vertebral column | anatomy | Britannica.com Vertebral column Alternative Titles: backbone, spinal column, spine Related Topics human body Vertebral column, also called spinal column, spine, or backbone, in vertebrate animals, the flexible column extending from neck to tail, made of a series of bones, the vertebrae. The major function of the vertebral column is protection of the spinal cord; it also provides stiffening for the body and attachment for the pectoral and pelvic girdles and many muscles. In humans an additional function is to transmit body weight in walking and standing. Human vertebral column. Encyclopædia Britannica, Inc. Each vertebra , in higher vertebrates, consists of a ventral body, or centrum, surmounted by a Y-shaped neural arch. The arch extends a spinous process (projection) downward and backward that may be felt as a series of bumps down the back, and two transverse processes, one to either side, which provide attachment for muscles and ligaments. Together the centrum and neural arch surround an opening, the vertebral foramen, through which the spinal cord passes.

The centrums are separated by cartilaginous intervertebral disks, which help cushion shock in locomotion. Vertebrae in lower vertebrates are more complex, and the relationships of their parts to those of higher animals are often unclear. In primitive chordates (e.g., amphioxus, lampreys) a rodlike structure, the notochord , stiffens the body and helps protect the overlying spinal cord. The notochord appears in the embryos of all vertebrates in the space later occupied by the vertebral bodies—in some fish it remains throughout life, surrounded by spool-shaped centrums; in other vertebrates it is lost in the developed animal. In primitive chordates the spinal cord is protected dorsally by segmented cartilages—these foreshadow the development of the neural arch of true vertebrae. Fish have trunk and caudal (tail) vertebrae; in land vertebrates with legs, the vertebral column becomes further subdivided into regions in which the vertebrae have different shapes and functions.

Crocodilians and lizards, birds, and mammals demonstrate five regions: (1) cervical , in the neck, (2) thoracic, in the chest, which articulates with the ribs, (3) lumbar, in the lower back, more robust than the other vertebrae, (4) sacral, often fused to form a sacrum , which articulates with the pelvic girdle , (5) caudal, in the tail. The atlas and axis vertebrae, the top two cervicals, form a freely movable joint with the skull . Similar Topics The Spinal Column The Spinal Column Other The Spinal Column The spine (also called the vertebral column or spinal column) is composed of a series of bones called vertebrae stacked one upon another. There are four regions of the spine: cervical (neck) lumbar (low back) sacral (pelvic) The cervical spine is made up of seven cervical vertebrae. The main function of the cervical spine is to support the weight of the head which is approximately 10-12 pounds. The cervical spine has the greatest range of motion, in part because of two specialized vertebra that move with the skull.

Cervical vertebrae are the smallest of the vertebrae. The first cervical vertebra is called the atlas and is significantly different from the other vertebrae. It is ring-like in shape with two large protrusions on the sides to support the weight of the head. The second cervical vertebra is called the axis.The axis is also unique in that it has a bony peg-like protrusion, called the dens or odontoid on its upper surface that fits within the ring of the atlas. The curve of the neck is described as a lordosis or lordotic curve, and looks like a “C” in reverse. The main function of the thoracic spine is to protect the organs of the chest, especially the heart and lungs. There are 12 thoracic vertebrae with one rib attached on each side, to create a thoracic cage, which protects the internal organs of the chest. The thoracic spine has a normal kyphosis, or “C” curve. The thoracic spine is less mobile than the cervical and lumbar spine because of the thoracic cage. The lumbar spine has five lumbar vertebrae, which are the largest vertebrae.

These vertebrae are also aligned in a reverse “C” like the cervical spine, creating a normal lumbar lordosis. The five lumbar vertebral bodies are the weight-bearing portion of the spine and are the largest in diameter compared to the thoracic and cervical vertebral bodies. They sit atop the sacrum, which is formed by five vertebrae fused together into a solid unit. There are usually no identifiable disc spaces between the sacral segments. At the end of the spinal column is the coccyx or tailbone. Most people have 33 vertebrae in total, although there may be 32 or 34. Variations are usually found in the lumbar or sacral regions. Vertebral column - CreationWiki, the encyclopedia of creation science Vertebral column Jump to: navigation , search The human vertebral column is a vital and complex component of the skeletal system that provides movement of the back and neck, and protection for the spinal cord. It is composed of multiple individual bones called vertebrae that are stacked one on top of the other forming a column, which is anatomically divided into five categories.

One of its major purposes is to protect the spinal cord (or spine) and the nerves that run through it, which are vital to the body's central nervous system . These nerves travel through a canal made by the vertebral foramen within the vertebrae. Due to its complexity and frequent use, this important piece of equipment is subject to complications related to several disorders and injuries. Many of the problems that occur are due to nerve compression by bones or muscles within the spine. Contents 9 External Links Function The skeleton is the body’s main support system and source of movement. The skeleton is divided into two major sections the axial and appendicular skeleton. The appendicular skeleton is the portion that attaches to the axial part of the body and has limbs attached to it. The axial skeleton is the portion that houses the vertebral column. Its function is to support and protect the head, neck, and trunk. The vertebral column has many important functions within the body. It is a source of protection for the spinal cord, a vital part of the body’s nervous system. It also plays a role in movement, specifically the body’s flexibility.(Wile, p80&87) Each of the bones has specific functions.

Like other bones in the body, the vertebrae produce red blood cells, are a source of mineral storage, protect organs and the spinal cord, attach ligaments, tendons, and muscles, act as a structural support, and provide flexibility and motion. [1] While the outer part of the vertebra is made up of cortical bone the inside consists of cancellous, or spongy, bone. The dense cortical bone is strong and solid and can protect the bone. The cancellous bone is made up of loosely knit structures. Inside the bone is bone marrow that forms red and white blood cells. [2] Human vertebral column. See: human skeleton . Ligaments in the spine attach the bones to each other and provide the vertebral column with a brace to protect from injuries. Such injuries include hyperextension and hyperflexion. As the body rests and as it moves it gives joints its stability. [3] The tendons are accountable for attaching muscles to the vertebra bones. These retain a certain elasticity to them because of the fibrous bands that make them up. They are a band of densely packed collagen fibers. [4] Muscles in the spine make up a very complex system made up of several different muscle types.

