Download Growth of the cartilage

Cartilage
It is a modified connective tissue providing strength, support and
varying degree of flexibility. Its ground substance is rubbery in
consistency.
It is formed of cells and fibers widely separated by extra cellular
matrix.
Cartilage cells
a. Chondrocyte in the mature cartilage, responsible for production
of ground substance and fibers.
b. Chondroblasts = present at the periphery of the cartilage.
Matrix
It consists of chondromucoprotein chondritin sulphate and
rubbery in consistency.
Fibers
Either collagen or elastic fibers similar in characteristic of those
present in the connective tissue
Depending on the type of fibers, cartilage is divided into:
 Hyaline cartilage.
 Fibro cartilage.
 Elastic cartilage.
Perichondrium
Free surfaces of both hyaline and elastic cartilage covered by
dense
Connective tissue called perichondrium, which consist of:
*Outer fibrous layer: consists of collagenous
bundles
rich in blood vessels
*Inner layer (cellular): formed of chondroblasts
which can be changed into chondrocytes.
Chondroblasts be divide and can secrete the
matrix resulting in growth of cartilage from its
periphery
Functions
 Supply the cartilage with blood and
nutrition.
 Growth of cartilage.
 Provide an attachment for muscle
General Comments:
*Cartilage is avascular (has no blood vessels), no lymphatic and no
innervation of its own.
*It got its O2 and nutrition through diffusion from surrounding
connective tissue.
*Blood vessels can pass through the cartilage in tunnels without
supplying it directly.
Calcification of cartilage:
 Matrix calcified in old age thus prevent diffusion and
subsequently chondrocytes die ( chest X-ray may show
calcified area in old age)
Regeneration of cartilage
 It occurs in young cartilage only.
The adult cartilage transform into scar tissue by
regeneration.
 Regadless to the type of the cartilage, the repair of
damaged cartilage occurs by formation of fibrocartilage i.e
(fibrous tissue).
Matrix or the ground substance
LM:
o Stained blue with basic dye (i.e. basophilic)
o Also show metachromasia i.e stain with metachromatic
stains (e.g. toludine blue) because it is very rich with
chondritin sulphuric acid.
o Usually appear homogenous.
o The basophilia is more around the chondrocytes due to
increase in concentration of glycosaminoglycan around
the lacunae (territorial matrix)
Chemically, it consists of proteoglycans rich in glycosaminoglycan
and chondroitin sulfate.
Cells of cartilage
o Young chondrocytes (chondroblasts) are flat basophilic
cells with oval nuclei. They are present at the periphery of
the cartilage under the perichondrium (may present in the
center during growth of cartilage) arrange in parallel
direction.
o Mature chondrocytes
 They are spherical cells.
 Stained in lacunae (spaces in the matrix).
 The cytoplasm of chondrocytes is basophilic with large
Nucleus with on or more prominent nucleoli.

EM= the cell are rich in rER, well-developed Golgi
apparatus, secreoary vesicles contain material needed
to maintain the matrix.
 Chondrocytes can divide so they may present single or
in groups (isogenous groups). When many
chondrocytes present in single lacunae, they form cell
nest (2 or 4 or 8 cells, forming isogenous groups).
If the cell die because its old or no blood supply
empty
lacunae.
Hyaline cartilage
Hyalos = glass
Hyaline = glassy.
 In fresh state, it appears as glassy whitish – blue structure.
 It is the commonest type of cartilage.
 Covered by perichondrium
Note = perichondrium is not present over the cartilage of
the articular surfaces of joints.
Sites:
 Costal cartilage in the chest.
 Cartilage of respiratory passages: nasal septum, nose,
trachea, bronchi, large bronchi, thyroid, cricoid
cartilage of larynx.
 Articular surfaces of the joint.
 Long bones in the skeleton of the foetus.
LM:
 Homogenous matrix.
 Contain delicate collagen fibers (acidophilic) – type II but
the basophilic property of the matrix masks its acidophilic
nature matrix.
(http://www.mc.ntu.edu.tw/department/anatomy/Histology/cartilage.html)
Early Age processing =
Lead to increase
Late
 Process of aging
collagen fibers in
hyaline cartilage and formation of fibro cartilage.
 Calcification of the cartilage.
Function
Acts as shock absorber and bearing surfaces and provides the
mechanism by which long bones grow in length.
Elastic cartilage
It is similar to hyaline cartilage but:
 The matrix is rich in elastic fibers.
 Elastic randomly distributed fewer at perichondrium.
 Its chondrocytes are derived from fibroblasts rather
than directly from mesenchyme.
Function = Provide extreme flexible support.
Site:
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Ear pinna, External auditory tube.
Medial part of the eustacian tube.
Epiglottis.
Cuneiform + cornicular cartilage of the larynx.
Fibro cartilage
 It is a combination of hyaline cartilage and dense
regular connective tissue.
 It has great tensile strength with considerable elasticity.
 It is characterized by the following:
o Matrix is acidophilic (due rich collagen).
o No perichondrium.
o The cartilage cells (chondrocytes) arrange in rows or
columns.
o Abundancy of collagen fibers ( arrang in bundles)
o chondrocytes arise from fibroblast.
Site
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Intervertebral disc.
Symphysis pubis, manubristernal joint.
Acetabulum (acetabular labrum) – hip joint.
Glenoid labrum (shoulder joint).
Articular disc e.g. sternoclavicular, menisci of the knee.
Certain tendentious in secretion.
Function
Shoclc absorber, functional support .
Growth of the cartilage
All cartilage develops from mesenchyme like other connective
tissue.
Growth of the cartilage occurred by two mechanisms
1- Interstitial growth
The cartilage cell in the center divide to form groups and secret
matrix
result in growth of matrix from the center
(length).
2- Appositional growth
= Young chondrocytes of perichondrium transformed into
mature cells which can divide and secret matrix, result in
peripheral growth
in width.
Clinical note:
Ankylosis mean:
Replacement of cartilage with bone in tissue =
as in a the letic foot or (joint)
Rupture disk
It is caused by tear in laminate of annulus fibrousus, which
leads to protrusion of nucleus pulposus (gelatinous substance)
It occurs commonly in the posterior part of the disk in the
lumbar region.
Slipped disk:
lumbar region
Severe pain
Rupture disk