Spine - Anatomy Pictures and Information Home > Skeletal System > Spine Spine Stretching down the midline of the trunk from the base of the skull to the coccyx, the spine plays an extremely important role in our bodies as it supports the upper body’s weight; provides posture while allowing for movement and flexibility; and protects the spinal cord. The spine, also known as the vertebral column or spinal column, is a column of 26 bones in an adult body – 24 separate vertebrae interspaced with cartilage, and then additionally the sacrum and coccyx.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image Vertebra and Spinal Cord, Cross-section Full Spine Description [Continued from above] . . . Prior to adolescence, the spine consists of 33 bones because the sacrum’s five bones and the coccyx’s four do not fuse together until adolescence. The vertebrae are named by the first letter of their region (cervical, thoracic, or lumbar) and with a number to indicate their position along the superior-inferior axis.

For example, the fifth lumbar vertebra (which is most inferior one, located beneath the fourth lumbar vertebra) is called the L5 vertebra. Each vertebra has several important parts: the body, vertebral foramen, spinous process, and transverse process. The body is the main weight-bearing region of a vertebra, making up the bulk of the bone’s mass. Extending from the body, the transverse processes are thin columns of bone that point out to the left and right sides of the body. The spinous process extends from the ends of the transverse processes in the posterior direction. Between the body, transverse processes and spinous process is the vertebral foramen, a hollow space that contains the spinal cord and meninges. Between the vertebrae of the spine are thin regions of cartilage known as the intervertebral discs. Intervertebral discs are made of an outer shell known as the annulus fibrosus and a soft, pulpy region known as the nucleus pulposus in the middle. The annulus fibrosus is made of tough fibrocartilage that binds the vertebrae together but is flexible enough to allow for our movements.

The inner nucleus pulposus acts as a shock absorber to support the body’s weight and prevent the vertebrae from painfully crashing into each other while under strain. The vertebrae of the spine align so that their vertebral canals form a hollow, bony tube to protect the spinal cord from external damage and infection. Between the vertebrae are small spaces known as intervertebral canals that allow spinal nerves to exit the spinal cord and connect to the various regions of the body. There are 5 major regions of the spine: Cervical: The 7 vertebrae in the neck form the cervical region of the spine. Cervical vertebrae are the thinnest and most delicate vertebrae in the spine but offer great flexibility to the neck. The first cervical vertebra, C1, supports the skull and is named “atlas” after the Greek titan who held the Earth on his shoulders. The skull pivots on the atlas when moving up and down. The second cervical vertebra, C2, is also known as the “axis” because it allows the skull and atlas to rotate to the left and right.

Thoracic: The 12 vertebrae in the chest region form the spine’s thoracic region. Thoracic vertebrae are larger and stronger than cervical vertebrae but are much less flexible. The spinous processes of the thoracic vertebrae point inferiorly to help lock the vertebrae together. A unique feature of the thoracic vertebrae is that each one forms joints with a pair of ribs to form the sturdy rib cage that protects the organs of the chest. Lumbar: The 5 vertebrae in the lower back form the lumbar region of the spine. Lumbar vertebrae are even larger and stronger than thoracic vertebrae, but are more flexible due to the lack of ribs in the lumbar region. All of the upper body’s weight bears down on the lumbar vertebrae, leading to many back problems in this region despite the size and strength of the vertebrae. Sacral: The sacral region of the spine contains only the sacrum, a single bone in the adult skeleton that is formed by the fusion of 5 smaller vertebrae during adolescence. The sacrum is a flat, triangular bone found in the lower back and wedged between the 2 hip bones.

Coccygeal: The spine’s coccygeal region contains only the coccyx, a single bone in the adult skeleton that is formed by the fusion of 4 tiny vertebrae during adolescence. The coccyx is often referred to as the human tailbone, as this region is homologous to the tail bones of animals that have tails. In humans, the coccyx bears our body weight when sitting down and provides attachment points for muscles of the pelvic and gluteal regions. While most people have a coccyx made of 4 fused vertebrae, the coccyx may consist of as few as 3 or as many as 5 vertebrae. The length of the coccyx has no effect on the body’s function. Prepared by Tim Taylor, Anatomy and Physiology Instructor Human Spine & Spinal Cord Picture C1 - S5 Vertebra Can learn to drive an adapted vehicle. Most likely will need to use a manual wheelchair. Should be able to cough productively (if abdominal muscles are intact). A fair to good ability to control and balance the body while in a seated position. Some patients will be capable of standing in a standing frame, while others may require the use of braces to walk.

Often will have little or no voluntary control of bowel or bladder function but can usually manage on their own with adaptive equipment. T1 - Comparatively speaking, T1 is the smallest of all thoracic vertebrae. The T1 vertebra is the first (uppermost) of the twelve (12) thoracic vertebrae that make up the central and largest section of the spinal column between the lumbar vertebrae below and the cervical vertebrae above. T2 - The second vertebra in the thoracic spine is responsible for helping to support the rib cage. The T2 vertebra possesses facets that create joints with two of the ribs, thus helping to keep the thoracic spine far more stable than the cervical spine in the neck or the lumbar spine in the lower back. T2 vertebra degeneration include: Herniated, bulging or prolapsed discs, Bone spurs, Facet disease, Forms of osteoarthritis and Traumatic or sports-related injuries. T3 - The third thoracic vertebrae is a small vertebra in the upper middle back that plays an integral role in supporting the rib cage. The anterior aspect of the upper thoracic spine is a difficult region to approach in spinal surgery.

T4 - Spinal cord transection at T4 results in severe damage of the nervous tissue, with impairment of motor, sensory and autonomic functions. T4 syndrome is a relatively uncommon condition in which spinal injury at the T4 vertebra causes a set of symptoms including diffuse arm pain and pins and needles or numbness in the upper arm. T5 - The T5 vertebra, as well as the rest of the thoracic spine, provides a stable foundation for the human rib cage. T6 - An injury at the level of T6 (thoracic) spinal cord results in damage to the autonomic nervous system, both the sympathetic and parasympathetic divisions, affecting the function of major abdominal organs. T7 - The T7 vertebra is in the middle of the twelve (12) thoracic vertebrae of the torso and the center of the spinal column. Thoracic vertebrae play an important role, not only in the protection of the spinal cord, but also in the protection of vital organs. A vertebral compression fracture refers to a break of the vertebral body, most often below the T7 level of the thoracic spine (upper back), and is most commonly caused by weakened bone resulting from osteoporosis.

