Cartilage

What Is Cartilage?

A flexible, semifirm connective tissue inhabiting different parts of the body, cartilage serves to support, cushion, and act as a shock absorber in articulations. Cartilage is part of several anatomical structures.

Types Of Cartilage

There are three general types of cartilage, each with particular features and functions.

Hyaline Cartilage

It is the most common type of cartilage in the body and is recognised by the smooth, glassy appearance it bears.

Description And Characteristics

• Translucent and glassy texture.

• Fine collagen fibres in composition.

• Provide a smooth surface for joints to move on.

Locations In The Body

• Nasal septum

• Trachea

• Larynx

• Articular surfaces of bones (joints)

Functions And Importance

• Reduce friction in joints

• Support and reinforcement of structure

• Provides for a template of bone growth during the development

Elastic Cartilage

Elastic cartilage is adaptable and resilient due to the abundance of elastic fibres.

Description And Features

• Yellowish colour due to elastic fibres.

• Very resilient and flexible.

• Both collagen and elastic fibres are present.

Location In The Body

• External ear (auricle)

• Epiglottis (part of the larynx)

Functions And Significance

• Provides flexible support to structures

• Maintains shape but allows for movement

• Protects the airway during deglutition

Fibrocartilage

Fibrocartilage is the most resilient type of cartilage and thus offers tensile strength and durability.

Description And Features

• Dense, fibrous texture

• Contains thick bundles of collagen fibers

• Resists compression and absorbs shock

Locations In The Body

• Intervertebral discs (between vertebrae)

• Menisci (knee joints)

• Pubic symphysis (joining the pelvic bones)

Functions And Significance

• Absorbs shock and reduces friction.

• Supports the weight of the body against gravity in the vertebral column and lower limb bones.

Structure Of Cartilage

Cartilage is a connective tissue consisting of cells embedded in an extracellular matrix that is dense and possesses elastic and viscoelastic properties.

Cell Types In Cartilage

There are several cell types in cartilage

• Very immature cells of the cartilage produce the extracellular matrix

• Cells undergo continuous division and synthesis of the matrix components

Chondrocytes

• Mature cartilage cells are embedded in the matrix.

• Maintenances of the cartilage matrix and controls of matrix composition.

Chondroclasts

• Cells responsible for the resorption of cartilage

• Assists in remodelling of cartilage during growth and repair

Extracellular Matrix (ECM)

The extracellular matrix forms an important component of the cartilage. In cartilages, it provides support to the structure by rendering it elasticity.

Structure

• Collagen fibres: tensile strength

• Proteoglycans: attract and hold large amounts of water, thus aiding in shock absorption.

• Water: Contributes elasticity and spring to the matrix

ECM In Cartilage Function

• Gives structure to cartilage and resists compression

• Gives elasticity, thus allowing for smooth movement at joints

• Allows for the exchange of nutrients and wastes through its gel nature

• Cartilage development and growth occur via a series of specific biological steps.

Formation And Growth Of Cartilage

Cartilage develops and grows through specific biological processes.

Chondrogenesis

Chondrogenesis is the process by which cartilage forms during development.

Cartilage Formation During Embryonic Development

• Mesenchymal cells undergo differentiation to become chondroblasts

• Chondroblasts produce extracellular matrix and differentiate into chondrocytes

• A cartilage model is formed that matures into cartilage

Mesenchymal Stem Cells

• Come to differentiate into chondroblasts during embryonic development

• Supply a source for repair or regeneration of cartilage

Mechanisms Of Growth

Cartilage increases in mass through growth and expands via specific mechanisms.

Appositional Growth

• Occurs at the surface of existing cartilage

• Chondroblasts in the perichondrium produce new cartilage matrix

• Increases in thickness

Interstitial Growth

• Takes place within the cartilage tissue.

• Chondrocytes divide and produce matrix and expand cartilage from within.

• Helps to increase the length of cartilage during development.

Functions And Role Of Cartilage

Cartilage performs many essential functions in the body.

Support And Structure

• Maintains the shape and structure of many body parts.

• Provides structural support for flexible areas such as the ear and nose.

Protection And Mobility Of Joints

• Cushions joints and reduces friction at joint surfaces as a result of movement.

• Allows for smooth and efficient movement between joint surfaces.

Growth And Development

• Part of the growth plates of long bones.

• Provides support for bone growth and elongation during development.

Cartilage Damage And Disorders

Cartilage is susceptible to disorders and injuries.

Common Disorders Of Cartilage

Various conditions are capable of causing damage to cartilage and affecting its normal function.

Osteoarthritis

• Degenerative joint disease is characterised by the wearing down of cartilage.

• Symptoms: Joint pain, stiffness and reduced mobility.

Rheumatoid Arthritis

• An autoimmune disorder causing inflammation and hence damage to the cartilage.

• Causes pain in the joints, swelling and finally deformity of joints.

Chondromalacia

• Softening up and thus cartilage damage typically affects the knee.

• Cause pain and discomfort mainly on movement.

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