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C01 10/31/2017 11:23:53 Page 1 1 1 The Normal Anatomy of the Neck David Bainbridge Introduction component’ of the neck is a common site of pathology, and the diverse forms of neck The neck is a common derived characteristic disease reflect the sometimes complex and of land vertebrates, not shared by their aquatic conflicting regional variations and functional ancestors. In fish, the thoracic fin girdle, the constraints so evident in this region [2]. precursor of the scapula, coracoid and clavi- Unlike the abdomen and thorax, there is no cle, is frequently fused to the caudal aspect of coelomic cavity in the neck, yet its ventral part the skull. In contrast, as vertebrates emerged is taken up by a relatively small ‘visceral on to the dry land, the forelimb separated from compartment’, containing the larynx, trachea, the head and the intervening vertebrae speci- oesophagus and many important vessels, alised to form a relatively mobile region – the nerves and endocrine glands. However, I neck – to allow the head to be freely steered in will not review these structures, as they do many directions. not represent an extension of the equine ‘back’ With the exception of the tail, the neck in the same way that the more dorsal locomo- remains the most mobile region of the spinal tor region does. column in modern-day horses. It permits a wide range of sagittal plane flexion and exten- sion to allow alternating periods of grazing Cervical Vertebrae 3–7 and predator surveillance, as well as frontal plane flexion to allow the horizon to be scan- Almost all mammals, including the horse, ned, and rotational movement to allow possess seven cervical vertebrae, C1 to C7 nuisance insects to be flicked off.
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