Vertebral Column. Structure and Function of the Vertebral Column Answer to: Identify the structure/region of the vertebral column described below: Consists of 12 vertebrae that are unfused. Typically, this posture occurs from holding the head in an excessively forward position for extended periods, as when reading a textbook resting on a table. Sometimes referred to as the tailbone, the coccyx is a small triangular bone consisting of four fused vertebrae (see Figure 8-17). Key Terms The exiting lumbosacral nerves must therefore travel a great distance inferiorly before reaching their corresponding intervertebral foramina. Start studying 8. The system of ligaments in the vertebral column, combined with the tendons and muscles, provides a natural brace to help protect the spine from injury. The craniocervical region allows about 40 degrees of lateral flexion to each side. When these natural curvatures are maintained, compressive forces can be shared by the tension produced from the stretched connective tissues and muscles located along the convex side of each curve. Each segment of the spinal cord provides several pairs of spinal nerves, which exit from vertebral canal through the intervertebral foramina. Because of excessive wear, arthritis, or advanced age, some intervertebral discs become dehydrated and lose their ability to act as shock absorbers and functional spacers within the cervical region. They have three main distinguishing features: Two cervical vertebrae that are unique. 30-35 Kinematics of craniocervical axial rotation. Flexion increases the diameter of the intervertebral foramen; extension, in contrast, decreases it (Figure 8-26). Flexion and Extension and the Effect on the Diameter of the Intervertebral Foramina. Over time, the muscles and ligaments of the upper cervical region shorten, adapting to the close proximity of the bony structures in this area. B, Superior view of the sixth thoracic vertebra. The rest of the cervical vertebrae (C3-C7) are considered typical and are described as follows. Protraction of the head is the result of flexion of the lower cervical vertebrae and extension—and typically hyperextension—of the upper craniocervical region (Figure 8-27, A). The lumbar vertebrae have massive, wide bodies, suitable for supporting the entire superimposed weight of the body (Figure 8-15). L1-L4 slightly convex, face lateral to anterior-lateral; L5 flat, face anterior and slightly lateral cervical curvature has 7 vertebrae, thoracic has 12 … • Justify the actions of the muscles within the anterior and posterior thoracolumbar region of the vertebral column. During extension, the inferior facets of the superior vertebra slide posteriorly and inferiorly—relative to the vertebra below it (, Rotation of the head and neck in the horizontal plane is an important motion, integral to vision and hearing. Wider than deep; have uncinate processes Adjacent vertebral bodies are separated by a fibrocartilaginous intervertebral disc. List and describe the bones and structures of the human thoracic cage. From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, St Louis, 2002, Mosby, Table 9-3. 10. The vertebral column is subdivided into 5 regions: Cervical, Thoracic, Lumbar, Sacrum and Coccyx. These conditions are congenital abnormalities. Intervertebral foramina allow protected passage of spinal nerves to and from the spinal cord. The vertebral column or the spine has 33 serially arranged units called as vertebrae which are placed dorsally. The combined motion of these joints allows about 45 degrees of rotation in either direction and is mechanically coupled with very slight amounts of lateral flexion secondary to the orientation of the facet joints (, The craniocervical region allows about 40 degrees of lateral flexion to each side. Adds stability to the vertebral column; limits extension or excessive lordosis in the cervical and lumbar regions The cervical and lumbar regions display a natural. Examples include epidural anaesthesia administration and lumbar puncture. As above Structure of the spine Upper Limb. It contains and protects the spinal cord As the name implies, an intervertebral foramen is created by the approximation of two adjacent vertebrae. Data are compiled from multiple sources (see text) and subject to large intersubject variations. • Cite the normal ranges of motion allowed for flexion and extension, lateral flexion, and axial rotation at the craniocervical and thoracolumbar regions of the vertebral column. We’ll look at the trunk in four sections. The mechanics of flexion are the reverse of the mechanics of extension (Figure 8-23, C). Introduction: The vertebral column known as spine is part of axial skeleton. Normal Curvatures List and describe the bones and structures of the human vertebral column. The movement that occurs between two vertebrae is typically only a few degrees; however, when added across several vertebrae, the motion allowed at any particular region can be quite substantial. ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 9-28. Describe the structure of the vertebral column. Each of these three regions allows flexion and extension, lateral flexion, and horizontal plane (axial) rotation. The posterior or dorsal surface of the sacrum is convex and rough, reflecting the numerous ligamentous and muscular attachments. ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 9-22. anterior spondylolisthesis Intervertebral discs play an extremely important role in absorbing and transmitting compression and shear forces throughout the spinal column. In this article, we shall look at the anatomy of the vertebral column – its function, structure, and clinical significance. Muscles of the Trunk The spatial orientation of the facet joints largely determines the direction and extent of motion allowed across a particular region of the vertebral column. Describe the structure of the vertebral column; Key Points. Clinical insight Figure 8-11 A, Superior view of the seven cervical vertebrae. Separation of S1 from the sacrum is termed “lumbarisation”, while fusion of L5 to the sacrum is termed “sacralisation”. Kinematics of craniocervical lateral flexion. • Identify the bones and bony features of the vertebral column and cranium. For example, osteophyte formation within the intervertebral foramen may cause compression of a, Comparison of the intervertebral foramen in a neutral position, A forward head posture is one of the most commonly observed faulty postures of the craniocervical region. The superior nuchal line is a ridge of bone that extends laterally from the occipital protuberance to the mastoid process. Likely more important, this near-frontal plane alignment between L5 and S1 helps prevent the lower lumbar vertebra from sliding anteriorly relative to the sacrum. Muscular attachments are indicated in red; superior attachments of the quadratus lumborum are shown in gray. Cervical spine makes up the neck and has 7 vertebrae. Note that these supporting ligaments of the spine are similar to any other ligaments found in the body; they can become torn, weak, or overly shortened if held in a shortened range for a long period of time. Furthermore, movement occurs within a plane relative to an associated axis of rotation coursing through the vertebral body (Figure 8-20). The deeply seated atlanto-occipital joint strongly resists rotation; rotation of the head therefore is the result of the atlas and the attached cranium rotating as a fixed unit relative to the axis (Figure 8-24, A). • Describe the motions of the spine that decrease and increase the diameter of the intervertebral foramen. The atlanto-axial joint is responsible for about half of the rotation that occurs in the craniocervical region. Each intervertebral disc is composed of three primary components: The nucleus pulposus, the annulus fibrosus, and the vertebral end plate (Figure 8-8). Describe the structure and function of an intervertebral disc. Vertebral foramen: enclosure formed by the body and vertebral arch coming together. thoracic outlet syndrome The rest of the cervical vertebrae (C3-C7) are considered typical and are described as follows. In the vertebrate spinal column, each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, the proportions of which vary according to the segment of the backbone and the species of vertebrate. The disc between C3 and C4 is healthy and well hydrated and is designed to prevent bone-on-bone compression of the vertebrae. The spine is known in anatomy as the vertebral column, or spinal column. Likely more important, this near-frontal plane alignment between L5 and S1 helps prevent the lower lumbar vertebra from sliding anteriorly relative to the sacrum. The normal curvatures of the spine provide strength and stability to the entire axial skeleton. Figure 8-26 Comparison of the intervertebral foramen in a neutral position (A) and in a fully flexed position (B). (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 9-21.) There are seven cervical vertebrae (C1–C7), 12 thoracic vertebrae (T1–T12), and five lumbar vertebrae (L1–L5). (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 9-30.) Consider this… The human vertebral column is composed of a set of natural curves, as is illustrated in Figure 8-1. When two vertebrae are compressed from the pressure of body weight or muscular forces, the nucleus pulposus is squeezed outward, producing tension within the annulus fibrosus (Figure 8-10). The vertical dens and nearly horizontal superior facets of the axis (C2) allow the ring-shaped atlas (C1) to rotate freely and securely about 45 degrees in either direction (Figure 8-24, A). Coccyx ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 9-3. The five different regions are shown and labelled. Axis (C2) Spinal nerves are described in much the same way as the vertebrae. Once again, this motion is guided by the 45-degree incline of the facet joints. 5. The annulus fibrosus is composed of 10 to 20 concentric rings of fibrocartilage that, in essence, encase the nucleus pulposus. Left and right inferior articular facets articulate with the vertebra below. Flexion and Extension (Sagittal Plane, Degrees) (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 9-47.) This tension stabilizes the spongy disc, converting it to a stable weight-bearing structure. 