9. cartilage

8/8/2019 9. Cartilage

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Ajman University of Science & Technology

acu y o en s y

Histology & Cell Biology

08 01 112

Dr. l-Moutassem Billah hair

Cartilage


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CartilageCartilage is a semi-rigid, avascular, form of supporting tissue

produced and maintained by the chondrocytes.

-

abundance of ground substance. Proteoglycans form aggregates, of one hundred

or more molecules, that make u the round substance and account or the

solid, yet flexible, consistency of cartilage. Proteoglycan aggregates mainly

consist of chondroitin sulfate and keratan sulfate with hyaluronic acid forming

t e centra ac one o t e matr x.- The solvation water of ground substance acts as a shock absorber or

, ,

articular cartilage.


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Cartilage- Cartilage is devoid of blood or lymphatic vessels (also nerves) and exchange of

metabolites between chondrocytes and surrounding tissues depends on

.

thickness and in sites of thick cartilage, cartilage canals convey small vessels

into the centre o the cartila e mass.

- Cartilage is found in specific locations in the body and forms structures that

have characteristic shapes. In adults, cartilage is found on the articularsurfaces of long bones and in the trachea, bronchi, nose, ears, larynx and

intervertebral disks. In the fetus, most long bones are initially represented by

.- Three different types of cartilage are distinguished on the basis of matrix

characteristics: * Hyaline cartilage (a homogeneous amorphous matrix)g ( g p x)** Elastic cartilage (elastic fibers and elastic lamellae)*** Fibrocartilage (large bundles of type I collagen)


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Cartilagear age eve opmen row :

Cartilage is developed by the differentiation of stellate-shaped primitive

, .

aggregate of cells is called a blastema of precartilage protochondral tissue.

The cells of the blastema, although in close apposition, begin to secrete cartilage

matrix and then referred to as chondroblasts. They progressively move apart as

they deposit matrix. When the cells have become completely surrounded byma r x, en ey are nown as c on rocy es. s eren a on an

maturation sequence is most advanced in the centre of a growing cartilage.

of extracellular matrix. Around the mature cartilage is a layer of condensed

connective tissue called perichondrium containing chondroblasts.

The growth of cartilage occurs by interstitial growth form within &

appositional growth at the periphery.


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Cartila e Appositional growth, the process that forms new cartilage cells from the

nner por on o e surroun ng per c on r um. on ro as s pro era e an

become chondrocytes once they have surrounded themselves with matrix and

are incor orated into the e istin cartila e. The new ibroblasts at the same

time, are produced to maintain the perichondrium.

Interstitial growth, the process that forms new cartilage from division ofchondrocytes within their lacunae. The daughter cells of the dividing

chondrocytes temporarily occupy the same lacuna, but they become separated

. ,and each cell occupies its own lacuna.

Thus the overall rowth is a re lection o the new matri that has been

formed both interstitially and appositionally.


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Cartilage

Chondrocytes:

- t the eri her o oun cartila e the chondroc tes have an elli tic sha e

with long axis parallel to the surface, while in centre they are round shape.- Chondrocytes vary in appearance according to their activity. Active cells

have the fine structure typical of cells that synthesize large amounts of protein

and polysaccharide (matrix materials) for secretion from the cell. In older, lessac ve ce s, ave re uce s ruc ure o syn es ze ac v y.

- Chondrocytes are located in matrix cavities known as lacunae.

- , ,compact groups (row) by a consequence of several successive divisions, without

significant additional matrix production. Such groups of chondrocytes (up to 8

cells) are called isogenous group.


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CartilagePerichondrium:

- It consists of dense connective tissue whose cells are indistinguishable from

ro asts. It s more t an s mp y a cover ng capsu e, owever, ecause t

serves as the source of new cartilage cells.

- .

inner layer cells are chondroblasts, which easily differentiate into chondrocytes.

- It contains the vascular su l or the avascular cartila e and also contains

nerve and lymphatic vessels.

- It is found around:

*all hyaline cartilage except in articular cartilage of joints, nasal and

costal cartilage, and in forming bone;

** elastic cartilage;

*** fibrocartilage has no perichondrium.


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Cartilage

It is bluish opalescent tissue that is widely distributed in the body and forms

- It is found in the nasal septum, larynx, tracheal rings, most articularsurfaces and the sternal ends of ribs.

- The matrix of hyaline cartilage appears in living state glassy. It consists of

two components, collagen fibrils (mainly type II) and ground substance.Collagen fibrils thin 20 nm in diameter and are arranged in a three-

dimensional felt-like pattern. In some locations, however, the collagen fibrils

.

three kinds of glycosaminoglycans hyaluronic acid, chondroitin sulfate and

keratan sulfate. Throughout the matrix there are lacunae, containing

chondrocytes.

- Mature hyaline cartilage is characterized by isogenous groups.


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CartilageElastic cartilage:

- It is found in the external ear (auricle), in the walls of the external auditory

cana an t e au tory Eustac an tu e, n t e ep g ott s, an n t e arynx.

- Components of elastic cartilage as in hyaline cartilage plus elastic fibers and

.

properties in addition to the resilience and pliability that are characteristic of

hyaline cartilage.

- Elastic cartilage in fresh statement has yellowish color, because of the

presence of elastin protein.

- In all locations there is surrounding perichondrium, such as that found around most hyaline cartilage.

- n e ya ne cart age, owever, t e matr x o e ast c cart age oes not

calcify.


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CartilageFibrocartilage:

- It has features intermediate between cartilage and dense fibrous connective

t ssue.

- It consists of alternating layers of hyaline cartilage matrix and thick layers

.

- It is less cellular than hyaline cartilage or elastic cartilage. Chondrocytes are

either sin le or in iso enous rou s, usuall arran ed in lon rows se arated

by bundles of collagen type I.

- It contains fewer glycosaminoglycans and many more collagen fibers.

- It is found in the intervertebral disks, some articular cartilage, the pubic

symphysis, and in association with dense collagenous tissues in joint capsules,

gaments an t e connect ons o some ten ons to one.

- It has no perichondrium (may by because it is not found alone).


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artila eIntervertebral disks:

Intervertebral disks existbetween vertebral bodies in

the spinal column. It consists

o an outer la er o fibrocartilage called annulus

fibrosus and a core of a

special liquid connective tissue

called nucleus pulposus.


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Cartilagear age repa r:

The ability of cartilage to repair itself is limited. Repair is due to activity

young individuals. In adults, the cells of the perichondrium proliferate toinitiate repair, but few cartilage cells, if any, are produced. The repair mostly

involves the production of dense connective tissue fibroses scar.

Calcification of cartilage & replacement by bone:It is a process in which calcium phosphate crystals become impregnated

in the cartilage matrix. Hyaline cartilage when calcified is generally replaced

y one. It occurs in t ree cases:a) Calcification of the portion of articular cartilage that is in contact with bone tissue;b) l ifi ti i rtil th t i b t t b r l d b b d h dr l ifi ti ) calcification in cartilage that is about to be replaced by bone endochondral ossification ;c) as a part of the aging process.

9. cartilage

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