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Brachial plexus quiz: follow roots to terminal branches

A plexus diagram becomes easier to study when every line answers a question: where did these fibers come from, and where do they go next? Learn the standard arrangement below, then test five relationships without looking back.

By CollegeWard · Updated · Foundational upper-limb anatomy

Roots, trunks, divisions, cords, branches

The usual roots of the brachial plexus are the anterior (ventral) rami of C5–T1. These are not the same anatomical structures as the ventral roots leaving the spinal cord. Variations exist, so this page describes the standard teaching pattern.

  1. Five roots: C5, C6, C7, C8, and T1.
  2. Three trunks: upper from C5–C6, middle from C7, and lower from C8–T1.
  3. Six divisions: each trunk forms an anterior and a posterior division.
  4. Three cords: lateral, medial, and posterior, named in relation to the second part of the axillary artery.
  5. Five major terminal branches: musculocutaneous, median, ulnar, axillary, and radial.

The lateral cord joins the anterior divisions of the upper and middle trunks. The medial cord continues the anterior division of the lower trunk. All three posterior divisions join the posterior cord. Reference: StatPearls: Brachial Plexus.

Which cord gives rise to each terminal nerve?

Selected cord-to-nerve relationships
NerveCord contributionOne motor association
MusculocutaneousLateralBiceps brachii
MedianLateral and medialPronator teres
UlnarMedialInterossei of the hand
AxillaryPosteriorDeltoid
RadialPosteriorTriceps brachii

These are study cues, not complete muscle or sensory distributions. The plexus also gives off branches before its terminal nerves. Reference: StatPearls: Shoulder and Upper Limb Nerves.

Five brachial plexus practice questions

Write down one choice for each question before revealing the answer. If you are unsure, sketch only the connections needed for that question instead of redrawing the whole plexus.

1. Which spinal nerve rami usually form the brachial plexus?

  1. Posterior rami of C5–T1
  2. Anterior rami of C1–C4
  3. Anterior rami of C5–T1
  4. Posterior rami of T1–T5
Show answer and explanation

C — Anterior rami of C5–T1. The word “roots” in a plexus diagram refers here to those rami. Keep this terminology separate from spinal cord roots.

2. Which contributions form the upper trunk in the usual arrangement?

  1. C5 and C6
  2. C7 alone
  3. C8 and T1
  4. All five roots
Show answer and explanation

A — C5 and C6. Compare this with the middle trunk from C7 and lower trunk from C8–T1 before moving on.

3. What forms the posterior cord?

  1. Only the posterior division of the upper trunk
  2. The anterior division of the lower trunk
  3. The anterior divisions of the upper and middle trunks
  4. The posterior divisions of all three trunks
Show answer and explanation

D — All three posterior divisions. Trace one division from each trunk. A posterior cord is not formed from only one trunk.

4. Which nerve receives contributions from both lateral and medial cords?

  1. Ulnar
  2. Median
  3. Axillary
  4. Musculocutaneous
Show answer and explanation

B — Median. Its lateral and medial roots join. “Medial cord” and “median nerve” are not interchangeable names.

5. Which pair consists of terminal branches of the posterior cord?

  1. Median and ulnar
  2. Ulnar and musculocutaneous
  3. Axillary and radial
  4. Median and musculocutaneous
Show answer and explanation

C — Axillary and radial. Both are terminal branches of the posterior cord. Other nerves also arise from that cord, so the pair is not its entire branch list.

A drawing exercise after the quiz

Use a blank page rather than tracing the reference. First write the five stage names across the top. Add the roots and trunks, then stop and check your work. Next add the divisions and cords. Finally add only the five terminal nerves in the table.

For every mistake, write a specific correction such as “I placed the median nerve on one cord only.” That gives you a prompt to revisit on another day. A page labeled simply “learn brachial plexus” gives you much less direction.

When the outline is comfortable, use your course atlas to add collateral branches, spatial relationships, and the required sensory territories. A schematic is a learning aid, not a substitute for three-dimensional anatomy.

Explore the visual atlasMake focused review prompts

Sources and scope

This is an original educational summary of the usual arrangement, not medical advice, a complete nerve atlas, or an independently clinician-reviewed reference. Anatomical variations and lesion localization require fuller course references.

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