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Introduction to Ligaments

The group of cells that have a similar structure and they combine together to perform a required function. In French, the word tissue means ‘to weave’. In animals, there are four different types of tissues, they are epithelial tissue, connective tissue, nervous tissue, and muscle tissue.


Let us learn more about ligament connective tissue: its structure, functions, and types

The ligament is a connective tissue that provides support to the organs and connects the bones together. They are short bands of tough and flexible tissue that are made up of lots of individual fibres. The human body is made up of approximately 900 ligaments. 


Ligament Structure

The building blocks of ligaments are collagen fibres. Each of the collagen fibres combines to form a bundle that is made up of a collagen matrix with scattered fibroblasts that are responsible for the synthesis and repair of collagen. 


The composition of the ligament is as follows: two-thirds of the ligament’s weight is water which provides its main characteristic feature viscoelastic properties. The remaining one-third is a mixture of collagen, glycoproteins, elastin, and proteoglycans.


At the molecular level, in the extracellular spaces, the collagen is synthesised as procollagen molecules, then the helical collagen molecules are arranged in a line to form fibrils and subsequently collagen fibres that make up the ligament. Lysyl oxidase is the enzyme that promotes the placement of cross-links within and in between the collagen molecules. The created crosslinking adds up tremendous characteristic strength to the ligamentous structures. 


The microstructure of ligamentous structures is made up of collagen bundles aligned along the long axis of the ligament with a crimp or “waviness” along its length. Crimp is said to play a specialised biomechanical role during the process of loading, by allowing the collagen fibres to straighten, so that the ligament may elongate without any kind of damage in the tissue under a constant or cyclically repetitive load.


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Ligament Function

The function of the ligaments is as follows:


  • Ligament tissue helps to keep the bones in a proper position at the joints.

  • It helps in the movement of bones.


Ligaments are typically used to link two bones, especially in the joints. They support the joint or hold the ends of two bones together like strong, firmly fastened straps or ropes. This prevents the bones of the joint from twiddling or moving too far apart and becoming dislocated. There are, however, some ligaments that aren't attached to any bones. For example, some ensure that internal organs remain in position. The womb, for example, is held in the correct place in the pelvis by ligaments.


Ligaments can also be used to connect two or more organs. Ligaments in the abdominal cavity, for example, keep the liver, intestine, and stomach in place. These ligaments frequently have sensitive structures running through them, such as blood arteries or gland ducts. Ligaments protect these structures by providing strong connective tissue that prevents them from bending, twisting, or tearing.


Ligaments, whether they connect bones or organs, help the body maintain stability. Their role is mirrored in their name, which is derived from the Latin word "ligare," which means "to bind" or "tie."


Types of Ligaments

  1. Articular Ligaments: 

Capsular ligaments are part of the articular capsule that surrounds synovial joints and they also provide mechanical reinforcements. 


  • The extracapsular ligaments join together with the available other ligaments to provide joint stability. 

  • The intracapsular ligaments are much less common and also provide stability for the larger range of motion. 

  • Cruciate ligaments are paired ligaments that are in the form of a cross.

Ligaments are viscoelastic, that is when under tension they can strain gradually, and when the tension is removed they can retain their original position. However, the only disadvantage is they cannot retain their original shape when extended past a certain point or for a prolonged period of time. Due to this reason, it is said that the dislocated joints should be set as quickly as possible. If the ligaments are stretched too much, then the joint will be weakened resulting in the dislocation of bones. 

  1. Peritoneal Ligaments: 

Certain folds of the peritoneum are referred to as ligaments. Peritoneal ligaments are peritoneal folds that connect viscera to viscera or connect the abdominal wall to the viscera. 


There are several named ligaments, which are usually named after the type of ligament they are: 


  • The Gastrocolic Ligament is a ligament that connects the stomach to the colon. 

  • The splenocolic ligament is a ligament that connects the spleen to the colon.

Examples include:

  • The hepatoduodenal ligament surrounds the hepatic portal vein present in the gastrointestinal tract and other vessels as they carry blood from the duodenum to the liver.

  • The broad ligament of the uterus is also a fold of the peritoneum.

  1. Fetal Remnant Ligaments:

Some of the tubular structures found during the fetal period are referred to as ligaments after which they close up and turn into cord-like structures.


Ligaments are similar to fasciae and tendons as they are all made of connective tissue. The only difference among them is in the connection that they make internally: ligaments connect one bone to another bone, where the tendons connect muscle to bone, and fasciae connect muscles to other muscles. All of these are found in the skeletal system of the human body. Ligaments cannot be regenerated naturally.

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Frequently asked questions

1. Define ligament. What is the function of ligaments?

A ligament is a type of connective tissue that supports the organs and links the bones together.

The ligament's role in the human body is as follows:

  • Ligament tissue aids in the appropriate alignment of the bones at the joints.

  • It facilitates bone mobility.

2. What is meant by ligament injury?

Ligaments are the bands of the tough, and elastic connective tissue that surrounds a joint to provide support and limits the movement of the joints. When the ligaments are damaged, the knee joints may become unstable. Ligament damage often happens from a sports injury and the damaged or torn ligament severely limits knee movement.

3. Difference between Tendons and Ligaments.

Tendons

Ligaments

It helps to connect the skeletal muscles to bones.

It helps to connect the bones to bones.

They are tough and elastic.

They are elastic and are less tough as compared to tendons.

It connects the end of the muscles to the bones.

It connects the end of the bones at joints.

Each muscle contains only one tendon.

Each joint contains many ligaments.

Proteoglycan content is low.

Proteoglycan content is comparatively more.

White in colour.

Yellow in colour.

The blood supply is poor.

Blood supply is very less as compared to tendons.

Fibroblasts are arranged continuously in a row.

Fibroblasts are scattered.

The fibres are compact and present in bundles parallelly.

They are packed compactly but not arranged in parallel bundles.

There are no further classifications.

They are classified into three types they are: Articular ligaments, Remnant ligaments, and Peritoneal ligaments