Most vertebral compression fractures result in a loss of more than 15% to 20% of the height of the vertebra. T8 - T8 vertebra is toward the lower (caudal) end of the twelve (12) thoracic vertebrae within the central, torso section of the spine. Like other spinal vertebrae, the T8 primarily protects and encases the spinal cord. The T8 is also at the same level as the xiphoid process. The eighth thoracic spinal nerve runs beneath the T8. Throughout the thoracic spine, discs like those above and beneath the T8 vertebra can become damaged and cause painful symptoms. T9 - T9 to T12 are known as the transition vertebrae. The lumbar cord is situated between T9 and T11 vertebrae. T9 to T12 injuries can be classified as either complete or incomplete injuries. Complete injuries result in the total loss of movement and sensation below the point of injury, while incomplete injuries indicate that some function below the level of injury is retained. T10 - T10 is situated at the umbilicus.

The T10 vertebra is near to the bottom of the twelve (12) thoracic vertebrae (T1-T12) within the torso and making up the central portion of the spinal column. This particular vertebra has a complete articular facet and the thoracic spinal nerves passes out under it. T10 innervates the muscles of the lower abdomen. It is part of the section of the spinal cord which is most vulnerable to injury due to the area's high level of flexibility. An injury in this area will most likely experience limited or complete loss of use of the muscles in the lower abdomen, buttocks, legs, and feet. Extent of disability is determined by damage done to the T10 vertebra. Partial damage may cause weakness, numbness, lack of muscle control, or loss of the use of one side of the lower body. Complete damage could result in the loss of use of the lower body (paraplegia). T11 - The ribs connected to T11 and T12 at the bottom of the thoracic spine do not attach the sternum in front, but do provide protection for the kidneys in the back of the body.

Because these levels have slightly less stability, they are slightly more prone to problems that can cause pain. A person with a T11 vertebral injury may have or recover sensations in the L1 through L4 dermatomes which include the front of the leg down to the mid-shin level. In addition, such a patient should recover hip extensors, knee extensors, and even ankle dorsiflexion. However, the sacral functions, including bowel and bladder and many of the flexor functions of the leg may be absent or weak. T12 - T12 ends just above the hip girdle. T12 bears the most weight of any thoracic vertebra, making it the strongest thoracic vertebra, but also the most susceptible to stress-related injuries. Compression fractures of the spine usually occur at the bottom part of the thoracic spine (T11 and T12) and the first vertebra of the lumbar spine (L1). The most common thoracic spinal cord injury involves T11 and T12. Lumbar Vertebrae (L1 to L5) Lumbar nerves (L1 to L5) injuries generally result in some loss of function in the hips and legs.

Often there is little or no voluntary control of bowel or bladder, but patients usually manage on their own with the use of special equipment. Depending on strength in the legs, some patients may need a wheelchair and may also walk with braces. The lumbar vertebrae graduate in size from L1 through L5. These vertebrae bear much of the body's weight and related biomechanical stress. The lumbar vertebrae are also the largest segments of the movable part of the vertebral column, and are characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body. Some individuals have four lumbar vertebrae, while others have six. Lumbar disorders that normally affect L5 will affect L4 or L6 in these individuals. L1 - The first lumbar vertebra is at the same level as the ninth rib. This level is also called the important transpyloric plane, since the pylorus of the stomach is at this level.

L2 - Injuries to the spinal column at L2 or lower will damage the tip of the spinal cord, called the conus, or the spray of spinal roots that are descending to the appropriate spinal vertebral levels to exit the spinal canal or the caudal equina. L3 - The L3 vertebra is in the middle of the five lumbar vertebrae in the lower back portion of the spinal column. The L3 vertebra, or third lumbar vertebra, is one of the most common sites for the occurrence of a herniated disc and other spinal conditions that can cause chronic lower back pain. A lot of motion in the back is divided between these five motion segments with segments L3 - L4 and L4 - L5 taking most of the stress. L3 - L4 and L4 - L5 segments are most likely to breakdown from wear and tear causing such conditions as osteoarthritis. L2 and L3 cover the front part of the thighs. L4 - The most likely to herniate ( herniated disc , bulging disk , compressed disk, herniated intervertebral disk, herniated nucleus pulposus, prolapsed disk, ruptured disk, slipped disk).

The effects of this can cause pain and numbness that can radiate through the leg and extend down to the feet (sciatica). Spondylolysis and spondylolisthesis are conditions that affect the moveable joints of the spine that help keep the vertebrae aligned one on top of the other. Spondylolysis is actually a weakness or stress fracture in one of the bony bridges that connects the upper and lower facet joints. This fracture can happen at any level of the spine but usually occurs at the fourth (L4) or fifth (L5) lumbar vertebra. L4 and L5 fractures are commonly the result of a high impact trauma from falls or motor vehicle accidents. L5 - The fifth lumbar vertebra (L5) is the largest of the five lumbar vertebrae and is considered an atypical vertebra due to its shape. As the last of the lumbar vertebrae, the L5 vertebra bears more body weight than any of the other 23 vertebrae that sit atop it in the vertebral column.

The L4 and L5 disc, in between the L4 and L5 vertebrae, can herniate or degenerate, leading to possible leg pain (sciatica) and/or lower back pain. The fifth lumbar vertebra is the most common site of spondylolysis and spondylolisthesis. Sacral Nerves (S1 to S5) injuries generally result in some loss of functionin the hips and legs. Little or no voluntary control of bowel or bladder, but patients can manage on their own with special equipment Most likely they will also still be able to walk. Sacral Nerves (S1 to S5) The sacrum is shaped different in males and females. In females the sacrum is shorter and wider than in males. The Sacrum is located behind the pelvis. Five bones (abbreviated S1 through S5) fused into a triangular shape, form the sacrum. The sacrum fits between the two hipbones connecting the spine to the pelvis located just below the lumbar vertebrae. The Sacrum consists of four or five sacral vertebrae in a child, which become fused into a single bone after age 26.

