Integumentary

• Tissue


  Group of specialized cells and extracellular substances surrounding them
• Histology


  Microscopic study of tissue structure
• Changes in tissues

  1. Development

  2. Growth

  3. Aging

  4. Trauma

  5. Disease
• Development


  The process whose specific outcome is the progression of a tissue over time, from its formation to the mature structure
• Growth


  The process by which a tissue increases its size
• Aging


  Tissues becoming more stiff, making organs, blood vessels, and airways more rigid. Cell membranes change, so many tissues have more trouble getting oxygen and nutrients and removing carbon dioxide and other wastes. Many tissues lose mass. This process is called atrophy (decrease in size of an organ or tissue)
• Trauma


  Soft tissue injuries occur when the body's muscles, tendons or ligaments experience a degree of trauma. These injuries happen suddenly or gradually as a result of overuse.
• Disease


  Hereditary (genetic) connective tissue diseases include Marfan syndrome, homocystinuria, and osteogenesis imperfecta. Acquired diseases include rheumatoid arthritis, systemic lupus erythematosus, rheumatic fever, and osteoarthritis.
• Skeletal muscles enlarge because skeletal muscle cells increase in size in response to exercise
• Reduced elasticity of blood vessels in aging people results from gradual changes in connective tissue
• Many tissue abnormalities, including cancer, result from changes in tissues that can be identified in microscopic examinations
• Epithelial tissue


  Covers the surfaces of the body, lines cavities and organs, and serves as a protective barrier. It can also be involved in absorption, secretion, and sensory functions.
• Epithelium


  • Covers and protects surfaces, both outside and inside the body, with very little extracellular material between the cells
  • Especially important in hollow organs with openings to the outside environment
  • Protects against foreign materials entering the body
• Characteristics common to most types of epithelial tissue

  • Mostly composed of cells
  • Covers body surfaces
  • Has an exposed surface
  • Attaches at the basal surface
  • Has specialized cell connections and matrix attachments
  • Is avascular
  • Is capable of regeneration
• Basal surface


  The surface of the cells that is anchored in place
• Basement membrane


  Provides structural support and helps cells to attach and anchor to the underlying tissues
• Lymphatic capillaries, liver sinusoids, and endocrine glands do not have basement membranes
• Lateral surface


  Where the epithelial cells are attached to each other
• Avascular


  Blood vessels in the underlying connective tissue do not penetrate the basement membrane to reach the epithelium
• How nonvascular epithelial tissue reaches the basement membrane

  1. Diffusion

  2. Interstitial fluid

  3. Basal lamina

  4. Transport proteins

  5. Cell-to-cell communication
• Diffusion


  The movement of molecules or particles from an area of higher concentration to an area of lower concentration, driven by the random thermal motion of particles
• Interstitial fluid


  A gel-like substance that bathes the cells of both vascular and nonvascular tissues, containing water, ions, gases, and small molecules
• Basal lamina


  The basement membrane, a specialized extracellular matrix that separates the epithelial tissue from the underlying connective tissue, providing structural support and regulating the passage of molecules
• Transport proteins


  Facilitate the movement of essential substances, such as ions and nutrients, from the interstitial fluid to the epithelial cells and vice versa
• Cell-to-cell communication


  Epithelial cells can communicate with neighboring cells and the underlying connective tissue through signaling molecules, helping regulate the exchange of substances
• Regeneration


  Epithelial tissue has the ability to replace damaged cells with new epithelial cells, with undifferentiated cells (stem cells) continually dividing and producing new cells
• Functions of epithelia


  • Protecting underlying structures
  • Acting as a barrier
  • Permitting the passage of substances
  • Secreting substances
  • Absorbing substances
• Major types of epithelia according to number of cells

  • Simple epithelium
  • Stratified epithelium
  • Pseudostratified columnar epithelium
• Pseudostratified columnar epithelium


  A special type of simple epithelium that appears to be stratified but consists of one layer of cells, with some cells taller and extending to the free surface while others are shorter and do not
• Three types of epithelium based on idealized shapes of the epithelial cells

  • Squamous (flat and scalelike)
  • Cuboidal (cube-shaped, about as wide as they are tall)
  • Columnar (tall and thin, similar to a column)
• Simple epithelium


  Consists of a single layer of cells with each cell extending from the basement membrane to the free surface