Questions and Answers
What is the origin of the Upper Trunk in the Brachial Plexus?
Which nerve is NOT a branch of the Medial Cord?
Which terminal branch is responsible for innervating the anterior compartment of the arm?
How many roots originate from the spinal cord to form the Brachial Plexus?
Signup and view all the answers
Which of the following Cords gives rise to the Axillary Nerve?
Signup and view all the answers
Identify the trunk that consists solely of the C6 root.
Signup and view all the answers
Which nerve is responsible for innervating the diaphragm?
Signup and view all the answers
Which nerve innervates the serratus anterior muscle?
Signup and view all the answers
What is the role of the suprascapular nerve?
Signup and view all the answers
Which of the following muscles is NOT innervated by the dorsal scapular nerve?
Signup and view all the answers
Which nerve is associated with the upper trunk of the brachial plexus?
Signup and view all the answers
Which nerves are branches of the lateral cord of the brachial plexus?
Signup and view all the answers
What spinal roots contribute to the lateral pectoral nerve?
Signup and view all the answers
Which root contributes to the lateral root of the median nerve?
Signup and view all the answers
Which nerve is primarily responsible for innervating the pectoralis major muscle?
Signup and view all the answers
What is the primary role of the musculocutaneous nerve?
Signup and view all the answers
Which nerve innervates the lower part of the subscapularis and teres major?
Signup and view all the answers
Which of the following nerves is responsible for innervating the latissimus dorsi muscle?
Signup and view all the answers
Which nerve is a terminal branch that contributes solely to the arm?
Signup and view all the answers
What is the primary contribution of the dorsal scapular nerve?
Signup and view all the answers
Which nerve originates from the lateral cord of the brachial plexus?
Signup and view all the answers
Which nerve innervates the pectoralis minor and major muscles?
Signup and view all the answers
Which of the following is NOT a branch of the medial cord?
Signup and view all the answers
What is the spinal root contribution of the medial root of the median nerve?
Signup and view all the answers
Identify the nerve that provides sensory innervation to the skin of the medial aspect of the forearm.
Signup and view all the answers
Which nerve is predominantly responsible for motor innervation to the anterior compartment of the arm?
Signup and view all the answers
What is the function of the ulnar nerve?
Signup and view all the answers
Which nerve is responsible for innervating the skin over the posterior aspect of the arm?
Signup and view all the answers
Which nerve contributes to the innervation of the diaphragm?
Signup and view all the answers
Which of the following structures does NOT originate from the trunks of the brachial plexus?
Signup and view all the answers
What is the role of the long thoracic nerve?
Signup and view all the answers
Which muscle is innervated by the radial nerve?
Signup and view all the answers
What spinal roots contribute to the axillary nerve?
Signup and view all the answers
Which of the following muscles is NOT primarily innervated by the radial nerve?
Signup and view all the answers
Which nerve provides sensory innervation to the skin of the posterior arm?
Signup and view all the answers
What is the role of the brachioradialis muscle, considering its innervation?
Signup and view all the answers
What is the primary function of the musculocutaneous nerve?
Signup and view all the answers
Which of the following describes a potential consequence of musculocutaneous nerve damage?
Signup and view all the answers
Which nerve pierces the coracobrachialis muscle?
Signup and view all the answers
Which area of skin is primarily affected by the lateral cutaneous nerve of the forearm?
Signup and view all the answers
What is the spinal root contribution of the musculocutaneous nerve?
Signup and view all the answers
What is the primary origin of the axillary nerve?
Signup and view all the answers
Which space does the axillary nerve pass through?
Signup and view all the answers
What is the primary sensory area affected by damage to the axillary nerve?
Signup and view all the answers
What loss of function occurs due to axillary nerve damage?
Signup and view all the answers
Which artery is closely related to the axillary nerve?
Signup and view all the answers
What is the proximal origin of the median nerve?
Signup and view all the answers
Which structure does the median nerve pass medial to in the cubital fossa?