These muscles play a vital role in the movement of the upper body by flexing, rotating, and extending. It also provides the vertebral column with a great amount of support and stability. [5] Column The vertebral column consists of four main regions. The cervical vertebrae are primarily for the neck as it moves and supports the head. It can be divided into two parts, the upper and lower parts. The upper part consists of two vertebrae called the atlas and axis. The atlas is formed specifically to support the head. It has a ring shape and looks different than other vertebrae. The posterior and anterior arches combine two lateral masses that form the atlas bone. The axis provides the head with movement by allowing it to pivot. It has a dens, or odontoid, process that projects upward and connects with the atlas. [6] The thoracic vertebrae supports the chest cavity of the body. They join with the rib cage as it wraps around the cavity. The only ribs that are not attached are the eleventh and twelfth, which are called floating ribs. The size of each bone increases from top to bottom. Unlike the cervical vertebrae, they are more limited as far as movement is concerned.

Each vertebra in this portion has a large intervertebral foramen for nerves, a long spinous process, and small pedicles. [7] The lumbar vertebrae supports the lower back. Just like the thoracic vertebrae, they too increase in size from top to bottom. Being at the bottom of the vertebral column, they support much of the weight. They also obtain a lot of biomechanical stress. They have long and wide pedicles and the spinous processes are different from the others in that they are horizontal and square shaped. Despite the fact that the intervertebral foramen are also large, nerve compression is common within the lumbar vertebrae. [8] The sacrum is located within the pelvic girdle and is made up of five separate bones that fuse together as a person matures. At the very end of the vertebral column is the coccyx, which is also a part of the pelvic girdle. It is made up of three bones and is commonly known as the tailbone. [9] Vertebra The structure of a vertebra. The vertebral column is a combination of several bones stacked on top of each other in a vertical fashion.

It is divided into five separate sections as noted above, each consisting of a different type of vertebra bone, called the cervical vertebrae, thoracic vertebrae, lumbar vertebrae, a sacrum, and a coccyx. The very first set is the cervical vertebrae which has seven bones. Being at the top of the spine, its main function is to support the head and the neck. Next, the thoracic vertebrae contain twelve vertebrae. It houses the body’s major organs and connects with the ribs within the thoracic cage. The lumbar vertebrae has five vertebrae too. Its purpose is to support the upper body regions such as the torso and the lower back. The lumbar and cervical vertebrae allow spinal nerves to enter and exit the spine. (Wile, p87-90) There are many intricate parts that make up each vertebra and its support system. The intervertebral disks serve two main functions within the vertebral column. First, it is located between each vertebra and helps to support it while keeping each of them connected. Because of its unique location, it helps to keep the bones from rubbing against the other.

The body of the vertebra is used to support the weight of the vertebral column. It is a major portion of the vertebra and takes up a significant section. The vertebral foramen is the continuous hole through which the spinal cord will travel through from when it enters to when it exits. This foramen is surrounded by a vertebral arch. (Wile, p87-90) There are also several processes that also pertain to each vertebra which give it the ability to move. The transverse process is found on either side of the vertebra. The spinous process, on the other hand, is found on the posterior side and slants downward. This is what a person can see and feel in the middle of their back. The muscles that correspond with this process impacts most of the spine's movement. The superior articular process and the inferior articular process work together for a common function. The superior articular process is found in the posterior region pointing up, while the inferior articular process is found, although posteriorly, on the underside at the base of the spinous process. Their names are thus because of their locations the superior, above, process and the inferior, below, process.

Together they overlap one another when the vertebrae are stacked. This allows the spine to move fluidly as they correspond with each other and also adding firmness. (Wile, p87-90) The annulus fibrosus is a sturdy structure that surrounds the nucleus pulposus, a gel-like center. The annulus fibrosus aids in spinal rotation, structural stability, and compressive stress. It is a combination of water and elastic collagen fibers. Its center, the nucleus pulposus, allows stress and weight to be distributed throughout the vertebra. It is made up of water, collagen, and proteoglycans. [10] The human vertebral column is a combination of both convex, kyphotic, and concave, lordotic, curves. [11] This arrangement of arcs provide the body with a spring that will help in impact absorption as the body moves. Depending on the view the cervical and lumbar vertebrae have a convex, or concave, curve, while the thoracic vertebrae and sacrum have a concave, or convex curve. These curves are not always present within the human body; they must take time to fully develop.

At birth the vertebral column is made up of a single concave curve. When the baby reaches two month of age it will develop the convex curve of the cervical vertebrae because the baby will need support as it lifts its head. At six months, as the baby learns to sit up, the convex curve of the lumbar vertebrae develops. (Wile, p87-88) Skull The vertebral column is the support system for the skull . The first cervical vertebra is connected to the base of the skull. Between the skull and the vertebra there are many neurological and vascular structures including an enormous amount of nerves , blood vessels, and ligaments crossing throughout that junction. A hole in the base of the skull, the foramen magnum, is where the spinal cord exits the cranium and aligns with the intervertebral foramen to enter into the spine. On either side of the foramen magnum there are two occipital condyles. These kidney shaped organs are attached to the articular facets of the atlas of the cervical vertebrae. Its main function is for balance. The ligament and muscles serve to not only hold the head to the body, but to keep the head perpendicular to the spine.

A big concern comes when the skull displaces from the vertebra as a result of a strike on the head. When this happens the nerves and blood vessels are at risk of becoming compressed by the muscles and ligaments which spasm in reaction to the hit. As a consequence there may become muscle problems, biomechanical changes in the spine, postural changes, and dysfunction in organs . [12] Spinal Cord This is a portion of the vertebral column. The spinal cord is a cylindrical structure that is held within the vertebral column. In combination with the brain, together they make up the central nervous system . It carries nerve impulses between the brain and the spinal nerves. [13] The spinal cord is responsible for several different functions within the body. These include transmissions of nerve impulses, sensory signals from peripheral regions to the brain, motor signals from the brain back to the peripheral regions and spinal reflexes, sensory information, and the response through motor impulses that control muscles. The spinal cord is basically an extension of the brain stem. From the brainstem it travels from the foramen magnum in the skull down to the first lumbar vertebra. When it tapers off, the tip of the cord is then called the conus medullaris.

As it runs through the vertebral column it is held in place by the denticulate ligaments. These ligaments are extensions of the pia mater, which are attached to the dural sheath, that run laterally. At the end it is then stabilized by the filum terminale, which is attached to the coccyx in the pelvic girdle by extension of the pia mater. The spinal cord is where several branches of spinal nerves join together by roots. The ventral roots and dorsal roots are the two main roots in the spinal cord. On the ventral side of the spinal cord, the ventral roots contain motor nerve axons and send nerve impulses from the spinal cord to the different skeletal muscles. On the dorsal side of the spinal cord, the dorsal root holds sensory nerve fibers. It is also responsible for transmitting nerve impulses from the peripheral regions to the spinal cord. [14] There are several different nerves that course throughout the vertebral column. They make up a total of thirty-one pairs of spinal nerves. [15] These include eight pairs of cervical nerves that run through the head and neck to the shoulders, arms, and hands.

