C5 spinal cord segment

At a glance

Level system

C5 segment (spinal cord level)

Lies opposite

C3 to C4 (vertebral levels)Model mapping; varies between people. Frostell et al. 2016; De Leener et al. 2018; Cadotte et al. 2014

Length along the cord

17.1 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 C5 nerve exits between the C4 vertebra and the C5 vertebra, above the C5 vertebra.Betts et al. 2022, §13.4

ISNCSCI key sensory point

Lateral (radial) side of the antecubital fossa, just proximal to the elbow creaseRupp et al. 2021; Kirshblum et al. 2011

ISNCSCI key muscle

Elbow flexors: tested by asking the person to flex the elbowRupp 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

  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 muscles (ISNCSCI)

  C5: elbow flexors

  In the standard neurological examination after spinal cord injury (ISNCSCI), the strength of the elbow flexors is the key test of segment C5. The muscle also receives other segments; the key muscle is a convention for testing, not the whole supply.

  Rupp et al. 2021; Betts et al. 2022, §11.5 · 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.

• The withdrawal reflex

  Pulling away from a hot stove or a tack. Pain excites the motor neurons of the withdrawing muscle and, through an inhibitory interneuron, quiets the opposing muscle so the movement is faster.