Signup and view all the answers
Which nerve branches off before the median nerve enters the carpal tunnel?
Signup and view all the answers
After passing through the carpal tunnel, what branches does the median nerve give off?
Signup and view all the answers
Which muscles does the median nerve innervate after passing through the carpal tunnel?
Signup and view all the answers
What condition is associated with the proximal lesion of the median nerve?
Signup and view all the answers
Which sign indicates an inability to flex the 2nd and 3rd fingers due to proximal median nerve injury?
Signup and view all the answers
Which fingers are primarily affected by the distal lesion of the median nerve?
Signup and view all the answers
What is lost in both proximal and distal median nerve injuries?
Signup and view all the answers
In a distal median nerve injury, what happens when a patient is asked to open their hand?
Signup and view all the answers
What sensory area is affected by proximal median nerve injury?
Signup and view all the answers
What is a common result of a proximal lesion of the median nerve?
Signup and view all the answers
What is indicated by the Benediction Sign?
Signup and view all the answers
Which fingers are typically unable to extend in a distal lesion of the median nerve?
Signup and view all the answers
What motor function is lost due to a proximal lesion of the median nerve specifically affecting the hand?
Signup and view all the answers
Which sensory area is affected by median nerve damage?
Signup and view all the answers
Which of the following describes a common finding in carpal tunnel syndrome?
Signup and view all the answers
What is the origin of the ulnar nerve?
Signup and view all the answers
Where does the ulnar nerve enter the anterior compartment of the forearm?
Signup and view all the answers
What is the course of the ulnar nerve as it descends in the arm?
Signup and view all the answers
What anatomical structure does the ulnar nerve pass superficial to in the hand?
Signup and view all the answers
Which fingers does the ulnar nerve primarily supply?
Signup and view all the answers
Where does the deep branch of the ulnar nerve enter?
Signup and view all the answers
Which muscle is primarily responsible for wrist adduction that may be impaired due to ulnar nerve damage?
Signup and view all the answers
What condition is characterized by the inability to extend the 4th and 5th fingers when trying to open the hand?
Signup and view all the answers
Which of the following is NOT a symptom of ulnar nerve damage?
Signup and view all the answers
What area of skin is primarily innervated by the ulnar nerve?
Signup and view all the answers
Which of the following muscles is affected by ulnar nerve injury affecting finger abduction and adduction?
Signup and view all the answers
What is a common consequence of long-term compression of the ulnar nerve?
Signup and view all the answers
What condition is characterized by the inability to extend the 4th and 5th fingers?
Signup and view all the answers
Which forearm action is primarily impaired by ulnar nerve damage?
Signup and view all the answers
Which area of the skin is affected by the ulnar nerve?
Signup and view all the answers
What muscle function is affected by ulnar nerve damage leading to loss of ability to abduct and adduct fingers?
Signup and view all the answers
What is the origin of the radial nerve?
Signup and view all the answers
Which structure does the radial nerve course beneath?
Signup and view all the answers
In which area does the radial nerve pass through while in the arm?
Signup and view all the answers
What spinal roots contribute to the radial nerve?
Signup and view all the answers
Where does the radial nerve travel after passing through the radial groove?
Signup and view all the answers
Which area is primarily affected by damage to the radial nerve?
Signup and view all the answers
What is the origin of the radial nerve?
Signup and view all the answers
Which structure does the radial nerve pierce?
Signup and view all the answers
What is a consequence of damage to the posterior compartment of the arm due to radial nerve injury?
Signup and view all the answers
What is the course of the radial nerve through the arm?
Signup and view all the answers
What position is characteristic of upper brachial plexus injuries?
Signup and view all the answers
Which nerves are typically affected by Erb-Duchenne palsy?
Signup and view all the answers
Which trunk of the brachial plexus is formed by the C5 and C6 roots?
Signup and view all the answers
What is a common cause of upper brachial plexus injuries?
Signup and view all the answers
What areas are innervated by the brachial plexus?
Signup and view all the answers
What type of injury involves all roots of the brachial plexus?