Twelve pairs of thoracic nerves which attach the upper areas of the abdomen and the muscles in the chest and back. Five pairs of lumbar nerves are responsible for producing nerves to the lower section of the back and to the legs. The five pairs of sacral nerves assist the lower sectors of the body such as the buttocks, anal and genital regions, legs, and feet. The dermatomes’ job is to supply the surface of the skin with nerve fibers from a single spinal root. [16] Spinal nerves exit the spinal cord by two means; these being the ventral root and the dorsal root. The first pair emerges from in between the occipital bone of the skull and the atlas of the spinal column. The remaining nerves come through the intervertebral foramen that rests in the center of each vertebra. The ventral and dorsal roots rest on both sides of the spinal cord. As the nerves exit the spinal column they divide up into several different branches: the dorsal ramus, ventral ramus, meningeal brach, and rami communicantes. The functions for each are specialized for specific portions of the body.

For example, the dorsal ramus is responsible for the dorsal section of the trunk of the body, while the ventral ramus is responsible for the ventral half of the body plus the upper and lower limbs. The ventral rami will conjoin together to form a network of interconnecting nerves that is called plexus. The plexus has fibers that are obtained from the spinal nerves and travel to one specific destination.The meningeal branch will go back into the vertebral column where is will assist the meninges, which are membranes that enclose the central nervous system that consist of the dura mater, the arachnoid mater and the pia mater, and the blood vessels within the vertebra. The rami communicantes will take care of the visceral functions such as heart rate, blood pressure, and respiration. [17] Injury There are multiple different injuries that the spinal column is susceptible to during a person’s lifetime. The most common of these are caused by three main reasons that cause severe pressure to be applied to the spine: longitudinal compression, hinging, and shearing. Longitudinal compression results when a person falls when landing hard on their feet.

This action puts immediate pressure on the bones in the spine by crushing the vertebra lengthwise against one another. Hinging results in cases such as whiplash when a person is in a situation where there is acceleration and then a sudden and violent recoil in motion. Shearing is the consequence of a fall when the body is pushed over with a great amount of force. The effects of shearing are actually caused by a combination of both hinging and excessive twisting of the spine. These three forms of abnormal pressure on the spine may cause dislocation to the vertebrae, fractures, and ruptured ligaments. Minor cases will only result in pain and swelling. In more severe cases the spinal cord may become a factor with nerve functions being affected and possibly cut off. [18] Herniated disc Diagram of a herniated disc. A herniated disc is caused by a crack in the annulus fibrosus, the outer layer. The vertebral disc is made up of strong connective tissues. Its function is to support the vertebral column by holding it together and to act as a cushion between each vertebra. When a person grows older the disk begins to lose its water content which is the main component that acts as padding between the bones in the spine.

When this happens it opens the window for problems such as displacement of the disc center. This displacement becomes a herniated, or ruptured, disc. Most of the trunk of the body’s weight puts pressure on the lower vertebrae, the lumbar vertebrae. Because of all the weight, herniated discs are common in the lower lumbar vertebrae, such as the two lumbar discs that are located at and below the waist. These complications lead to even more problems involving the nerves. When nerves are compressed by the bones in the spine it can cause numbness, tingling, pain, weakness in the legs, and back pains. These symptoms are the consequence of sciatica. Sciatica is an additional condition that occurs in 1-2% of people between the ages of 30-50. [19] For people with herniated discs there are multiple treatment options available. Those with minor problems are 80-90% likely to have no need for any surgical operations. When these occurrences become apparent the first few weeks will generally be on an observational basis.

Some other non-surgical options available are resting, anti-inflammatory medications, analgesic drugs for the pain, physical therapy, exercise, or epidural steroid injection therapy. The goals for these treatments are to relieve some of the irritation caused to the nerves and to improve the overall physical condition of the disc. By strengthening the disc it will help protect and stabilize the vertebral column and increase its overall usage. If surgery does become necessary, the success rate is in the 90+ percentile in relieving leg pains. The surgery is only responsible for decreasing the pain and weakening of the muscles, but it will not return any lost leg strength. Although it may help relieve some of the back pains, their overall success rate is not as high. The main purpose of the surgery is to cut down nerve irritation by fixing any compression (discectomy or partial discectomy) and removing part of the herniated disc. By taking a surgical standpoint there are always complications that may arise. In this particular case, bleeding, tearing, and infection are common after effects of surgery. In addition, 5% of all patients will experience another rupture of the disc following the first.

[20] Spinal cord injury surgery Main Article: Scoliosis Scoliosis is a disorder in the spine where there is an abnormal curve to the vertebral column. While normal vertebral columns have a convex and a concave curve, a person with scoliosis will have additional curves to either of its sides. This accumulation of curves will create a corkscrew effect because of the twisting nature of the bones. This abnormality is often times hereditary, being passed down from generation to generation. It is most often found in females rather than males. The average age when obtaining this oddity is commonly after the age of 10, but it is not restricted to any specific age range. [21] Different forms of scoliosis can be divided into four categories (three specific): functional, degenerative, neuromuscular, and then others. Functional scoliosis is the result of dysfunctions in other parts of the body that disrupt the spine. Degenerative scoliosis is when arthritis takes control of the spine and causes tissues and muscles to weaken in the vertebral column, allowing the spine to curve unnaturally.

Neuromuscular scoliosis is the worst of all because it is the result of a lack of full bone formation or when the vertebrae fail to separate. The other types of scoliosis are generally caused by a benign tumor(s) on the spine. The type of disorder is deciphered upon the individual based on the causes and the age of the person when the curvature began to develop. [22] While professionals have yet to find the cure for this disorder, doctors have designed several treatment options for those seeking medical attention. There are three main treatment options available for patients: observation, bracing, or surgery. The different types of scoliosis will generally have different treatment plans depending on the severity of each case. Treatment for functional types will not affect the spine directly; the only way to fix the spine will be to treat the specific body part that is disturbing the spine. For degenerative cases there are several options such as physical therapy, various exercises, chiropractic, or surgery. If surgery is requested the goal of it would be to decompress or remove the bone spurs that are compressing the nerves or fusion which will help to correct the curve by stabilizing the spine.

