mammalian cervical vertebra 7

Vertebra prominens is the proper name for the seventh cervical vertebra. The most distinctive characteristic of this vertebra is the existence of a long and prominent spinous process which is palpable from the skin surface, hence the name. This spinous process is thick, nearly horizontal in direction, not bifurcated, but terminating in a tubercle to which the lower end of the ligamentum nuchae is attached. The seventh cervical vertebra (C7) has the most prominent spinous process only in about 70% of people; in the remainder, either C6 or T1 (the first thoracic vertebra) will be the most prominent. The transverse processes are of considerable size, their posterior roots are large and prominent, while the anterior are small and faintly marked; the upper surface of each has usually a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation. The foramen transversarium may be as large as that in the other cervical vertebrae, but is generally smaller on one or both sides; occasionally it is double, sometimes it is absent. On the left side it occasionally gives passage to the vertebral artery; more frequently the vertebral vein traverses it on both sides; but the usual arrangement is for both artery and vein to pass in front of the transverse process, and not through the foramen. Sometimes the anterior root of the transverse process attains a large size and exists as a separate bone, which is known as a cervical rib.