Transcript Histology - Study Windsor

Cartilage Histology
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Skeletal system
 The skeletal system is composed of highly specialized
forms of supporting/connective tissue, based on
collagen and acellular matrix, and the synthetic cells
which produce them.
 Cartilage and bone are two specialized types of
connective tissue.
 Both tissues are of mesenchymal origin.
 Both are composed of cells that secrete an extracellular
matrix (ECM).
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Cartilage
 Cartilage is avascular and possesses no
lymph vessels or nerves and the
exchange of metabolites between
chondrocytes and surrounding tissues
depends on diffusion.
 Cartilage form with the differentiation of
primitive mesenchymal cells to form
cartilage precursor cells called
chondroblasts.
 Each chondroblast then form mature
cartilage cells, known as chondrocytes
reside in lacunae.
 Each lacuna is surrounded by a
basophilic region known as territorial
region or matrix. The area of lighter
basophilia is the inter-territorial zone..
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Chondrocytes
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Cartilage
 Most mature cartilage have a surrounding layer called the
perichondrium, divided into an inner cellular and an outer fibrous
layer.
 Perichondrium have the capacity to transform into chondroblasts
and form new cartilage by appositional growth.
 There is very limited capacity in mature cartilages masses for
interstitial growth by further division of chondrocytes.
 The hyaline cartilage of the articular surfaces of joints
does not have perichondrium on the surface, and has
no capacity to regenerate new cartilage after damage.
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Growth of cartilage
 Appositional growth - the process that forms
new cartilage at the surface of an existing
cartilage, by the development of new cells
from the chondrogenic layer of the
perichondrium. This type of growth results in
the formation of new chondrocytes.
 Interstitial growth, the process that forms
new cartilage within an existing cartilage
mass by the mitotic division of chondrocytes
within their lacunae cells. This type of growth
occurs only during the early stages of
cartilage formation and the epiphyseal
plates of long bones.
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3 Types of cartilage
 Hyaline cartilage - the most common form and the matrix
contains type II as the principal collagen type.
 Elastic cartilage is more pliable and distensible, in addition
to collagen type II, an abundance of elastic fibres within its
matrix.
 Fibrocartilage, present in regions of the body subject to
great stress or the demands of weight bearing, is
characterized by a dense network of coarse type I collagen
fibres.
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Hyaline cartilage
 The most common cartilage, is noted for the smooth
homogeneous appearance of its ECM ("hyaline" =
resembling glass).
 Hyaline cartilage makes up the fetal skeleton until it
is replaced with bone, the anterior portion of the ribs
(costal cartilage), and respiratory structures (trachea
and bronchi). It also forms the epiphyseal growth
plate in long bone and the articular cartilage of
synovial joints.
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Hyaline cartilage matrix
 A. Chondrocytes
 B. Three major class of molecules:
 1. Collagen molecules-major matrix protein (type II)
and other types VI, IX, X and XI.
 2. Proteoglycan – 3 types of GAGA (hyaluronan,
chondroitin and keratin sulfate)
 The chondroitin and keratin sulfate are joined to a core protein
to form a proteoglycan monomer. Aggrecan molecules have a
large negative charge with an affinity for water.
 3.Glycoproteins:
 Noncollagenous and nonproteoglycan-linked glycoproteins.
 Anchorin, tenascin, and fibronectin,chondronectin.
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Molecular structure of Hyaline
cartilage matrix
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Hyaline cartilage
 Perichondrium is a layer of dense connective tissue that
surrounds hyaline cartilage except at articular surfaces. These
have the capacity to transform into chondroblasts and form new
cartilage by appositional growth.
 The matrix that is adjacent to chondrocytes is called the
territorial matrix. The basophilia is due to the high
concentration of negative ions (chondroitin and keratin
sulfate), poor in collagen.
 As the ions diffuse further away from the cell, the basophilia is
less intense, reflecting the decrease in negative ion
concentration.
 Mature chondrocytes are characterized by small nuclei with
dispersed chromatin and basophilic, granular cytoplasm,
reflecting a well developed rough endoplasmic reticulum.
 Cytoplasm is rich in glycogen and lipid droplets
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Hyaline cartilage
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Degeneration of hyaline
cartilage
 Degeneration of hyaline cartilage occurs when
chondrocytes undergo hypertrophy and die and
the matrix becomes calcified, a process that
becomes more frequent with age.
 Degeneration of hyaline cartilage is a normal
part of endochondral bone formation. This type
of bone formation allows the lengthening of long
bones like the femur, and starts in the epiphysis
of the long bone.
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Elastic cartilage
 Elastic cartilage occurs in the external ear and
external auditory canal, the epiglottis,
eustachian tubes and the larynx.
