Cartilage
Dr. Sami Zaqout IUG Faculty of Medicine
Cartilage
• Definition: It is a firm, rigid, flexible dense C.T. It
is poor in blood supply.
• Structure: It is formed of:1. Cartilage Cells; Young and mature Chondrocytes.
2. C.T. Fibres; Collagenous and elastic C.T. fibres.
3. Matrix; formed of collagen embedded in
chondroitin sulphates and glycoproteins.
Dr. Sami Zaqout IUG Faculty of Medicine
Cartilage Cells
• 1. Young Chondrocytes (Choudroblasts)
• They are flat cells with flat nuclei.
• Their cytoplasm is basophilic, it contains all
organoids and inclusions.
• They are present mainly under the
perichondrium.
Dr. Sami Zaqout IUG Faculty of Medicine
Cartilage Cells
• 2. Mature Chondrocytes
• They are oval or rounded cells with rounded nuclei.
• Their cytoplasm is basophilic, it contains all
organoids and inclusions. It is rich in glycogen, fat
and phosphatase enzymes.
• Chondrocytes are present usually in groups called
Cell Nests.
Dr. Sami Zaqout IUG Faculty of Medicine
Cartilage Cells
• The groups of cartilage cells are surrounded
with a space called lacuna, outside this lacuna
the matrix is condensed forming a capsule.
• Function Of Mature Chondrocytes: They
synthesize (form) type II Collagen,
proteoglycans, hyaluronic acid chondroprotein
(glycoprotein).
Dr. Sami Zaqout IUG Faculty of Medicine
Matrix Of Cartilage
• It is rubbery in consistancy.
• It is formed of proteins called proteoglycans,
hyaluronic acid, glycoprotein and type II collagen.
• It is basophilic in staining, it can be stained blue with
hematoxylin and metachromatic stains.
Dr. Sami Zaqout IUG Faculty of Medicine
Types Of Cartilage
• The cartilage cells and the C.T. fibres are
embedded in a rubbery matrix in order to
form the following three types of cartilage:
1. Hyaline cartilage (it appears glassy).
2. Elastic fibro-cartilage (contains elastic fibres).
3. White fibro-cartilage (contains white
collagenous bundles).
Dr. Sami Zaqout IUG Faculty of Medicine
Hyaline Cartilage
• It is the commonest type of cartilage.
• It appears, when fresh, translucent and pale blue
in colour. Therefore it is called hyaline.
• The matrix is poor in blood supply. The blood
vessels which appear in the matrix pass through
it on their way to supply other tissues.
• Hyaline cartilage is covered by a vascular
membrane or perichondrium, which is not
present over the cartilage which covers the
articular surfaces of joints.
Dr. Sami Zaqout IUG Faculty of Medicine
Hyaline Cartilage
• The perichondrium is formed of :
• a) Outer Fibrous Layer of collagenous
bundles, rich in B.V. and fibroblasts.
• b) Inner Chondrogenic Layer formed of
chondroblasts which can be changed into
chondrocytes.
• These chondroblasts can divide and can
secrete new matrix this will result in growth of
cartilage at its periphery.
Dr. Sami Zaqout IUG Faculty of Medicine
Dr. Sami Zaqout IUG Faculty of Medicine
• Photomicrograph of hyaline
cartilage.
• Chondrocytes are located in
matrix lacunae, and most
belong to isogenous groups.
The upper and lower parts
of the figure show the
perichondrium stained pink.
• Note the gradual
differentiation of cells from
the perichondrium into
chondrocytes. H&E stain.
Low magnification.
Dr. Sami Zaqout IUG Faculty of Medicine
•
•
•
Diagram of the area of transition
between the perichondrium and
the hyaline cartilage.
As perichondrial cells
differentiate into chondrocytes,
they become round, with an
irregular surface.
Cartilage (interterritorial) matrix
contains numerous fine collagen
fibrils except around the
periphery of the chondrocytes,
where the matrix consists
primarily of glycosaminoglycans;
this peripheral region is called the
territorial, or capsular, matrix.
Dr. Sami Zaqout IUG Faculty of Medicine
Hyaline Cartilage
• Functions of perichondrium :
• 1. Because of its vascularity, it supplies the
cartilage with blood and nourishment.
• 2. Its chondroblasts can secrete matrix during
growth of cartilage.
• 3. It provides an attachment for the muscles
under the perichondrium there is a basophilic
homogeneous matrix formed of glycoprotein
(proteoglycan) and fine collagenous fibres.
Dr. Sami Zaqout IUG Faculty of Medicine
Hyaline Cartilage
• Embedded in the matrix there are:
• Two Types of cartilage cells:
• a) Young Chondrocytes or Chondroblasts. They
are flat cells surrounded by spaces or lacunae.
They have flat nuclei and basophilic cytoplasm.
They are present as single cells under the
perichondrium. With growth of cartilage,
chondroblasts are transformed into mature
Chondrocytes.
Dr. Sami Zaqout IUG Faculty of Medicine
Hyaline Cartilage
• b) Mature Chondrocytes : They are spherical
cells with rounded nuclei and basophilic
cytoplasm rich in phosphatase enzyme. Each
cell is present in a space called lacuna. During
growth, chondrocyte can divide giving rise to 2
or 4 or 8 chondrocytes. These groups of
chondrocytes are surrounded with lacuna and
capsule and are called Cell Nests.
Dr. Sami Zaqout IUG Faculty of Medicine
Hyaline Cartilage
• Sites Of Hyaline Cartilage :
• 1. Costal Cartilages which are present in the
thoracic cage.
