Tissues

• General Characteristics of Epithelial Tissue

  • Cover organs and the body• Line body cavities• Line hollow organs• Have a free surface• Have a basement membrane• Are 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 Epithelium

  • Single layer of flat cells• Substances pass easily through• Line air sacs• Line blood vessels• Line lymphatic vessels
• Simple Cuboidal

  Single layer of cube-shaped cells• Line kidney tubules• Cover ovaries• Line ducts of some glands
• Simple Columnar


  Single layer of elongated cells• Nuclei usually near the basement• Membrane at same level• Sometimes possess cilia• Sometimes possess microvilli• Often have goblet cells• Line uterus, stomach, intestines
• Pseudostratified columnar

  Single layer of elongated cells• Nuclei at two or more levels• Appear striated• Often have cilia• Often have goblet cells• Line respiratory passageways
• Stratified Squamous

  • Many cell layers• Top cells are flat• Can accumulate keratin• Outer layer of skin• Line oral cavity, vagina, andanal canal
• Stratified Cuboidal

  • 2-3 layers• Cube-shaped cells• Line ducts of mammary glands,sweat glands, salivary glands, andthe pancreas
• Stratified Columnar

  • Top layer of elongated cells• Cube-shaped cells in deeperlayers• Line part of male urethra andpart of pharynx
• Transitional


  • Many cell layers• Cube-shaped and elongated cells• Line urinary bladder, ureters, and part of urethra
• Connective Tissue


  General characteristics:• Most abundant tissue type• Many functions:• Bind structures• Provide support and protection• Serve as frameworks• Fill spaces• Store fat• Produce blood cells• Protect against infections• Help repair tissue damage• Have an extracellular matrix• Have varying degrees of vascularity• Have cells that usually divide
• Adipose Tissue

  • Adipocytes• Cushions• Insulates• Store fats• Beneath skin• Behind eyeballs• Around kidneys and heart
• Reticular Connective Tissue

  • Composed of reticular fibers• Supports internal organ walls• Walls of liver, spleen,lymphatic organs