2. Figure 8-18 Primary ligaments that stabilize the vertebral column. Each region permits flexion and extension, lateral flexion, and axial rotation—rotation in the horizontal plane. By convention, movement at any spinal region is defined by the direction of motion of a point on the anterior side of the vertebrae. Distal muscular attachments are indicated in gray, proximal attachments in red. The terms craniocervical region and neck are used interchangeably. They are structurally specialised to support the weight of the torso. Fig 4 – Herniation of an intervertebral disc. As shown in Figure 8-24, the craniocervical region rotates about 90 degrees to each side, allowing nearly 180 degrees of rotational motion. This orientation has an important impact on the kinematics of this region—a point that is revisited later in this chapter. The nuchal lines provide cranial attachments for numerous muscles and ligaments. Rotation of C2-C7 is guided primarily by the oblique orientation of the facet joints. B, Extension of the vertebral column increases cervical and lumbar lordosis but decreases (straightens) thoracic kyphosis. The nerve roots are labeled on the right. This has clinical relevance in cases of a stenosed (narrowed) intervertebral foramen. curvatures increase resilience and flexibility of the spine. This can be confusing because the more visible (and palpable) spinous process rotates to the left—in the opposite direction. Facet (apophyseal) joints are formed by the articulation between the inferior facets of one vertebra and the superior facets of the vertebra below. Typical Vertebrae Although highly variable, the line of gravity acting on a person with ideal posture passes through the mastoid process of the temporal bone, anterior to the second sacral vertebrae, slightly posterior to the hip, and slightly anterior to the knee and ankle (Figure 8-3). Cite the regions of the vertebral column and list the number vertebrae in each region of the adult vertebral column. For example, C3 indicates the third cervical vertebrae from the top of the cervical spine. Kinematics of the Vertebral Column This alignment favors lateral flexion and may help accommodate the natural “hip-hiking” motions that occur during walking and running. But opting out of some of these cookies may affect your browsing experience. Comparison of Vertebrae at Different Regions Describe the cross-sectional structure of a vertebra. It consists of a sequence of vertebrae (singular = vertebra), each of which is separated and united by an intervertebral disc. Normally, there are 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal segments. The superior facets of the axis (C2) are relatively flat, matching the flattened inferior facets of the atlas. Functional Considerations Ligaments aid in joint stability during rest and movement and help prevent injury from hyperextension and hyperflexion (excessive movements). Osteology They are strengthened by several ligaments: Fig 8 – Ligaments of the lumbar vertebrae. Key Terms. Axis: forms an axis that structures can attach to, such as the ribs and head • Identify the normal curvatures of the vertebral column, and explain how these curves provide spinal stability. The posterior longitudinal ligament is weaker and prevents hyperflexion. Many persons exhibit poor posture as a result of muscular tightness or weakness, trauma, poor habit, body fat distribution, disease, or heredity. Locate and identify bones of the thoracic cage. Considered typical thoracic vertebrae nutation A, Neutral position of the vertebral column during standing. The movement that occurs between two vertebrae is typically only a few degrees; however, when added across several vertebrae, the motion allowed at any particular region can be quite substantial. T1 and T10-T12 Bifid Two large concave superior facets sit on top of these lateral masses to accept the large convex occipital condyles, forming the atlanto-occipital joint. Elongated and taut tissues are indicated by thin black arrows. Intervertebral foramina allow protected passage of spinal nerves to and from the spinal cord. The first two cervical vertebrae, called the atlas (C1) and the axis (C2), are unique even to the cervical region. Figure 8-22 Typical spatial orientations for selected superior facet surfaces of the cervical, thoracic, and lumbar vertebrae. The transverse processes of the cervical vertebrae possess transverse foramina (Figure 8-11, A), which serve as a protective passageway for the vertebral artery as it courses toward the brain. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 9-48. The C4-C5 intervertebral disc, however, is degenerated and almost flat. Limit contralateral lateral flexion Herniation of an intervertebral disc occurs when the nucleus pulposus ruptures, breaking through the annulus fibrosus. Discuss the role of hormones and bone cells in bone remodeling 7. Figure 8-4 displays five commonly observed abnormal or “faulty” postures. The body of a vertebra is the large cylindrical mass of bone that serves as the primary weight-bearing structure throughout the vertebral column. The craniocervical region allows about 40 degrees of lateral flexion to each side. 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