Skip to content
Robotic Spine Universe

Structures · Spinal cord segments

C4 spinal cord segment

The piece of spinal cord that gives rise to the C4 pair of spinal nerves. Segment names use the spinal cord level system, which does not line up with the vertebrae.

Show in the 3D spineSee what it connects to in the body

At a glance

Level system
C4 segment (spinal cord level)
Lies opposite
C2 to C3 (vertebral levels)Model mapping; varies between people. Frostell et al. 2016; De Leener et al. 2018; Cadotte et al. 2014
Length along the cord
15.6 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 C4 nerve exits between the C3 vertebra and the C4 vertebra, above the C4 vertebra.Betts et al. 2022, §13.4
ISNCSCI key sensory point
Over the acromioclavicular jointRupp et al. 2021; Kirshblum et al. 2011

Cross-section at C4

left ventral hornright ventral hornleft intermediate zoneright intermediate zoneleft dorsal hornright dorsal hornAnteriorPosteriorLR
Regions in this section (text list)
  • left ventral horn
  • right ventral horn
  • left intermediate zone
  • right intermediate zone
  • left dorsal horn
  • right dorsal horn

Grey matter and white-matter tracts at this level. Outline from the PAM50 template and atlas, cut at the segment midpoint. De Leener et al. 2018; Lévy et al. 2015

Open this section in the viewer

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

    Phrenic nerve: neck segments drive breathing

    The diaphragm is driven by the phrenic nerve, a branch of the cervical plexus. Its roots are classically C3, C4 and C5; dissection studies find two-root and one-root patterns too.

    Betts et al. 2022, §13.4; Sharma et al. 2025 · Show on the body

  • Spinal nerves and plexuses

    Brachial plexus: the nerves of the arm

    Spinal nerves from the lower neck and first thoracic segment regroup in the brachial plexus and become the nerves of the arm.

    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

Read more

  • Breathing and the spinal cord

    How the brainstem's breathing rhythm reaches the diaphragm and rib muscles through the cord. Why the phrenic nerve's origin in the mid-neck matters after a 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.

For learning only. Levels and sizes vary between people; nothing here describes a particular person or gives medical advice. Sources: Betts et al. 2022, §13.2; Frostell et al. 2016; De Leener et al. 2018; Cadotte et al. 2014; Betts et al. 2022, §13.4; Rupp et al. 2021; Kirshblum et al. 2011; Sharma et al. 2025.