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The laminae of the fifth sacral vertebra, and sometimes those of the fourth, do not meet at the back, resulting in a fissure known as the sacral hiatus in the posterior wall of the sacral canal. The sacral canal is a continuation of the spinal canal and runs throughout the greater part of the sacrum. Above the sacral hiatus, it is triangular in ...
The lumbar cistern is part of the subarachnoid space.It is the space within the thecal sac which extends from below the end of the spinal cord (the conus medularis), typically at the level of the first to second lumbar vertebrae down to tapering of the dura at the level of the second sacral vertebra.
As the spinal cord terminates at the L1–L2 level, other segments of the spinal cord would be positioned superior to their corresponding bony vertebral body. For example, the T11 spinal segment is located higher than the T11 bony vertebra, and the sacral spinal cord segment is higher than the L1 vertebral body. [7]
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
In humans, the sciatic nerve is formed from the L4 to S3 segments of the sacral plexus, a collection of nerve fibres that emerge from the sacral part of the spinal cord. The lumbosacral trunk from the L4 and L5 roots descends between the sacral promontory and ala, and the S1 to S3 roots emerge from the ventral sacral foramina.
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. [1] [2] These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. [1]
Onuf's nucleus is a distinct group of neurons located in the ventral part of the anterior horn of the sacral region of the human spinal cord involved in the maintenance of micturition and defecatory continence, as well as muscular contraction during orgasm. It contains motor neurons, and is the origin of the pudendal nerve.
Tarlov cysts, are type II innervated meningeal cysts, cerebrospinal-fluid-filled (CSF) sacs most frequently located in the spinal canal of the sacral region of the spinal cord (S1–S5) and much less often in the cervical, thoracic or lumbar spine. They can be distinguished from other meningeal cysts by their nerve-fiber-filled walls.