Signup and view all the answers
What is a typical symptom of brachial plexus injury?
Signup and view all the answers
Which nerves are affected by lower brachial plexus injuries?
Signup and view all the answers
What condition results in claw hand due to paralysis of the intrinsic hand muscles?
Signup and view all the answers
Which nerve roots are affected in Klumpke's paralysis?
Signup and view all the answers
What is a notable symptom associated with Horner's syndrome linked to the lower trunk?
Signup and view all the answers
Which of the following is NOT a consequence of excessive superior pull of the lower trunk?
Signup and view all the answers
Which nerve is affected leading to paralysis of forearm flexors and extensors in Klumpke's paralysis?
Signup and view all the answers
Study Notes
Brachial Plexus Overview
- Composed of a network of nerves that innervate the upper limb.
Supraclavicular Part
- Divided into Roots and Trunks.
Roots
- Originates from the spinal cord.
- Includes spinal segments:
- C4
- C5
- C6
- C7
- C8
- T1
Trunks
- Formed from the Roots, categorized as:
- Upper Trunk: C4, C5
- Middle Trunk: C6
- Lower Trunk: C7, C8, T1
Cords
- Three Cords arise from the Trunks:
-
Lateral Cord
- Contains Lateral Pectoral Nerve
- Musculocutaneous Nerve
- Lateral Root of the Median Nerve
-
Posterior Cord
- Comprises Axillary Nerve
- Radial Nerve
-
Medial Cord
- Includes Medial Pectoral Nerve
- Ulnar Nerve
- Medial Root of the Median Nerve
-
Lateral Cord
Infraclavicular Part
- Mainly formed by the Cords which lead to the Terminal Branches.
Terminal Branches
- Key nerves that innervate different regions of the upper limb:
- Musculocutaneous Nerve
- Axillary Nerve
- Radial Nerve
- Median Nerve
- Ulnar Nerve
- Dorsal Scapular Nerve
- Long Thoracic Nerve
Supraclavicular Part: Branches
- The supraclavicular part of the brachial plexus comprises roots and upper trunk branches.
Roots
-
Dorsal scapular nerve
- Arises from C5, innervates rhomboid major, rhomboid minor, and levator scapulae muscles.
-
Long thoracic nerve
- Innervates the serratus anterior muscle, important for scapular movement.
-
Phrenic nerve
- Also derived from C5, primarily responsible for motor supply to the diaphragm, essential for respiration.
Upper Trunk
-
Nerve to subclavius
- Supplies the subclavius muscle, which stabilizes the clavicle.
-
Suprascapular nerve
- Innervates supraspinatus and infraspinatus muscles, crucial for shoulder stability and movement.
Five Roots (Ventral Rami)
- Consists of contributions from five terminal roots:
-
Dorsal scapular nerve (C5)
- Provides assistance to the phrenic nerve.
-
C5, C6, C7, C8, T1
- These nerve roots contribute to forming the brachial plexus, essential for upper limb innervation.
-
Dorsal scapular nerve (C5)
Infraclavicular Part of the Brachial Plexus
- Comprises nerves originating from the cervical and thoracic spinal cord targeting upper limbs.
- Located below the clavicle, consists of three cords: lateral, medial, and posterior.
Lateral Cord Branches
- Lateral root of the median nerve: Formed from C6 and C7 nerve roots, plays a role in sensation and motor functions of the forearm and hand.
- Musculocutaneous nerve: Arises from C5 to C7, innervates the flexor muscles in the anterior compartment of the arm.
- Lateral pectoral nerve: Originates from C5, C6, and C7, primarily innervates the pectoralis major muscle, involved in shoulder movements.
Posterior Cord Branches
- Upper subscapular nerve (C5): Innervates the upper part of the subscapularis muscle.
- Lower subscapular nerve (C6): Supplies the lower part of subscapularis and teres major muscles.
- Thoracodorsal nerve (C6/7/8): Innervates the latissimus dorsi muscle, aiding in arm movement.