The sacrum forms the back wall of the pelvic girdle and moves with it. The first three vertebrae in the sacral have transverse processes which come together to form wide lateral wings called alae. These alae articulate with the blades of the pelvis (ilium). As part of the pelvic girdle, the sacrum forms the back wall of the pelvis and also forms joints at the hip bone called the sacroiliac joints. The sacrum contains a series of four openings on each side through which the sacral nerves and blood vessels run. The sacral canal runs down the center of the sacrum and represents the end of the vertebral canal. Back pain or leg pain ( sciatica ) can typically arise due to injury where the lumbar spine and sacral region connect (at L5 - S1) because this section of the spine is subjected to a large amount of stress and twisting. People with rheumatoid arthritis or osteoporosis are inclined to develop stress fractures and fatigue fractures in the sacrum. The bottom of the spinal column is called the coccyx or tailbone. It consists of 3 to 5 bones that are fused together in an adult. Many muscles connect to the coccyx.

Sacral Nerves (S1 to S5) injuries generally result in some loss of function in the hips and legs. Little or no voluntary control of bowel or bladder, but can manage on their own with special equipment Most likely will be able to walk. S1 - L5 to S1 Isthmic Spondylolisthesis: A small fracture in the facet joints can allow the L5 vertebra to slip forward over the S1 vertebra, impinging the nerve root and leading to leg pain and other symptoms. L5-S1 disc herniation: Occurs when the inner portion leaks out and touches the nearby nerve root, causing pain to radiate in the lower back and/or down the leg. L5-S1 degenerative disc disease: If the L5-S1 disc is compromised, the L5-S1 disc itself can become a source of lower back and/or leg pain. S2 - S2 is located at the level of posterior superior iliac spine. S2 covers the back of the thighs. S3 - S3 cover the medial side of the buttocks. S4 - S4-5 covers the perineal region.

S5 - S5 is the lowest dermatome and represents the skin immediately at and adjacent to the anus. This chart is a guide, with general information only; impairments and rehabilitation potential can vary depending on the type and severity of SCI . Lumbar Vertebrae - Anatomy Pictures and Information Home > Skeletal System > Spine > Lumbar Vertebrae Lumbar Vertebrae The lumbar vertebrae consist of five individual cylindrical bones that form the spine in the lower back. These vertebrae carry all of the upper body’s weight while providing flexibility and movement to the trunk region. They also protect the delicate spinal cord and nerves within their vertebral canal. Found along the body’s midline in the lumbar (lower back) region, the lumbar vertebrae make up the region of the spine inferior to the thoracic vertebrae in the thorax and superior to the sacrum and coccyx in the pelvis....

Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Vertebra and Spinal Cord, Cross-section Full Lumbar Vertebrae Description [Continued from above] . . . The lumbar vertebrae are stacked to form a continuous column in order from superior (L1 or first lumbar vertebra) to inferior (L5 or fifth lumbar vertebra). Together they create the concave lumbar curvature in the lower back. Connecting each vertebra to its neighboring vertebra is an intervertebral disk made of tough fibrocartilage with a jelly-like center. The outer layer of the intervertebral disk, the annulus fibrosus, holds the vertebrae together and provides strength and flexibility to the back during movement. The jelly-like nucleus pulposus acts as a shock absorber to resist the strain and pressure exerted on the lower back. The lumbar vertebrae are the some of the largest and heaviest vertebrae in the spine, second in size only to the sacrum.

A cylinder of bone known as the vertebral body makes up the majority of the lumbar vertebrae’s mass and bears most of the body’s weight. Posteriorly the body is connected to a thin ring of bone known as the arch. The arch surrounds the hollow vertebral foramen and connects the body to the bony processes on the posterior of the vertebra. The vertebral foramen is a large, triangular opening in the center of the vertebra that provides space for the spinal cord, cauda equina, and meninges as they pass through the lower back. Extending from the vertebral arch are several bony processes that are involved in muscle attachment and movement of the lower back. The spinous process extends from the posterior end of the arch as a thin rectangle of bone. It serves as a connection point for the muscles of the back and pelvis, such as the psoas major and interspinales. On the left and right lateral sides of each vertebra are the short, triangular transverse processes. The transverse processes form important connection points for many muscles, including the rotatores and multifidus muscles that extend and rotate the trunk.

Unlike the cervical vertebrae in the neck, the lumbar vertebrae lack the transverse foramina in the transverse processes, and also lack facets to either side of the body. The fifth lumbar vertebra is distinct from the L1-4 vertebrae in being much larger on its front side than in the back. Its spinous process, on the other hand, is smaller than in the other lumbar vertebrae with a wide, four-sided shape that comes to a rough edge and a thick notch. Prepared by Tim Taylor, Anatomy and Physiology Instructor Chapter 39: The vertebral column Chapter 39: The vertebral column Vertebral column in general The vertebral column usually consists of 33 vertebrae: 24 presacral vertebrae (7 cervical, 12 thoracic, and 5 lumbar) followed by the sacrum (5 fused sacral vertebrae) and the coccyx (4 frequently fused coccygeal vertebrae). The 24 presacral vertebrae allow movement and hence render the vertebral column flexible. Stability is provided by ligaments, muscles, and the form of the bones.

The abbreviations C., T., L., S., and Co. are used for the regions, and these are sometimes followed by V. for vertebra or N. for nerve. Curvatures. The adult vertebral column presents four anteroposterior curvatures: thoracic and sacral, both concave anteriorly, and cervical and lumbar, both concave posteriorly (fig. 39-1 ). The thoracic and sacral curvatures, termed primary, appear during the embryonic period proper, whereas the cervical and lumbar curvatures, termed secondary, appear later (although before birth) and are accentuated in infancy by support of the head and by the adoption of an upright posture. Parts of a Vertebra. A typical vertebra consists of (1) a body and (2) a vertebral arch, which has several processes (articular, transverse, and spinous) for articular and muscular attachments. Between the body and the arch is the vertebral foramen: the sum of the vertebral foramina constitutes the vertebral canal, which houses the spinal cord (fig. 39-2 ).

