Anatomy Exam 3: Brachial Plexus

The Brachial plexus originates in the ________ regions and send nerves to ______________.

Shoulders

All arm muscles

The ________ is the major network that provide _______ and ___________ to the upper extremity

Brachial Plexus,

Motor

Sensory innervations

Where does the brachial plexus originate

Ventral Rami of the spinal nerves C5-T1

What muscles does the brachial plexus supply?

Shoulder

Arm

Forearm

Hand

What does the brachial plexus allow FUNCTIONALLY?

Complex movement patterns needed for grasp, manipulation, and all upper-limb occupational activities

What can damage do to part of this brachial network?

Weakness

Loss of sensation

Functional impairment

The roots are...

Anterior rami of spinal nerves emerging from the cervical spine

What does each root in the brachial plexus carry?

Motor and Sensory fibers

Which root is responsible for upper limb movement (shoulder, elbow flexion)

C5-C6

Which root controls the extensors of arm/forearm?

C7

Which root controls intrinsic hand muscles and finger flexors?

C8-T1

Each ______ splits into anterior and ______ divisions that form cords.

Trunk

Posterior

C5-C6 control the...

Upper trunk

C7 controls the....

Middle trunk

C8-T1 controls the...

Lower trunk

What does the ANTERIOR division of the brachial plexus supply?

Flexor compartments (front of arm/forearm)

What does the POSTERIOR division of the brachial plexus supply?

Extensor compartments (back of arm/forearm)

Where is the LATERAL CORD relative to the axillary artery?

Formed from anterior divisions of upper and middle trunks (C5-C7)

Where is the POSTERIOR CORD relative to the axillary artery?

Form all three posterior divisions (C5-T1)

Where is the MEDIAL CORD relative to the axillary artery?

Form anterior division of lower trunk (C8-T1)

What are the terminal branches of the brachial plexus?

Musculocutaneous Nerve

Axillary Nerve

Radial Nerve

Median Nerve

Ulnar Nerve

What nerves spinal roots is C5-C7?

Musculocutaneous nerve

What muscles innervate the musculocutaneous nerve?

Biceps Brachii

Brachialis

Coracobrachialis

What are key motions/ functions of musculocutaneous nerve?

Elbow Flexion

Forearm supination

What is the sensory area of the musculocutaneous nerve?

Lateral forearm

What nerve's spinal roots is C5-C6?

Axillary Nerve

What muscles innervate the axillary nerve?

Deltoids

Teres minor

What are the key motions/functions of the axillary nerve?

Shoulder abduction

External rotation

What is the sensory area of the axillary nerve?

Lateral Shoulder

What nerve's spinal roots is C5-T1?

Radial Nerve

What muscles innervate the radial nerve?

Triceps

Anconeous

Wrist/Finger EXTENSORS

Brachioradialis

What are the key motions/function of the radial nerve?

Elbow Extension

Wrist/Finger/Thumb Extensor

Supination

What are the sensory areas for the radial nerve?

Posterior arm/forearm

Dorsum of hand

What nerve's spinal roots is also C5-T1?

Median Nerve

What muscle innervate the median nerve?

Pronator

Thenar Muscles

Wrist/finger FLEXORS

1st and 2nd lumbricals

What are the key motions/function of the median nerve?

Wrist Flexion

Thumb Opposition

Pronation

What are the sensory areas for the median nerve?

Palmar thumb

Index, Middle, and Half of ring finger

What nerve's spinal roots is C8-T1?

Ulnar Nerve

What muscles innervate the ulnar nerve?

Flexor Carpi Ulnaris

Flexor Digitorum Profundus

Interossei

Hypothenar

3-4 Lumbricals

What are the key motions/function of the ulnar nerve?

Finger Abduction/Adduction

Grip Strength

Fine Motor

What are the sensory areas for the ulnar nerve?

Medial hand

5th finger

Half of ring finger

What is the root origin for DORSAL SCAPULAR nerve?

C5

What muscles innervate the dorsal scapular?

Rhomboids

Leavator Scapulae

Key functions of dorsal scapular?

Retracts/elevates scapula

What is the root origin for the LONG THORACIC nerve?

C5-C7

What muscles innervate the long thoracic nerve?

Serratus Anterior

Key functions of the long thoracic nerve?

