The caudal cervical vertebrae the a chelonian are fused come the carapace, and aggressive manipulation that the head and neck can an outcome in a cervical spinal injury.

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From: Mader's Reptile and also Amphibian Medicine and Surgery (Third Edition), 2019

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Sentiel Rommel, man E. ReynoldsIII, in Encyclopedia of marine Mammals (Second Edition), 2009

C Cervical Region

Cervical vertebrae (Figs. 3, 4A) space cranial to the rib-bearing vertebrae the the thorax. Many mammals have seven cervical vertebrae; yet all the sirenians and the two-toed sloth (Choloepus) have actually six and also the three-toed sloth (Bradypus) has nine. Serial fusion (ankylosis) of two or more cervical vertebrae is common in cetaceans, yet all cetaceans have actually seven cervical vertebrae. Contradictory to what has been report in some released works, the cervical vertebrae in part cetaceans (e.g., the narwhal, beluga, and river dolphins) room unfused and administer considerable neck mobility.


The an initial two cervical vertebrae are named the atlas (C1) and also the axis (C2). Unlike all various other vertebrae, the atlas and axis of many mammals room not be separate by one intervertebral disk but rather by a synovial joint, similar to the skull-atlas share (Fig. 4A); the forms of these very first two vertebral joints dictate the variety of motion between the skull and also the vertebral column. Typical skull movements on the atlas room up-and-down and also side-to-side (Fig. 4A). The axis has actually an elongated centrum, the dens (odontoid process), which restricts motions between the atlas and axis to rotations. Check these limit on yourself by bending and also twisting her head and neck. Head nodding, together in expressing “yes,” is constrained through the skull-atlas joint; head rotations express “no,” space constrained by the atlas-axis joint.


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Typically, the permanently aquatic maritime mammals have fairly short necks; in contrast, the pinnipeds have relatively long necks. Compare of the skeletons of the seal and also sea lion reveals the they have similar neck lengths, although outside appearance is really different. Seals often hold your heads close come the thorax, which reasons the neck to kind a deep “S” curve, providing them v a “slingshot potential” because that grasping prey (or inattentive handlers).

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Cervical vertebrae may have distinctive transverse foramina that safeguard blood vessels when the neck is flexed. Transverse foramina are particularly distinct in the cervical vertebrae that the carnivorous maritime mammals. A pair that notches (or foramina) in the neural arch of the atlas might be existing (Fig. 4A); these openings space for the first spinal nerve pair the exits the neural canal between the back of the skull and also the neural arch of C1. Rarely, one find cervical ribs, which room moveable expansions of the ventral transverse processes; cervical ribs perform not prolong to the sternum.