin production from UV light exposure
  • Increased melanin production from hormones like estrogen and melanocyte-stimulating hormone
• Blood flow through the skin

  Imparts a reddish hue, with increased blood flow intensifying the red color (e.g. blushing, inflammation), and decreased blood flow and oxygen causing a bluish color (cyanosis)
• Birthmarks

  Congenital disorders of the blood vessels (capillaries) in the dermis
• Carotene

  A yellow pigment found in plants that can accumulate in the lipids of the stratum corneum and adipocytes, causing the skin to appear yellowish if consumed in large amounts
• Scattering of light by collagen produces a bluish color in the skin
• Subcutaneous tissue

  Where the skin rests, attaching it to the underlying bone and muscle and supplying it with blood vessels and nerves