Types And Importance Of Cranial Base Synchondroses
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Answer. Most of the bones of the cranial base are formed by the cartilaginous process. Later, the cartilage is replaced by the bone. However, certain bands of cartilage remain at the junction of various bones. These are called as synchondrosis.
- They are important growth sites of cranial base.
- Important synchondrosis found in cranial base are:
- Spheno-occipital synchondrosis
- Sphenoethmoidal synchondrosis
- Intersphenoidal synchondrosis
- Intraoccipital synchondrosis.
Sphenooccipital Synchondrosis
- Sphenooccipital Synchondrosis is the cartilaginous junction between sphenoid and occipital bones.
- Sphenooccipital Synchondrosis is believed to be the principal growth cartilage of cranial base during childhood.
- Sphenooccipital Synchondrosis remains active upto the age of 12-15 years. The sphenoid and the occipital segments then become fused in the midline area by 20 years of age.
- Sphenooccipital Synchondrosis provides a pressure or compression adapted bone growth, in contrast to the tension adapted growth seen in sutures. This is because the cranial base supports the weight of brain and face which bears down on synchondrosis in midline of cranial base.
- The structure of a synchondrosis is like two epiphyseal plates positioned back-to-back and separated by a common zone of reserve cartilage.
- Direction of growth in spheno-occipital synchondrosis is upwards. It therefore, carries anterior part of cranium bodily forward.
Sphenoethmoidal Synchondrosis
This is a cartilaginous band between the sphenoid and ethmoid bones. It is believed to ossify by 5–25 years of age. But exactly it is not known.
Intersphenoid Synchondrosis
It is a cartilaginous band between the two parts of the sphenoid bone. It is believed to ossify at birth.
Intraoccipital Synchondrosis
This ossifies by 3–5 years of age.
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