In addition to the transverse and spinous processes, which serve as short levers, the 12 thoracic vertebrae are connected by joints with paired, long levers, namely the ribs. The bodies of the vertebrae are separated from each other by intervertebral discs. The body is mainly spongy bone and red marrow, but the margins of the upper and lower surfaces consist of a ring of compact bone, the vertebral end-plates. The body is marked on its sides by vascular foramina. The vertebral arch consists of right and left pedicles (which connect it to the body) and right and left laminae. The transverse processes emerge laterally at the junction of the pedicles and laminae, and the spinous process proceeds posteriorly from the union of the laminae. The superior and inferior articular processes project vertically from the vertebral arches on each side and bear articular facets. When vertebra are in their anatomical position, notches between adjacent pedicles form intervertebral foramina, each of which typically transmitsneural structures including a spinal ganglion and a ventral root of a spinal nerve. Relationship of Spinal Nerves to Vertebrae.

The first cervical nerve emerges between the skull and the atlas, and cervical nerves C2 to 7 continue to leave the vertebral canal above the correspondingly numbered vertebrae. C8 emerges between the C7 and T1 vertebrae, and the remaining spinal nerves leave below the correspondingly numbered vertebrae. Regional characteristics of vertebrae The vertebrae of each region have special characteristics, which are now described. Cervical Vertebrae. The seven vertebrae of the neck are characterized by an opening in each transverse process known as a foramen transversarium. The upper six pairs of foramina transversaria transmit the vertebral artery. The C1 vertebra, which supports the skull, is termed the atlas, and C2, which serves as a pivot for the atlas, is termed the axis. Atlas (fig. 39-3 ). The atlas (C1), which has neither body nor spinous process, consists of two lateral masses connected by a short anterior and a longer posterior arch. Each lateral mass presents upper and lower facets, for the occipital condyle of the skull and for the axis, respectively. The transverse processes are long and are vaguely palpable in vivo immediately below the auricle.

The anterior arch presents an anterior tubercle in front (for the anterior longitudinal ligament) and a facet posteriorly (for the dens of the axis). The posterior arch is grooved above for the vertebral artery and the small C1 nerve on each side, and it presents a posterior tubercle behind. Axis (fig. 39-4 ). The axis (C2) is characterized by the dens (or odontoid process), which projects upward from the body and articulates with the anterior arch of the atlas. The dens is anchored to the occipital bone (by apical and alar ligaments) and is limited behind by the transverse ligament of the atlas (fig. 39-3 ). It is frequently claimed that the dens represents the body of the atlas, but this is doubtful. * Remaining cervical vertebrae (fig. 39-5 ). The lower cervical vertebrae, C2 to 6 are typical and present short, bifid spinous processes. The bodies are small and oval in shape. There are superiorly-projecting lips at the superolateral borders of the vertebral bodies. These closely match indentations in the lateral border of inferior aspect of the vertebral body above.

Each transverse process, pierced by a foramen transversarium, ends laterally in anterior and posterior tubercles, which are connected by an "intertubercular lamella" or bar. # The bars are grooved by the ventral primary rami of the spinal nerves, which pass posterior to the foramina transversaria. The anterior tubercles of C6 vertebra are large and are termed the carotid tubercles, because the common carotid arteries can be compressed against them. C7 vertebra has a long, non-bifid spinous process and is known as the vertebra prominens. (The spinous processes of C6 and 7 and T1 are usually visible in vivo when the neck is flexed.) The anterior tubercles (costal processes) of C7 vertebra may develop separately as cervical ribs. (Lumbar ribs are less frequent.) Thoracic Vertebrae (figs. 39-5 , 39-6 and 39-7 ). It should be noted that all vertebrae are dorsal, although only 12 are thoracic. The 12 vertebrae of the thorax bear the ribs.

The T1 vertebra (like C.V.7) is transitional in appearance. T2 to 8 vertebra are typical thoracic vertebrae with a kidney shaped body (fig. 39-5 ). Demifacets for the heads of the ribs (see fig. 20-3 ) are found supeiorly and inferiorly at the junction of the body and pedicle. The transverse processes of T1 to 10 have costal facets for the tubercles of the ribs. The spinous processes are long, slender, and sloping: their tips lie opposite the subjacent body or even at the level of the intervertebral disc below the subjacent body. The various facets for the ribs on T1 and on T9 to 12 veertebral bodies are arranged differently. T11 and 12 are transitional in form, i.e., partly resembling lumbar vertebrae. A humped back is termed kyphosis. Lumbar Vertebrae (figs. 39-8 and 39-9 ). The five vertebrae between the thorax and sacrum are large and present neither foramina transversaria nor costal facets (fig.

39-5 ). The body is kidney shpaed, and the pedicles and laminae are short and thick. The part of the lamina between the superior and inferior articular processes is known as the pars interarticularis and is liable to injury in some people (resulting in spondylolisthesis, i.e., a slipping forward of the body of one vertebra on the vertebra or sacrum below it). A mamillary process projects posteriorward from the superior articular process. The transverse process, which corresponds to a rib, is long and thin, and an accessory process may project inferiorward from its root. The spinous processes are quadrilateral and project horizontally backward. The fifth lumbar vertebra, usually the largest vertebra, is mainly responsible for the lumbosacral angle (between the lumbar part of the column and the sacrum). Excessive "hollowing" of the back is termed lordosis. Sacrum (figs. 39-10 and 39-11 ).

Five (sometimes six) vertebrae are fused in the adult to form the sacrum, which can be felt below the "small of the back." The sacrum articulates above with L5, laterally with the hip bones, and inferiorly with the coccyx. It has a roughly triangular appearance with a pelvic and dorsal surface, a lateral mass on each side, and a base and apex. The pelvic surface, concave and facing antero-inferiorly, presents four paired sacral foramina for the ventral primary rami of sacral nerves 1 to 4. The dorsal surface, convex and facing posterosuperiorly, presents a modified series of spinous processes termed the median sacral crest and four paired sacral foramina for the dorsal primary rami of sacral nerves 1 to 4. Below, the sacrum shows right and left sacral cornua, which bound a variable gap termed the sacral hiatus. An anesthetic for the spinal nerves may be injected extradurally through the sacral hiatus (caudal analgesia). The cornua articulate with corresponding horns on the coccyx.