- Radial nerve (C5-T1): Major nerve supplying the posterior arm and forearm, responsible for wrist and finger extension.
- Axillary nerve (C5/6): Innervates the deltoid and teres minor muscles, involved in shoulder abduction.
Branches of the Brachial Plexus
- Musculocutaneous nerve (C5-C7): Supplies muscles of the anterior arm and sensory innervation to the lateral forearm.
- Axillary nerve (C5-C6): Also innervates shoulder muscles, particularly effective in arm elevation.
- Radial nerve (C5-T1): Critical for arm and hand movements; injury can lead to wrist drop.
- Median nerve (C6-T1): Controls most forearm flexors and some hand muscles; significant in hand function.
- Ulnar nerve (C7-T1): Innervates the intrinsic muscles of the hand; important for fine motor control.
Three Cords Structure
- Lower subscapular nerve (C5-C6): Contributes to the innervation of the subscapularis and teres major.
- Thoracodorsal nerve: Central role in innervating the latissimus dorsi from the posterior cord.
- Upper subscapular nerve (C5-C6): Affects upper subscapularis muscle function.
Contributions from Three Trunks
- Phrenic nerve (C5): Vital for diaphragm function, impacting respiration.
- Dorsal scapular nerve (C5): Innervates the rhomboid muscles and levator scapulae, assisting in scapular movement.
- Suprascapular nerve (C5-C6): Provides sensory and motor function to the supraspinatus and infraspinatus muscles, important for shoulder stability.
Six Divisions and Their Function
- Lateral pectoral nerve (C5-C7): Innervates the pectoralis major, involved in shoulder movement.
- Long thoracic nerve (C5-C7): Innervates serratus anterior, crucial for scapular protraction.
- Medial pectoral nerve (C8-T1): Patriciate in innervating pectoralis major and minor.
- Medial cutaneous nerve of arm (C8-T1): Provides sensory innervation to the skin of the medial arm.
- Medial cutaneous nerve of forearm (C8-T1): Supplies sensory innervation to the skin of the medial forearm.
Medial Cord Branches
- Medial pectoral nerve (C8/T1) innervates pectoralis minor and major muscles.
- Medial cutaneous nerve of the arm (C8/T1) provides sensory innervation to the skin of the medial arm.
- Medial cutaneous nerve of the forearm (C8/T1) supplies sensation to the skin of the medial forearm.
- Ulnar nerve (C8/T1) is responsible for innervating muscles in the forearm and hand.
- Medial root of the median nerve (C8/T1) contributes to the median nerve's function in the forearm and hand.
General Overview of Brachial Plexus
- Three cords are part of the brachial plexus: lateral, medial, and posterior.
- Six divisions arise from these cords, with each cord giving rise to specific branches.
- Five major branches originate from the plexus: musculocutaneous, axillary, radial, median, and ulnar nerves.
Additional Branches and Contributions
- Musculocutaneous nerve (C5-C7) arises from the lateral cord; important for flexing the elbow.
- Axillary nerve (C5-C6) innervates the deltoid and teres minor muscles, important for shoulder movement.
- Radial nerve (C5-T1) supplies muscles in the posterior compartment of the arm and forearm.
- Median nerve (C6-T1) is essential for hand function, innervating many flexor muscles.
- Ulnar nerve (C7-T1) innervates intrinsic muscles of the hand, crucial for fine motor skills.
Subscapular Nerves
- Lower subscapular nerve (C5-C6) innervates the subscapularis and teres major muscles.
- Middle subscapular nerve (C6-C8) also known as thoracodorsal nerve, supplies latissimus dorsi muscle.
- Upper subscapular nerve (C5-C6) innervates the upper part of the subscapularis muscle.
Trunks and Additional Contributions
- Three trunks are created by the merging of ventral rami from spinal nerves.
- Phrenic nerve (C5) is crucial for diaphragm function and breathing.
- Dorsal scapular nerve (C5) innervates the rhomboids and levator scapulae muscles.