Because neuromuscular scoliosis is generally more severe, surgery is most often inevitable for its patients. For other types, specifically those who have tumors, surgery will remove the tumor and correct the spine. [23] Featured Article featured articles . References Wile, Jay L., Shannon, M., The Human Body: Fearfully and Wonderfully Made! Apologia Educational Ministries, Inc. pg. 80, 87-90. Vertebral Column Spine Universe. by Keith Bridwell, MD 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 Spine Anatomy Overview: Spinal Cord, Discs, Nerve Roots, Facet Joints, Ligaments, Muscles The three main functions of the spine are to: Protect the spinal cord, nerve roots and several of the body’s internal organs. Provide structural support and balance to maintain an upright posture. Enable flexible motion. Regions of the Spine Typically, the spine is divided into four main regions: cervical, thoracic, lumbar and sacral. Each region has specific characteristics and functions. Cervical Spine The neck region of the spine is known as the Cervical Spine. This region consists of seven vertebrae, which are abbreviated C1 through C7 (top to bottom). These vertebrae protect the brain stem and the spinal cord, support the skull, and allow for a wide range of head movement. The first cervical vertebra (C1) is called the Atlas.

The Atlas is ring-shaped and it supports the skull. C2 is called the Axis. It is circular in shape with a blunt peg-like structure (called the Odontoid Process or “dens”) that projects upward into the ring of the Atlas. Together, the Atlas and Axis enable the head to rotate and turn. The other cervical vertebrae (C3 through C7) are shaped like boxes with small spinous processes (finger-like projections) that extend from the back of the vertebrae. Thoracic Spine Beneath the last cervical vertebra are the 12 vertebrae of the Thoracic Spine. These are abbreviated T1 through T12 (top to bottom). T1 is the smallest and T12 is the largest thoracic vertebra. The thoracic vertebrae are larger than the cervical bones and have longer spinous processes. In addition to longer spinous processes, rib attachments add to the thoracic spine’s strength. These structures make the thoracic spine more stable than the cervical or lumbar regions. In addition, the rib cage and ligament systems limit the thoracic spine’s range of motion and protect many vital organs.

Lumbar Spine The Lumbar Spine has 5 vertebrae abbreviated L1 through L5 (largest). The size and shape of each lumbar vertebra is designed to carry most of the body’s weight. Each structural element of a lumbar vertebra is bigger, wider and broader than similar components in the cervical and thoracic regions. The lumbar spine has more range of motion than the thoracic spine, but less than the cervical spine. The lumbar facet joints allow for significant flexion and extension movement but limit rotation. Sacral Spine 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. The last lumbar vertebra (L5) articulates (moves) with the sacrum. Immediately below the sacrum are five additional bones, fused together to form the Coccyx (tailbone). The Pelvis and the Skull Although not typically viewed as part of the spine, the pelvis and the skull are anatomic structures that closely inter-relate with the spine, and have a significant impact on the patient’s balance.

Spinal Curves When viewed from the front (Coronal Plane) the healthy spine is straight. (A sideways curve in the spine is known as scoliosis.) When viewed from the side (Sagittal Plane) the mature spine has four distinct curves. These curves are described as being either kyphotic or lordotic. A kyphotic curve is a convex curve in the spine (i.e. convexity towards the back of the spine). The curves in the thoracic and sacral spine are kyphotic. A lordotic curve is concave (i.e. concavity towards the back of the spine), and is found in the cervical and lumbar levels of the spine. Vertebral Structures All vertebrae consist of the same basic elements, with the exception of the first two cervical vertebrae. The outer shell of a vertebra is made of cortical bone. This type of bone is dense, solid and strong. Inside each vertebra is cancellous bone, which is weaker than cortical bone and consists of loosely knit structures that look somewhat like a honeycomb. Bone marrow, which forms red blood cells and some types of white blood cells, is found within the cavities of cancellous bone.

Vertebrae consist of the following common elements: Veterbral Body The largest part of a vertebra. If looked at from above it generally has a somewhat oval shape. When looked at from the side, the vertebral body is shaped like an hourglass, being thicker at the ends and thinner in the middle. The body is covered with strong cortical bone, with cancellous bone within. Pedicles These are two short processes, made of strong cortical bone, that protrude from the back of the vertebral body. Laminae Two relatively flat plates of bone that extend from the pedicles on either side and join in the midline. Processes There are three types of processes: articular, transverse and spinous. The processes serve as connection points for ligaments and tendons. The 4 articular processes link with the articular processes of adjacent vertebrae to form the facet joints. The facet joints, combined with the intervertebral discs, allows for motion in the spine. The spinous process extends posteriorly from the point where the two laminae join, and acts as a lever to effect motion of the vertebra.

Endplates The top (superior) and bottom (inferior) of each vertebral body is “coated” with an endplate. Endplates are complex structures that “blend” into the intervertebral disc and help support the disc. Intervertebral Foramen The pedicles have a small notch on their upper surface and a deep notch on their bottom surface. When the vertebrae are stacked on top of each other the pedicle notches form an area called the intervertebral foramen. This area is of critical importance as the nerve roots exit from the spinal cord through this area to the rest of the body. Facet Joints The joints in the spinal column are located posterior to the vertebral body (on the backside). These joints help the spine to bend, twist, and extend in different directions. Although these joints enable movement, they also restrict excessive movement such as hyperextension and hyper-flexion (i.e. whiplash). Each vertebra has two facet joints. The superior articular facet faces upward and works like a hinge with the inferior articular facet (below).

Like other joints in the body, each facet joint is surrounded by a capsule of connective tissue and produces synovial fluid to nourish and lubricate the joint. The surfaces of the joint are coated with cartilage that helps each joint to move (articulate) smoothly. Intervertebral Discs Between each vertebral body is a "cushion" called an intervertebral disc. Each disc absorbs the stress and shock the body incurs during movement and prevents the vertebrae from grinding against one another. The intervertebral discs are the largest structures in the body without a vascular supply. Through osmosis, each disc absorbs needed nutrients. Each disc is made up of two parts: the annulus fibrosis and the nucleus pulposus. Annulus Fibrosus The annulus is a sturdy tire-like structure that encases a gel-like center, the nucleus pulposus. The annulus enhances the spine’s rotational stability and helps to resist compressive stress. The annulus consists of water and layers of sturdy elastic collagen fibers. The fibers are oriented at different angles horizontally similar to the construction of a radial tire. Collagen gains its strength from strong fibrous bundles of protein that are linked together.

