Upper Limb Nerves: Brachial Plexus Formation and Innervation

What is a spinal nerve?

A mixed nerve formed from the union of a dorsal root (sensory fibers) and a ventral root (motor fibers).

How many pairs of spinal nerves are there?

31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

How do C1-C7 spinal nerves exit the vertebral canal?

They exit superior to the vertebrae for which they are named.

Where does the C8 spinal nerve exit?

Between C7 and T1 vertebrae.

How do T1 and inferior spinal nerves exit the vertebral canal?

They exit inferior to the vertebrae for which they are named.

What happens to the ventral rami of spinal nerves T1-T12?

They form intercostal nerves (or subcostal nerve T12).

What are the major plexuses formed by ventral rami?

Cervical plexus (C1-C4), Brachial plexus (C5-T1), Lumbar plexus (T12-L4), Sacral plexus (L4-S4).

What is the brachial plexus?

A network of nerves formed from the ventral rami of C5-T1.

What are the components of the brachial plexus?

Roots, Trunks, Divisions, Cords, and Branches.

What are the terminal branches of the brachial plexus?

Musculocutaneous, Median, Ulnar, Radial, and Axillary nerves.

What spinal levels contribute to the Musculocutaneous nerve?

C5, C6, and C7.

What muscles does the Musculocutaneous nerve innervate?

All muscles of the anterior arm.

What spinal levels contribute to the Median nerve?

C5-T1.

What does the Median nerve innervate?

All but 1½ muscles of the anterior forearm and 5 intrinsic hand muscles.

What spinal levels contribute to the Ulnar nerve?

C8 and T1.

What does the Ulnar nerve innervate?

1½ muscles in the anterior forearm and all but 5 intrinsic hand muscles.

What spinal levels contribute to the Radial nerve?

C5-T1.

What does the Radial nerve innervate?

All muscles of the posterior arm and forearm.

What spinal levels contribute to the Axillary nerve?

C5 and C6.

What muscles does the Axillary nerve innervate?

Deltoid and teres minor muscles.

What is the function of the Long Thoracic nerve?

Innervates the serratus anterior muscle.

What is the function of the Thoracodorsal nerve?

Innervates the latissimus dorsi muscle.

What is the significance of herniated intervertebral discs?

They can impact the spinal nerves and their function.

How do you draw the brachial plexus?

Use 3 Y's, 1 M, 1 X, and a backslash to represent its structure.

What is the role of the cervical plexus?

Provides sensory and motor innervation to the neck and parts of the shoulder.

What is the role of the lumbar plexus?

Innervates the lower abdominal wall, anterior and medial thigh.

What is the role of the sacral plexus?

Innervates the pelvis and lower limb.