tissue

• Four major types

  1. Epithelial
  2. Connective (many components)
  3. Muscle
  4. Nervous
• EPITHELIAL TISSUES

  CHARACTERISTICS

  • Cells are closely packed without any intercellular spaces
  • Lie on basement membrane
• General characteristics – EPITHELIAL TISSUES

  • cover organs and the body

  • line body cavities

  • line hollow organs

  • have a free surface

  • have a basement membrane

  • avascular

  • cells readily divide

  • cells tightly packed

  • cells often have desmosomes

  • function in protection, secretion, absorption, and excretion

  • classified according to cell shape and number of cell layers
• Simple squamous –

  o single layer of flat cells

  o substances pass easily through

  o line air sacs

  o line blood vessels

  o line lymphatic vessels
• Simple cubodial –

  o single layer of cube-shaped cells

  o line kidney tubules

  o cover ovaries

  o line ducts of some glands
• Simple columnar –

  o single layer of elongated cells

  o nuclei usually near the basement

  o membrane at same level

  o sometimes possess cilia

  o sometimes possess microvilli

  o often have goblet cells

  o line uterus, stomach, intestines
• Pseudostratified columnar –

  o single layer of elongated cells

  o nuclei at two or more levels

  o appear striated

  o often have cilia

  o often have goblet cells

  o line respiratory passageways
• Keratinised Squamous Epithelium (skin)

  • Found on dry surfaces subjected to wear and tear.
  • Consists of dead epithelial cells that have lost their nuclei and contain the protein keratin.
  • Sites
  • Skin, hairs and nails
• Non-Keratinised Epithelium

  • Protects moist surfaces subjected to wear and tear and prevents them from drying out.
  • Sites
  • Conjunctiva of the eyes, the lining of the mouth, the vagina.
• Stratified squamous –

  • many cell layers
  • top cells are flat
  • can accumulate keratin
  • outer layer of skin
  • line oral cavity, vagina, and anal canal
• Stratified cuboidal –

  • 2-3 layers
  • cube-shaped cells
  • line ducts of mammary glands, sweat glands, salivary glands, and the pancreas
• Stratified columnar –

  • top layer of elongated cells
  • cube-shaped cells in deeper layers
  • line part of male urethra and part of

  pharynx
• Transitional –

  • many cell layers
  • cube-shaped and elongated cells
  • line urinary bladder, ureters, and part of urethra
• TRANSITIONAL EPITHELIUM

  • Composed of several layers of pear shaped cells which are very elasticn and have the capacity of dividing themselves.
  • Sites
  • Lines several parts of the urinary tract including the bladder.
• TYPES OF EPITHELIAL MEMBRANES

  Serous (GI tract?)

  • line body cavities that do not open to the outside
  • reduce friction
  • inner lining of thorax and abdomen
  • cover organs of thorax and abdomen
  • secrete serous fluid

  Mucous

  • line tubes and organs that open to outside world
  • lining of mouth, nose, throat, etc.
  • secrete mucus

  Cutaneous

  • covers body
  • skin

  Synovial

  • composed entirely of skin connective tissue
  • lines joints