The Cell Theory

  1. all organisms are composed of cells
  2. every cell comes from preexisting cell
  3. all vital functions occur within cells
  4. cells carry hereditary information for metabolism and reproduction.

Animals have a level of organization

  1. Cells form tissue
  2. Different tissues make up organs
  3. Several organs are found within an organ system
  4. Organ systems make up the organism

Histology: the study of tissues

Tissue: group of closely related cells, adapted to carry out specific functions.


There are 4 major types of tissue in complex animals:

  1. Epithelial tissue: covers body surface, lines body cavities
  2. Connective tissue: binds and supports body parts
  3. Muscular tissue: Causes body parts to move
  4. Nervous tissue: responds to stimuli and transmits impulses from one body part to another

Epithelial Tissue (epithelium)

Five basic types of epithelium [fig. 3.24]:  web links from the University of Wisconsin La Crosse

  1. simple squamous (fig. 3.24a)
  2. simple cuboidal (fig. 3.24b)
  3. simple columnar (fig. 3.24c, d)
  4. stratified squamous (fig. 3.24e)
  5. transitional

gland: one or more epithelial cells that secretes a special product

CONNECTIVE TISSUE: cells in a matrix

Types (8) of Connective Tissue:  web links from the University of Wisconsin La Crosse

  1. loose ordinary (figure 3.24g)
  2. fibrous-dense ordinary (figure 3.24h)
  3. fibrous-elastic
  4. reticular
  5. adipose tissue (figure 3.24f)
  6. cartilage (figure 3.24i, j, k)
  7. bone (figure 3.24l)
  8. blood (figure 3.24m) and lymph:


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