• 2. Cartilage of respiratory passages as in :
nose, trachea, bronchi, thyroid and cricoid
cartilages of the larynx.
• 3. Long bones in the skeleton of foetus.
• 4. Articular surfaces of joints (cartilage here
is not covered with perichondrium).
Dr. Sami Zaqout IUG Faculty of Medicine
Yellow Elastic Fibro-Cartilage
• This type of cartilage is similar in its structure
to hyaline cartilage BUT:
• a) The matrix is rich in elastic fibres which
surround the cartilage cells. The elastic fibres
are continuous with those of the
perichondrium.
• b) This cartilage is flexible and is yellow in
colour due to presence of elastic fibres.
Dr. Sami Zaqout IUG Faculty of Medicine
Dr. Sami Zaqout IUG Faculty of Medicine
• Photomicrograph of
elastic cartilage, stained
for elastic fibers. Cells
are not stained.
• This flexible cartilage is
present, for example, in
the auricle of the ear
and in the epiglottis.
• Resorcin stain. Medium
magnification.
Dr. Sami Zaqout IUG Faculty of Medicine
Yellow Elastic Fibro-Cartilage
• Sites Of Elastic Fibro-Cartilage
• 1. Ear Pinna, External Ear and Eustachian
tube.
• 2. Epiglottis, aretenoid, corniculate and
cuniform cartilages of the larynx.
Dr. Sami Zaqout IUG Faculty of Medicine
White Fibro-Cartilage
• Characteristics Of White Fibro-Cartilage :
• 1. It is similar to hyaline cartilage but it is very
rich in type I collagen fibres.
• 2. Its matrix is acidophilic due to presence of
type I collagen fibres.
• 3. It has less abundant matrix.
• 4. It is formed of chondrocytes similar to those
of hyaline cartilage.
Dr. Sami Zaqout IUG Faculty of Medicine
White Fibro-Cartilage
• 5. The cartilage cells are arranged in rows or in
columns.
• 6. The cartilage cells are present in a single form
or in groups of two cells.
• 7. The rows of cartilage cells are separated by
acidophilic collagenous bundles.
• 8. The white fibro-cartilage is not covered by
perichondrium but it is surrounded by dense
fibrous tissue rich in blood capillaries from which
it is nourished.
Dr. Sami Zaqout IUG Faculty of Medicine
Dr. Sami Zaqout IUG Faculty of Medicine
• Photomicrograph of
fibrocartilage. Note the
rows of chondrocytes
separated by collagen
fibers.
• Fibrocartilage is
frequently found in the
insertion of tendons on
the epiphyseal hyaline
cartilage.
• Picrosirius hematoxylin
stain. Medium
magnification.
Dr. Sami Zaqout IUG Faculty of Medicine
White Fibro-Cartilage
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•
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Sites Of White Fibro-Cartilage In The Body
1. Present in the intervenebral discs.
2. In the semilunar cartilage of knee joints.
3. In the symphysis pubis, acetabulum and in the
glenoid cavity.
• 4. In the discs between sterno-clavicular and
mandibular joints.
• 5. In the terminal parts of the muscle tendons
and in the tendon grooves.
Dr. Sami Zaqout IUG Faculty of Medicine
Functions Of Cartilage
• 1. Cartilage helps in maintaining the patency of
respirator) passages.
• 2. Cartilage and bone form the skeleton of the
body.
• 3. Cartilage forms a smooth firm surface for the
articular surfaces of joints.
• 4. Cartilage is essential for growth of bone before
and after birth.
• 5. Cartilage and bone protect essential organs as
lung, brain and bone marrow.
Dr. Sami Zaqout IUG Faculty of Medicine
Growth Of Cartilage
• Young cartilage can grow out by two different
methods :
• 1. Interstitial Growth: The cartilage cells in the
centre divide to form groups of young
chondrocytes. They secrete the matrix resulting in
growth of the cartilage from
• 2. Appositional Growth: The chondroblasts of the
perichondrium become transformed into
chondrocytes which can divide and can secrete the
matrix. They cause growth of cartilage at its
periphery resulting in an increase in its width.
Dr. Sami Zaqout IUG Faculty of Medicine
MEDICAL APPLICATION
• Cartilage cells can give rise to benign (chondroma) or
malignant (chondrosarcoma) tumors
• In contrast to other tissues, hyaline cartilage is more
susceptible to degenerative aging processes.
• Calcification of the matrix, preceded by an increase in
the size and volume of the chondrocytes and followed
by their death, is a common process in some cartilage.
• Asbestiform degeneration, frequent in aged cartilage,
is due to the formation of localized aggregates of thick,
abnormal collagen fibrils.
Dr. Sami Zaqout IUG Faculty of Medicine
MEDICAL APPLICATION
• Rupture of the annulus fibrosus, which most
frequently occurs in the posterior region where
there are fewer collagen bundles, results in
expulsion of the nucleus pulposus and a
concomitant flattening of the disk.
• As a consequence, the disk frequently dislocates
or slips from its position between the vertebrae.
If it moves toward the spinal cord, it can
compress the nerves and result in severe pain
and neurological disturbances.
Dr. Sami Zaqout IUG Faculty of Medicine
MEDICAL APPLICATION
• The pain accompanying a slipped disk may be
perceived in areas innervated by the
compressed nerve fibers usually the lower
lumbar region.
Dr. Sami Zaqout IUG Faculty of Medicine