- Suprascapular nerve (C5-C6) innervates the supraspinatus and infraspinatus muscles, important for shoulder stability.
- Long thoracic nerve (C5-C7) innervates the serratus anterior muscle, which aids in scapular movements.
Muscular Innervation
-
Radial Nerve: Supplies muscles primarily in the posterior compartment of the arm and forearm.
- Originates from spinal roots C5, C6, C7, C8, T1.
- Innervates major muscles including:
- Triceps brachii (long, medial, and lateral heads)
- Anconeus
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
- Extensor indicis
-
Axillary Nerve: Provides innervation to specific shoulder muscles.
- Arises from spinal roots C5, C6.
- Innervates:
- Teres minor
- Deltoid
- Has variable contribution to brachioradialis, which is also involved in forearm flexion.
- Extensor carpi radialis longus and brevis
- Supinator
Functional Notes
- Brachioradialis, although a posterior compartment muscle, functions primarily as a flexor of the forearm due to its innervation from a posterior division nerve.
Cutaneous Innervation
- Major cutaneous nerves include:
- Axillary Nerve: Innervates skin over the lateral shoulder.
- Radial Nerve: Innervates skin over the posterior aspect of the arm and forearm.
Musculocutaneous Nerve
- Originates from the lateral cord of the brachial plexus, specifically spinal nerves C5, C6, and C7.
- Courses through the arm by piercing the coracobrachialis muscle.
- Located between the brachialis and biceps brachii muscles in the anterior compartment of the arm.
- Damage to this nerve results in:
- Loss of elbow flexion, affecting activities requiring pulling or lifting.
- Diminished forearm supination, impacting the ability to rotate the palm upward.
- Muscle wasting of the biceps brachii, leading to a noticeable decrease in muscle mass.
- Sensory loss in the skin of the lateral forearm due to involvement of the lateral cutaneous nerve of the forearm.
Axillary Nerve
- (Note: No information provided on the axillary nerve, further details are required for study notes.)
Axillary Nerve Overview
- Originates from the posterior cord of the brachial plexus at spinal levels C5 and C6.
Course and Location
- Passes through the quadrangular space.
- Runs around the surgical neck of the humerus.
Anatomical Relations
- Accompanied by the posterior circumflex humerii artery and vein.
Damage and Clinical Implications
- Damage can lead to loss of deltoid muscle function, specifically:
- Impaired abduction of the arm between 15° and 90°.
- Atrophy of the deltoid muscle, leading to a distinct wasting appearance.
- Sensory loss may occur in the skin over the lateral aspect of the deltoid area.
Median Nerve: Overview
- Originates from medial and lateral roots of the medial and lateral cords of the brachial plexus.
- Spans from spinal segments C6 to T1.
Course of the Median Nerve
- Travels through the anterior compartment of the arm.
- Positioned medial to the brachial artery in the cubital fossa.
- Passes between the heads of the pronator teres muscle.
- Located between the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) muscles.
- Runs lateral to the palmaris longus tendon at the wrist.
Branches and Functions
- Enters the carpal tunnel at the wrist.
- Gives off the anterior interosseous nerve in the forearm.
- Before entering the carpal tunnel, it provides a palmar cutaneous branch that supplies the skin over the flexor retinaculum.
- After traversing the carpal tunnel, it branches into:
- Recurrent branch which innervates thenar muscles and lateral lumbricals.
- Palmar digital branches supplying sensation to 3½ fingers.
Median Nerve Damage
Proximal Lesion of Median Nerve
- Typically caused by supracondylar fractures.
- Motor Effects: Impact on both forearm and hand function.
- Loss of nearly all forearm flexors, except for 1½ muscles supplied by the ulnar nerve, leading to a forearm that is supinated and adducted.
- Inability to flex the thumb and perform opposition, resulting in the "Ape hand" appearance.
- Loss of function of the two lateral lumbricals affects the ability to flex the index and middle fingers at the metacarpophalangeal (MCP) joints and prevents full extension at the interphalangeal (IP) joints.
