W8 L6
Lecture 6 – The peripheral nervous system,
upper limb plexus, terminal branches
and compartmentalisation
CHI108 W8 L6 flashcards
Learning objectives
1. Identify the neural make up (spinal nerve root levels) and the structural arrangement of the
identified plexus.
2. Describe the anatomical courses and pathways of the terminal branches.
3. Review the muscles that reside in each compartment and their nerve supply.
4. Review the collateral branches associated with the brachial plexus: Suprascapular and
infraclavicular parts
__________________________________________________________________________
Peripheral nervous system
• Sensory and motor components of each nerve
• Sensory: input, afferent cutaneous innervation and proprioceptive information
• All the nervous system does is sense information from the internal and external environment and
inform the CNS that change has occurred
• Motor: output, efferent motor innervation
• The CNS then responds to the stimulus at either the cord level (reflex) or alternatively at higher
Spinal enlargements
levels, the brainstem, cerebellum, basal ganglia, thalamus or cerebrum
Spinal enlargements
• Spinal cord enlargements are the direct consequence of increased quantities of gray matter
(lower motor neurons, interneurons and afferent input) at those specific segmental levels
• The enlargements of the spinal cord supply the quantity of neural machinery necessary to
operate the limbs
• Proximally the first enlargement is the cervical enlargement from C5 to T1, which controls and
coordinates bilaterally the upper limb muscles
• Maximum circumference 38 mm
• The reason behind the enlargement of the cervical region is because of the increased neural
input and output to the upper limbs
Brachial plexus
• Five roots
○ C5 and C6 merge to establish the upper trunk, C7 continuously forms the middle trunk, and
C8 and T1 merge to establish the lower trunk
• Three trunks
○ Superior (upper) C5-C6, middle C7, inferior (lower) C8, T1
• Six divisions
○ Each trunk then splits in two, to form six divisions
○ Three anterior and three posterior
• Three cords
○ These six divisions regroup to become the three cords
○ Posterior, lateral and medial cords
• Five terminal branches
○ Musculocutaneous n., axillary n., radial n., median n. and ulnar n., which all have specific
sensory, motor and proprioceptive functions
Schematic representation of the structure of the brachial plexus
• a. shows names and sequence of the various components of the brachial plexus Brachial plexus
• b. shows the relationship of the lateral, medial, and posterior cords of the brachial plexus to the
axillary artery
• c. shows the subdivision of the brachial plexus cords into their main branches
• The brachial plexus is formed by a network of nerves from the lower four cervical nerves and first
thoracic nerve (C5, C6, C7, C8, and T1)
• The brachial plexus supplies afferent and efferent nerve fibres to chest, shoulder, arm and hand
The axilla
• The axilla is the pyramidal space inferior to the glenohumeral joint and superior to the axillary
fascia at the junction of the arm and thorax
• Providing a passageway for the neurovascular structures that serve the upper limb
• The apex of the axilla constitutes the cervico-axillary canal
• The canal forms a passageway between the neck and axilla, bounded by the lateral aspect of the
1st rib, posterior aspect of the clavicle, and superior edge of the scapula
• The axilla has an apex, base, and four walls (three of which are muscular)
• The axilla contains:
○ Large nerves that make up the cords and branches of the brachial plexus Location, boundaries, and contents of the axilla
○ Blood vessels (axillary artery and vein)
○ Lymphatic vessels and nodes
○ Axillary fat
CHI108 Page 1
Lecture 6 – The peripheral nervous system,
upper limb plexus, terminal branches
and compartmentalisation
CHI108 W8 L6 flashcards
Learning objectives
1. Identify the neural make up (spinal nerve root levels) and the structural arrangement of the
identified plexus.
2. Describe the anatomical courses and pathways of the terminal branches.
3. Review the muscles that reside in each compartment and their nerve supply.
4. Review the collateral branches associated with the brachial plexus: Suprascapular and
infraclavicular parts
__________________________________________________________________________
Peripheral nervous system
• Sensory and motor components of each nerve
• Sensory: input, afferent cutaneous innervation and proprioceptive information
• All the nervous system does is sense information from the internal and external environment and
inform the CNS that change has occurred
• Motor: output, efferent motor innervation
• The CNS then responds to the stimulus at either the cord level (reflex) or alternatively at higher
Spinal enlargements
levels, the brainstem, cerebellum, basal ganglia, thalamus or cerebrum
Spinal enlargements
• Spinal cord enlargements are the direct consequence of increased quantities of gray matter
(lower motor neurons, interneurons and afferent input) at those specific segmental levels
• The enlargements of the spinal cord supply the quantity of neural machinery necessary to
operate the limbs
• Proximally the first enlargement is the cervical enlargement from C5 to T1, which controls and
coordinates bilaterally the upper limb muscles
• Maximum circumference 38 mm
• The reason behind the enlargement of the cervical region is because of the increased neural
input and output to the upper limbs
Brachial plexus
• Five roots
○ C5 and C6 merge to establish the upper trunk, C7 continuously forms the middle trunk, and
C8 and T1 merge to establish the lower trunk
• Three trunks
○ Superior (upper) C5-C6, middle C7, inferior (lower) C8, T1
• Six divisions
○ Each trunk then splits in two, to form six divisions
○ Three anterior and three posterior
• Three cords
○ These six divisions regroup to become the three cords
○ Posterior, lateral and medial cords
• Five terminal branches
○ Musculocutaneous n., axillary n., radial n., median n. and ulnar n., which all have specific
sensory, motor and proprioceptive functions
Schematic representation of the structure of the brachial plexus
• a. shows names and sequence of the various components of the brachial plexus Brachial plexus
• b. shows the relationship of the lateral, medial, and posterior cords of the brachial plexus to the
axillary artery
• c. shows the subdivision of the brachial plexus cords into their main branches
• The brachial plexus is formed by a network of nerves from the lower four cervical nerves and first
thoracic nerve (C5, C6, C7, C8, and T1)
• The brachial plexus supplies afferent and efferent nerve fibres to chest, shoulder, arm and hand
The axilla
• The axilla is the pyramidal space inferior to the glenohumeral joint and superior to the axillary
fascia at the junction of the arm and thorax
• Providing a passageway for the neurovascular structures that serve the upper limb
• The apex of the axilla constitutes the cervico-axillary canal
• The canal forms a passageway between the neck and axilla, bounded by the lateral aspect of the
1st rib, posterior aspect of the clavicle, and superior edge of the scapula
• The axilla has an apex, base, and four walls (three of which are muscular)
• The axilla contains:
○ Large nerves that make up the cords and branches of the brachial plexus Location, boundaries, and contents of the axilla
○ Blood vessels (axillary artery and vein)
○ Lymphatic vessels and nodes
○ Axillary fat
CHI108 Page 1