Nucleus Pulposus The center portion of each intervertebral disc is a filled with a gel-like elastic substance. Together with the annulus fibrosus, the nucleus pulposus transmits stress and weight from vertebra to vertebra. Like the annulus fibrosus, the nucleus pulposus consists of water, collagen and proteoglycans. However, the proportion of these substances in the nucleus pulposus is different. The nucleus contains more water than the annulus. The Spinal Cord and Nerve Roots The spinal cord is a slender cylindrical structure about the width of the little finger. The spinal cord begins immediately below the brain stem and extends to the first lumbar vertebra (L1). Thereafter, the cord blends with the conus medullaris that becomes the cauda equina, a group of nerves resembling the tail of a horse. The spinal nerve roots are responsible for stimulating movement and feeling. The nerve roots exit the spinal canal through the intervertebral foramen, small openings between each vertebra. The brain and the spinal cord make up the Central Nervous System (CNS).

The nerve roots that exit the spinal cord/spinal canal branch out into the body to form the Peripheral Nervous System (PNS). Between the front and back portions of the vertebra (i.e. the mid-region) is the spinal canal that houses the spinal cord and the intervertebral foramen. The foramen are small openings formed between each vertebra. These “holes” provide space for the nerve roots to exit the spinal canal and to further branch out to form the peripheral nervous system. Brain Stem Connects the spinal cord to other parts of the brain. Spinal Cord Carries nerve impulses between the brain and spinal nerves. Cervical Nerves (8 pairs) These nerves supply the head, neck, shoulders, arms, and hands. Thoracic Nerves (12 pairs) Connects portions of the upper abdomen and muscles in the back and chest areas. Lumbar Nerves (5 pairs) Feeds the lower back and legs. Sacral Nerves (5 pairs) Supplies the buttocks, legs, feet, anal and genital areas of the body. Dermatomes Areas on the skin surface supplied by nerve fibers from one spinal root.

Ligaments, Muscles and Tendons Ligaments Ligaments and tendons are fibrous bands of connective tissue that attach to bone. Ligaments connect two or more bones together and also help to stabilize joints. Tendons attach muscle to bone. They vary in size and are somewhat elastic. The system of ligaments in the vertebral column, combined with the tendons and muscles, provides a natural type of brace to help protect the spine from injury. Ligaments keep a joint stable during rest and movement. Further, ligaments help to prevent injury from hyper- extension and flexion movements. Anterior Longitudinal Ligament (ALL) Primary spine stabilizer. About one inch wide, the ALL runs the entire length of the spine from the base of the skull to the sacrum. It connects the front (anterior) of the vertebral body to the front of the annulus fibrosis. Posterior Longitudinal Ligament (PLL) Primary spine stabilizer. About one inch wide, the PLL runs the entire length of the spine from the base of the skull to sacrum. It connects the back (posterior) of the vertebral body to the back of the annulus fibrosis.

Supraspinous Ligament This ligament attaches the tip of each spinous process to the other. Interspinous Ligament This thin ligament attaches to another ligament, called the ligamentum flavum, that runs deep into the spinal column. Ligamentum Flavum The strongest ligament. This yellow ligament is the strongest one. It runs from the base of the skull to the pelvis, in front of and between the lamina, and protects the spinal cord and nerves. The ligamentum flavum also runs in front of the facet joint capsules. Muscles and Tendons The muscular system of the spine is complex, with several different muscles playing important roles. The primary function of the muscles is to support and stabilize the spine. Specific muscles are associated with movement of parts of the anatomy. For example, the Sternocleidomastoid muscle assists with movement of the head, while the Psoas Major muscle is associated with flexion of the thigh. Muscles, either individually or in groups, are supported by fascia. Fascia is strong connective tissue. The tendon that attaches muscle to bone is part of the fascia.

The muscles in the vertebral column serve to flex, rotate, or extend the spine. Spinal Conditions Dr. Andrew Moulton treats the following conditions. Select a condition from the list below for more information. What does the human backbone protect? | Reference.com What does the human backbone protect? A: Quick Answer The human backbone, also referred to as the vertebral column, protects the spinal cord. The spinal cord serves as a link between the body and the brain, therefore needs protection to prevent irreversible damage, as it is unable to repair itself. Full Answer In an adult, the vertebral column is made up of 26 bones, from the neck all the way down to the sacrum and coccyx. Children have 33 bones as some of the bones within the sacrum and coccyx fuse together during adolescence. Each bone, or vertebrae, of the spine lines up so the spinal cord can pass through the hollow center. There are small gaps between each vertebrae, called "intervertebral canals," where nerves branch off from the spinal cord and connect the brain to the rest of the body.

Unit 2- Vertebral Column, Spinal Cord, Meninges - StudyBlue Good to have you back! If you've signed in to StudyBlue with Facebook in the past, please do that again. Unit 2- Vertebral Column, Spinal Cord, Meninges Unit 2- Vertebral Column, Spinal Cord, Meninges amy s. What does vertebral column consist of? vertebrae 3. has attachments for ribs, muscles, ligaments Advertisement ) present at birth, concave anteriorly thoracic and sacral develop after birth, convex anteriorly cervical and lumbar two processes that connect lamina to body lamina two flattened processes that connect pedicles to spinal processes all the vertebral foramina form the? vertebral canal which contains the spinal cord and meninges superior vertebral notch indentation of the body and superior articular process inferior vertebral notch adjacent superior and inferior vertebral notches what passes thru intervertebral foramen? spinal nerve or posterior/dorsal and anterior/ventral roots characteristics of cervical vertebrae have short anterior and posterior tubercles facets= transverse uncinate process=curved what is special about cv6?

