lecture cartilage and bone 2009
TRANSCRIPT
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Histology Department
Medical Faculty
University of Sumatera Utara
Lecture : Histology of
Cartilage and Bone
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CARTILAGE
Early Fetal Life: Forms most of the skeleton
Persists in adults over the
articular surfaces of bones Sole skeletal support in the
respiratory passage and
parts of the ear
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Collagenous Fibers for increase in the tensile
strength
Elastic Fibers
different regions of for elasticity
MATRIX contains:
Adapt the tissue
to
the mechanical
requirements of
the
different
regions ofthe body
without
permanent
distortion
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MESENCHYME surrounding the enlarging mass of cartilage iscompressed and forms a fibrous envelope the PERICHONDRIUM.
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TWO PROCESSES BY WHICH
CARTILAGE GROWS:
1. Interstitial or ENDOGENOUS
1. Expansion of cartilage from within
2. Results from mitotic division of pre
existing chondrocytes2. Appositional or EXOGENOUS
1. addition of new layers of cartilage to
one surface
2. results from differentiation within theinner layer of PERICHONDRIUM
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CartilageA. Contains water, but no nerves, vascular & lymph
vessels
B. There are 3 basic types.
1. Hyaline - smooth, glassy, highly collagenica.articular - jointsb. costal - ribsc. respiratoryd. laryngeal - larynxe. nasal
2. Elastica. external earb. epiglottis
3. Fibrocartilagea. intervertebral discsb. knee joints
Note: The differences in the KIND and ABUNDANCE OFFIBERS incorporated within the matrix form the basis of
classification
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HYALINE CARTILAGE
appears as a translucent, bluish-white
mass in fresh conditions
forms the articular surfaces to bone within
joints, the costal cartilages,and the
cartilages of the nose, larynx, trachea, and
the bronchi
in the fetus, nearly all the skeleton is first
laid down as HYALINE cartilage, which is
replaced later by bone.
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ELASTIC CARTILAGE
fresh elastic cartilage has a yellowish color owing to thepresence of elastin in the elastic fibers
found in the external ear, the walls of the externalauditory canals, the eustachian tubes, the epiglottis, andthe cuneiform cartilage in the larynx.
Elastic cartilage is essentially identical to hyalinecartilage except that it contains an ABUNDANT
NETWORK OF FINE ELASTIC FIBERS in addition to thecollagen fibers.
frequently found to be gradually continuous with hyalinecartilage
Like hyaline cartilage possesses a perichondrium.
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FIBROCARTILAGE
transitional form between cartilageand dense connective tissue
occurs where a tough support or
tensile strength is required found in the intervertebral disc of
certain other joints
NEVER occurs alone, but merges
gradually into neighboring hyalinecartilage or with dense fibroustissue.
Lacks a perichondrium.
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REGENERATION OF
CARTILAGE TISSUE
Except in young children damagedcartilage regenerates withdifficulty and often incompletely.
It is by an activity of theperichondrium which invades theinjured area and generates newcartilage.
In extensively damaged areas andoccasionally in small areas, theperichondrium produces a scar ofDENSE CONNECTIVE TISSUEinstead of forming a NEW
CARTILAGE
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Bone as a Tissue
Connective tissue with a matrix
hardened by minerals (calcium
phosphate)
Individual bones consist of bone
tissue, marrow, blood, cartilage
and periosteum
Continually remodels itself Functions of the skeletal system
support, protection, movement,
electrolyte balances, acid-base
balance and blood formation
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65% inorganic (Ca)
35% organic
(34% collagen, ..)
(1% cells)
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Shapes of Bones
Long bones levers
acted upon by muscles
Short bones glideacross one another in
multiple directions
Flat bones protect soft
organs
G l F t f
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General Features of
Bones
Shaft (diaphysis) = cylinder of compact bone marrow cavity (medullary cavity) lined with
endosteum (osteogenic cells and reticular
connective tissue) Enlarged ends (epiphyses)
spongy bone covered by compact bone
enlarged to strengthen joint and attach ligaments
Joint surface covered with articular cartilage Shaft covered with periosteum
outer fibrous layer of collagen
inner osteogenic layer of bone forming cells
Epiphyseal plate (growth plate)
St t f
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Structure of a
Long Bone
Compact and
spongy bone
Marrow cavity
Articular cartilage
Periosteum
St t f Fl t
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Structure of a Flat
Bone External and
internal surfacescomposed of
compact bone
Middle layer isspongy bone and
bone marrow
Skull fracture may
leave inner layer ofcompact bone
unharmed
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Bone cells
C ll f O
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Cells of Osseous
Tissue (1)
Osteogenic cells in endosteum, periosteum or central canals
give rise to new osteoblasts
arise from embryonic fibroblasts
multiply continuously
Osteoblasts mineralize organic matter of matrix
Osteocytes are osteoblasts trapped in the matrix they formed
cells in lacunae connected by gap junctions inside canaliculi
C ll f O
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Cells of Osseous
Tissue (2)
Osteoclasts develop in bone marrow by fusion of 3-
50 stem cells
Reside in pits that they ate into the bone
M t i f O
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Matrix of Osseous
Tissue Dry weight = 1/3 organic and 2/3
inorganic matter Organic matter
collagen, glycosaminoglycans,proteoglycans and glycoproteins
Inorganic matter 85% hydroxyapatite
10% calcium carbonate
other minerals (fluoride, potassium,magnesium)
Combination provides for strength andresilience minerals resist compression; collagen
resists tension
bone adapts by varying proportions
