Strength against compression is provided by a spool-shaped cylinder, the centrum, that articulates front and back with adjacent centra. The coccyx is formed by the fusion of four small coccygeal vertebrae. The neural and hemal spines, lying in the same sagittal plane as the vertebrae, can be rigidly connected to them, since almost no dorsoventral movement is required. The descending tracts are composed of white matter. The anterior thoracic spinal blood supply is more complicated and potentially more prone to disastrous complications. Unfortunately, this angle 55° has not been found in any living animal.
The nuchal ligament is attached to the cervical spinous processes and superiorly to the base of the skull, out to the external occipital protuberance. This structure provides padding between the bones during weight bearing, and because it can change shape, also allows for movement between the vertebrae. Each of these openings is called a posterior dorsal sacral foramen or anterior ventral sacral foramen. The function of lower motor neurons can be divided into two different groups: the lateral corticospinal tract and the anterior cortical spinal tract. From each pedicle a broad plate, a lamina, projects backwards and medialwards to join and complete the vertebral arch and form the posterior border of the vertebral foramen, which completes the triangle of the vertebral foramen. Each vertebra is a complex of several firmly joined pieces Bertin, 1958a , composed of cartilage in elasmobranchs, and of bone in most adult teleosts. The ligamentum flavum is made of yellowish fibro-elastic tissue, hence its name, which means yellow ligament.
This includes seemingly unlikely animals such as the giraffe, the camel, and the blue whale, for example. The spinal column or vertebral column extends from the skull to the pelvis and is made up of 33 individual bones termed vertebrae. All vertebrates have a spinal cord. This cancellous bone is in turn, covered by a thin coating of or compact bone , the hard and dense type of osseous tissue. The shape and orientation of the articular processes vary in different regions of the vertebral column and play a major role in determining the type and range of motion available in each region. The three primary functions of each vertebra are to bear body weight, to anchor muscles and ligaments, and to protect the spinal cord.
The Vertebral Column as a Whole · · · Henry Gray 18211865. From this vertebral body, sclerotome cells move dorsally and surround the developing , forming the. In a full-grown giraffe, each cervical vertebra is 11 inches tall. The single sacrum, which is also part of the pelvis, is formed by the fusion of five sacral vertebrae, though in about 33% percent of the population T12 is fused to the sacrum or S1 remains unfused. This condition is most common in the lumbosacral region, but it may occur in the thoracic or cervical region, or the arches throughout the whole length of the canal may remain incomplete.
Together, the vertebrae and intervertebral discs form the vertebral column. The ligamentum flavum unites the lamina of adjacent vertebrae. Cervical Vertebrae Typical cervical vertebrae, such as C4 or C5, have several characteristic features that differentiate them from thoracic or lumbar vertebrae. The supraspinous ligament is located on the posterior side of the vertebral column, where it interconnects the spinous processes of the thoracic and lumbar vertebrae. The cervical vertebrae attach the skull to the rest of the body, and create the structure for the neck of an animal. They range in number from a few to fifty, depending on the length of the animal's tail. The supraspinous ligament connects the spinous processes of the thoracic and lumbar vertebrae.
Other cells move distally to the costal processes of to form the ribs. This is simply not true. The thoracic curve, concave forward, begins at the middle of the second and ends at the middle of the twelfth thoracic vertebra. The superior articular process of the sacrum, one of which is found on either side of the superior opening of the sacral canal, articulates with the inferior articular processes from the L5 vertebra. The vertebrae are subdivided into cervical, thoracic, and lumbar regions. The neural arches cover the spinal cord and extend to the hemal arches, which cover the bottom of the notochord and allow for rib attachments.
The vertebral column is moved by wide muscles Figure 52-3. Curvatures of the vertebral column The adult vertebral column does not form a straight line, but instead has four curvatures along its length see. Tendons attach muscle to bone. Tendons vary in size and are somewhat elastic and attach bones to muscles. Protection against this movement is particularly important in the neck, where extreme posterior bending of the head and neck can stretch or tear this ligament, resulting in a painful whiplash injury. The arch is formed by the paired pedicles and paired laminae. In support of this explanation it has been found that in one or two individuals who were left-handed, the convexity was to the left side.
Thoracic vertebrae also have articulation facets on the body and transverse processes for attachment of the ribs. The lumbar enlargement handles sensory input and motor output coming from and going to the legs. The superior and inferior articular processes of the cervical vertebrae are flattened and largely face upward or downward, respectively. In extreme cases, surgery may be required. The rib of the same number generally articulates with both the cranial superior part of the body and the transverse process of the thoracic vertebrae of the same number. Intermuscular bones are also discussed in Chapter 5. At each of these joints the zygapophyses are reduced and the adjacent vertebral faces form a lateral hinge.
Some rotation can occur between the thoracic vertebrae, but their connection with the prevents much flexion or other movement. If the axon enters above level T6, then it travels in the fasciculus cuneatus, which is lateral to the fasiculus gracilis. Most of the evidence of the earliest sharks and other vertebrates has been found by remnants of their teeth and bony outer armor. In the posterior neck, the supraspinous ligament enlarges to form the nuchal ligament, which attaches to the cervical spinous processes and to the base of the skull. Most have thirteen, but only have eleven. The auricular surfaces are articulation sites on the lateral sacrum that anchor the sacrum to the hipbones to form the pelvis. The dura mater protects the spinal cord.