entry point for ventral artery (via the transverse foramen) where the artery will ascend in to the skull atlas widest vertebra that supports occipital condyles of skull at its superior articular process surface/facet has no spinous process or body but anterior and posterior arches small body has transverse foramen and on superior aspect has a groove for the vertebral artery axis strongest of cervical vertebra with bifid spinous process dens/odontoid process which is rotation pt for skull dens held by transverse ligament of atlas thoracic vertebrae spinous processes are long, triangular, and oblique caudally articulates with the ribs-costal surfaces/facets plane of facets=coronal plane rib articulations head of rib=one or more on the body of the vertebrae also on intervertebral disc tubercle of rib=on each transverse process lumbar vertebrae spinous process short, thick, broad, directed posteriorly extra processes for muscle attachment facet=sagittal plane all vertebrae fused into the sacrum=articulates with ilium of the hip spines not prominent -vertebral canal becomes sacral canal anterior and posterior sacral foramina are similar to intervertebral foramina coccyge

al vertebrae vertebral arch incomplete or lacking synovial joints -articular processes of adjacent vertebrae -surrounded by capsular ligaments -surface of articular process is covered with hyaline cartilage called facet intervertebral discs separate bodies of the vertebrae from one another make up under 1/5 of total length of column none between CV1 and CV2 2 parts of intervertebral discs annulus fibrosus=outer portion made up of collagen fibers and fibrocartiledge nucleus pulposus=inner portion is gelatinous and has high water content anterior longitudinal ligament runs on anterior surface of the bodies of the vertebrae from CV1 to the sacrum -starts out narrow and widens as it goes down cord -prevents hyperextension due to fibrous nature posterior longitudinal ligament on posterior surface of the bodies of the vertebrae from the axis to the sacrum found w/in vertebral canal broadens over intervertebral disks and narrows over vertebral bodies ligamentum flavum yellow elastic ligament attaching lamina to lamin of adjacent vertebrae -found w/in vertebral canal -extends transversely from mid-line to articular processes supraspinous ligament strong fib

rous cord, which connects spinous processes of each vertebra from CV7 to sacrum ligamentum nuchae upward extension of supraspinous ligament from CV7 spine to external occipital protuberance midline structure which serves for attachments of muscles capsular ligaments surround synovial joints between adjacent articular processes inferiorly and superiorly interspinous and intertransverse ligaments join?

adjacent spinous and transverse processes atlantooccipital joints articulations btwn superior articular process/lateral masses of CV1 and occipital condyles of the skull anterior and posterior atlantooccipital membranes connect the margins of the foramen magnum of the skull and anterior and posterior arches of CV1 in combo w/ longitudinal band forms the cruciate ligament, holds the dens of C2 against the anterior arch of C1 zygoapophyseal joints are..? zygoapophyseal joints: used for 3 things: 1. mechanical support can form a joint with other vertebrae when stacked they are lateral extensions of vertebral body 3 zygapophysial joints and their mvmt limitations 1. cervical-transverse-flexion and extension laterally 2. thoracic-coronal-flexion, limits extension 3. lumbar-saggital-flexion and extension, cannot rotate too much intervertebral joints: what is the purpose and what makes it up? cushion between vertebrae-thin layer of cartilage 1.

anulus fibrosus what is annulus fibrosus made of collagen fibers and fibrocartiledge rupture or weakining and extrusion of intervertebral disc capsular ligament encapsulates joint and ligament and can contain synovial fluid which lubricates joint Describe Supraspinous ligament and ligamentum nuchae •Supraspinous ligament connects tips of the vertebral spinousprocesses from CVII to the sacrum •CVII up to the skull the ligament becomesstructurally different and is called the ligamentum nuchae •Ligamentum nuchaeis shaped like a triangle the base runs from the occipital protuberance to theforamen magnum. The apex is attached to the tip of the spinousprocess of CVII supraspinal ligament prevents extreme flexion and helps attach several muscles to midline interspinous ligament runs between adjacent spinous processes atlas + axis=? what holds dens in place? transverse ligament=acts as brace what other ligaments hold the dens? alar ligaments The tectorial membrane is a superior extension of the posterior longitudinal ligament.

When the tectorial membrane is reflected posteriorly, the cruiciform and alar ligaments are seen (for bigger pic. see slide 61) articular capsule cruciform ligament of atlas made of...? longitudinal fasicles epidural fat w/epidural veins Denticulate ligament A band of fibrous pia mater extending along the spinal cord on each side between the dorsal and ventral roots of the spinal nerves Pierces the arachnoid and is attached to the dura mater at 21 points Stabilizes the spinal cord within the vertebral canal where to take out CSF and why? between L1 and L2 because we want to avoid spinal cord What vessels supply blood to the spinal cord? Anterior (1) and posterior spinal arteries (2) segmental arteries veins are present as plexus (internal and external) what is nucleus pulposus made of ? gelatinous and high water content what holds bodies of vertebrae and discs together? anterior and posterior longitudinal ligaments Is there an intervertebral disc btwn CV1 and CV2? no anterior and posterior atlantooccipital membranes connect what?

margins of foramen magnum of the skull and the anterior and posterior arches of CV1 transverse ligament of the atlas cruciform ligament formed by bands of the transverse ligament that extend to the body of CV2 Alar ligaments -Paired ligaments on either side of dens, extending to occiput -Limit rotation of atlanto-axial joint tectorial ligament continuation of posterior longitudinal ligament atlantoaxial joints 2 lateral=between superior articular processes/lateral masses of CV1 and CV2 one medial=between dens of CV2 and anterior arch of CV1 permits rotation of skull and CV1 and CV2 as a unit spinal cord is made up of... white and gray matter Thoracic Vertebrae Home > Skeletal System > Spine > Thoracic Vertebrae Thoracic Vertebrae The thoracic vertebrae are a group of twelve small bones that form the vertebral spine in the upper trunk. Thoracic vertebrae are unique among the bones of the spine in that they are the only vertebrae that support ribs and have overlapping spinous processes.

Like all other vertebrae, the thoracic vertebrae help to support the weight of the upper body and protect the delicate spinal cord as it runs through the vertebral canal. The thoracic vertebrae are located in the thorax posterior and medial to the ribs. They form the region of the spinal column inferior to the cervical vertebrae of the neck and superior to the lumbar vertebrae of the lower back.... 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 Thoracic Vertebrae Description [Continued from above] . . . Each thoracic vertebra is named for its position within the spine, from the first thoracic vertebra (T1) on the superior end to the twelfth thoracic vertebra (T12) on the inferior end. The spinal column formed by the thoracic vertebrae protrudes posteriorly to form the convex thoracic curve of the spine.

The thoracic vertebrae are medium in size – larger and thicker than the cervical vertebrae above them, but smaller and thinner than the lumbar vertebrae below. The T1 vertebra is the smallest and closely resembles the cervical vertebrae, while the T12 vertebra is the largest and most similar to the lumbar vertebrae. The intermediate vertebrae all follow the trend of increasing size from superior to inferior as a result of the greater body weight supported by the inferior vertebrae. The bulk of the bony mass of the thoracic vertebrae is located within a cylindrical region known as the vertebral body or centrum. Each thoracic vertebra supports a pair of ribs and contains a pair of smooth, concave joint-forming processes known as facets on its sides. The ribs are anchored to the spine by the planar joints formed between the vertebrae and the ribs. The first nine thoracic vertebrae (T1 through T9) contain a pair of demi-facets, where a facet is split between two adjacent vertebral bodies.

