Cartilage
Dr. Amam Ali Amam
PhD: Periodontal Disease
Cartilage, Definition
Is a special form of connective tissue in which
the firm consistency of the extra-cellular matrix
allows the tissue to bear mechanical stresses.
Is a semi-rigid form.
Cartilage
Cartilage is characterized by:
an extracellular matrix enriched with
glycosaminoglycans and proteoglycans,
macromolecules that interact with
collagen and elastic fibers.
Cartilage, Functions
1- Bearing mechanical stresses.
2- Support soft tissue.
3- Shock-absorbing and sliding area for joints
and facilitates bone movements.
(Because it is smooth surfaced and resilient)
4- Developmental and growth of long bones
before and after birth.
Cartilage is a connective tissue
We have to study :
• 1- cells
• 2- fibers
• 3- ground substance
Cartilage consist of:
1- Cells
Called Chondrocytes
2- Extracellular matrix
1- Fibers
2- Ground
substance
1- Hyaluronic acid.
1- Collagen.
2- Proteoglycans.
2- Elastic .
3- Small amount of
several glycoproteins
Chondrocyte
• It is derived from chondroblast, which
resembles fibroblast
• It synthesizes and secretes the extracellular
matrix .
• It is interapted in the matrix that it secretes!
• Histological: it is seen in cavities called
lacunae.
3 Types of cartilage
Variations in the composition of these matrix
components produce three types of cartilage
adapted to local biomechanical needs.
1- Hyaline cartilage.
2- Fibro cartilage.
3- Elastic cartilage.
Articular cartilage.
1- Hyaline cartilage.
It is the most common type & the best studied
of the three forms.
Small aggregation of chondrocytes embedded
in an amorphous matrix of ground substance
reinforced by collagen fibers ( II )
1- Hyaline cartilage, cont...
Location:
1- in the articular surfaces of the movable joints.
2- in the walls of larger respiratory passage
(nose, larynx, trachea, bronchi).
3- the ventral ends of the ribs
40 % of the dry weight of Hyaline Cartilage consist of :
1- collagen
embedded in a firm
2- hydrated gel
of Proteoglycans.
3- structural
Glycoproteins
Hyaline cartilage
Hyaline cartilage
Cartilage matrix
2- Fibro cartilage.
Is a tissue intermediate between dense
connective tissue and hyaline cartilage.
Is a combination of dense supporting tissue
and cartilage.
Presents in regions of the body subjected to
pulling forces.
Is characterized by a matrix containing a dense
network of coarse type I collagen fibers.
It contains chondrocytes (singly or groups).
2- Fibro cartilage, cont...
It is found at :
- intervertebral discs.
- the symphysis pubica.
- the knee joint.
- the mandibular joint.
- the sternoclavicular Joint.
- the shoulder Joint.
- Ligaments and the connections of some
tendons of bone.
Fibrocartilage
3- Elastic cartilage.
Elastic Cartilage, characterized by its great
pliability, contains significant amounts of the
protein elastin in the matrix.
The more pliable and distensible elastic
cartilage possesses, in addition to collagen type
II, an abundance of elastic fibers within its
matrix.
3- Elastic cartilage, cont...
Elastic Cartilage is found in:
- The auricle of the ear.
- The walls of the external auditory canal.
- The auditory (Eustachian) tube.
- The epiglottis.
- The larynx.
Elastic Cartilage possesses a
perichondrium (like hyaline cartilage) .
Elastic cartilage
Articular cartilage
Covers the surface of the bones of movable
joints.
Is devoid of perichondrium.
Is sustained by the diffusion of oxygen and
nutrients from the synovial fluid.
Perichondrium
At the periphery of mature cartilage is a zone
of condensed supporting tissue called
perichondrium containing chondroblasts with
cartilage – forming potential .
Perichondrium
• Is a sheath of dense connective tissue that
surrounds cartilage in most places, forming
an interface between the cartilage and the
tissue supported by the cartilage.
Most cartilage is devoid of blood vessels
Perichondrium
• All cartilage is covered by a layer of dense
connective tissue (perichondrium)
(except in the articular cartilage of joints & fibro cartilage).
• It’s essential for the growth & maintenance of
cartilage.
• It’s rich in collagen type I fibers & contains
numerous fibroblasts.
• contains nerves lymphatic vessels.
Cartilage Properties
•
•
•
•
•
Nutrition
Growing
Regenerating
Degenerative
Histogenesis
Cartilage Properties
• In all 3 forms, Cartilage is avascular (no vascular).
Nutrition: is nourished by the diffusion of nutrients
from capillaries in adjacent connective tissue
(perichondrium) or by synovial fluid from joint
cavities.
• Cartilage has no lymphatic vessels or nerves.
Growth : 1- Interstitial growth
2- Appositional growth
The Growth of Cartilage
1- Interstitial growth:
Resulting from the mitotic
2- Appositional growth
division of preexisting
Resulting from the
Chondrocytes.
differentiation of
Less important process.
perichondrial cells.
important in increasing the
Grows in girth only by
length of long bones
opposition.
occurs during the early
phase of cartilage formation.
Histogenesis
A- mesenchyme.
B- Mitotic Proliferation of mesenchyme.
C- Chondroblasts. D- rise to isogenous group.
Perichondrium & Hyaline cartilage
Degenerative changes
• Hyaline cartilage is more susceptible to
degenerative aging processes ( in contrast of
other tissues).
• Calcification of the matrix, preceded by an
increase in the size & volume of the
chondrocytes and followed by their death.
Poor Regeneration of Cartilage Tissue
• Except in young children, damage cartilage
regenerates with difficulty & often
incompletely by activity of the perichondrium,
which invades the injured area and generates
new cartilage
Fibrocartilage, young animal
Chondrocytes
Collagen