The lateral part or mass of the sacrum, lateral to the sacral foramina, consists of the fused transverse processes (including their costal elements). Its superior surface is frequently termed the ala. The superolateral part of the lateral mass presents the auricular (ear-shaped) surface for articulation with the hip bone (sacro-iliac joint). The surface is limited behind by an area (sacral tuberosity) for interosseous ligaments. The base, formed by the suprior part of the first sacral vertebra, presents a prominent anterior margin termed the promontory (fig. 39-11 ). Superior articular processes articulate with the fifth lumbar vertebra. The sacral canal (which contains the dura, cauda equina, and filum terminale) extends from the base to the sacral hiatus. The apex of the sacrum may be fused with the coccyx. Coccyx (fig. 39-10 ). The vertebrae (usually four) below the sacrum are variably fused in the adult to form the coccyx, which resembles a miniature sacrum in shape. Development of vertebrae (figs.

39-12 and 39-13 ) Vertebrae develop in mesenchyme and cartilage during the embryonic period proper, and most begin to ossify during fetal life. Typically, a vertebra at birth shows three ossific areas, one for the centrum (defined in fig. 39-14 ) and one for each half of the neural arch. At about puberty, ossific centers appear in the margins of the upper and lower surfaces of the body (ring epiphyses) and at the tips of the various processes. Developmental failure of half a vertebra (hemivertebra) is one cause of lateral curvature (scoliosis). Failure of fusion of the halves of one or more neural (future vertebral) arches is termed spina bifida. The meninges alone (meningocele), or the spinal cord and meninges (meningomyelocele), may protrude through the defect (spina bifida cystica). When the defect is skeletal rather than neural, it may be concealed by the skin (although sometimes marked by a tuft of hair) and is termed spina bifida occulta. In the sacrum, this is quite common.

Surface anatomy The spinous processes of the vertebrae are palpable in the median furrow of the back. The external occipital protuberance is palpable in adults. The spines of vertebrae C6, C7, and T1 are usually prominent and palpable, and they are made more conspicuous by flexion of the neck and trunk. In the thoracic region, the spinous process of each vertebra extends to the level of at least the body of the vertebra below. The inferior angle of the scapula is frequently at the level of the spinous process of T7. A horizontal plane between the highest points of the iliac crests (supracristal plane) is usually at the level of the spinous process of L4, and this is used as a landmark for lumbar puncture. A needle introduced here should enter the subarachnoid space after 4 to 6 cm. The posterior superior iliac spine is commonly marked by a skin dimple (fig. 39-15 ). Additional reading Kohler, A., and Zimmer, E. A.

Borderlands of the Normal and Early Pathologic in Skeletal Roentgenology, 3rd ed" trans, by S. P. Wilk, Grone & Stratton, New York, 1968. This classic study of the entire skeleton is available in a more recent edition in German. Schmorl, G., and Junghanns, H., The Human Spine in Health and Disease, 2nd ed., trans. by E. F. Besemann, Grone & Stratton, New York, 1971. This well known work is an important account of the normal and abnormal vertebral column. Questions 39-1 How many vertebrae are movable? 39-1 The 24 "presacral" vertebrae are movable. Eighty-nine per cent of people have 24 presacral vertebrae, 6 per cent have 23, and 5 per cent have 25 (P. E. Bomstein and R. R. Peterson, Am. J. Phys. Anthropol., 25:139-146, 1966).

39-2 Which curvatures first appear in the vertebral column? 39-2 The thoracic and sacral curvatures are primary (appearing during embryonic life). The cervical and lumbar curvatures are secondary (appearing during fetal life and accentuated during infancy). 39-3 How many processes characterize a vertebral arch? 39-3 A typical vertebral arch is characterized by at least seven processes: four articular, two transverse, and one spinous. Lumbar vertebrae have small, additional (mamillary and accessory) processes. The axis has an odontoid process (the dens) but no superior articular processes (merely facets). The atlas has only transverse processes. 39-4 Where are the intervertebral foramina and what do they contain? 39-4 The intervertebral foramina are between adjacent pedicles, and typically each contains a spinal ganglion and a ventral root (or rootlets) of a spinal nerve (see fig. 41-3 ). 39-5 Between which vertebrae does the C8 nerve emerge? 39-5 C8 nerve root emerges between C7 and T1 vertebrae.

Hence the remaining spinal nerves below leave inferior to the correspondingly numbered vertebrae. 39-6 What are the key features of the cervical, thoracic, lumbar, and sacral vertebrae? 39-6 The key features of cervical, thoracic, lumbar, and sacral vertebrae are, respectively, foramina transversaria, articulation with ribs, absence of both of the above features, and fusion. 39-7 How many dorsal vertebrae are present in the body? 39-7 All 33 vertebrae are dorsal. Twelve are thoracic. 39-8 What is the pars interarticularis? 39-8 The pars interarticularis, visible on oblique radiographs of the lumbar vertebrae (see fig. 39-9 ), is the part of the neural arch between the superior and inferior articular processes. The slipping forward of a vertebral body (e.g., L5) is termed spondylolisthesis (Gk, vertebral slipping) and usually involves fracture at the pars interarticularis. Case Report.

A 50-year-old nurse complained of numbness of the right big toe, a burning pain down the lateral side of the right leg and foot, bowel and bladder problems, and weakness of the lower limbs. She developed a marked depression over the spinous process of L5. At operation, spondylolisthesis of L5 on S1 was found, with defective partes interarticulares of L5 and protrusion of the L4/5 disc. The leg pains were caused by compression of L5 nerve roots from alterations of the L5/S1 facets. Bowel and bladder difficulties were produced by compression of the cauda equina from gross distortion of the vertebral canal. Decompression by removal of some bone near the pedicles relieved the symptoms (G. Austin, The Spinal Cord, Thomas, Springfield, Illinois, 1961). Numerous case studies on anatomy have been described by E. Lachman (Case Studies in Anatomy, 3rd ed., Oxford University Press, New York, 1981) and also by L. K. Schneider (Anatomical Case Histories, Year Book, Chicago, 1976).

