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The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, ... L4-L5 L5-S1; Flexion/
The sacral spinal nerve 1 (S1) is a spinal nerve of the sacral segment. [1] It originates from the spinal column from below the 1st body of the sacrum.
The fifth lumbar spinal nerve 5 (L5) [5] originates from the spinal column from below the lumbar vertebra 5 (L5). L5 supplies many muscles, either directly or through nerves originating from L5. They are not innervated with L5 as single origin, but partly by L5 and partly by other spinal nerves. The muscles are: gluteus maximus muscle mainly S1
L5 – On the dorsum of the foot at the third metatarsophalangeal joint. S1 – On the lateral aspect of the calcaneus. S2 – At the midpoint of the popliteal fossa. S3 – Over the tuberosity of the ischium or intragluteal fold; S4 and S5 – In the perianal area, less than one cm lateral to the mucocutaneous zone
The thoracic, lumbar, and sacral nerves are then numbered by the vertebra above. In the case of a lumbarized S1 vertebra (also known as L6) or a sacralized L5 vertebra, the nerves are typically still counted to L5 and the next nerve is S1. Scheme showing structure of a typical spinal nerve 1. Somatic efferent. 2. Somatic afferent. 3,4,5.
The sciatic nerve comprises nerve roots L4, L5, S1, S2, and S3 in the spine. [26] These nerve roots merge in the pelvic cavity to form the sacral plexus and the sciatic nerve branches from that. Sciatica symptoms can occur when there is pathology anywhere along the course of these nerves. [27]
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.
The majority of disc herniations occur in the lumbar spine (95% at L4–L5 or L5–S1). [21] The second most common site is the cervical region (C5–C6, C6–C7). The thoracic region accounts for only 1–2% of cases.