CARTILAGINOUS JOINTS: CLASSIFICATION AND CHARACTERISTICS - ANATOMY AND PHYSIOLOGY - 2024

The cartilaginous joints are those joints that are joined by hyaline cartilage or fibrocartilage. The bone surfaces in this type of joint are usually flat or concave, and therefore, although they are mobile, their mobility is limited.

Hyaline cartilage is a fairly firm type of specialized connective tissue that has the consistency of soft plastic. The function of the cartilaginous joints is to give a little more flexibility between the bones which generates slight movements, however this movement is not as free as the synovial joint.

In the same way, it acts as a shock absorber, as it has elastic resistance to pressure due to high mechanical loads. It is the type of joint that forms amphiarthrosis, or semi-mobile joints.

Classification of cartilaginous joints

The classification of these joints is based mainly on the moment of development of the bone system and the type of fibrocartilaginous tissue.

Primary cartilaginous joint (synchondrosis)

A synchondrosis is formed when the adjacent bones are united by the hyaline cartilage, staying in direct contact with it.

There are temporary synchondrosis as a result of the gradual ossification of the hyaline cartilage that occurs over the years when reaching maturity.

They generally do not allow movement during this stage, acting more like a kind of "hinge", allowing the growth of adjacent bones, such as the occipital and sphenoid bones, and between the sphenoid and ethmoid bones of the skull floor.

Another example of this type of joint is the joint between the epiphyses and the diaphysis of a long growing bone, the costochondral joint, and the first chondrosternal joint.

In the skull, synchondroses form between the occipital, temporal, sphenoid, and ethmoid bones of the developing chondrocranium and provide early support for brain development.

Secondary cartilaginous joint (symphysis)

A symphysis, also known as a fibrocartilaginous joint, is a joint in which two bone structures fuse through fibrocartilage, which allows the existence of a pseudo cavity inside, similar to a rudimentary synovium.

Generally, these types of joints are found in the vertebral column (spinal), and all but one contain fibrocartilage, this being very strong because it is made up of numerous bundles of thick collagen fibers.

The only symphysis that does not have fibrocartilage is the one found in the suture between the two halves of the mandible, called symphysis menti or mandibular symphysis.

A particularly interesting symphysis is the pubic symphysis, which consists of a fibrocartilaginous disc sandwiched between the articular surfaces of the pubic bones, covered by hyaline cartilage.

Its main function is to perform a small amount of movement under physiological conditions; in most adults up to 2 mm of displacement and 1 ° of rotation.

It resists tensile, shear, and compressive forces, and is flexible enough to act as a hinge allowing each of the two hip bones to rock up and out a little, as ribs do during inspiration. from air.

This flexibility changes during pregnancy and delivery, as the ligaments around the pubic symphysis become flexible, so that the child can "snap in" and then traverse without difficulty or complications.

References

1. Becker, I., Woodley, SJ, & Stringer, MD (2010). The adult human pubic symphysis: a systematic review. Journal of Anatomy, Taken from doi.org
2. Biology Online Dictionary (2008)._ Cartilaginous joint. Taken from biology-online.org
3. Human Anatomy._Types of Joints. Taken from mananatomy.com
4. Physical anthropology and human anatomy laboratory._ Support material "joints" generalities of joints. Taken from anatomiahumana.ucv.cl
5. Michael A. MacConaill (2017)._ Joint. Encyclopædia Britannica. Taken from britannica.com.