Hi t l f C t
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Histology of Compact
Bone
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Compact Bone
Osteon = basic structural unit cylinders formed from layers (lamellae)
of matrix around central canal
(osteonic canal) collagen fibers alternate between right- and
left-handed helices from lamella to lamella
osteocytes connected to each otherand their blood supply by tiny cell
processes in canaliculi Perforating canals or Volkmanncanals vascular canals perpendicularly joining
central canals
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Blood Vessels of Bone
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Spongy Bone
Spongelike appearance formed by
plates of bone called trabeculae
spaces filled with red bone marrow
Trabeculae have few osteons or central
canals
no osteocyte is far from blood of bone
marrow
Provides strength with little weight
trabeculae develop along bones lines of
stress
S B St t
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Spongy Bone Structure
and Stress
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Bone Marrow
In medullary cavity (long bone) and
among trabeculae (spongy bone)
Red marrow like thick blood
reticular fibers and immature cells
Hemopoietic (produces blood cells)
in vertebrae, ribs, sternum, pelvic
girdle and proximal heads of femur
and humerus in adults
Yellow marrow
fatty marrow of long bones in adults
Gelatinous marrow of old age
yellow marrow replaced with reddish
jelly
Intramembranous
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Intramembranous
Ossification
Condensation of mesenchyme intotrabeculae
Osteoblasts on trabeculae lay down
osteoid tissue (uncalcified bone) Calcium phosphate is deposited in the
matrix forming bony trabeculae ofspongy bone
Osteoclasts create marrow cavity Osteoblasts form compact bone at
surface
Surface mesenchyme produces
periosteum
Intramembranous
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Intramembranous
Ossification 1
Produces flat bones of skull and clavicle.
Intramembranous
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Intramembranous
Ossification 2
Note the periosteum and osteoblasts.
Stages of Endochondral
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Stages of Endochondral
Ossification
Endochondral
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Endochondral
Ossification 1
Bone develops from pre-existingmodel perichondrium and hyaline cartilage
Most bones develop this process Formation of primary ossificationcenter and marrow cavity in shaft ofmodel
bony collar developed by osteoblasts chondrocytes swell and die
stem cells give rise to osteoblasts andclasts
bone laid down and marrow cavitycreated
Primary Ossification Center
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Primary Ossification Center
and Primary Marrow Cavity
Endochondral
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Secondary ossification centers andmarrow cavities form in ends ofbone
same process
Cartilage remains as articularcartilage and epiphyseal (growth)plates
growth plates provide for increase inlength of bone during childhood andadolescence
by early twenties, growth plates aregone and primary and secondarymarrow cavities united
Endochondral
Ossification 2
S d O ifi ti C t
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Secondary Ossification Centers
and Secondary Marrow Cavities
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The Metaphysis
Zone of reserve cartilage = hyaline
cartilage
Zone of proliferation
chondrocytes multiply forming columns offlat lacunae
Zone of hypertrophy = cell enlargement
Zone of calcification
mineralization of matrix
Zone of bone deposition
chondrocytes die and columns fill with
osteoblasts
osteons formed and spongy bone is created
Fetal Skeleton at 12
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Fetal Skeleton at 12
Weeks
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Bone Growth and
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Bone Growth and
Remodeling
Bones increase in length interstitial growth of epiphyseal plate
epiphyseal line is left behind when cartilage gone
Bones increase in width = appositional growth osteoblasts lay down matrix in layers on outer
surface and osteoclasts dissolve bone on innersurface
Bones remodeled throughout life Wolffs law of bone = architecture of bonedetermined by mechanical stresses
action of osteoblasts and osteoclasts
greater density and mass of bone in athletes or
manual worker is an adaptation to stress
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Dwarfism
Achondroplastic long bones stop growing
in childhood normal torso, short limbs
spontaneous mutationduring DNA replication
failure of cartilage growth
Pituitary lack of growth hormone
normal proportions withshort stature
Other Factors
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Other Factors
Affecting Bone Hormones, vitamins and growth factors
Growth rapid at puberty
hormones stimulate osteogenic cells,
chondrocytes and matrix deposition in
growth plate girls grow faster than boys and reach full
height earlier (estrogen stronger effect)
males grow for a longer time and taller
Growth stops (epiphyseal platecloses)
teenage use of anabolic steroids =
premature closure of growth plate and
short adult stature
Fractures and Their
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Fractures and Their
Repair
Stress fracture caused bytrauma
car accident, fall, athletics, etc
Pathological fracture in boneweakened by disease
bone cancer or osteoporosis
Fractures classified bystructural characteristics
break in the skin
multiple pieces
Types of Bone
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Types of Bone
Fractures
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Healing of Fractures 1
Normally 8 - 12 weeks (longer in
elderly)
Stages of healing
fracture hematoma (1) - clot forms, then
osteogenic cells form granulation tissue
soft callus (2)
fibroblasts produce fibers and fibrocartilage
hard callus (3)
osteoblasts produce a bony collar in 6 weeks
remodeling (4) in 3 to 4 months
spongy bone replaced by compact bone
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Healing of Fractures 2
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