Cartilage - Islamic University of Gazasite.iugaza.edu.ps/sizaqout/files/2012/02/Cartilage.pdf ·...

Dr. Sami Zaqout IUG Faculty of Medicine

Cartilage


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.


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.


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.


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).


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.


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).


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.


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.


• 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.


• 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.


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.


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.


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.


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).


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.


• 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.


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.


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.



• 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.


• 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.



• 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.


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.


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.


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.


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.


MEDICAL APPLICATION

• The pain accompanying a slipped disk may be perceived in areas innervated by the compressed nerve fibers usually the lower lumbar region.

Cartilage - Islamic University of Gazasite.iugaza.edu.ps/sizaqout/files/2012/02/Cartilage.pdf ·...

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