Fontanelle

See also: Fontanelle (homonymy)

The fontanelles are membranous spaces separating different the Os from the Crâne.

The osseous reinforcement of the Carapace of the tortoises also presents fontanelles, the of comparable nature membranous one.

The fontanelles ones allow a continuation of the development of cranium and brain.

In the tortoises, they play a similar part during the growth of the carapace. For certain species, the fontanelles ones persist during all the life, and confer lightness on the carapace.

At the human ones

In the adult, the cranium does not present almost any more space to the junction between the bones. In the child, on the other hand, more precisely in the infant, four fontanelles appears because ossification is not accomplished:
  • fontanelle former (bregmatic) or the large fontanelle one, has a form of rhombus from 3 to 4 centimetres broad, it is located between the frontal bones and parietal on the top of cranium. It is easily locatable with the touch because the skin is flexible and elastic there. It will disappear between 8th and the 18th month from the child.
  • fontanelle posterior (lambdatic) or the small fontanelle one, of triangular form (0,5 cm broad), it is located between the parietal bones and the occipital bone , being smaller it is not easily locatable. It will be closed again at the end of the 3rd month.
  • fontanelles the sphénoïdales (pteric) is located in the side area of cranium and are closed thanks to the fusion of the bone sphénoïde, temporal, zygomatic and frontal on each side of cranium. This fusion forms the ptérion, an anatomical reference mark.

The fontanelles ones allow the growth of the Encéphale, which is still important before the two years age, and a certain flexibility of cranium facilitating the childbirth.

Examination of the fontanelles ones

The examination of the fontanelles ones, i.e. palpation, is practiced during the neurological examination of the newborn. It makes it possible to detect some Pathologie S neurological which results in certain modifications of the aspect of the fontanelles ones:

  • a depression of fontanelle former, makes it possible to detect a Déshydratation (the fontanelle mark the hollow of the finger).
  • a projection of fontanelles can translate an intracranial hypertension making it possible to diagnose a Hydrocéphalie or a Méningite (it should well be distinguished from the normal projection when the baby cries or shouts).
  • a delay in the closing of fontanelle former can characterize Rachitisme.
  • a premature closing of fontanelles (the Craniosténose), involves a volume of cranium lower than the normal.

The fontanelle former one allows also an examination of the brain by echography.

In various animals

The fontanelles ones of the foal persist until worms the two years age.

In the carapace of the tortoises

The fontanelles ones of the carapace of the overlapping Tortue remain generally open all its life during.

The carapace of the Tortue lute is formed practically more only by the fontanelles ones, the osseous part being reduced to alignments of ossicles called hulls.

Zh-yue: 腦囟

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