These nerves supply function to the bladder, bowels, genitals, and legs. These nerves run through the canal and then out through their respective intervertebral foraminae. Pressure on the conus can cause impaired bowel and bladder control, and numbness around the anus and genitals (‘saddle anaesthesia’).īelow the ending of the spinal cord, the canal is occupied by the spinal nerves (also known as the ‘cauda equina’ which means ‘horses tail’, named after its appearance). The lower portion of the spinal cord is known as the ‘conus’ or ‘conus medullaris’. The spinal cord ends in the upper lumbar spine (usually at L1). As a result, pressure on these structures may occur. When the size of these tunnels is reduced, there is less room for the spinal nerves. The spinal canal and intervertebral foraminae in the lumbar spine (lower back) are bony tunnels through which the spinal nerves (nerve roots) run. Spinal nerves run through these compartments. The area of the spinal canal immediately underneath the facet joint is known as the subarticular compartment or lateral recess. Facet joints form part of the roof of the spinal canal. They allow movement between adjacent vertebrae and help to keep the spine stable. The spine is divided into separate regions the lower back (known as the lumbar. The facet joints are small joints on each side at the back of the spine. Vertebrae, cartilage discs and the spinal cord canal. They are often removed (laminectomy) to decompress the nerves in the spinal canal.
#SPINE BONES SKIN#
They meet in the midline, giving rise to the spinous process (the ridges that can be felt through the skin at the back of the spine). The laminae are ‘shingles’ of bone lying over the back of the spinal canal. It is the strongest part of the disc and it encloses the central nucleus and holds it under pressure to prevent it from rupturing. The annulus is a ring-like frame of fibres which connects each vertebral bone. There are no blood vessels or nerves in the nucleus, The rest of the nucleus is made up of connective tissue cells, collagen fibres, and a small amount of cartilage. It is a clear, jellylike material that is made up of 88 percent water in young adults.Īs the body ages and/or degenerates, the amount of water in the nucleus reduces. The nucleus functions as a primary shock absorber. The central soft and juicy nucleus is a sphere-shaped structure that allows tilting, rotating, and gliding movements in the spine. Each intervertebral disc has a strong outer ring of fibres (‘annulus’), and a soft, jelly-like centre (nucleus). A single disc sits between each vertebra. The coccyx is composed of 4 very small bones fused together, and forms the tailbone at the lowest part of the spinal column.The intervertebral discs are soft structures which act as shock absorbers between each of the vertebrae (bones) in the spine.
The sacrum is composed of 5 bones fused together. The lowest portion of the spine, the part that is connected to the pelvis, is called the sacrum. Understandably, the lumbar spine is the most commonly injured region of the spinal column. The lumbar vertebrae are the largest in the spine and bear the majority of the body’s weight, and endure significant loading and stress. There is significant flexion and extension movement in the lumbar spine, but minimal rotation. The lower portion of the spine is called the lumbar spine, and is composed of 5 vertebrae. There is very little movement or bending of the thoracic spine, and because of this, the thoracic spine is very strong and typically resists injury. The thoracic vertebrae are firmly connected to the ribs and breastbone (sternum). The middle portion of the spine is called the thoracic spine, and is composed of 12 vertebrae. The cervical spine also has small openings on each side the spine, for a special blood vessel carrying blood to the brain, called the vertebral artery. The cervical spine is extremely flexible, and therefore is quite prone to injury. Except for the 1st and 2nd cervical vertebrae, all vertebrae have three joints at each level, an intervertebral disc in the front and two facet joints in the back. The upper portion of the spine is called the cervical spine, and is composed of 7 vertebrae. The facet joints have a strong, outer joint capsule. The facet joints are small synovial joints on the back part of the spine on each side, connecting near the lamina.
The disc acts as a shock absorber and allows motion and bending of the spine. The soft inner portion is called the nucleus pulposis, and the stronger outer ring is called the annulus fibrosis. The intervertebral disc is a soft cartilage cushion with two layers. The complex interaction between these three joints at each spinal level allows significant flexibility of the spine, but also ensures stability and resistance to injury. The facet joints join near the back part of the spine on each side, near the lamina. Each vertebra is connected to an adjacent vertebra by three joints: an intervertebral disc and two facet joints.
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