The cells of an animal all contain the same DNA, however they have specialized throughout a process of differentiation to become unique, both functionally and structurally.
Animal cells can be divided into 4 main tissue types:
- Muscle Tissues: Muscles are unique cells in our body for their ability to contract which changes both the length and shape of the cell. A group of muscle cells contracting together can produce a large force and movement in the body. There are three types of muscle: skeletal (voluntary contraction), cardiac (of the heart) and smooth (involuntary muscle). Both skeletal and cardiac contain sarcomeres, which give the muscle a striated appearance.
- Nervous Tissue: There are two main types of cells in the nervous system: neurons and glia. Neurons are specialized cells responsible for signal transduction in our body. Glia are support cells that support and insulate neurons.
- Epithelial Tissue: Epithelial cells line the outer surfaces of organs and blood vessels, as well as the inner surfaces of lumens. They maintain a strong barrier between different types of environments. There are three main shapes of epithelial cells: squamous (flat), columnar (tall), and cuboidal (square).
- Connective Tissues: Composed mainly of secreted proteins, connective tissue is found between other types of tissues. Adipose (fat), bone and blood are all examples of connective tissues.