Brachial Plexus

Question 1

What is the brachial plexus?

Answer 1

network of nerves that sends signals from spinal cord to shoulder, arm & hand
- passes through neck

Question 2

What is the brachial plexus made up of?

Answer 2

Divided into 5 parts:
- roots
- trunks
- divisions
- cords
- branches

Acronym: RUGBY TEAMS DONT COVER BRUISES

No functional differences between the parts

Question 3

What are the roots?

Answer 3

It is formed by the anterior rami (divisions) C5, C6, C7, C8 & T1 nerves

These nerves then enter base of neck

Anterior rami= when paired spinal nerves leave spinal cord via intervertebral foramen they divide into anterior & posterior ramps thus anterior rami

Question 4

What are the trunks?

Answer 4

At base of neck, the roots converge to form 3 trunks.

Superior trunk – a combination of C5 & C6 roots.
Middle trunk – continuation of C7.
Inferior trunk – combination of C8 & T1 roots.

Question 5

What are the divisions?

Answer 5

Each trunk divides into 2 branches w/ the posterior triangle of neck
-1 division moves anteriorly (toward the front of the body)- anterior division
- other posteriorly (towards the back of the body)- posterior division

In total= 3 anterior & 3 posterior nerves

they leave the posterior triangle & enter axilla

Question 6

What are cords?

Answer 6

Once anterior & posterior divisions enter axilla, they combine together to form 3 cords
- named by their position relative to the axillary artery.

Lateral cord is formed by:
- anterior division of the superior trunk
- anterior division of the middle trunk

Posterior cord is formed by:
- posterior division of the superior trunk
- posterior division of the middle trunk
- posterior division of the inferior trunk

Medial cord is formed by:
- anterior division of the inferior trunk.

Cords give rise to the major branches of brachial plexus

Question 7

What are the major branches?

Answer 7

In axilla (found on proximal aspect of the upper limb) the 3 cords give rise to 5 major branches.

Nerves continue into the upper limb to provide innervation to the muscles & skin

Branches of the lateral cord: median nerve & musculotaneous nerve
- Acronym: MONSTER MUNCH

Branches of posterior cord: axillary & radial nerve
- Acronym: ANCIENT RUINS ig?

Branches of medial cord: median & ulnar nerve
- Acronym: MAGIC UMBRELLA

1. Musculocutaneous Nerve:
   - Roots: C5, C6, C7.
   - Motor Functions: Innervates brachialis, biceps brachii & coracobrachialis muscles.
   - Sensory Functions: lateral cutaneous branch of the forearm, which innervates the lateral half of the anterior forearm, & small lateral portion of the posterior forearm.
2. Axillary nerve:
   - Roots: C5 and C6.
   - Motor Functions: Innervates teres minor & deltoid muscles.
   - Sensory Functions: superior lateral cutaneous nerve of arm, which innervates inferior region of the deltoid
3. Median Nerve:
   - Roots: C6 – T1.
   - Motor Functions: Innervates most flexor muscles in the forearm, the thenar muscles & 2 lateral lumbricals of index & middle fingers.
   - Sensory Functions: palmar cutaneous branch, which innervates lateral part of palm, & the digital cutaneous branch, which innervates lateral 3 & a half fingers on the anterior (palmar) surface of the hand.
4. Radial Nerve:
   - Roots: C5 – T1.
   - Motor Functions: Innervates triceps brachii, & muscles in the posterior compartment of the forearm (which are primarily, but not exclusively, extensors of the wrist & fingers).
   - Sensory Functions: Innervates posterior aspect of arm &forearm, & posterolateral aspect of the hand.
5. Ulnar nerve:
   - Roots: C8 and T1.
   - Motor Functions: Innervates muscles of hand (apart from the thenar muscles & 2 lateral lumbricals), flexor carpi ulnaris & medial half of flexor digitorum profundus.
   - Sensory Functions: Innervates anterior & posterior surfaces of the medial one & half fingers, & associated palm area.

Question 8

Draw out the brachial plexus.

Answer 8

https://www.notion.so/PBL-week-11-92f7a1365c35422b8d2810696c535658

Question 9

Other nerves?

Answer 9

There are smaller nerves that arise in each part:
- Roots: dorsal scapular nerve + long thoracic nerve
- Trunks: suprascapular nerve + nerve to subclavius
- Lateral cord: Lateral pectoral nerve
- Medial cord: medial pectoral nerve, medial cutaneous nerve of arm + medial cutaneous nerve of forearm
- Posterior cord: superior subscapular nerve + inferior subscapular nerve

Long thoracic nerve
- arises just above clavicle from proximal portion of brachial plexus
- from roots of spinal nerves C5, C6 & C7.
- innervates serratus anterior muscle- moves the scapula to allow for overhead lifting of the arm
- provides sole motor innervation so therefore damage to nerve= winging of scapula
- damage= lymph clearance on breast cancer