Brachial Plexus, Anatomy of Brachial plexus

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What is the Brachial Plexus?

The brachial plexus is a network of nerves that connects the nerves in the arm and stems from nerve roots in the cervical (neck) and upper trunk (torso) regions of the spinal cord (C5-T1). The motions of your wrists, hands, and arms are controlled by these nerves, allowing you to raise your arm, type on a computer, or throw a baseball. 

The brachial plexus nerves are sensory and extend to the skin. For example, they may inform you that the pan you just took is too hot to hold.

Brachial Plexus Anatomy

The brachial plexus nerves branch and merge from the roots via the shoulder and down the arm, and are divided into several sections: trunks, divisions, cords, and branches. These portions are not functionally distinct, however they do assist in explaining the brachial plexus' complicated structure.

Roots

The anterior rami of the spinal nerves that make up the brachial plexus are referred to as the 'roots.' The anterior rami of spinal nerves C5, C6, C7, C8, and T1 are located here.

The anterior and posterior ramus of each spinal nerve are then separated. The anterior rami of spinal nerves C5-T1 produce the roots of the brachial plexus. 

 

These nerves emerge at the base of the neck and run between the anterior and medial scalene muscles.

 

Trunks

The roots of the brachial plexus unite at the base of the neck to form three trunks. The relative anatomical placement of these structures is used to name them: 

 

C5 and C6 roots combine to form a superior trunk. 

C7 continues in the middle trunk. 

C8 and T1 roots combine in the inferior trunk. 

The trunks pass the posterior triangle of the neck and proceed laterally.

 

Divisions

Within the posterior triangle of the neck, each trunk splits into two branches. One division goes Anteriorly(toward the front of the body), while the other moves Posteriorly(toward the back of the body). As a result, they're referred to as the anterior and posterior divisions.

 

Cords

When the anterior and posterior divisions have entered the axilla, they combine together to form three cords.

The lateral cord is formed by:

· The anterior division of the superior trunk

· The anterior division of the middle trunk

The posterior cord is formed by:

· The posterior division of the superior trunk

· The posterior division of the middle trunk

· The posterior division of the inferior trunk

The medial cord is formed by:

· The anterior division of the inferior trunk.

 

Branches

Five primary nerve branches run down the arm from the brachial plexus: 

 

The Musculocutaneous nerve:- The musculocutaneous nerve originates from nerve roots C5-C7 and flexes muscles in the upper arm at the shoulder and elbow. 

The axillary nerve:- which originates from the C5 and C6 nerve roots, aids shoulder rotation and allows the arm to raise away from the body. 

The median nerve:- which originates in the C6-T1 nerve roots, allows movement in the forearm and parts of the hand.

 

The radial nerve:- originates in the C5-T1 nerve roots and regulates muscles in the upper arm, elbow, forearm, and hand. 

The Ulnar nerve:- which is rooted in C8-T1, is responsible for fine motor control of the fingers.