39-9 What are the chief contents of the sacral canal? 39-9 The sacral canal contains the dura, cauda equina, and filum terminale. Above S2, a subarachnoid space is also present (see fig. 41-1 ). 39-10 What is the ossific status of a typical vertebra at birth? 39-10 At birth, a typical vertebra shows three primary ossific areas, one for the centrum and one for each half of the neural arch. (The centrum does not correspond to the whole of the body: see fig. 39-14 .) The three primary areas become united by bone in early childhood (3 to 6 years). A number of secondary centers (the ring epiphyses and centers for the tips of the transverse and spinous processes) appear at about puberty. 39-11 How is surgical access to the spinal cord achieved? 39-11 Surgical access to the spinal cord and nerve roots is achieved by sectioning the laminae (laminectomy) on each side of several vertebrae. 39-12 What is spina bifida?

39-12 Spina bifida is a developmental anomaly in which the halves of one or more neural (future vertebral) arches have failed to fuse. The spinal cord and meninges (myelomeningocele), or the meninges alone (meningocele), may protrude through the defect (spina bifida cystica). When the defect is skeletal rather than neural, it is termed spina bifida occulta; this defect is found in the sacrum in approximately one fifth of the general population (A. C. Berry, J. Anal., 120:519,1975), although the incidence is minute in certain peoples (J. I. Levy and C. Freed, J. Anal., 114:449, 1973). 39-13 Which Latin and Greek roots are used with reference to the vertebral column? 39-13 The Latin roots spino- and vertebro- are used with reference to the vertebral column (e.g., in spinotransverse and vertebrocostal).

Greek roots with a similar significance are spondyl- and rhachi- (e.g., in spondylolisthesis and rachischisis, the latter meaning "vertebral cleft" and used for an open spina bifida, especially one that extends along many vertebrae). Figure legends Figure 39-1 The primary (1, thoracic; 2, sacral) and secondary (3, cervical; 4, lumbar) curvatures of the vertebral column. Figure 39-2 The parts of a vertebra (T.V.6) seen from above and from the right side. Adjacent intervertebral notches form intervertebral foramina for the transmission of nerves. Figure 39-3 The atlas from above. Muscle origins and the superior vertebral artery are shown on the right side. (After Frazer.) Figure 39-4 lateral and posterosuperior views of the axis. Figure 39-5 Various vertebrae from lateral, superior, and posterior aspects. Figure 39-6 The positions, lengths, and directions of (A) the spinous processes and (B) the transverse processes.

The vertebrae in black mark the levels at which a change in direction of curvature occurs. Figure 39-7 Thoracic vertebrae (and C7 and L1). Note the bodies, pedicles, transverse and spinous processes, and costrotransverse joints. (Courtesy of V.C. Johnson, M.D., Detroit, Michigan.) Figure 39-8 Lumbar vertebrae and female pelvis. Figure 39-9 Oblique view of the lumbar vertebrae. Note the very small twelfth rib, the joints between the articular processes ofthe lumbar vertebrae (the arrow indicates the joint between L1 and L2), and the sacrum. In this view the outline of a Scotch terrier is formed by the transverse process (snout, overlapping the vertebral body), the superior articular process (ear), and the inferior articular process (forepaw). The neck of the dog corresponds to the important pars interarticularis, injury to which may result in spondylolisthesis. Figure 39-10 Female sacrum and coccyx. A, Pelvic and, B, dorsal aspects showing muscular and ligamentous attachments.

C, Right lateral aspect in the anatomical position. Figure 39-11 Female and male sacra from above. The superior aspect of the lateral part is the ala. Figure 39-12 Scheme of horizontal sections of vertebrae, showing what are thought to be corresponding parts. Note that the costal element forms a part of the transverse process of a cervical vertebra. It forms the rib in the thoracic region, most of the transverse process in the lumbar region, and the greater portion of the lateral part of the sacrum. In the cervical vertebra, the posterior tubercle of the transverse process should probably also be shaded as part of the costal element. Figure 39-13 Variations in vertebrae. B shows the common arrangement. In A, "cranial shift," a cervical rib articulates with C7 and rib 12 is small. In B, L5 is partially "sacralized" and S5 is partially freed. In C, "caudal shift," rib 12 is large and a small lumbar rib is present.

S1 vertebra is partially "lumbarized" and Co.1 is incorporated into the sacrum. (After Schinz et al.) Figure 39-14 The neural arch and centrum (left half of figure), and the vertebral arch and body (right half). The terms centrum and neural arch refer to those parts of a vertebra ossified from primary centers. The terms vertebral arch and body are descriptive terms generally applied to adult vertebrae. The body of a vertebra includes the centrum and part of the neural arch. The vertebral arch, therefore, is less extensive than the neural arch. Note that the rib articulates with the neural arch and not with the centrum. Figure 39-15 Some surface landmarks of the back. (From Royce, L Surface Anatomy, Davis, Philadelphia, 1965,) * See F. A. Jenkins, Anat. Rec., 164:173-184, 1969.

# The part of a cervical vertebra that corresponds to a rib is probably the transverse process lateral to the foramen transversarium and including the anterior and posterior tubercles as well as the "intertubercular lamella" (or so-called costotransverse bar). See A. J. E. Cave, J. Zool., 177:377-393, 1975. Only the anterior tubercle is shaded in figure 39-12 . Jump to: Lumbar Spine Anatomy, Diagram & Function | Body Maps Written and medically reviewed by the Healthline Editorial Team Co-developed by: In Depth: Lower Back and Superficial Muscles The muscles of the lower back help stabilize, rotate, flex, and extend the spinal column, which is a bony tower of 24 vertebrae that gives the body structure and houses the spinal cord. The spinal cord and its nerves are the means by which the body and brain communicate with one another. Together, the brain and spinal cord make up the central nervous system.

