ELASTIC CARTILAGE: CHARACTERISTICS, HISTOLOGY, FUNCTIONS - ANATOMY AND PHYSIOLOGY - 2025

The elastic cartilage is one of the three types of cartilage that can be found in the human body. It contains a large amount of elastin, which will give it a characteristic yellowish color and greater elasticity than hyaline and fibrous cartilage.

Cartilage itself is a connective tissue (skeletal) that can be part of the skeleton of some lower vertebrates. They can function as extensions of bone structures or by helping to shape structures such as the nose, larynx and ears.

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This type of cartilage is characteristic of the pinna, although it is also present in the external auditory canal, the Eustachian tube and some laryngeal cartilages such as the epiglottis, providing support to prevent their collapse.

Characteristics, histology and structure

Cartilage tissue in general is made up of:

- Cell types called chondrocytes that, although they are in a smaller proportion and arranged in gaps within the tissue, help to maintain it.

- A highly specialized extracellular matrix (accounting for more than 95% of the cartilage) that is solid and flexible.

The components of the extracellular matrix of elastic cartilage are highly varied, since they contain type II collagen fibers, glycosaminoglycans (GAGs), proteoglycans and multi-adhesive proteins. It should be noted that histologically this type of cartilage is very similar to vitreous or hyaline cartilage.

In addition to these components, these cartilage in particular have elastic fibers and branched elastic sheets composed mainly of elastin, which distinguish them from other types of cartilage. This material confers unique elastic properties in addition to the compliance and malleability characteristic of hyaline cartilage.

Unlike hyaline cartilage, the extracellular matrix of elastic cartilage does not calcify during the aging process.

Growth and training

Elastic cartilage increases in size through two types of growth: interstitial and appositional growth. However, the growth of cartilaginous tissues is generally limited in adulthood. In the first of the types of growth, new cartilage forms on the surface of a pre-existing cartilage.

New cartilaginous cells arise from the innermost layer of the perichondrium that surrounds the elastic cartilage. At first they are similar to fibroblasts, but later they differentiate into chondroblasts that synthesize the carlylaginous matrix and type II collagen fibers. A process that increases the mass of cartilage.

In interstitial growth, new cartilage cells arise from the mitotic division of chondrocytes present in gaps within the extracellular matrix of cartilage.

This is possible as chondrocytes retain the ability to divide and the surrounding cartilaginous matrix is ​​compliant, supporting the additional secretory activity.

Features

The main function of this type of cartilage is to provide a flexible support to the structures where it is located.

In general, cartilage tissue is of great importance during the first stages of embryonic development where it practically constitutes the skeleton / mold that later becomes calcified.

However, cartilage in general has a poor capacity for recovery or regeneration in the event of injuries, even if the latter are minor.

Only in those cases where the injury involves the perichondrium, there is a certain degree of repair thanks to the pluripotent progenitor cells that exist in it. However, the new cells that are produced are still quite few. In most cases there is rather a substitution by bone tissue or fibrous cartilage.

Some surgical interventions for cartilaginous tissue repair are based on perichondrium grafts.

Pathologies related to elastic cartilage

One of the best characterized pathologies to date and that directly affects the integrity of the elastic cartilage is relapsing polychondritis (RP).

This pathology is a condition of autoimmune origin and a recurrent course in which the cartilaginous tissue involved becomes episodically, chronically and multi-systemic inflamed and is imminently degraded. Studies reveal the presence of antibodies against type II collagen, which is essential in the constitution of cartilaginous tissues.

RP is rare and very difficult to diagnose, occurring approximately 3.5 cases per million inhabitants. Generally, the pathology affects women more than men in a 3: 1 ratio, with an average age regardless of sex at the time of diagnosis of 47 years.

The elastic cartilages present in the ear and nose are the most affected by this pathology causing auricular chondritis and nasal chondritis respectively. Despite this, hyaline joint cartilage and fibrous cartilage can also be affected, causing non-erosive arthritis, ocular symptoms, and costochondral symptoms.

For nasal chondritis, in about 20% of cases there is posterior deformation of the nasal bridge or "saddle nose".

Differences with other cartilage

Elastic cartilage, although it has a composition and histology similar to hyaline cartilage and fibrous cartilage, presents clear differences with the latter.

The hyaline cartilage is the most widespread in the body, forming a fundamental part of the fetal skeletal tissue, the episiary discs, the articular surfaces, the costal cartilages, the nasal cavity, the pharynx, the tracheal rings and the cartilaginous gill plates.

This provides cushioning to the joints, being structural support of the respiratory system. Although this type of cartilage has a perichondrium, in cases such as joints it is absent. On the other hand, it tends to calcify with aging and does not have an intricate network of elastic fibers.

In contrast, fibrous cartilage is found in intervertebral discs, articular discs, wrist joint, and tendon attachments, resisting deformation by external pressures. This type of cartilage does not have perichondrium, presents calcification and has a large number of fibroblasts as a component.

References

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