Cartilage

2. There are four basic types of tissues in the
1. Epithelial tissue
2. Connective tissue
3. Muscle tissue
4. Nervous tissue

3. CONNECTIVE TISSUE
• The connective tissue is found throughout the body and as its name indicates it binds or supports
the other tissues of the body.
• The connective tissue consists of cells and extracellular matrix which is
secreted by the cells themselves.
• The matrix itself is made up of two components: (a) fibers, and (b) ground substance.
• Thus the three essential components of connective tissue are:
1. Ground substance
2. Fibers
3. Cells

4. CELLS
The cells of the connective tissue are of two types:
1.Fixed cells: These are long-lived cells and form stable
population of cells that remain in the connective tissue
2. Free cells : Are short-lived wandering cells
that are continually replaced from cells of blood, i.e. they
enter the connective tissue from blood usually during
inflammation.

5. Classification of Connective Tissue
1. Connective tissue proper
(a) Loose (areolar) connective tissue
(b) Dense regular connective tissue
(c) Dense irregular connective tissue
(d) Elastic connective tissue
(e) Adipose connective tissue
(f) Reticular connective tissue
2. Specialized connective tissue
(a) Bone
(b) Cartilage
(c) Blood

6. • The cartilage is a specialized connective tissue which provides rigidity along with
elasticity.
• Hence it is found in those areas of the body, where both rigidity and elasticity
are required.
• It consists of chondrocytes embedded in a gel-like matrix.
• Phylogenetically, the cartilage tissue is older than bone tissue.
• Most of the bones in the intrauterine life are preformed in cartilage.
• The cartilages which are replaced by bones are called temporary cartilages and those
that persist throughout life are called permanent cartilages.
INTRODUCTION

7. The following are the functions of the cartilage:
1. Provides rigidity and support to soft tissues.
2. Provides smooth gliding surface for articulation.
3. Enables development and growth of long bones.

8. The cartilage has all common features of connective tissue,
which include the following:
1. Cells
2. Fibers
3. Ground substance

9. Cells of the cartilage are of the following three types:
1. Chondrogenic cells: found in the perichondrium, where
they undergo mitosis and differentiate into chondroblasts.
2. Chondroblasts: young cartilage cells occupying small
spaces (lacunae) and may undergo mitosis.
3. Chondrocytes: mature cartilage cells which reside in
lacunae. They form isogenous cell clusters surrounded
by territorial matrix.
CELLS

10. Cartilage has the following two types of fibers:
1. Type I collagen fibers in fibrocartilage.
2. Type II collagen fibers in hyaline and elastic cartilages.
Fibers

11. Ground substance:
It consists of:
1. Proteoglycans, specifically chondroitin sulphate and
keratan sulphate.
2. Glycoproteins, viz. chondronectin and chondrocalcin
(a calcium-binding protein).
3. Water (tissue fluid) contributes to 75% hydration of the
ground substance (high degree of hydration).

12. GROWTH OF CARTILAGE
The cartilage grows by both appositional and interstitial methods.
1. Appositional growth: In this, layers of new cartilage are
deposited at the surface beneath the perichondrium. The
new cartilage is formed by chondroblasts derived from
perichondrium. By appositional growth the cartilage
increases in width.
2. Interstitial growth: It occurs due to increase in size and
the number of existing cells and by an increase in the
amount of intercellular matrix, due to proliferation of
chondrocytes by mitosis in the center of cartilaginous
model. By interstitial growth the cartilage increases in
length.

13. CHARACTERISTIC FEATURES OF CARTILAGE
The distinguishing features of cartilage are as follows:
1. It is avascular and receives its nutrition by diffusion
through the ground substance from nearest capillaries.
2. It has no lymphatics.
3. It has no nerves, hence it is insensitive.
4. It is surrounded by perichondrium.
5. It grows by appositional as well as by interstitial
methods of growth.
6. When cartilage calcifies, chondrocytes die because
they are deprived of nutrition by diffusion.

14. TYPES OF CARTILAGE
The cartilages are classified into three types
1. Hyaline cartilage
2. Elastic cartilage
3. Fibrocartilage

15. Hyaline cartilage (Gk. hyalos = transparent stone):
• It appears bluish-white and transparent
• It contains very fine collagen fibers having same refractive
index as that of ground substance.
• It is the most widely distributed cartilage in the body
• All the long bones in the body are preformed in
hyaline cartilage.
Found in - Articular surfaces, wall of large respiratory passages
– larynx, trachea, bronchi
Epiphyseal plate
Ventral ends of ribs

16. Elastic cartilage:
• It is made up of numerous chondrocytes
embedded in matrix containing rich network of yellow elastic
fibers.
• The sites of distribution of elastic cartilage include
pinna of the ear, epiglottis.

17. Fibrocartilage:
• It appears white and opaque due to abundance
of collagen fibers in it.
• The collagen fibers are arranged in bundles.
• The chondrocytes are few, small and scattered singly or
arranged in rows.
• It is formed at sites subjected to great pressure like
intervertebral disc.