The spine’s four sections, from top to bottom, are the cervical (neck), thoracic (abdomen,) lumbar (lower back), and sacral (toward tailbone). Throughout the spine, intervertebral discs made of cushioning material both pad and connect the vertebrae. The lumbo-sacral spine includes: Lumbar vertebrae: Numbered L1 through L5, these odd-shaped vertebrae signal the end of the typical bones of the spinal column. Sacrum: This triangle-shaped bone is made up of five fused vertebrae. It fits like a wedge into the back of the pelvis at the hips. Coccyx: This small bone is better known as the tailbone. Muscles connect to the vertebrae and bones via ligaments, flexible bands of fibrous tissue. The deep muscles of the back fit into or affix parts of themselves to the grooves in the spinous processes, or the protrusion of the bone than can be felt through the skin. Important muscles of the lumbar spine include: Multifidus: This long muscle travels nearly the entire length of the back. It stabilizes and rotates the lumbar spine.

Longissimus: Another long muscle, this one begins in the middle of the lumbar spine and continues up to the transverse process. Spinalis: This superficial muscle begins as a thick tendon from the sacrum and travels up into the neck, inserting at the spinous processes of the cervical vertebrae. Lower back pain is a common ailment. This can arise for reasons ranging from improper posture to a compression fracture. Lower back issues can put pressure on the lumbar spine nerves and create even stronger pain as the nerves become pinched or irritated from friction. Some common causes of reoccurring lower back pain include: Muscle injury, which can occur from overuse or a sudden injury Fractured vertebrae Herniated disc, or damage to the cushioning between vertebrae Spinal stenosis, or narrowing of the spinal canal Osteoarthritis, a degenerative bone disease Debugging Tools How Many Vertebrae Does a Human Being Have? Test What You Know! Follow Us How Many Vertebrae Does a Human Being Have? Test What You Know! The human vertebral column comprises 33 vertebrae that collectively protect the spinal cord and support the entire skeletal framework of the body.

The current article provides a brief description of the number of vertebrae in humans beings along with their respective location. Advertisement Gravity makes you look shorter! Gravitational force compresses your vertebral column, and it can elongate by 2-3 inches in the absence of gravity. The vertebral column (backbone or spine) is a characteristic feature of vertebrates. Extending from the base of the skull to the pelvis, it forms the axis of their skeletons. It is made up of individual units called vertebrae, within which the spinal cord is enclosed. This structure provides protection to the spinal cord, and also influences the overall posture of the animal. Other functions include structural support for head, shoulders and chest; as well as balance and weight distribution for maintaining flexibility and mobility. The vertebral column of an adult human being is composed of 33 vertebrae, of which 24 are known as articulating or movable vertebrae, and are separated from each other by an intervertebral disc. The remaining 9 vertebrae lack the intervertebral disc and form two sets of fused structures. The total length of an adult vertebral column is about 71 cm in men and about 61 cm in women.

Do you know how many vertebrae does a human being have? Classified into five categories depending on their location in the body, the total number of vertebrae in human beings are: ♦ Cervical: 7 (C1 to C7) ♦ Thoracic: 12 (T1 to T12) ♦ Lumbar: 5 (L1 to L5) ♦ Sacral: 5 (S1 to S5, fused) ♦ Coccygeal: 4 (Co1 to Co4, fused) Total number = 33 A detailed account of the number of vertebrae in human beings as well as their names and characteristics have been provided below. Cervical (n = 7) Numbered as C1 to C7, the cervical vertebrae are present in the neck region with C1 present closest to the skull. These are smaller as compared to the other articulating vertebrae. C1 or atlas is the topmost vertebra of the spinal column, and supports the head. It freely rotates over a pivot formed by the next vertebra C2 which is termed axis or epistropheus.

Together, the atlas and axis form the joint through which the skull and spine are connected. The next four vertebrae, C3 to C6, share a similar structure, and have short and bifid spinous processes. The last vertebra in this region, C7, has long and prominent spinous process, and hence is also called vertebra prominens. Spinous process is the region for attachment of muscles and ligaments. Thoracic (n = 12) These are present in the chest region, and are designated as T1 to T12. These vertebrae have special facets for the attachment of ribs. The vertebral bodies are heart-shaped and intermediate in size as compared to the cervical and lumbar vertebrae. Being attached to the rib cage they provide lesser flexibility. Lumbar (n = 5) The five lumbar vertebrae are present in the lower back region between the rib cage and the pelvis, and are termed L1 to L5. They enable flexion and extension movements, and help to support body weight. The vertebra body is larger than the cervical and thoracic vertebrae, and is kidney-shaped.

The fifth lumbar vertebra or L5, is generally the largest of all vertebrae. Sacral (n = 5) Sacrum is a triangular, shield-shaped bony structure present below the lumbar vertebrae, and forms the posterior pelvic wall. It supports and strengthens the pelvis. The sacrum is formed by the fusion of 5 (sometimes 6) vertebrae known as the sacral vertebrae named as S1 to S5. Initially they exist as separate vertebrae, and begin to fuse after the age of 18. The fusion completes between the ages of 25 to 33. Coccygeal (n = 4) The last segment of the vertebral column is a structure called coccyx or tailbone, and represents a vestigial tail in humans. It is formed by the fusion of four small vertebrae designated as Co1 to Co4. Similar to the sacral vertebrae, these vertebrae too exist separately in the first two decades of life. The coccyx serves as an anchor for certain pelvic muscles and ligaments.

The supporting structure called vertebral column is thus made up of 26 bones including 24 vertebrae and a sacrum and coccyx. Reshma Jirage The Vertebral Column - Joints - Vertebrae - Vertebral Structure The Vertebral Column Last Updated: December 23, 2016 Contents The vertebral column is a vertical series of approximately 33 small bones (known as vertebrae), which are separated by intervertebral discs. It can be separated into five different regions, with each region characterised by a different vertebral structure. In this article, we shall look at the anatomy of the vertebral column – its structure, joints and ligaments. Functions The vertebral column has four main functions: Protection – encloses and protects the spinal cord within the spinal canal. Support – carries the weight of the body above the pelvis. Axis – forms the central axis of the body. Movement – has roles in both posture and movement. Adapted from work by Pereru [CC BY-SA 3.0], via Wikimedia Commons Fig 1 – The vertebral column viewed from the side. The five different regions are shown and labelled.