- When asked to make a fist, the thumb and lateral two lumbricals remain extended, producing the "Benediction sign."
Distal Lesion of Median Nerve
- Commonly associated with carpal tunnel syndrome.
- Motor Effects: Primarily affects hand function.
- Loss of intrinsic muscles in the thumb, middle, and index fingers.
- Loss of two lateral lumbricals causes inability to flex the index and middle fingers at MCP joints and limits full extension at IP joints.
- When asked to open the hand, the 2nd and 3rd fingers remain flexed, and the thumb is unable to oppose.
Key Functional Losses
- Proximal median nerve injury results in inability to flex the 2nd and 3rd fingers.
- Distal median nerve injury hinders the ability to extend the 2nd and 3rd fingers.
Sensory Loss
- Sensory impairment includes loss of sensation on the palmar surface and lateral 3½ digits.
Proximal Lesion of Median Nerve
- Often occurs due to supracondylar fractures.
- Results in loss of function in all forearm flexors, except those innervated by the ulnar nerve, leading to a forearm positioned in supination and adduction.
- Thumb functions significantly impaired: loss of thumb flexion and opposition, resulting in an "Ape hand" appearance.
- Affects 2 lateral lumbricals, causing inability to flex index and middle fingers at the MCP joints and lack of full extension at the IP joints.
- When asked to make a fist, the thumb and lateral 2 fingers remain extended, producing the "Benediction Sign."
Distal Lesion of Median Nerve
- Commonly associated with carpal tunnel syndrome.
- Primarily impacts intrinsic muscles of the hand affecting the thumb, index, and middle fingers.
- Loss of function in 2 lateral lumbricals results in similar inability to flex index and middle fingers at the MCP joints and achieve full extension at the IP joints.
- When instructed to open the hand, the 2nd and 3rd fingers remain flexed and the thumb loses its ability to oppose.
Median Nerve Injury - Proximal
- Inability to flex the 2nd and 3rd fingers.
Median Nerve Injury - Distal
- Inability to extend the 2nd and 3rd fingers.
Sensory Loss
- Sensory deficits occur in the palmar surface and lateral 3 1/2 digits.
Ulnar Nerve Overview
- Originates from the medial cord of the brachial plexus, specifically from spinal roots C8-T1.
- Responsible for innervation of the little finger, ring finger, and part of the hand.
Course of the Ulnar Nerve
- Descends along the medial side of the brachial artery until it reaches the coracobrachialis muscle's insertion.
- Pierces the intermuscular septum to enter the posterior compartment of the arm.
- Located posterior to the medial epicondyle of the humerus, an important anatomical landmark.
- Enters the anterior compartment of the forearm through the space between the two heads of the flexor carpi ulnaris (FCU).
- Travels along the lateral border of the FCU towards the wrist.
- Runs between the flexor digitorum superficialis (FDS) laterally and the flexor digitorum profundus (FDP) medially.
- Passes superficially to the flexor retinaculum before entering the hand.
- The deep branch of the ulnar nerve proceeds into Guyon’s canal, which is crucial for further innervation of the hand.
Anatomical Context
- The pathway of the ulnar nerve is significant for its clinical relevance in conditions such as "cubital tunnel syndrome."
- Understanding its course aids in diagnosing nerve compression or injury related to the hand and forearm.
Ulnar Nerve Injury
- Common injury locations include the elbow, wrist, and other specific points along the nerve path.
- Forearm muscle function is affected, leading to:
- Impaired wrist adduction, typically assisted by the flexor carpi ulnaris (FCU).
- Reduced flexion of the little and ring fingers, impacting FCU and the medial half of the flexor digitorum profundus (FDP).
Motor Function Impairments
- Inability to abduct and adduct fingers due to affected interosseous muscles.
- Long-term compression can lead to noticeable atrophy in the hypothenar muscles (muscles at the base of the little finger).
Ulnar Claw Hand
- The condition is characterized by:
- Loss of function in the medial two lumbricals, which affects finger movement.
