FORM FOLLOWS FUNCTION
Figure 2. The Spinal Column
Figure 3. Thoracic Vertebra
Figure 4. Mid-Back Vertebra
Figure 5. Lumbar Vertebra
Again, this can vary from breed to breed, so one must be familiar with the standard that is specific to their breed of dog. On physi- cal examination, the curves are a bit more evident. However, even when placing your hands on the dog, it may still be difficult to feel the curves due to the condition of the thoracic vertebrae at the first thoracic spine; run your forefinger or thumb down the middle of the neck toward the backline until you can feel a bump in the pathway, somewhere (hopefully) between the tips of the shoulder blades. The largest part of the vertebra is the body (B). There are several smaller projections from the central part of the bone, with smaller surfaces that articulate with similar projections on neighboring vertebrae. Projecting from the top of the vertebra is the top spine (SP – Spinous Process), which functions as a base for muscular attachment. The shape and size of the spinous process varies in the different regions of the spine, according to the amount of muscle attachment needed, and can vary (sometimes widely) from breed to breed. More spinous projections for muscle attachment are found on either side of the vertebra. The transverse processes (TP) are situated at somewhat right angles to the long axis and the mam- millary processes (MP) extending from side-to-side. The large hole in the vertebra (VF) is the vertebral opening (foramen) through which the spinal cord passes. The shape and size of the individual vertebra are determined by the function of that section of the spinal column. We will separate the spinal column into four basic sections; the neck (cervical), the chest (thoracic), and the loin (lumbar), plus the sacrum and the tail (caudal). It is relatively easy to see the differences in the shape of these three vertebrae, from the first thoracic vertebra to the thorac- ic vertebra, from the mid-back, and then from the lumbar section. (See Figures 3, 4 & 5.)
General terminology used when discussing the spinal column as a whole is the “topline’” of the dog. The topline begins behind the ears at the occiput, proceeds over the neck, withers, back, and croup, ending at the set-on of the tail. In some breed standards, the term is used to mean the “backline,” which is only a section of the topline from the withers to the base of the tail. The spine functions to support the head, fore and hindquar- ters, and rib cage, and to support and protect the internal organs. This column of vertebrae allows for movement of the head and back of the animal. The encasing and protection of the spinal cord, which transmits messages to and from the brain and through- out the body, is a major function of the spinal column. The spine also serves a vital part in transmitting the force generated by the hind limbs throughout the rest of the body in order to propel the dog forward. A quick overall assessment of the spine will tell us that the spi- nal column is made up of multiple bones (50 in number) called vertebra, which form a sort of chain through which the individual vertebra move against one another. There are five sections of the vertebral column; cervical (neck), thoracic (chest), lumbar (loin), sacrum and coccygeal (tail). Each vertebra has its own identify- ing number. Cervical are numbered C1-C7, Thoracic are T1-T13, Lumbar are L1-L7, and Sacral are S1-S5. The coccygeal vertebrae vary in number from none (no tail) to anywhere from 20-25. Most breeds average 23 coccygeal vertebrae, designated by using Cd and a number. While many a standard may call for a dead level topline, there is a curvature of the spine that can be seen in Figure 2 and is dem- onstrated by the dashed line. Because of the length of coat and the musculature that is overlaid onto the spine, as well as the varying lengths of the spinous processes, the topline can appear to be flat.
92 | SHOWSIGHT MAGAZINE, OCTOBER 2021
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