 The histological structure of elastic cartilage is
similar to that of hyaline cartilage, but elasticity
is due to bundles of elastic fibres in the cartilage
matrix.
 Collagen (stained red) is a major constituent of
the cartilage matrix and makes up the bulk of the
perichondrium (P) intermingled with a few elastic
fibres.
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Elastic cartilage
• Elastic cartilage has
elastic fibers in its ECM.
• Elastic fibers provide
an increased amount of
flexibility designed to
withstand repeated
flexions and extensions.
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Elastic cartilage
 Elastic cartilage possesses a perichondrium and is
nearly identical to hyaline cartilage except for a
network of elastic fibers.
 Elastic cartilage contains type II collagen, and is
less prone to degeneration than hyaline
cartilage and is located in areas where flexible
support is required.
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Elastic cartilage – elastin fibers in the matrix
Perichondrium
Chondroblasts
Chondrocytes
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Fibrocartilage
 Fibrocartilage is found in the intervertebral discs,
pubic symphysis, meniscus of knee and insertion of
tendons to bone.
 Fibrocartilage lacks an identifiable perichondrium.
 It has a matrix with large bundles of type I collagen
in addition to type II collagen imparts resistance to
compression.
 Fibrocartilage is a combination of dense connective
tissue and cartilage (alternating layers of cartilage
matrix and thick layers of dense collagen fibres).
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Fibrocartilage
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Fibrocartilage between two pieces of bone
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Clinical Correlation
Achondroplasia
 Most common form of inherited dwarfism.
 Hereditary defect
 Autosomal dominant
 Mutation in fibroblast growth factor receptor 3 (FGFR3)
 Mutations cause a gain of function of the FGFR3 gene,
resulting in decreased endochondral ossification, inhibited
proliferation of chondroblasts in growth plate cartilage,
decreased cellular hypertrophy, and decreased cartilage
matrix production.
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Achondroplasia
 Long bones are short and
thick.
 Short extremitiesdwarfism.
 Cranial and vertebral
bones spared, relatively
large head and trunk.
 Normal intelligence, life
span and reproductive
ability.
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Osteoarthritis
 Osteoarthritis is a degenerative
joint disease due to excessive wear
and tear leading to degenerative
change in the articular cartilages of
both opposing bone ends which
participate in the joint.
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Osteoarthritis
• Articular cartilage has no perichondrium
• Renewal process of mature cartilage is very
slow due to stable type II collagen and low
activity of metalloproteinase
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Disc degeneration and
prolapse
 The intervertebral discs act as shock absorbers, supporting
and springing the vertebral column and are particularly
vulnerable to damage because of the weight they have to
support.
 These can lead to weakening of the annulus fibrosus which
may give way, allowing the soft central nucleus pulposus to
extrude (disc prolapse) through into the spaces beneath the
ligaments and elsewhere. This leads to soft tissue swelling
around the protrusion, and may involve the spinal nerves
emerging from the spinal column.
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Disc degeneration and
prolapse
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What type of basic tissue type is cartilage?
a. Muscle
b. Nervous
c. Cartilage
d. Epithelium
e. Connective tissue
How many types of cartilage are there?
a. 1
b. 2
c. 3
d. 4
e. 5
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What do you call the space where a chondrocyte sits
in?
a. Space of Disse
b. Space of Mall
c. Vacuole
d. Lacuna
e. Howship's Lacuna
What stain would be best to demonstrate the elastic fibers in
elastic cartilage?
a. Wright's stain
b. Hematoxylin and eosin stain
c. Sudan stain
d. Silver impregnation
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e. Resorcin fuchsin and orcein
Which type of cartilage is found in the walls of the
eustachian tube?
a. Hyaline cartilage
b. Elastic cartilage
c. Fibrocartilage
d. All of the above
e. None of the above
Which type of cartilage forms the skeleton of the fetus?
a. Hyaline cartilage
b. Elastic cartilage
c. Fibrocartilage
d. All of the above
e. None of the above
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Which type of cartilage forms the intervertebral disc?
a. Hyaline cartilage
b. Elastic cartilage
c. Fibrocartilage
d. All of the above
e. None of the above
What type of tissue makes up the "Adam's apple"?
a. Hyaline cartilage
b. Fibrocartilage
c. Elastic cartilage
d. Both a and b
e. Both a and c
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Which type of cartilage is characterized by the
presence of elastic fibers?
a. Hyaline cartilage
b. Elastic cartilage
c. Fibrocartilage
d. All of the above
e. None of the above
Which type of cartilage is highly vascular?
a. Hyaline cartilage
b. Elastic cartilage
c. Fibrocartilage
d. All of the above
e. None of the above
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