- When attempting to open the hand, the patient is unable to extend the 4th and 5th fingers.
- Flexion of the thumb remains intact due to the median nerve's functionality.
Sensory Loss
- Sensation loss occurs in the skin areas innervated by the ulnar nerve, affecting the medial one and a half digits and the medial forearm.
Ulnar Nerve Damage
- Ulnar nerve injury commonly occurs at four specific locations along its pathway.
- Forearm muscles affected include:
- Impaired wrist adduction due to dysfunction of the flexor carpi ulnaris (FCU).
- Reduced flexion of the little and ring fingers, impacted by FCU and the medial half of the flexor digitorum profundus (FDP).
Effects on Hand Function
- Inability to abduct and adduct the fingers due to involvement of all interosseous muscles.
- Long-term compression can lead to hypothenar muscle atrophy.
- Condition known as "ulnar claw hand" arises from:
- Loss of function in the medial two lumbricals.
- Patient struggles to open the hand as the 4th and 5th fingers cannot extend, creating a claw-like appearance.
- Thumb flexion remains possible due to intact median nerve function.
Sensory Implications
- Sensory loss occurs in the medial 1.5 digits and the medial side of the forearm due to disrupted nerve signals.
Brachial Plexus Overview
- The Brachial Plexus is a crucial nerve network responsible for upper limb innervation.
- Comprised of supraclavicular (Roots, Trunks, Cords) and infraclavicular (Cords, Terminal Branches) parts.
Supraclavicular Part
- Composes Roots from spinal nerves C4-T1.
- Forms Trunks:
- Upper Trunk (C4, C5)
- Middle Trunk (C6)
- Lower Trunk (C7, C8, T1)
- Three Cords arise from Trunks:
- Lateral Cord
- Posterior Cord
- Medial Cord
Infraclavicular Part
- Contains Terminal Branches that arise from the Cords.
Cords and Their Branches
-
Lateral Cord:
- Lateral Pectoral Nerve
- Musculocutaneous Nerve
- Lateral Root of the Median Nerve
-
Posterior Cord:
- Upper Subscapular Nerve
- Thoracodorsal Nerve
- Lower Subscapular Nerve
- Axillary Nerve
- Radial Nerve
-
Medial Cord:
- Medial Pectoral Nerve
- Ulnar Nerve
- Medial Cutaneous Nerve of the Arm and Forearm
Terminal Branches
- Major branches include:
- Musculocutaneous Nerve
- Axillary Nerve
- Radial Nerve
- Median Nerve
- Ulnar Nerve
- Dorsal Scapular Nerve
- Long Thoracic Nerve
Injury Insights
- Musculocutaneous Nerve damage results in loss of elbow flexion and diminished forearm supination.
- Axillary Nerve damage leads to inability to abduct the arm between 15° and 90° and deltoid atrophy.
Median Nerve Damage
-
Proximal Lesion (e.g., supracondylar fractures):
- Causes loss of forearm flexors, thumb flexion, thumb opposition (Ape hand), and affects lateral 2 lumbricals leading to Benediction Sign.
-
Distal Lesion (e.g., carpal tunnel syndrome):
- Affects intrinsic muscles causing inability to flex or extend 2nd and 3rd fingers accordingly.
Ulnar Nerve Pathway and Damage
- Originates from the Medial Cord between C8-T1.
- Damage effects:
- Impaired wrist adduction, flexion of ring and little fingers, inability to abduct/adduct fingers.
- Long-term compression can lead to atrophy of hypothenar muscles and Ulnar Claw Hand, resulting in loss of function in the 4th and 5th fingers.
Radial Nerve Overview
- Originates from the Posterior Cord (C5-T1).
- Runs through the triangular space and radial groove, innervating various muscles of the posterior compartment of the arm, including extensors.
Anatomical Summary
- The Brachial Plexus serves as a comprehensive network for motor and sensory innervation of the upper limb, with distinct branches converting complex spinal inputs into action.
Radial Nerve Overview
- Originates from the posterior cord of the brachial plexus, with spinal roots from C5 to T1.
