Cartilage: Why are they CTs?
– Cells, extracellular fibers, and matrix
• Collagen & Elastic fibers
• Glycoproteins: Gel-like matrix
• Fibroblast-type cells
– General functions of mechanical &
physiological support and protection
• Structural framework
• Reserves of Ca & P
Interrelated with other CT’s in history
A specialized CT in which the firm
ECM allows the tissue to bear
mechanical stresses without
SOLID yet FLEXIBLE
Sulfated GAGs – keratan sulfate, chondroitin
Non-sulfated GAG – hyalurinic acid (backbone
of the complex)
Chondronectin and chondrocalcin
No mineral (inorganic) component
no calcium salt
Water (tissue fluid) – highly hydrated (75%)
Collagen Type I – in fibrocartlage
Collagen Type II – in hyaline cartilage
(except in articular cartilage)
Elastic fibers - in elastic cartilage
Ground substance components interact with the
Variations in the composition of these matrix
components produce three types of cartilage.
Molecular organization in cartilage matrix. Link proteins noncovalently
bind the protein core of proteoglycans to the linear hyaluronic acid
molecules. The chondroitin sulfate side chains of the proteoglycan
electrostatically bind to the collagen fibrils, forming a cross-linked matrix.
The oval outlines the area shown larger in the lower part of the figure.
Fibroblast-like – progenitor cells
Cells in the perichondrium (inner layer)
Also refered as Chondrogenic cells
Undergo mitosis and differentiate into --
Synthesize the precursors of extracellular fibers
and other organic subs. in the matrix
when surrounded by the matrix, they acquire
lacunae and transform into --
Cells in the matrix, still mitotic, still
synthesizing the materials in the matrix.
Vary in shape and size
Elliptical; parallel to the cart.
surface - young
Round – mature cartilage
Cytoplasm – finely granular,
Well developed rER and Golgi c.-
Inclusions – fat droplets, glycogen
Possess cytoplasmic processes
Nucleus – ovoid; chromatin
concentated on inner nuclear
mem.; 1 or more nucleoli
Mesenchymal cells differentiated into
chondroblasts which became its precursorial
Chondroblast mitosis isogenous groups
grow and begin synthesis of ground
substance and fibrous extracellular (EC)
Secretion of EC materials trap each
chondroblasts in the matrix thereby
separating the cells (interstitial growth).
Chondrocytes develop and maintain matrix
Develops from somites and somatopleure of mesoderm (mesenchyme)
A. mesenchyme condenses to form cellular primordium
B. chondroblasts form and begin secreting matrix
C. cells separate from chondrocytes
D. cartilage grows by interstitial growth – isogenous groups.
There are no capillaries
within the cartilage
the vascular supply for
the avascular cartilage
and also contains nerves
and lymphatic vessels.
is a sheath of
dense irregular CT
cartilage in most
places, forming an
the cartilage and
supported by the
Chondrocytes respire under low O2 tension since
it is devoid of capillaries.
metabolize glucose mainly by anaerobic
glycolysis to produce lactic acid.
Nutrients from the blood cross the perichondrium
to reach more deeply placed cartilage cells by
diffusion and transport of water and solute
promoted by the pumping action of intermittent
cartilage compression and decompression.
which covers the
surfaces of the
bones of movable
This cartilage is
sustained by the
diffusion of oxygen
and nutrients from
the synovial fluid.
The most common and best studied of the
Fresh hyaline cartilage - bluish-white and
In embryo: A temporary skeleton until it
is gradually replaced by bone.
Perichondrium is well-defined.
In adult mammals: This cartilage is
located in the
articular surfaces of the movable joints
walls of larger respiratory passages
(nose, larynx, trachea, bronchi),
ventral ends of ribs, where they
articulate with the sternum
epiphyseal plate, where it is
responsible for the longitudinal growth
Articular cartilage on surfaces
of movable joints
Ventral ends of ribs,
where cartilage articulate
with the sternum.
Epiphyseal plate, where it
is responsible for the
longitudinal growth of bone
Larynx, thyroid cart., cricoid cart.
Fresh form –
yellowish due to
elastin in the fibers.
Identical to hyaline
cartilage except that
it contains an
abundant network of
fine elastic fibers in
addition to collagen
type II fibrils.
its elasticity is derived
from the presence of
numerous bundles of
branching elastic fibres in
the cartilage matrix
this network of elastic
fibres (stained black in
this preparation) is
particularly dense in the
immediate vicinity of the
red) is also a major
constituent of the
cartilage matrix and
makes up the bulk of
the perichondrium P
intermingled with a
few elastic fibres.
Found in the auricle of the ear
walls of the external auditory canals
the auditory (eustachian) tubes
cuneiform cartilage in the larynx.
• utilizes the structural
support and flexibility which
elastic cartilage provides.
• leaf-shaped flap of tissue,
the epiglottis, closes the
opening into the larynx
A tissue intermediate between dense connective
tissue and hyaline cartilage.
It is always associated with dense CT, and the
border areas between these two tissues are not
clear-cut, showing a gradual transition.
Chondrocytes are either singly or in isogenous
groups, arranged in long rows separated by
coarse collagen type I fibers . Because it is rich in
collagen type I, the fibrocartilage matrix is
Perichondrium is poorly defined.
found where strong support and the
ability to withstand heavy pressure
attachments of certain ligaments to the
cartilaginous surface of bones
and in the symphysis pubis.
Intervertebral Disks (IVD)
IVD are symphysial joints that unite vertebral bodies.
permit movement between the vertebral bodies while
maintaining a union of great strength.
acts as a lubricated cushion that prevents adjacent vertebrae
from being eroded by abrasive forces during movement of
the spinal column.
• The IVDs have two components: the
fibrous annulus fibrosus (AF) and the
nucleus pulposus (NP).
• The nucleus pulposus serves as a
shock absorber to cushion the impact
external layer of dense CT
mainly composed of overlapping laminae of fibrocartilage in which
collagen bundles are orthogonally arranged in adjacent layers.
The multiple lamellae provide the disk with unusual resilience
that enables it to withstand the pressures generated by impinging
derived from the embryonic notochord
consists of a few rounded cells embedded in a viscous matrix rich
in hyaluronic acid and type II collagen fibrils
In children, the nucleus pulposus is large, but it gradually
becomes smaller with age and is partially replaced by
Assignment: Read about
Growth of cartilage tissues
Also for growth in
length of long bones.
Possible only in
Occurs at the edges
A function of the
Interstitial growth Appositional growth
In young cartilage,
substance is still
malleable and the
the capacity to
1. Mitosis of young chondrocytes.
2. Daughter cells secrete precursor
materials for ECM.
Secretory capacity of daughter cells is limited,
the amt. of intercellular substance they
deposit is also limited.
Result: Isogenous groups (chondrocytes that
lie close to each other up to maturity.)
1. Intercellular substance becomes rigid
with age, interstitial growth ceases.
1. Cells in perichondrium differentiate into
2. Matrix is made and laid down, lacunae
3. Shape of structure can be changed
May be localized
1. Same process as interstitial growth:
Cartilage has very limited repair capability
Cartilage is AVASCULAR!
Dependent on diffusion kinetics
If chondrocytes live, matrix can be replaced
Chondrocyte loss means loss of structure
Some limited regeneration by differentiation of
cells from perichondrium.
Injury to articular cartilage not a good thing: no
Usual “repair” by fibrosis & collagen proliferation
Calcification may occur.