Meanwhile, the first, tenth, eleventh, and twelfth (T1, T10, T11 and T12) vertebrae all contain a pair of full facets on their vertebral bodies to support ribs. T1 is unique among all thoracic vertebrae in supporting two pairs of ribs through a pair of facets and a pair of demi-facets. Between the vertebral bodies of the thoracic vertebrae are the tough, rubbery intervertebral disks. Each disk is made of an outer shell of fibrocartilage known as the annulus fibrosus, which holds the vertebrae in place while providing a small range of motion between them. Inside the annulus fibrosus is the gel-like nucleus pulposus that acts as a soft shock absorber to prevent collisions between the vertebrae. Posterior to the vertebral bodies are thin bony rings known as the vertebral arches. Each vertebral arch surrounds and protects a hollow vertebral foramen that provides space for the spinal cord and spinal nerves. A pair of transverse processes extends from the lateral sides of each vertebral arch to support the ribs and provide attachment sites for the rotatores and multifidus muscles of the back.

At the posterior end of the vertebral arch, each thoracic vertebra extends posteriorly and inferiorly to form the spinous processes. Each spinous process supports several muscles of the back to provide movement to the trunk and spine region. The spinous processes also overlap each other slightly to provide extra support and rigidity to the thoracic region and prevent extraneous movements. Two pairs of articular processes extend superiorly and inferiorly toward the neighboring vertebrae, in order to help stabilize the spine and connect the thoracic vertebrae to one another and to the C7 and L1 vertebrae. Flat planar joints form between the articular processes of these neighboring vertebrae, allowing the bones to move independently while maintaining the strength and stability of the spinal column. The superior articular processes end in smooth surfaces facing posteriorly to meet the articular process of the vertebra above. On the inferior end, the inferior articular processes end in smooth, flat surfaces facing anteriorly to meet the next vertebra.

The T1 and T12 vertebrae are the exceptions to this rule; T1 features a superior articular process resembling those of the cervical vertebrae, while the inferior articular process of T12 resembles those of the lumbar vertebrae. Prepared by Tim Taylor, Anatomy and Physiology Instructor Spine Anatomy, Anatomy of the Human Spine Anatomy of the Human Spine Overview The spine is made of 33 individual bones stacked one on top of the other. This spinal column provides the main support for your body, allowing you to stand upright, bend, and twist, while protecting the spinal cord from injury. Strong muscles and bones, flexible tendons and ligaments, and sensitive nerves contribute to a healthy spine. Yet, any of these structures affected by strain, injury, or disease can cause pain. Spinal curves When viewed from the side, an adult spine has a natural S-shaped curve. The neck (cervical) and low back (lumbar) regions have a slight concave curve, and the thoracic and sacral regions have a gentle convex curve (Fig. 1). The curves work like a coiled spring to absorb shock, maintain balance, and allow range of motion throughout the spinal column.

Figure 1. The spine has three natural curves that form an S-shape; strong muscles keep our spine in alignment. Figure 2. The five regions of the spinal column. The muscles and correct posture maintain the natural spinal curves. Good posture involves training your body to stand, walk, sit, and lie so that the least amount of strain is placed on the spine during movement or weight-bearing activities (see Posture ). Excess body weight, weak muscles, and other forces can pull at the spine's alignment: An abnormal curve of the lumbar spine is lordosis, also called sway back. An abnormal curve of the thoracic spine is kyphosis, also called hunchback. An abnormal curve from side-to-side is called scoliosis. Muscles The two main muscle groups that affect the spine are extensors and flexors. The extensor muscles enable us to stand up and lift objects. The extensors are attached to the back of the spine. The flexor muscles are in the front and include the abdominal muscles. These muscles enable us to flex, or bend forward, and are important in lifting and controlling the arch in the lower back. The back muscles stabilize your spine.

Something as common as poor muscle tone or a large belly can pull your entire body out of alignment. Misalignment puts incredible strain on the spine (see Exercise for a Healthy Back ). Vertebrae Vertebrae are the 33 individual bones that interlock with each other to form the spinal column. The vertebrae are numbered and divided into regions: cervical, thoracic, lumbar, sacrum, and coccyx (Fig. 2). Only the top 24 bones are moveable; the vertebrae of the sacrum and coccyx are fused. The vertebrae in each region have unique features that help them perform their main functions. Cervical (neck) - the main function of the cervical spine is to support the weight of the head (about 10 pounds). The seven cervical vertebrae are numbered C1 to C7. The neck has the greatest range of motion because of two specialized vertebrae that connect to the skull. The first vertebra (C1) is the ring-shaped atlas that connects directly to the skull. This joint allows for the nodding or “yes” motion of the head.

The second vertebra (C2) is the peg-shaped axis, which has a projection called the odontoid, that the atlas pivots around. This joint allows for the side-to-side or “no” motion of the head. Thoracic (mid back) - the main function of the thoracic spine is to hold the rib cage and protect the heart and lungs. The twelve thoracic vertebrae are numbered T1 to T12. The range of motion in the thoracic spine is limited. Lumbar (low back) - the main function of the lumbar spine is to bear the weight of the body. The five lumbar vertebrae are numbered L1 to L5. These vertebrae are much larger in size to absorb the stress of lifting and carrying heavy objects. Sacrum - the main function of the sacrum is to connect the spine to the hip bones (iliac). There are five sacral vertebrae, which are fused together. Together with the iliac bones, they form a ring called the pelvic girdle. Coccyx region - the four fused bones of the coccyx or tailbone provide attachment for ligaments and muscles of the pelvic floor.

While vertebrae have unique regional features, every vertebra has three functional parts (Fig. 3): Figure 3. While vertebrae have unique regional features, every vertebra has three main parts: body (purple), vertebral arch (green), and processes for muscle attachment (tan). a drum-shaped body designed to bear weight and withstand compression (purple) an arch-shaped bone that protects the spinal cord (green) star-shaped processes designed as outriggers for muscle attachment (tan) Intervertebral discs Each vertebra in your spine is separated and cushioned by an intervertebral disc, keeping the bones from rubbing together. Discs are designed like a radial car tire. The outer ring, called the annulus, has criss-crossing fibrous bands, much like a tire tread. These bands attach between the bodies of each vertebra. Inside the disc is a gel-filled center called the nucleus, much like a tire tube (Fig. 4). Figure 4. Intervertebral discs (purple) are made of a gel-filled center called the nucleus and a tough fibrous outer ring called the annulus. The annulus pulls the vertebral bodies together against the resistance of the gel-filled nucleus. Discs function like coiled springs.

