Ossification of axis

Ossification of axis
The axis is ossified from five primary and two secondary centers.

The axis is ossified from five primary and two secondary centers.

The body and vertebral arch are ossified in the same manner as the corresponding parts in the other vertebrae, viz., one center for the body, and two for the vertebral arch.

The centers for the arch appear about the seventh or eighth week of fetal life, while the centers for the body appear in about the fourth or fifth month.

The dens or odontoid process consists originally of a continuation upward of the cartilaginous mass, in which the lower part of the body is formed.

About the sixth month of fetal life, two centers make their appearance in the base of this process: they are placed laterally, and join before birth to form a conical bilobed mass deeply cleft above; the interval between the sides of the cleft and the summit of the process is formed by a wedge-shaped piece of cartilage.

The base of the process is separated from the body by a cartilaginous disk, which gradually becomes ossified at its circumference, but remains cartilaginous in its center until advanced age.

In this cartilage, rudiments of the lower epiphysial lamella of the atlas and the upper epiphysial lamella of the axis may sometimes be found.

The apex of the odontoid process has a separate center which appears in the second and joins about the twelfth year; this is the upper epiphysial lamella of the atlas.

In addition to these there is a secondary center for a thin epiphysial plate on the under surface of the body of the bone.

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Axis (anatomy) — Bone: Axis (anatomy) Second cervical vertebra, or epistropheus, from above …   Wikipedia

  • skeleton — skeletonless, adj. skeletonlike, adj. /skel i tn/, n. 1. Anat., Zool. the bones of a human or an animal considered as a whole, together forming the framework of the body. 2. any of various structures forming a rigid framework in an invertebrate.… …   Universalium

  • bone — /bohn/, n., v., boned, boning, adv. n. 1. Anat., Zool. a. one of the structures composing the skeleton of a vertebrate. b. the hard connective tissue forming the substance of the skeleton of most vertebrates, composed of a collagen rich organic… …   Universalium

  • Bône — /bohn/, n. former name of Annaba. * * * I Rigid connective tissue of vertebrates, consisting of cells embedded in a hard matrix. Bones serve as the body s supporting framework, provide muscle attachment points for movement, protect the internal… …   Universalium

  • fish — fishless, adj. /fish/, n., pl. (esp. collectively) fish, (esp. referring to two or more kinds or species) fishes, v. n. 1. any of various cold blooded, aquatic vertebrates, having gills, commonly fins, and typically an elongated body covered with …   Universalium

  • Fish — /fish/, n. Hamilton, 1808 93, U.S. statesman: secretary of state 1869 77. * * * I Any of more than 24,000 species of cold blooded vertebrates found worldwide in fresh and salt water. Living species range from the primitive lampreys and hagfishes… …   Universalium

  • center — 1. The middle point of a body; loosely, the interior of a body. A c. of any kind, especially an anatomical c.. 2. A group of nerve cells governing a specific function. SYN: centrum [TA]. [L. centrum; G. kentron] active c …   Medical dictionary

  • Os — Pour les articles homonymes, voir OS. Os désigne aussi bien un tissu conjonctif solidifié que l une de ces structures individuelles, ou les organes, dans lesquels ils sont formés, et que l on trouve chez de nombreux animaux …   Wikipédia en Français

  • Os (matière) — Os Pour les articles homonymes, voir OS. Os désigne aussi bien un tissu conjonctif solidifié que l une de ces structures individuelles, ou les organes, dans lesquels ils sont formés, et que l on trouve chez de nombreux animaux …   Wikipédia en Français

  • Os long — Os Pour les articles homonymes, voir OS. Os désigne aussi bien un tissu conjonctif solidifié que l une de ces structures individuelles, ou les organes, dans lesquels ils sont formés, et que l on trouve chez de nombreux animaux …   Wikipédia en Français

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”