Structure and Functions of White Fibrous Tissue
As indicated on the page about classification of (animal) tissue types, White Fibrous Tissue is a form of mature (rather than embryonic) connective tissue, and is one of the forms of dense connective tissue.
There are three (3) types of dense connective tissue.
The 3 forms of Dense Connective Tissue:
White fibrous tissue is connective tissue in which there is a greater proportion of white inelastic fibres than of elastic fibres. The dominance of the (white, inelastic) collagen fibres contributes to the considerable mechanical strength of white fibrous tissue.
Structure of White Fibrous Tissue:
White fibrous tissue is described in the classic text "Gray's Anatomy" as "a true connecting structure".
The main constituent of white fibrous connective tissue is the protein collagen.
White fibrous tissue is dense regular connective tissue that has a silvery white colour/appearance and is physically tough, yet pliable. It consists of fibroblasts interspersed among many collagen fibres which are often aligned in the same direction, forming a mechanically strong structure.
- Collagen fibres are also known as "collagenous fibres", "white fibres", and (in American Texts) as "collagen fibers". They range in diameter from less than 1 um (1 um = 1 micrometer = 10-6m = 0.000001 meters ) to about 12 um.
- Fibroblast cells are widely distributed throughout connective tissues and are necessary for production of the precursors of collagen, elastic fibres, and reticular fibres (which are microscopic, non-elastic branching fibres).
Fibroblast cells (called "fibrocytes") are often found lying in rows along the bundles of (white) collagen fibres.
Functions of White Fibrous Tissue:
White fibrous tissue connects structures that require a mechanically strong bond.
The main functions of white fibrous tissue involve supporting and protecting the surrounding structures.
White fibrous tissue is an important part of many structures within the body. Its functions can therefore be identified according to the type of structure formed by a particular area of white fibrous tissue. For example, when in the form of:
- Ligaments, white fibrous tissue (in this case often with a higher proportion of elastin fibres to increase the elasticity/extensibility of the tissue with minimal compromise to the mechanical strength of the structure) attaches bones to other bones.
- Tendons, white fibrous tissue attaches muscles to bones and/or other structures.
- Membranes, white fibrous tissue protects structures within the body, including for example, organs such as the kidneys (in the case of the kidneys, through the membrane forming the capsule of the kidney).
Note that some texts classify these tissues as "dense irregular connective tissues" because the tissue forming some membrane capsules is not arranged with as clearly repeating structure aas that found in e.g. tendons. However, although the arrangement of the tissue structures may differ, their composition (of collagen fibres and fibrocytes) is still very similar.
Locations in the body:
Specific examples of areas of the body in which white fibrous tissue may be found include:
- The Eyes - the sclera (of the eye) is formed of white fibrous tissue intermixed with fine elastic fibers; flattened connective-tissue corpuscles.
- The Musculo-Skeletal System - e.g. modified synovial structures, a "bursa" is a small fluid-filled sac formed from white fibrous tissue and lined with synovial membrane. This is not a part of all joints but when present provides a cushion between bones and tendons.
Warning of possible confusion:
Other types of (animal, including human) tissue include the word "white" in their name and/or description but do not necessarily have connection or similarity with the connective tissue described here as "white fibrous tissue" - other than their name, and perhaps to some extent their colour.
Other "White" tissues:
The following are listed for reference and completeness.
White Blood Cells (leucocytes)
The laymens' terms for the three main constituents of blood are "Red Blood Cells", "Blood Platelets" and "White Blood Cells". The scientific term for "white blood cells" is "leucocytes". For more information see "Structures and Functions of Blood Tissue".
The Central Nervous System (CNS) consists of both "white matter" and "grey matter". The "white matter" consists of myelinated axons, the myelin sheaths of which cause the tissue to have a pale/white appearance.
White Muscle Fibre
"White Muscle Fibre" is a part of skeletal muscle that has a fast twitch response, which is concerned with rapid intermittent movement.