Endochondral & Intramembranous Types of Growth,

7/27/2019 Endochondral & Intramembranous Types of Growth,

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ENDOCHONDRAL & INTRAMEMBRANOUS

TYPES OF GROWTH,

SYNCHONDROSIS,

DIFFERENCE BETWEEN GROWTHSITE &

GROWTH CENTER


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ENDOCHONDRAL OSSIFICATIONThe formation of bone in which a

cartilage template is graduallyreplaced by a bone matrix, as

in the formation of long bones

Endochondral bone formation

involves production of bone

in areas where there are high

levels of compression. Thus it

is seen in the cranial base

and in movable joints.


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STAGES OF ENDOCHONDRAL OSSIFICATION


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During endochondral

bone formation, the

first step is thedifferentiation of

mesenchymal cells

into chondrocytes

These chondrocytesform a rough model

which is enclosed by

perichondral cells

Cartilage mass grows

both by interstitial

growth and by

apposition


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Cartilage cells hypertrophy and their matrix begins to get calcified


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During this time, blood

vessels penetrate

the cartilage mass

from the

perichondrium


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These penetrating blood

vessels carry un

differentiated

mesenchymal cells

along with them,

which get converted

into osteoblasts


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Osteoblasts subsequently deposit bone

and bone spicules are formed


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Gradually the cartilage mass

is replaced by bone


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IMPORTANCE OF ENDOCHONDRAL

OSSIFICATION

Cartilage behaves like a soft tissue and

growth takes place both by interstitial

growth and appositional growth. In bone,

interstitial growth is not possible

Cartilage unlike bone is a pressure adapted

tissue and can grow in heavy pressureareas, e.g. cranial base.

Direction of growth is not unidirectional like

bone. Linear growth takes place allowing

lengthening of bone.


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INTRAMEMBRANOUS OSSIFICATION

the development of bone within connective tissue,without any intermediate formation of cartilage, is

known as Intramembranous ossification.

Membranous ossification or bone formation occurs on theouter surface of bone (periosteum), inner surface

(endosteum),sutures, etc.

All bones formed this way are flat


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STAGES OF INTRAMEMBRANOUS BONE

FORMATION


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IMPORTANCE OF MEMBRANOUS

OSSIFICATION

Membranous ossification or growth is seen in

areas of tension

Growth takes place outward or externally


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SYNCHONDROSISA form of articulation in which the

bones are rigidly fused by

cartilage.

Synchondroses are the remains of

the primary cartilaginous skeleton .

They are predominantly seen in thecranial base

growth sites in the base of skull.


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EXAMPLES OF SYNCHONDROSIS JOINT

sternocostal joint

(where the first ribmeets the sternum)

temporary form of joint

called epiphyseal

growth plate, where

the cartilage is

converted into bone

before adult life.


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TYPES OF SYNCHONDROSIS

Synchon droses Age of fusion

Intersphenoidal synchondroses At birth

Spheno-occipital

synchondroses

20 years

Spheno-ethmoidal

synchondroses

Exactly not known


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Grow th Site Grow th centre/growth f ield

Is any location or place where growth

takes place

Is any location or place where

genetically controlled growth takes

place

Is a region of periosteal or sutural bone

formation and remodeling resorptionadaptive to environment

Are places of ossification with tissue

separating force

Sites of growth when transplanted to

another area do not continue to grow

Centres of growth when transplanted

to another area continues to grow

Marked response to external

influences

Less response to external influence

.More response to functional needs


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Grow th si te Grow th centre / grow th

field

All growth sites are not growth centres All growth centres are growth sites

Theories of growth are not based ongrowth site

Various theories of growth are basedon the place where growth centre is

expressed

Growth site do not control the overall

growth of the bone

Growth centre controls the overall

growth of the bone


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Endochondral & Intramembranous Types of Growth,