Vertebral Structure All vertebrae share a basic common structure. They each consist of a vertebral body, situated anteriorly, and a posterior vertebral arch. Vertebral Body The vertebral body is the anterior part of the vertebrae. It is the weight-bearing component, and its size increases as the vertebral column descends (having to support increasing amounts of weight). The superior and inferior aspects of the vertebral body are lined with hyaline cartilage. Adjacent vertebral bodies are separated by a fibrocartilginous intervertebral disc. © 2015-2016 TeachMeAnatomy.com [CC-BY-NC-ND 4.0] Fig 1.2 – Herniation of an intervertebral disc. The intervertebral disc is a fibrocartilaginous cylinder that lies between the vertebrae, joining them together. They act to permit the flexibility of the spine, and also act as a shock absorber. In the lumbar and thoracic regions they are wedge shaped, supporting the curvature of the spine. There are two regions in the vertebral disc; the nucleus pulposus and annulus fibrosus.

The annulus fibrosis is tough and collagenous, surrounding the nucleus pulposus. The nucleus pulposus is jelly-like, and is located posteriorly. In a herniation of the intervertebral disc, the nucleus pulposus ruptures, breaking through the annulus fibrosus. This most commonly occurs in a poste, putting pressure on the spinal cord, resulting in a variety of neurological and muscular symptoms. Vertebral Arch The vertebral arch refers to the lateral and posterior parts of the vertebrae. With the vertebral body, the vertebral arch forms an enclosed hole, called a vertebral foramen. The foramina of the all vertebrae line up to form the vertebral canal, which encloses the spinal cord. The vertebral arches have a number of bony prominences, which act as attachment sites for muscles and ligaments: Pedicles: There are two of these, one left and one right. They point posteriorly, meeting the flatter laminae. Lamina: The bone between the transverse and spinal processes. Transverse processes: These extend laterally and posteriorly away from the pedicles. In the thoracic vertebrae, the transverse processes articulate with the ribs.

Articular processes: At the junction of the lamina and the pedicles, superior and inferior processes arise. These articulate with the articular processes of the vertebrae above and below. Spinous processes: Posterior and inferior projection of bone, a site of attachment for muscles and ligaments. Fig 1.3 – Superior view of a lumbar vertebrae, showing its characteristic features. Classifications of Vertebrae Fig 1.3 – Distinguishing features of a cervical vertebrae. Note the triangular shape of the vertebral foramen. There are seven cervical vertebrae in the human body. They have three main distinguishing features: The spinous process bifurcates into two parts, and so is known as a bifid spinous process. There are two transverse foramina, one in each transverse process. These conduct the vertebral arteries. The vertebral foramen is triangular in shape There are some cervical vertebrae that are unique. C1 and C2 (called the atlas and axis respectively), are specialised to allow for the movement of the head. The C7 vertebrae has a much longer spinous process, which does not bifurcate. For more on the cervical spine, click here .

Thoracic Vertebrae The twelve thoracic vertebrae are medium-sized, and increase in size as they move down the back. Their main function is to articulate with ribs, producing the bony thorax . Each thoracic vertebrae has two ‘demi facets‘ on each side of its vertebral body. These articulate with the head of the respective rib, and the rib inferior to it. On the transverse processes of the thoracic vertebrae there is a costal facet for articulation with its respective rib. The spinous processes are slanted inferiorly and anteriorly. This offers increased protection to the spinal cord, preventing an object like a knife entering the spinal canal through the intervertebral discs. In contrast to the cervical vertebrae, the vertebral foramen is circular. For more on the thoracic spine, click here . Fig 1.3 – Lateral view of a thoracic vertebrae. Lumbar Vertebrae These are the largest of the vertebrae, of which there are five. They act to support the weight of the upper body, and have various specialisations to enable them do this. Lumbar vertebrae have very large vertebral bodies, which are kidney-shaped.

They lack the characteristic features of other vertebrae, with no transverse foramina, costal facets, or bifid spinous processes. However, like the cervical vertebral, they have a triangular shaped vertebral foramen. Sacrum and Coccyx © 2015-2016 TeachMeAnatomy.com [CC-BY-NC-ND 4.0] Fig 1.4 – Diagram of the sacrum and coccyx, articulating with the pelvic bones The sacrum is a collection of five fused vertebrae. It is described as an upside down triangle, with the apex pointing inferiorly. On the lateral walls of the sacrum are facets, for articulation with the pelvis at the sacro-iliac joints. The coccyx is a small bone, which articulates with the apex of the sacrum. It is recognised by its lack of vertebral arches. Due to the lack of vertebral arches, there is no vertebral canal, and so the coccyx does not transmit the spinal cord. Joints For every vertebrae, there are five articulations. The vertebral bodies indirectly articulate with each other, and the articular processes also form joints.

The vertebral body joints are cartilaginous joints, designed for weight-bearing. The articular surfaces are covered by hyaline cartilage, and are connected by a fibrocartilage intervertebral disc. There are two ligaments that strengthen these joints; the anterior and posterior longitudinal ligaments. The anterior longitudinal ligament is thick and prevents hyperextension of the vertebral column. The posterior longitudinal ligament is weaker and prevents hyperflexion. The joints between the articular facets are called facet joints. These allow for some gliding motions between the vertebrae. They are strengthened by various ligaments: Ligamentum Flavum: extends from lamina to lamina. Interspinous and Supraspinous ligaments: These join the spinous processes together. The interspinous ligaments attach between processes, and the supraspinous ligaments attach to the tips. Intertransverse ligaments: extends between transverse processes. Clinical Relevance: Abnormal Morphology of the Spine Fig 1.5 – Radiograph of scoliosis of the spine.

There are several clinical syndromes resulting from an abnormal curvature of the spine: Kyphosis: Excessive thoracic curvature, causing a hunchback deformity. Lordosis: Excessive lumbar curvature, causing a swayback deformity. Scoliosis: A lateral curvature of the spine, usually of unknown cause. Cervical Spondylosis: A decrease in the size of the intervertebral foramina, usually due to degeneration of the joints of the spine. The smaller size of the intervertebral foramina puts pressure on the exiting nerves, causing pain.

Question: The lumbar region of the human body contains how many vertebrae?
Answer: 5