Editing Axis (anatomy)
Appearance
Content that violates any copyrights will be deleted. Encyclopedic content must be verifiable through citations to reliable sources.
Latest revision | Your text | ||
Line 52: | Line 52: | ||
The centres for the arch appear about the seventh or eighth week of fetal life, while the centres for the body appear in about the fourth or fifth month. |
The centres for the arch appear about the seventh or eighth week of fetal life, while the centres for the body appear in about the fourth or fifth month. |
||
The dens, or odontoid process, |
The dens, or [[odontoid process]], consist originally of a continuation upward of the cartilaginous mass, in which the lower part of the body is formed. |
||
During about the sixth month of fetal life, two centres 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. |
During about the sixth month of fetal life, two centres 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. |
||
Line 58: | Line 58: | ||
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. |
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 |
In this cartilage, rudiments of the lower epiphyseal lamella of the atlas and the upper [[Epiphyseal plate|epiphyseal]] lamella of the axis may sometimes be found. |
||
The apex of the |
The apex of the odontoid process has a separate centre that appears in the second and joins about the twelfth year; this is the upper epiphyseal lamella of the atlas. |
||
In addition to these, there is a secondary centre for a thin epiphyseal plate on the undersurface of the body of the bone. |
In addition to these, there is a secondary centre for a thin [[epiphysial plate|epiphyseal plate]] on the undersurface of the body of the bone. |
||
==Clinical significance== |
==Clinical significance== |