Brachial Plexus made Easy and Simple!

Brachical plexus in Simple and Easier way:-

• So Plexus simply means "Collection of Nerve Fibres"

So By name :-Brachial Plexus means -"Collection of Nerve fibres of Brachium (Arm)."

• Plexuses Inside Human Body :-

When the Anatomists were exploring the human body they found out several bundles of nerve fibres which are connected both physically and functionally and they called these bundles later as "Plexus" Depending on their location they are of different types like :- Brachial Plexus and Sacral plexus etc.

• Origin of Brachial Plexus :-

Now the Brachial  plexus is actually formed by major contribution from - C5,C6,C7,C8and T1 Spinal Nerves ,sometimes the C4 and T2 Nerves do get involved in this plexus formation

• If the contribution from C4 is very high in Brachial plexus formation than it is known as :- Pre-Fixed brachial plexus.
• If the contribution from T2 is very high in Brachial plexus formation than it is known as :- Post-Fixed brachial plexus.

The Ventral rami of these spinal Nerves is the starting of brachial plexus formation.

• Ventral Ramus of Spinal Nerve:-

Not going into super details of ventral ramus, I hope you know it and if don't than I suggest you to get an idea what it is.

just to get an idea :-

• Roots of Brachial Plexus :-

The Primary ventral ramus of these spinal nerves are known as "Roots" in Brachial plexus.

So It is Ramus in context of Spinal nerve and it is known as Root in context of "Brachial Plexus"

So in Short What you call as Root in Brachial plexus is nothing but the Ventral Ramus of concerned Spinal Nerve and not to forget that Ramus caontain both motor and sensory fibres.

Note:- "Dorsal ramus does not contribute in formation of Brachial plexus"

Location of Roots of Brachial Plexus:-

"Roots/Ventral ramus of the spinal nerve lies deep in the neck behind scalenus medius muscle"

• Trunks in Brachial Plexus:-

The Roots of Spinal Nerve combine together both physically and functionally to form a structure known as "Trunk of Brachial Plexus".

Now the Interesting part is that it is very "Specific" . I mean to say :-

1. Root of C5 and C6 Spinal Nerve join together to form "Upper Trunk"
2. Root of C8 and T1 Spinal Nerve joint together to form "Middle Trunk"
3. Root of C7 Spinal Nerve does not comine/join with anyone and run alone to form "Middle Trunk"

• Divisions in Brachial Plexus:-

Each Trunk now Divides to give two divisions : "Anterior division" and "Posterior division".

that means there are total 6 divions in Brachial Plexus , 3 anterior and 3 posterior .

Location of Divisions of Brachial Plexus:-

Divisions of brachial plexus are located behind the clavicle.

• Cords in Brachial plexus:-

Divisions from various Trunks join to form "Cords of Brachail plexus"

1. Anterior Division of "UPPER" and "MIDDLE" Trunk join to form the "Lateral Cord of Brachial Plexus"
2. Poserior Division from "UPPER" "MIDDLE" and "LOWER" Trunk join to form the "Posterior Cord of Brachial Plexus"
3. Anterior Division of LowerTrunk Runs alone to Form "Medial Cord of Brachial Plexus"

Location of Cords :-

The Cords of Brachial Plexus can be seen in axilla.

• Branches(Arising Nerves) in Brachial Plexus:-

Nerves arises from many parts in brachial pleuxs , they can emerge directly from the root or they can emerge from trunk part and most of the branches arises from the cords.

Branches from Root Of C5 Spinal Nerve:-

2 Nerves arise from the Root/Ventral ramus of C5 spinal nerve :-

1. Dorsal Scapular nerve..
2. Long thoracic nerve/Nerve to Serratusd anterior

Note:- Long thoracic arises from the contribution of C5,C6 and C7 nerves ventral rami, not just alone from C5 spinal nerve ventral ramus.

See the image below:-

Observe the two marked nerves arising from the Roots in Brachial pleuxs

Nerves arising from Trunks in Brachial Plexus:-

Remember the nerves arises inly from the upper trunk , no direct nerves arises from middle or lower thunk 

NOTE:- Some books also use words linke superior, middle and inferior (Trunks) instead of upper , middle and lower .

Two Nerves arises from the Upper trunk :-

1. Supra scapular nerve.
2. Nerve to Subclavius.

See the Marked Nerves in Image below:-

Nerves from Cords in Brachial Plexus:-

Branches from the Lateral Cord:-

1. Lateral Pectoral Nerve.(C5-C7)
2. Musculocutaneous Nerve.(C5-C7)
3. Lateral root of Median Nerve.(C5-C7)

All have Root Value of (C5-C7)

NOTE:- Median Nerve is slightly different as is is formed by two Roots , yeah so in short it arises by Combination of "Lateral Root of Median Nerve+ Medial Root of Median Nerve".

Branches from the Medial Cord:-

Five branches arise from the Medial cord :- (Mnemonic-MMMMU)

1. Medial Root of Median nerve.(C8 and T1)
2. Medial Cutaneous nerve of arm.(C8 and T1)
3. Medial Cutaneous nerve of forearm.(C8 and T1)
4. Medial Pectoral Nerve.(C8 and T1)
5. Ulnar Nerve.(C7,C8 and T1)

NOTE:-Ulnar Nerve arises from the Medial cord but still it contains the C7 spinal nerve apart from C8 and T1 as seen in others branches , it is because some nerve fibres from C7 join the Ulnar nerve.

Branches from the Posterior cord:

5 Branches arises from the Posterior cord:-(Mnemonic-STAR)

1. Upper sub-scapular nerve.(C5,C6)
2. Lower sub-scapular nerve.(C5,C6)
3. Thoraco-dorsal nerve./Nerve to lattisimus dorsi.(C6,C7,C8)
4. Axillary nerve.(C5,C6)
5. Radial nerve.(C5,C6,C7,C8,T1).

That was all from my side 

Signing off---

Bhavesh Saini.