A tissue is a group of the same kind of cells that together carry out a specific function. For example, adipose tissue, blood, bone, cartilage, enamel, ivory (dentin), ligament, muscle, skin, wood.

Organs are formed by the functional grouping together of multiple tissues.


1   Etymology

2   Study

The study of tissues is called histology.

3   Substance

4   Classification

4.1   Animal

Animal tissues can be grouped into four basic types: connective, epithelial, muscle and nervous tissue.

4.1.1   Connective

Connective tissue is characterized by a few cells in a non-living extracellular matrix. Examples of connective tissue include adipose tissue, blood, bone, and cartilage.

All connective tissue consists of three main components: fibers, (elastic and collagenous fibres), ground substance and cells, except blood and lymph_ which lack fiber. The ground substance is an amorphous gel-like substance surrounding the cells.

Connective tissue can be broadly subdivided into connective tissue proper, special connective tissue, and series of other, less classifiable types of connective tissues. Connective tissue proper consists of loose connective tissue and dense connective tissue (which is further subdivided into dense regular and dense irregular connective tissues.) Special connective tissue consists of reticular connective tissue, adipose tissue, cartilage, bone, and blood. Other kinds of connective tissues include fibrous, elastic, and lymphoid connective tissues.

A fibroblast is a type of cell that synthesizes the extracellular matrix and collagen,[1] the structural framework (stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells of connective tissue in animals.

4.1.2   Epithelial

Epithelial tissue includes three shapes of cells: squamous, cuboidal, and columnar, Epithelial tissue is always underlaid by a basement membrane. Epithelial tissue can be arranged one of two ways, depending on the relationship between the location of the cells relative to the position of the basement membrane: simple epithelial tissue, in which all of the epithelial cells touch the basement membrane, or stratified epithelial tissue, in which there are several layers of cells and not all touch the basement membrane. Thus, cells may be arranged/classified in the following categories:

  • These are simple squamous cells.
  • These are simple cuboidal cells.
  • These are simple columnar cells.
  • These are stratified squamous cells.
  • The trachea is lined with pseudostratified ciliated columnar epithelium. Smoking first paralyzes the cilia, then destroys cells. If a person stops smoking, the damage can heal and the cells grow back.

4.1.4   Nervous

The nervous system is comprised of two types of cells, including nerve tissue.

5   Tumor

A tumor is a mass of tissue that has grown abnormally and excessively (neoplasm).

Tumors have 5x amount of blood as normal flesh.

Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body.

Tissue viscoelasticity. The extensible elements in your musculoskeletal system have taken on a certain 'set' after prolonged immobilization. That's why normal sleep is best in a large bed to permit frequent involuntary re-posturing during sleep.

It is well known that joints and other connective tissues demonstrate viscoelastic properties. Along with the muscles that surround the joint you also stretch the passive structures such as the ligaments and joint capsule in the area.