Definitions

ligament

ligament

[lig-uh-muhnt]
ligament, strong band of white fibrous connective tissue that joins bones to other bones or to cartilage in the joint areas. The bundles of collagenous fibers that form ligaments tend to be pliable but not elastic. They therefore permit freedom of movement within a certain limited range while holding the attached bones firmly in place. For example, the ligaments at the knee limit the movement of the lower leg to a certain range. Other types of ligaments form fibrous sheets that support such internal organs as the kidneys and the spleen.

Tough fibrous band of connective tissue that supports internal organs and holds bones together properly in joints. It is composed of dense bundles of fibres and spindle-shaped cells (fibroblasts and fibrocytes), with little ground substance. White ligament is rich in sturdy, inelastic collagen fibres; yellow ligament is rich in tough elastic fibres, which allow more movement. Seealso tendon.

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In anatomy, the term ligament is used to denote three different types of structures:

  1. Fibrous tissue that connects bones to other bones. They are sometimes called "articular ligaments, "fibrous ligaments", or "true ligaments".
  2. A fold of peritoneum or other membrane
  3. The remnants of a tubular structure from the fetal period of life

The first meaning is most commonly what is meant by the term "ligament". After briefly discussing the other two types of ligaments, the remainder of this article will focus upon the first type.

The study of ligaments is known as desmology (from Greek δεσμός, desmos, "string"; and -λογία, -logia).

Peritoneal ligaments

Certain folds of peritoneum are referred to as ligaments.

Examples include:

Fetal remnant ligaments

Certain tubular structures from the fetal period are referred to as ligaments after they close up and turn into cord-like structures:

Fetal Adult
ductus arteriosus ligamentum arteriosum
extra-hepatic portion of the fetal left umbilical vein ligamentum teres hepatis (the "round ligament of the liver").
intra-hepatic portion of the fetal left umbilical vein (the ductus venosus) ligamentum venosum
distal portions of the fetal left and right umbilical arteries medial umbilical ligaments

Articular ligaments

In its most common use, a ligament is a short band of tough fibrous dense regular connective tissue composed mainly of long, stringy collagen fibers. Ligaments connect bones to other bones to form a joint. (They do not connect muscles to bones; that is the function of tendons.) Some ligaments limit the mobility of articulations, or prevent certain movements altogether.

Capsular ligaments are part of the articular capsule that surrounds synovial joints. They act as mechanical reinforcements. Extra-capsular ligaments join bones together and provide joint stability.

Ligaments are only elastic; when under tension, they gradually lengthen. (Unlike tendons which are inelastic). This is one reason why dislocated joints must be set as quickly as possible: if the ligaments lengthen too much, then the joint will be weakened, becoming prone to future dislocations. Athletes, gymnasts, dancers, and martial artists perform stretching exercises to lengthen their ligaments, making their joints more supple. The term double-jointed refers to people who have more elastic ligaments, allowing their joints to stretch and contort further. The medical term for describing such double-jointed persons is hyperlaxity and double-jointed is a synonym of hyperlax.

The consequence of a broken ligament can be instability of the joint. Not all broken ligaments need surgery, but if surgery is needed to stabilise the joint, the broken ligament can be joined. Scar tissue may prevent this. If it is not possible to fix the broken ligament, other procedures such as the Brunelli Procedure can correct the instability. Instability of a joint can over time lead to wear of the cartilage and eventually to osteoarthritis.

Examples:

Knee

Head and neck

Pelvis

Thorax

Wrist

See also

References

External links

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