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The Human Body

Author(s): Deanne Erdmann MS

Tissues in the Human Body

Tissues are groups of cells similar in structure and function. The four primary categories of tissues are epithelial, connective, muscular, and nervous.

  • Epithelial tissues cover the outer and inner surfaces of the body, serving as "gatekeepers" for the passage of materials. Epithelial cells have glandular roles, secreting substances such as mucous and hormones. Some simple epithelial tissues consist of only one layer, while stratified epithelial tissues are comprised of multiple layers. The shape of the cell on the outer surface (columnar, cuboidal, or squamous) facilitates identification of epithelial tissues.
  • Connective tissues help to bind, support, and join other tissues. The cells of connective tissues are sparsely arranged in a profuse extracellular matrix which can be fluid (as in blood), flexible (as in cartilage) or hard and crystalline (as in bone). 
  • Muscle tissues, composed of cells called fibers, are unique in the abundance and arrangement of actin and myosin filaments, which enable muscle to contract. In humans, there are three types of muscle tissues: smooth, cardiac, and skeletal.
  • Nerve tissues are comprised primarily of neurons (nerve cells), which detect stimuli and send responses in the form of electrochemical charges called impulses. Nerve tissues include a variety of supporting cells called neuralgia and Schwann cells. These cells support, insulate, and eliminate foreign materials in and around neurons.