Prevents scapular winging

What is the origin for the SUPRASCAPULAR nerve?

C5-C6 (Upper Trunk)

What muscles innervate the suprascapular nerve?

Supraspinatus

Infraspinatus

Key functions of the suprascapular nerve?

Shoulder abduction

External rotation

What is the origin of the LATERAL PECTORAL nerve?

Lateral Cord

What muscles innervate the lateral pectoral nerve?

Pectoralis Major

Key functions of lateral pectoral nerve?

Shoulder Adduction

Internal Rotation

What is the origin of the MEDIAL PECTORAL nerve?

Medial Cord

What muscles innervate the medial pectoral nerve?

Pectoralis Major

Pectoralis Minor

Key functions of medial pectoral nerve?

Assists Scapular depression/protraction

What is the origin of the THORACODORSAL nerve?

Posterior cord

What muscles innervate the thoracodorsal nerve?

Latissimus Dorsi

Key functions of thoracodorsal nerve?

Shoulder Extension

Shoulder Adduction

What is the origin of the UPPER SUBSCAPULAR nerve?

Posterior Cord

What muscles innervate the upper subscapular muscle?

Subscapularis

Key functions of the upper subscapular nerve?

Internal rotation

Glenohumeral stability

What is the origin of the LOWER SUBSCAPULAR nerve?

Posterior Cords

What muscles innervate the lower subscapular nerve?

Subscapularis

Teres Major

Key function of lower subscapular nerve?

Humeral Adduction

Humeral Internal rotation

What is the origin of the Medial Cutaneous nerve?

Medial Cord

What muscles innervate the medial cutaneous nerve?

Sensory ONLY

Key functions of Medial cutaneous nerve?

Skin of medial arm and forearm

Dermatomes represent ____ _______ innervated by a single spinal root.

Skin Regions

Dermatome Root Level C5 supplies regions?

Lateral Arm

Deltoid Region

Functional Example of dermatome root level C5?

Shoulder Abduction Sensation

Dermatome root level C6 supplies which region?

Lateral Forearm

Thumb

Functional Example of dermatome root level C6?

Elbow Flexion

Thumb Sensation

Dermatome level C7 supplies which region?

Middle Finger

Functional Example of dermatome root level C7?

Triceps Reflex

Wrist Extension

Dermatome root level C8 supplied which region?

Ring and Little finger

Functional Example of dermatome root level C8?

Finger Flexion and Grip

Dermatome root level T1 supplies which region?

Medial Forearm and Arm

Functional Example of dermatome root level T1?

Hand Intrinsics

Fine Motor

Myotomes correspond to _____ ______ supplied by a single spinal root.

Muscle Groups

Myotomes root level C5 primary movement is?

Shoulder Abduction

Examples of Myotome C5 muscles are?

Deltoid

Supraspinatus

Myotomes root level C6 primary movement is?

Elbow Flexion

Wrist Extension

Examples of Myotome C6 muscles are?

Biceps

Brachioradialis

Myotomes root level C7 primary movement is?

Elbow Extension

Wrist/Finger Extension

Examples of Myotome C7 muscles are?

Triceps

Wrist Extensors

Myotomes root level C8 primary movement is?

Finger Flexion

Examples of Myotome C8 muscles are?

Flexor Digitorum Profundus

Flexor Digitorum Superficialis

Myotomes root level T1 primary movement is?

Finger Abduction/Adduction

Examples of Myotome T1 muscles are?

Interossei

Lumbricals

Sensory testing: light touch purpose?

Tests cutaneous sensation (cotton, brush)

Sensory testing: Pinprick purpose?

Test protective sensation

Sensory testing: Temperature purpose?

Identifies nerve injury or recovery

Sensory testing: Vibration (tuning fork) purpose?

Detects large-fiber sensory function

Sensory testing: Semmes-Weinstein Monofilament purpose?

Measures protective sensation threshold

Sensory testing: Two-point discrimination purpose?

Assesses tactile acuity, especially fingertips

Grip and Pinch strength test what?

Measure functional hand performance

Observation of Atrophy?

Indicated chronic nerve injury (thenar wasting in median nerve palsy)

Common site of injury for a HIGH radial nerve?

Axilla ("crutch palsy")

Mid Humerus ("Saturday night palsy")

What is the deformity called for injury in radial nerve?

Wrist drop