Cartilage: Structure, Types & Functions

Cartilage is a non-vascular connective tissue that supports the other tissues throughout the body. It provides protection and supports the structure of the body. It is primarily made up of water and exists in the nose, airway, joints, ear, and intervertebral disc of the spine. 

• Cartilage is a semi-transparent tissue that protects the joints of the body.
• It is divided into three categories namely elastic, hyaline and fibro cartilage. 
• Chondrocytes are specialized cells that are responsible for making of cartilage.
• It produces a mixture of collagen, proteoglycans, and other non-collagen proteins.
• Cartilage does not contain any blood veins and nerves.
• Hence, these types of connective tissues are insensitive.
• It also provides protection to the spinal cord.
• The tissues are quite flexible and can easily be damaged.

 Key Terms: Cartilage, Chondrocytes, Tissue, Extracellular Matrix, Collagens, Bones, Proteoglycans, Spinal Cord, Nerves, Blood Veins, Joints

---

What is Cartilage?

[Click Here for Sample Questions]

Cartilage is a type of connective tissue that provides protection to the long bones found at the joints. The bones found at the joints are called articular cartilage. It helps in the facial movement. Cartilage makes up the skeleton of the mammalian embryos before the formation of the bone.

• Cartilage provides support to the external ear along with the septum of the nose.
• The tissue works as a template for ossification.
• It is found in some of the certain primitive vertebrates, including sharks and lampreys. 
• Cartilage forms a dense network of collagen fibres embedded in gelatinous ground substance.
• Sports injury or trauma cause damage to the cartilage.

Read More: Types of joints

---

Structure of Cartilage

[Click Here for Sample Questions]

The structure of cartilage consists of following components:

Chondroblasts

During embryonic development, the cell is formed by the combination of chondroitin sulfate, hyaluronic acid, water, and collagen fibers. They are responsible for the production of the elements of the extracellular matrix when they are mobile. 

Chondrocytes

Chondroblasts are surrounded by the matrix of chondroitin sulfate, hyaluronic acid, water, and collagen fibers. They become immobile and are referred to as the chondrocytes.

• Single or more chondrocytes occupy a place known as the lacunae.
• Chondrocytes help in joint articulation in the articular cartilage of the joint.
• They control and regulate the existing extracellular matrix. 

Read More:

Fibroblasts

All types of connective tissues comprise fibroblasts. The fibroblasts in the cartilages produce type 1 collagen. They sometimes get converted into chondrocytes. 

Extracellular matrix

The cartilage structure consists of more matrix than cells because there is a low oxygen environment and there is no vasculature. As a result, there are limited metabolic activities and no growth of new cartilage tissue which is a reason for the degenerative joint pain in the elderly.

• Extracellular matrix consists of three elements: collagen, proteoglycans, and non-collagenous proteins. 

Read More: Difference between bones and cartilages 

---

Function of Cartilage

[Click Here for Sample Questions]

The various functions of cartilage are as follows:

• Cartilages support the embryo and act as a cushion to the bone.
• It promotes rapid growth and development of the musculoskeletal system.
• It initiates smooth facial movement.
• The tissue provides support to the septum and tip of the nose. 
• It prevents damage and abrasion in the places where two bones meet each other.
• It acts as a shock absorber and reduces friction between the joints.
• The trachea is surrounded by rings of cartilage to prevent damage and collapse.
• The upward and outward movement of the rib cage during inhalation is due to the cartilage.
• Cartilages help in the bone repair found in the embryos.

Read More: Difference between pharynx and larynx

---

Types of Cartilage

[Click Here for Sample Questions]

Cartilage is divided into three types which are as follows:

Elastic Cartilage

Elastic Cartilage is the flexible part of the body, including the larynx, external ear (auricle or pinna), epiglottis and eustachian tube. It is formed by combining type II collagen fibres and elastic fibres.

• Elastic Cartilage provides flexibility and resilience to the structures. 
• It is unorganized, yellow, and surrounded by perichondrium.
• It appears as a dark bundle under the microscope. 

Read More:

Hyaline Cartilage

Hyaline Cartilage has a smooth surface made up of a combination of collagen fibres, making it hard and flexible. It has an elastic material that is bluish-white in colour.

• It contains chondroitin sulfate, fine collagen fibres, and chondrocytes. 
• Hyaline Cartilage is spread to the articular surfaces of the rib tips.
• The long bones, parts of the skull and the trachea rings are parts of hyaline cartilage.

Fibrous Cartilage

Fibrous Cartilage is made up of type II and type I collagen fibres. It consists of dense ligament and tendon tissues. Fibrocartilage is made up of cartilaginous and fibrous tissues in a wide proportion. 

• The fibrous tissue is responsible for the flexibility and the toughness.
• Cartilaginous tissue is responsible for elasticity. 
• Fibrocartilages are found in the annulus fibrosus of the intervertebral disc.
• It is also found in pubic symphysis, temporal mandibular joint, and menisci. 

Read More: Difference between ligament and tendon

---

Things to Remember

• Cartilage is a flexible tissue that contains 65-80% of water.
• It is responsible for holding tubes in the body.
• The tissue provide cushion to the skeletal system.
• Non Collagenous proteins found in the extracellular matrix maintain and organize the structure of the cartilage.
• The composition of the extracellular matrix affects the function of the articular cartilage. 
• Hyaline cartilage is the important type of cartilage among the three types of cartilage.