Cartilage and bone
 Mechanic and supporting function
 Origin: embryonic mesenchyme
 Structure:
 cells (chondrocytes – in cartilage
osteocytes, osteoblasts, osteoklasts – in bone)
 Extracellular matter
 homogenous, amorphous substance
 fibers (collagen or elastic – in cartilage, only collagen – in bone)
Cartilage properties
 Avascular tissue, without nerves,
 Decreased reparative ability, regeneration from
perichondrium
 Perichondrium – dense collagen c. t. attached to
cartilage
 inner chondrogenic layer
 outer c. t. layer
Cell of cartilage
 chondroblasts
 immature chondrocytes in inner
layer of perichondrium
 chondrocytes – in
cartilage
 basofilic cells → proteosynthesis,
mitochondria, GER, Golgi
apparatus, cytoskeleton.
 produce amorphous matrix and
fibers.
 Chondrocytes
– isogenous groups,
– lacunae,
– basophilic capsule
of teritorial matrix
 Isogenous group +
adjacent area of extracellular
matter
(territorial matter)
= chondron
Extracellular matter
 Collagen II or I fibers
 Elastic fibers
 Glykosaminoglycans
–hyaluronic acid,
chondroitin-sulphate
 Proteoglycans
 Glykoproteins
Types of cartilage
 Hyaline (hyalos=glass) – the most frequent,
precursor of many bones in skeleton,
covers articular surfaces, forms part of ribs
skeleton of the nose, trachea, larynx
 Elastic - auricula, tuba auditiva, larynx,
epiglottis
 Fibrocartilage - intervertebral discs,
symphysis pubis, articular discs and
meniscus
Elastic cartilage
 elastic fibers in
amorphous matrix;
special staining:
resorcin, fuchsin
and orcein.
 Chondrocytes
Fibrocartilage
 Chondrocytes
 Thick bundles of
collagenous fibers
 matrix
 without perichondrium
Bone
 specialized form of c. t.
Bone tissue structure
 Bone cells
 Extracellular matrix
 Organic – colagenos fibers
– amorphous matrix
 Inorganic – minerals
 Periosteum
Bone tissue
 Periosteum – covers outer surface
of bone:
 Inner layer
(osteoblasts, fibroblasts)
 outer layer
(only fibroblasts)
Periosteum is attached by
Sharpey‘s fibers.
 Endosteum – membrane with one
layer of cells (osteoblasts,
osteoclasts), covers inner surface
of bone turned to the bone cavity)
Bone cells
 osteoprogenitor
cells – stem cells,
in periosteum a
endosteum
 osteoblasts
produce organic
matter, and
transform into
osteocytes
Osteocyte
 In lakuna,
 Numerous
processes
in canaliculi
ossium (cell
communication)
Osteoclasts
 large cells (up to 100
µm), polynucleated
cells (up to 50 N),
arrise by fussion of
monocytes
 in Howship‘s lakune
 lysosomal enzymes
digest collagen fibers
Bone matrix
 collagen fibers –
collagen I (cca 90
% of org. matter)
 amorphous
matrix –
osteoid.
 strength of matrix
is caused by
content of
inorganic salts
(hydroxylapatite).
Types of bone tissue
 2 types: /according to arrangement of collagen fibers/
 Fibrillar (woven) bone
 Lamellar bone
 compact – wall of long bone diaphysis,
surface layer of epiphysis
 spongy /trabecular/ – inner part of epiphysis
Lamellar bone
 Lamellae – thin
plates with regularly
arranged collagen
fibers
 Haversian systems
- osteons
 Circumferential
lamellae
 outer
 inner
 Interstitial lamellae
Haversian system – osteon
Lamellar bone
Haversian and Volkmann‘s canals
Lamellar bone – spongy type
 Matrix is also organized into the lamellae, but dont
form Haversian systems.
Histogenesis of bone tissue
 Endochondral ossification – hyaline cartilage is
model for bone
(long bones)
 Intramembranous ossification – mesenchyme
membrane is model, mesenchymocytes differentiate
into osteoblasts
(skull bone, part of mandibule and clavicula)
Intramembranous ossification
Endochondral ossification
Periosteal bone collar
Undifferentiated cells in the
perichondrium become osteoblasts,
and
the perichondrium is now
the periosteum.
Chondrocytes at the center of the
growing (proliferating zone)
cartilage model enlarge (zone of
hypertrophy).
The matrix calcifies (zone of
calcification) and chondrocytes
die. The rest of matrix form
trabecular processes – spicules.
Blood vessels penetrate cartilage
and carry the osteoblasts from
periosteum. Osteoblasts cover the
spicules and produce osteoid
(ossification zone).
Ossification spreads in long axis
of bone.
Osteoclasts resorb primitive bone
(zone of resorption) and
medullary cavity is formed.
Simillar process begins in epiphyses.
Ossification spread radially.
Also epiphyseal plates ossify at the end
of body growth (cca 18 years).
Endochondral
ossification
 Zone of normal
cartilage
 Zone of proliferated
cartilage
 Zone of hypertrophic
cartilage
 Zone of calcification
 Line of erosion
 Zone of ossification
 Zone of resorption
Bone growth
 cannot occur interstitally as cartilage growth
does, because its rigid, mineralized matrix
traps osteocytes and prevents them from
dividing mitotically. Growth occurs in two
directions:
 in length, by maintenance and growth of
epiphyseal plate of cartilage. These plates
allow a bone to expand lengthwise.
 in diameter, by continuous formation of bone
around the periphery of the diaphysis.
Normal hyaline cartilage
Proliferating cartilage
(growth)
Hypertrophic cartilage
Calcified cartilage
 - calcified matrix
LINE of EROSION
spicules
blood vessels
osteoid
osteoblasts
 
B
O
N
E
Endochondral ossification
Osteoclasts