Columna Vertebral Anatomy PDF

## 7.8 Hueso hioides - Describe the relationship of the hyoid bone to the skull. The hyoid bone (U-shaped) is a unique component of the axial skeleton because it does not articulate with any other bone. It is suspended from the styloid processes of the temporal bones by ligaments and muscles. Loc...

## 7.8 Hueso hioides - Describe the relationship of the hyoid bone to the skull. The hyoid bone (U-shaped) is a unique component of the axial skeleton because it does not articulate with any other bone. It is suspended from the styloid processes of the temporal bones by ligaments and muscles. Located on the anterior surface of the neck between the mandible and the larynx (see Fig. 7.15a), this bone supports the tongue, and is the point of insertion for some muscles of the tongue, neck, and pharynx. The hyoid bone consists of a horizontal body and paired projections called lesser horns and greater horns (Fig. 7.15b, c). Muscles and ligaments insert into the body and the paired projections. The hyoid bone and the cartilages of the pharynx and trachea often fracture during strangulation. Consequently, they are carefully examined in an autopsy when strangulation is suspected as the cause of death. ## FIGURE 7.15 Hyoid bone. The hyoid bone supports the tongue, and it is the point of insertion for the muscles of the tongue, neck, and pharynx. ## 7.9 Columna vertebral - Identify the areas and normal curvatures of the vertebral column and describe its structural and functional characteristics. The vertebral column (Fig. 7.16), also called the spine, spinal column, or backbone, comprises about two-fifths of total height and is composed of a series of bones called vertebrae. The vertebral column, sternum, and ribs constitute the skeleton of the trunk of the body. The vertebral column consists of bone and connective tissue; the spinal cord, which it surrounds and protects, consists of nerves and connective tissues. At about 71 cm (28 in) in the average adult male and 61 cm (24 in) in the average adult female, the vertebral column functions as a strong, flexible rod with components that can move forward, backward, laterally, and rotate. Besides containing and protecting the spinal cord, it supports the head and serves as the point of attachment for the ribs, the pelvic girdle, and muscles of the back and upper limbs. The total number of vertebrae during initial development is 33. As the child grows, several vertebrae in the areas of the sacrum and coccyx fuse. Consequently, the adult vertebral column normally has 26 vertebrae (Fig. 7.16a). These are distributed as follows: - 7 cervical vertebrae ( *cervic* = neck) in the neck region. - 12 thoracic vertebrae ( *thorax* = chest) posterior to the rib cage. - 5 lumbar vertebrae ( *lumb-* = loin) that support the dorsal column. - 1 sacrum (sacral bone), consisting of 5 fused sacral vertebrae. - 1 coccyx (shaped similar to the beak of a cuckoo), which generally consists of 4 fused coccygeal vertebrae. The cervical, thoracic, and lumbar vertebrae are movable, but the sacrum and coccyx are not. Each of these regions will be discussed in detail below. ## Curvatures of the vertebral column When observed from posterior or anterior, the vertebral column of an adult appears to be straight. But when viewed from the side, it reveals four slight curvatures called normal curvatures (Fig. 7.16b). In relation to the front of the body, the cervical and lumbar curvatures are convex (protruding) and the thoracic and sacral curvatures are concave (retracted). The curvatures of the vertebral column strengthen it, help maintain balance in the upright position, absorb stress during walking, and help protect the vertebrae from fractures. ## FIGURE 7.16 Vertebral column. The numbers in parentheses in (a) indicate the number of vertebrae in each region. The relative size of the disc is magnified in (d). The adult vertebral column normally contains 26 vertebrae. ## Discs intervertebrales The intervertebral discs ( *inter* = between) are found between the bodies of adjacent vertebrae, from the second cervical vertebra to the sacrum (Fig. 7.16d), and represent about 25% of the height of the vertebral column. Each disc has an outer fibrous ring consisting of fibrocartilage and is called the annulus fibrosus ( *anulus* = ring-shaped). The inner substance is soft, pulpy, and highly elastic and is called the nucleus pulposus. ## FIGURE 7.17 Structure of a typical vertebra, illustrated by a thoracic vertebra. In (b), the vertebra is projected from the foramen intervertebral for clarity. A vertebra consists of a vertebral body, a vertebral arch, and several processes. ## Vértebras cervicales The bodies of the cervical vertebrae (C1-C7) are smaller than all other vertebral bodies, except for those that make up the coccyx (Fig. 7.18a). However, their vertebral arches are larger. All cervical vertebrae have three foramens: one vertebral and two transverse (Fig. 7.18c). The vertebral foramens of the cervical region are the largest of the column because they enclose the cervical enlargement of the spinal cord. Each transverse process of a cervical vertebra contains a transverse foramen through which the vertebral artery and the nerve fibers and the vein that accompany it pass. The spinous processes of C2 to C6 usually are bifid, that is, they branch into two small projections at their tips (Fig. 7.18a, c). The first two cervical vertebrae differ considerably from the rest. The atlas (C1), named after the mythological Atlas who held up the world on his shoulders, is the first cervical vertebra below the skull (Fig. 7.18a, b). The atlas is a bony ring with an anterior arch and a posterior arch, and large lateral masses. It has no body or spinous process. The superior surfaces of the lateral masses, called superior articular facets, are concave. They articulate with the condyles of the occipital bone to form the pair of atlanto-occipital joints. These joints allow the head to move forward to express affirmation. The inferior surfaces of the lateral masses, the inferior articular facets, articulate with the second cervical vertebra. The transverse processes and the transverse foramens of the atlas are rather large. The second cervical vertebra (C2), the axis (Fig. 7.18a, d, e), has a body in effect. A peg-like process called the dens or odontoid process projects upward through the anterior portion of the vertebral foramen of the atlas. It acts as the pivot point on which the atlas and head rotate. This arrangement permits side-to-side movements of the head, such as when one says “no.” The joint formed between the anterior arch of the atlas and the odontoid process of the axis, and between their articular facets, is called the atlantoaxial joint. In some traumatic injuries, the odontoid process of the axis may become lodged in the medulla oblongata of the brain. This type of injury is the usual cause of death from cervical trauma. The cervical vertebrae from the third through the sixth (C3-C6), pictured as a typical vertebra in Figure 7.18c, follow the structural patterns of the typical vertebra already described. The seventh cervical vertebra (C7), called the vertebra prominens, is different (see Fig. 7.18a). Its spinous process is large and undivided, and can be seen and felt at the base of the neck. Otherwise, it is a typical vertebra. ## Vértebras torácicas The thoracic vertebrae (T1-T12; Fig. 7.19) are considerably larger and stronger than the cervical vertebrae. The spinous processes of T1 to T10 are long, laterally flattened, and project downward. Because of their ==End of OCR for page 1==