LO: Explain the function of a nerve plexus. Identify the nerve roots that supply the brachial plexus and describe the five regions of the brachial plexus

Brachial plexus

• Plexus - area where lots of peripheral nerves needed, multiple spinal nerve roots which merge and divide to become peripheral nerves
• Brachial = arm
  • Majority of the nerves from this plexus will be associated with the upper limb
• Spinal nerves - C5, C6, C7, C8 and T1
  

Roots

• C5, C6, C7, C8, T1
• Between vertebrae

Trunks

• C5 and C6 - upper trunk
• C7 - middle trunk
• C8 and T1 - lower trunk

Divisions

• Upper and middle trunk - anterior division
• Upper, middle and lower trunk - posterior division
• Lower trunk - anterior division

Posterior cord

• Union of upper, middle and lower trunk
• Beneath axillary artery
  

Medial and lateral cords

• Upper and middle trunks - lateral cord
  

• Lower trunk - medial cord

Nerves

• Musculocutaneous - lateral cord
• Ulnar - medial cord
• Median - lateral and medial cord
• Axillary - posterior cord
• Radial - posterior cord

flowchart LR
	A[Upper trunk]
	B[Middle trunk]
	C[Lower trunk]
	D[Anterior division]
	D2[Anterior division]
	E[Posterior division]
	F[Medial cord]
	G[Lateral cord]
	H[Posterior cord]
	I[Musculocutaneous nerve]
	J[Ulnar nerve]
	K[Median nerve]
	L[Axillary nerve]
	M[Radial nerve]
	
	
	
	C5 --- link[ ]:::hidden
	C6 --- link
	link --> A
	C7 --> B
	C8 --- meet[ ]:::hidden
	T1 --- meet
	meet --> C
	A --- join[ ]:::hidden
	B --- join
	join --> D
	C --> D2
	C --- trio[ ]:::hidden
	B --- trio
	A --- trio
	trio --> E
	E --> H
	D2 --> F
	D --> G
	G --> I
	G --- cross[ ]:::hidden
	F --- cross[ ]:::hidden
	cross --> K
	F --> J
	H --> L
	H --> M
	
	classDef hidden display: none;

• 5 spinal nerve roots (C5, C6, C7, C8, T1)
• 5 peripheral nerves (musculocutaneous, median, radial , ulnar, axillary)

LO: Describe the dermatome distribution and myotomes of the upper limb

Dermatomes of the upper limb

• Top shoulder - C4
• Thumb - C6
• Between thumb and top of shoulder - C5
• 2nd, 3rd, 4th fingers and palm - C7
• Pinky (5th) - C8
• Medial arm - T1
• Armpit - T2

Myotomes

• C5:
  • Shoulder flexion
  • Shoulder abduction
• C6:
  • Shoulder flexion
  • Wrist extension
• C7:
  • Shoulder extension
  • Wrist flexion
  • Finger extension
• C8:
  • Thumb flexion
  • Finger flexion
• T1:
  • Thumb flexion
  • Finger abduction

LO: Describe the course, location, sensory and motor components of the major peripheral nerves that leave the brachial plexus

Musculocutaneous

• Anterior arm
• Coracobrachialis
• Brachialis
• Biceps brachii
  
• Motor = flexion:
  • Elbow
• Sensory:
  • Lateral forearm

Axillary

• Shoulder joint and deltoid
• Motor:
  • Abduction of shoulder
• Sensory:
  • Regimental badge/shoulder tip

Median

• Anterior forearm
• Except medial half of flexor digitorium profundus and flexor carpi ulnaris
• Motor:
  • Flexion = elbow, wrist and proximal interphalangeal (PIP)
  • Actions at the thumb
• Sensory:
  • Lateral palm and lateral palmar digits

Ulnar

• Anterior forearm
• Half of flexor digitorium profundus and flexor carpi ulnaris
• Intrinsic hand muscles
• Motor:
  • Flexion
  • Wrist/hand - medial side
• Sensory:
  • Palmar and dorsal ring and little finger

Radial

• Posterior arm, posterior forearm and hand
• Motor:
  • Extension
  • Elbow/wrist/hand
• Sensory:
  • Posterior upper limb

LO: Describe the location where the peripheral nerves of the upper limb are susceptible to injury and relate this to presentation