Histology Tissue Types

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Epithelia

Epithelia receive its name because it covers all of the external surfaces of the body (epi = on top of). It also covers the surfaces of other tubular structures. Because of its position within the body one of its major functions is that of protection. Epithelia can also serve secretory and absorptive functions. Epithelia are characteristically formed by tightly packed cellular elements, and a highly reduced extracellular matrix. Cells forming epithelia are tightly packed by specialised structures that aid in keeping the epithelial cells together. A basement membrane can be found that attaches the epithelia to the underlying connective tissue. Epithelial tissue are also said to be avascular, since they do not contain any blood vessels. Nutrition to the epithelial cells is therefore provided by difussion from the underlying connective tissue. Glands are also found in epithelial tissue, which provide secretions that may vary in function depending on the gland. Epithelia are classified by the number of cell layers in the tissue and the shape of the cells in the outermost layer.

Connective

Connective tissue receives its name because of its ability to connect different tissue types in the body. Connective tissue are primarily classified on the basis of the components of the extracellular matrix (fibres and ground substance).

Muscle

Muscle tissue is formed primarily by contractile cells known as muscle fibres. These cells tend to be elongated in shape and contain in their cytoplasm cytoskeletal components (actin and myosin) that allow them to contract under specific conditions.

Nervous

Nervous tissue originates from the embryonic ectoderm.

References

1. Ham, A. W. (1970). Tratado de Histologia (Sixth.). Mexico: Interamericana.
2. Kerr, J. (2010). Functional histology (2nd ed.). Chatswood N.S.W.: Elsevier Mosby Australia.
3. Tortora, G., & Derrickson, B. (2009). Principles of anatomy and physiology (12th ed.). Hoboken NJ: John Wiley & Sons.

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