TISSUE

• The human body is composed of approximately 200 distinctly different types of cells
• These cells are organized into four basic tissues that, in turn, are assembled to form organs
• A basic knowledge of the general characteristics and cellular composition of the tissues is essential in histology
• Four basic tissues


  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
• Epithelial tissue


  Covers body and lines body cavities
• Epithelial tissue characteristics


  • Cells packed closely together with little matrix
  • Classified by shape of cells
  • Classified by arrangement of cells
• Shapes of epithelial cells

  • Squamous
  • Cuboidal
  • Columnar
  • Transitional
• Simple epithelium


  Describes a single layer of cells
• Stratified epithelium


  Describes epithelium consisting of multiple layers
• Pseudostratified epithelium


  Describes a single layer of cells of different sizes, giving the appearance of being multilayered
• Simple squamous epithelium


  Single layer of scalelike cells adapted for transport (e.g., absorption)
• Stratified squamous epithelium


  Several layers of closely packed cells specializing in protection
• Simple columnar epithelium


  Tall, column-like cells arranged in a single layer; contain mucus producing goblet cells; specialized for absorption
• Stratified transitional epithelium


  Up to 10 layers of roughly cuboidal cells that distort to squamous shape when stretched; found in body areas that stretch, such as urinary bladder
• Pseudostratified epithelium


  Single layer of distorted columnar cells; each cell touches basement membrane
• Simple cuboidal epithelium


  Single layer of cubelike cells often specialized for secretory activity
• Connective tissue


  Most abundant and widely distributed tissue in body, with many different types, appearances, and functions
• Connective tissue characteristics


  • Relatively few cells in intercellular matrix
  • Many different types, appearances, and functions
• Types of connective tissue

  • Areolar tissue
  • Adipose tissue
  • Reticular tissue
  • Dense fibrous tissue
  • Bone tissue
  • Cartilage tissue
  • Blood tissue
• Areolar tissue


  Fibrous glue (fascia) that holds organs together; collagenous and elastic fibers, plus a variety of cell types
• Adipose tissue


  Lipid storage, metabolism regulation; brown fat produces heat
• Reticular tissue


  Delicate net of collagen fibers, as in bone marrow
• Dense fibrous tissue


  Bundles of strong collagen fibers; example is tendon
• Bone tissue


  Matrix is calcified; functions as support and protection
• Cartilage tissue


  Matrix is consistency of gristle-like gel; chondrocyte is cell type
• Blood tissue


  Matrix is fluid; functions are transportation and protection
• Muscle tissue types


  • Skeletal muscle tissue
  • Cardiac muscle tissue
  • Smooth muscle tissue
• Skeletal muscle tissue


  Attaches to bones; also called striated or voluntary; control is voluntary
• Cardiac muscle tissue


  Also called striated involuntary; composes heart wall; ordinarily cannot control contractions with intercalated disc
• Smooth muscle tissue


  Also called nonstriated (visceral) or involuntary; found in blood vessels and other tube-shaped organs
• Nervous tissue


  Function is rapid communication between body structures and control of body functions
• Neurons


  Conduction cells; all neurons have cell body and two types of processes: axon and dendrite
• Axon


  Carries nerve impulse away from cell body
• Dendrites


  Carry nerve impulse toward the cell body
• Glia (neuroglia)


  Supportive and connecting cells