Ossification of frontal bone

  The frontal bone is ossified [Fig. 3] in membrane from two primary centers, one for each half, which appear toward the end of the second month of fetal life, one above each supraorbital margin.

1. From each of these centers ossification extends upward to form the corresponding half of the squama, and backward to form the orbital plate.
2. The spine is ossified from a pair of secondary centers, on either side of the middle line; similar centers appear in the nasal part and zygomatic processes.
3. At birth the bone consists of two pieces, separated by the frontal suture, which is usually obliterated, except at its lower part, by the eighth year, but occasionally persists throughout life.
4. It is generally maintained that the development of the frontal sinuses begins at the end of the first or beginning of the second year, but Onodi’s researches indicate that development begins at birth.
5. The sinuses are of considerable size by the seventh or eighth year, but do not attain their full proportions until after puberty.

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.