Tendon
From Wikipedia, the free encyclopedia
A tendon (or sinew) is a tough band of fibrous connective tissue that connects muscle to bone or muscle to muscle and is designed to withstand tension. Tendons are similar to ligaments except that ligaments join one bone to another. Tendons and muscles work together and can only exert a pulling force.
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[edit] Composition
Tendons are made of tough tissue composed mainly of water, type-I collagen and cells called tenocytes or tendinocytes. Minor fibrillar collagens, fibril-associated collagens and proteoglycans are present in small quantities and are critical for tendon structure. Most of the strength of tendon is due to the vertical, hierarchical arrangement of densely-packed collagen fibrils. Tenocytes are specialized fibroblasts responsible for the maintenance of collagen structure.
[edit] Anatomy
The origin of a tendon is where it joins to a muscle. Collagen fibers from within the muscle organ are continuous with those of the tendon. A tendon inserts into bone at an enthesis where the collagen fibers are mineralised and integrated into bone tissue.
Tenocytes produce collagen molecules which aggregate end-to-end and side-to-side to produce collagen fibrils. Fibril bundles are organised by tenocytes to form fibres. Collagen fibres coalesce into macroaggregates. Groups of macroaggregates are bounded by connective tissue endotendon and are termed fascicles. Groups of fascicles are bounded by the epitendon and peritendon to form the tendon organ.
Blood vessels may be visualised within the endotendon running parallel to collagen fibres, with occasional branching transverse anastomoses.
The internal tendon bulk is thought to contain no nerve fibres, but the epi- and peritendon contain nerve endings, while Golgi tendon organs are present at the junction between tendon and muscle.
Tendon length varies in all major groups and from person to person. Tendon length is practically the discerning factor where muscle size and potential muscle size is concerned. For example, should all other relevant biological factors be equal, a man with a shorter biceps tendon and a longer biceps muscle will have greater potential for muscle mass than a man with a longer tendon and a shorter muscle. Cases in point: successful bodybuilders will generally have short tendons and are said to have 'great genetics.' Examples of people with short tendons (in particular the upper arms) are Casey Viator and Arnold Schwarzenegger[citation needed]. Tendon length is determined exclusively by genetics.[citation needed] However muscles can be shortened by repetitve trauma, the forearms are often the most affected due to their use in every upper body movement.
[edit] Other information
Tendonitis refers to inflammation of a tendon.
The Achilles tendon is a particularly large tendon connecting the heel to the muscles of the calf. It is so named because the mythic hero Achilles was said to have been killed due to an injury at this spot.
Sinew was also widely used in the medieval times as a form of ancient elastic. Some specific uses include using sinew as thread for sewing, attaching feathers to arrows (see fletch), lashing tool blades to hafts, etc. It also recommended in survival guides as a material from which strong ropes can be made for items like traps or living structures.
Tendon (particularly beef tendon) is used as a food in some Asian cuisines (often served at Yum Cha or Dim Sum restaurants). One popular dish is Suan Bao Niu Jin, where the tendon is marinated in garlic. There is a recipe for braised tendons here.
[edit] See also
[edit] References
- Tendons & Ligaments in Journal of Musculoskeletal & Neuronal Interactions; 2005, 5(1): Eds. Lyritis GP & Jee WSS