The criss-crossing fibers of the annulus pull the vertebral bodies together against the elastic resistance of the gel-filled nucleus. The nucleus acts like a ball-bearing when you move, allowing the vertebral bodies to roll over the incompressible gel. The gel-filled nucleus is composed mostly of fluid. This fluid absorbed during the night as you lie down and is pushed out during the day as you move upright. With age, our discs increasingly lose the ability to reabsorb fluid and become brittle and flatter; this is why we get shorter as we grow older. Also diseases, such as osteoarthritis and osteoporosis, cause bone spurs (osteophytes) to grow. Injury and strain can cause discs to bulge or herniate, a condition in which the nucleus is pushed out through the annulus to compress the nerve roots causing back pain. Vertebral arch & spinal canal On the back of each vertebra are bony projections that form the vertebral arch. The arch is made of two supporting pedicles and two laminae (Fig. 5). The hollow spinal canal contains the spinal cord, fat, ligaments, and blood vessels.

Under each pedicle, a pair of spinal nerves exits the spinal cord and pass through the intervertebral foramen to branch out to your body. Figure 5. The vertebral arch (green) forms the spinal canal (blue) through which the spinal cord runs. Seven bony processes arise from the vertebral arch to form the facet joints and processes for muscle attachment. Surgeons often remove the lamina of the vertebral arch (laminectomy) to access and decompress the spinal cord and nerves to treat spinal stenosis, tumors, or herniated discs. Seven processes arise from the vertebral arch: the spinous process, two transverse processes, two superior facets, and two inferior facets. Facet joints The facet joints of the spine allow back motion. Each vertebra has four facet joints, one pair that connects to the vertebra above (superior facets) and one pair that connects to the vertebra below (inferior facets) (Fig. 6). Figure 6. The superior and inferior facets connect each vertebra together. There are four facet joints associated with each vertebra. Ligaments The ligaments are strong fibrous bands that hold the vertebrae together, stabilize the spine, and protect the discs.

The three major ligaments of the spine are the ligamentum flavum, anterior longitudinal ligament (ALL), and posterior longitudinal ligament (PLL) (Fig. 7). The ALL and PLL are continuous bands that run from the top to the bottom of the spinal column along the vertebral bodies. They prevent excessive movement of the vertebral bones. The ligamentum flavum attaches between the lamina of each vertebra. Figure 7. The ligamentum flavum, anterior longitudinal ligament (ALL), and posterior longitudinal ligament (PLL) allow the flexion and extension of the spine while keeping the vertebrae in alignment. Spinal cord The spinal cord is about 18 inches long and is the thickness of your thumb. It runs within the protective spinal canal from the brainstem to the 1st lumbar vertebra. At the end of the spinal cord, the cord fibers separate into the cauda equina and continue down through the spinal canal to your tailbone before branching off to your legs and feet. The spinal cord serves as an information super-highway, relaying messages between the brain and the body. The brain sends motor messages to the limbs and body through the spinal cord allowing for movement.

The limbs and body send sensory messages to the brain through the spinal cord about what we feel and touch. Sometimes the spinal cord can react without sending information to the brain. These special pathways, called spinal reflexes, are designed to immediately protect our body from harm. The nerve cells that make up your spinal cord itself are called upper motor neurons. The nerves that branch off your spinal cord down your back and neck are called lower motor neurons. These nerves exit between each of your vertebrae and go to all parts of your body. Any damage to the spinal cord can result in a loss of sensory and motor function below the level of injury. For example, an injury to the thoracic or lumbar area may cause motor and sensory loss of the legs and trunk (called paraplegia). An injury to the cervical (neck) area may cause sensory and motor loss of the arms and legs (called tetraplegia, formerly known as quadriplegia). Spinal nerves Thirty-one pairs of spinal nerves branch off the spinal cord. The spinal nerves act as telephone lines, carrying messages back and forth between your body and spinal cord to control sensation and movement. Each spinal nerve has two roots (Fig. 8).

The ventral (front) root carries motor impulses from the brain and the dorsal (back) root carries sensory impulses to the brain. The ventral and dorsal roots fuse together to form a spinal nerve, which travels down the spinal canal, alongside the cord, until it reaches its exit hole - the intervertebral foramen (Fig. 9). Once the nerve passes through the intervertebral foramen, it branches; each branch has both motor and sensory fibers. The smaller branch (called the posterior primary ramus) turns posteriorly to supply the skin and muscles of the back of the body. The larger branch (called the anterior primary ramus) turns anteriorly to supply the skin and muscles of the front of the body and forms most of the major nerves. Figure 8. The ventral (motor) and dorsal (sensory) roots join to form the spinal nerve. The spinal cord is covered by three layers of meninges: pia, arachnoid and dura mater. The spinal nerves are numbered according to the vertebrae above which it exits the spinal canal.

The 8 cervical spinal nerves are C1 through C8, the 12 thoracic spinal nerves are T1 through T12, the 5 lumbar spinal nerves are L1 through L5, and the 5 sacral spinal nerves are S1 through S5. There is 1 coccygeal nerve. Figure 9. The spinal nerves exit the spinal canal through the intervertebral foramen below each pedicle. The spinal nerves innervate specific areas and form a striped pattern across the body called dermatomes (Fig. 10). Doctors use this pattern to diagnose the location of a spinal problem based on the area of pain or muscle weakness. For example leg pain ( sciatica ) usually indicates a problem near the L4-S3 nerves. Figure 10. A dermatome pattern shows which spinal nerves are responsible for sensory and motor control of specific areas of the body. Coverings & spaces The spinal cord is covered with the same three membranes as the brain, called meninges. The inner membrane is the pia mater, which is intimately attached to the cord. The next membrane is the arachnoid mater. The outer membrane is the tough dura mater (Fig. 8).

Between these membranes are spaces used in diagnostic and treatment procedures. The space between the pia and arachnoid mater is the wide subarachnoid space, which surrounds the spinal cord and contains cerebrospinal fluid (CSF). This space is most often accessed when performing a lumbar puncture to sample and test CSF or during a myelogram to inject contrast dye. The space between the dura mater and the bone is the epidural space. This space is most often accessed to deliver anesthetic numbing agents, commonly called an epidural, and to inject steroid medication (see Epidural Steroid Injections ). Sources & links

Question: What does the vertebral column protect?
Answer: The spinal cord