L1 spinal cord segment

At a glance

Level system

L1 segment (spinal cord level)

Lies opposite

T11 (vertebral level)Model mapping; varies between people. Frostell et al. 2016; De Leener et al. 2018; Cadotte et al. 2014

Length along the cord

16.6 mmMeasured on one model: the Visible Human male, imaged as a supine cadaver. Not a normal range. De Leener et al. 2018; Frostell et al. 2016

Its nerve

The L1 nerve exits between the L1 vertebra and the L2 vertebra, below the L1 vertebra.Betts et al. 2022, §13.4

ISNCSCI key sensory point

Midway between the key points for T12 and L2Rupp et al. 2021; Kirshblum et al. 2011

What the sources say

“The posterior horn is responsible for sensory processing.” Betts et al. 2022, §13.2

“The anterior horn sends out motor signals to the skeletal muscles.” Betts et al. 2022, §13.2

Connections to the rest of the body

• Spinal nerves and plexuses

  Lumbar plexus: the front of the thigh

  The lumbar nerves form the lumbar plexus, which supplies the pelvic region and the front of the thigh.

  Betts et al. 2022, §13.4 · Show on the body

• Key sensory points (ISNCSCI)

  Key sensory points: one patch of skin per segment

  The examination tests light touch and pinprick at one key point per segment on each side, from C2 behind the ear to S4–5 beside the anus. The points here were placed on this body by following the standard’s written descriptions from bony landmarks, so they are approximate.

  Rupp et al. 2021; Kirshblum et al. 2011 · Show on the body

• Sympathetic outflow

  Sympathetic outflow: thoracic and upper lumbar cord

  Every sympathetic signal to the body leaves the cord between T1 and L2, from neurons in the lateral horn, and passes through the chain of ganglia beside the vertebral column.

  Wulf and Tom 2023; Betts et al. 2022, §15.1 · Show on the body

• Sympathetic outflow

  Pancreas: sympathetic from T6–L2

  Sympathetic neurons for the pancreas sit in the lateral horn of segments T6 to L2. A spinal cord injury above these segments cuts them off from the brain's control, though they still work as part of spinal reflexes.

  Wulf and Tom 2023 · Show on the body

• Sympathetic outflow

  Kidneys: sympathetic from T11–L1

  Sympathetic neurons for the kidneys sit in the lateral horn of segments T11 to L1. A spinal cord injury above these segments cuts them off from the brain's control, though they still work as part of spinal reflexes.

  Wulf and Tom 2023 · Show on the body

• Sympathetic outflow

  Bladder and urethra: sympathetic from T11–L2

  Sympathetic neurons for the bladder and urethra sit in the lateral horn of segments T11 to L2. A spinal cord injury above these segments cuts them off from the brain's control, though they still work as part of spinal reflexes.

  Wulf and Tom 2023 · Show on the body

Read more

• Autonomic outflow and the bladder

  Where the cord sends its automatic, involuntary commands. Sympathetic outflow leaves from the thoracic and upper lumbar cord, parasympathetic from the brainstem and sacral cord, and the bladder shows how both work with voluntary control.

• Brain–spine interfaces

  A digital bridge around a spinal cord injury. Implants read movement intentions from the cortex and turn them into stimulation of the lumbar cord, so that a person with paralysis can stand and walk under their own control.

• Central pattern generators

  The spinal circuits that can produce the rhythm of stepping on their own. Graham Brown's half-centre idea, where the circuits sit, and why they matter for walking again after spinal cord injury.

• Spinal cord injury

  What happens when the cord is damaged, how the standard examination classifies the injury by level and completeness, which functions depend on the level, and what research is trying to restore.

• Vertebral and spinal cord levels

  Why "L1" can mean two different places. The vertebrae and the spinal cord segments have their own numbering, and below the neck they drift apart, because the column grows longer than the cord.