- Courses through the triangular space and radial groove, navigating below the brachioradialis muscle.
Key Anatomical Features
- The nerve pierces the supinator muscle to form the posterior interosseous branch.
- The superficial branch of the radial nerve is located beneath the brachioradialis and crosses the floor of the anatomical snuff box.
Clinical Implications of Damage
- Injury in the posterior compartment of the arm can result in:
- Loss of ability to extend the elbow.
- Diminished capability for supination of the forearm.
- Damage in the posterior compartment of the forearm leads to:
- "Wrist drop," a condition characterized by inability to extend the wrist.
- Sensory loss occurs in the skin covering the posterior aspect of the arm, forearm, and hand.
Upper Trunk Injuries
- Upper brachial plexus injuries are characterized by the "waiter's tip position," where the limb hangs by the side, is medially rotated, and the forearm is pronated.
- Trauma during birth or other traumatic incidents often leads to this condition.
- Erb-Duchenne palsy affects the C5 and C6 spinal nerves, resulting in weakness of the shoulder and arm.
Anatomy of the Brachial Plexus
- The brachial plexus is constructed from the ventral rami of spinal nerves C5-T1, forming a network that innervates the shoulder, arm, forearm, and hand.
- It consists of five major branches: musculocutaneous, axillary, radial, median, and ulnar nerves.
- The brachial plexus is organized into five sections:
- Roots: Composed of the five spinal nerves (C5-T1).
-
Trunks: Three trunks formed from the roots:
- Upper trunk: C5 and C6
- Middle trunk: C7
- Lower trunk: C8 and T1
- Divisions: Each trunk splits into anterior and posterior divisions.
-
Cords: Formed by the merging of divisions into three cords:
- Lateral cord: Anterior divisions of the upper and middle trunks.
- Posterior cord: Posterior divisions of all three trunks.
- Medial cord: Anterior division of the lower trunk.
- Branches: Final branches innervate muscles and skin of the upper limb.
Brachial Plexus Injuries
- Injuries can cause varying symptoms including weakness, numbness, or paralysis based on the injury location.
- Types of brachial plexus injuries include:
- Upper brachial plexus injuries: Affect C5 and C6 roots, usually from neck stretching (e.g., during car accidents).
- Lower brachial plexus injuries: Involve C8 and T1 roots, often due to birth injuries or shoulder trauma.
- Total brachial plexus injuries: Involve all roots, typically the result of severe neck or shoulder trauma.
Inferior (Lower) Trunk
- Excessive superior pull can result in the dysfunction of the lower trunk.
- Involvement of C8-T1 nerves leads to loss of function in radial, ulnar, and median nerves.
- Klumpke's paralysis manifests as a total claw hand, affecting all fingers due to the loss of all lumbricals, forearm flexors, and extensors.
- Paralysis of intrinsic hand muscles results in distinct deformities of the hand.
- Numbness occurs in the C8/T1 dermatome distribution area.
- T1 nerve root’s proximity to the T1 sympathetic ganglion can cause Horner's syndrome, characterized by ptosis (drooping eyelid) and miosis (constricted pupil).
Augusta Déjerine-Klumpke
- Born on October 15, 1859, in San Francisco, California.
- Passed away on November 5, 1927, in Paris, France, at the age of 68.
- An American national known for contributions to neuroanatomy.
Six Divisions of the Brachial Plexus
-
Three Trunks: Upper, Middle, and Lower trunks each have different nerve contributions.
- Upper Trunk: Contains the subclavius nerve (C5).
- Contributions to the phrenic nerve originate from C5.
- Dorsal scapular nerve derives from C5.
- Suprascapular nerve comes from the C5-C6 nerve roots.
- Long thoracic nerve is formed from C5-C7 roots.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz delves into the Brachial Plexus, focusing on its supraclavicular part, including the roots and trunks. Test your knowledge on the spinal nerves involved and their divisions into trunks and cords. Perfect for anatomy and medical students!
