Lecture 6: Intro to brachial plexus and shoulder girdle muscles Flashcards
What is the major nerve network supplying the upper limb?
Brachial Plexus
The brachial plexus s formed by the union of what?
Anterior Rami (C5-T1)
Where is the gap that the brachial plexus passes through?
Between the anterior and middle scalene muscles.
In the inferior part of the neck, the roots of the brachial plexus unite to form what three trunks?
-Superior Trunk (C5 & C6)
-Middle Trunk (continuation of C7)
-Inferior Trunk (C8 & T1)
As the brachial plexus passes posterior to the clavicle it divides into two compartments, what are these compartments?
-Anterior (flexor) compartment
-Posterior (extensor) compartment
The division of the brachial plexus forms three chords. What are they?
1) Anterior divisions of the superior and middle trunks
2) Anterior division of the inferior trunk
3) Posterior divisions of all three trunks
Anterior divisions of the superior and middle trunks form what?
Lateral chord
Anterior division of the inferior trunk form what?
Medial chord
Posterior divisions of all three trunks form what?
Posterior chord
The brachial plexus is divided into what two parts by the clavicle?
Supraclavicular & Infraclavicular
What are the four branches of the supraclavicular part of the plexus?
1) Dorsal scapular nerve (C5 root)
2) Long thoracic nerve (C5,6,7)
3) Nerve to subclavius (From superior trunk)
4) Suprascapular nerve (from superior trunk)
The median and lateral cords of the plexus join to form what?
Median nerve
What parts make up the infraclavicular part of the plexus?
-Branches of the lateral cord
-Branches of the medial cord
-Branches of the posterior cord
What are the branches of the the lateral cord?
1) Lateral pectoral nerve
2) Musculocutaneous nerve
What are the branches of the medial cord?
1) Medial pectoral nerve
2) Medial cutaneous nerve of arm
3) Medial cutaneous nerve of forearm
4) Ulnar nerve
What are the branches of the posterior cord?
1) upper subscapular nerve
2) Thoracodorsal nerve
3) Lower subscapular nerve
4) Axillary Nerve
5) Radial nerve
Review nerves and locations on back of card:
The brachial plexus in situ:
-Lateral to cervical spine
- Passes through scalene muscles
-Heads inferolaterally to travel underneath the clavicle and enter the axilla/armpit
-Associated with arterial supply of upper limb
The subclavian artery transitions to what as it passes under the clavicle?
Axillary artery
What is the formation of the plexus?
-Remember “5-3-6-3-5
“Real Texans Drink Cold Beer”
5 roots
3 trunks
6 divisions
3 cords
5 terminal branches
What is the arrangement of the terminal branches? “MARMU”
Musculocutaneous
Axillary
Radial
Median
Ulnar
What are the roots of the brachial plexus?
Anterior branches of fully formed spinal nerves
Which nerves make up the brachial plexus?
C5,6,7,8 & T1
Which trunks make up the brachial plexus?
Superior, Middle. Inferior
How many divisions?
6 divisions
-2 (superior trunk)
-2 (middle trunk)
-2 (inferior trunk)
Where do the 6 divisions pass under?
Clavicle and head towards the axilla
After the brachial plexus enters the axilla, they combine together to form three cords.
Lateral
Posterior
Medial
(their positions are named relative to the axillary artery)
The brachial plexus cords then form the terminal branches, what are they?
-musculocutaneous nerve (lateral cord)
-Axillary & Radial nerves (Posterior cord
-Median nerve (lateral & medial cord)
-Ulnar nerve (medial cord)
Which part of the brachial plexus passes through the scalenes muscles in the neck?
Roots
Review nerve locations:
What are the origins and insertions of the trapezius muscle?
O: upper trap-External occipital protuberance & the medial superior nuchal line of the occipital bone, the ligamentum nuchae, the SP’s of C7
Middle trap: SP of T1-T5
Lower trap: SP of T6-T12
I: Lateral 1/3 of clavicle; acromion, spine of scapula
What action do the upper traps perform?
Elevation and upwardly rotate the scapula & extend the neck
What action do the middle traps perform?
Retraction of the scapula
What action do the lower traps perform?
Depression and aid in upward rotation of the scapula
What is the origin and insertion of the rhomboids minor?
O: SP’s of C7-T1
I: Medial (vertebral) border of scapula at the root of the spine
What are the origins and insertions of rhomboids major?
O: SP’s of T2-T5
I: Medial (vertebral) border of scapula inferior to spine
What actions do the rhomboids perform?
Upward rotation and downward rotation
What are the origins and insertions of levator scapula?
O: TP’s of C1-C4
I: Medial border of the scapulae (above the spine of the scapula)
What are the actions of the levator scapulae?
Elevate the scapula
What are the origins and insertions of Pectoralis minor?
O: 3rd-5th rib
I: Coracoid process
What nerve innervates the pectoralis minor?
Medial nerve
What nerve innervates the rhomboids?
Dorsal scapular
What nerve innervates the traps?
Spinal accessory nerve (CN XI)
What are the actions of the pectoralis minor?
-stabilization, depression, abduction or protraction, internal rotation, and downward rotation of the scapula
What is the origin and insertion of the Subclavius?
O: First rib
I: Subclavian groove of the clavicle
What nerve innervates the subclavius?
Nerve to subclavius
What is the origin and insertion of Serratus anterior?
O: upper 9 ribs
I; Anterior surface of vertebral (medial) border of scapula
What nerve innervates the serratus anterior?
Long thoracic nerve (C5,6,7)
What is paralysis of the serratus anterior, due to injury of the long thoracic nerve called?
Winged scapula
What happens during winged scapula?
Inferior angle of the medial border of the scapula is excessively prominent.
What actions does winged scapula make difficult?
Pushing actions or raising arm above head
What are the origins and insertions of the pectoralis major?
O: Clavicular head-Medial half of clavicle.
-Sternocostal head -sternum & costal cartilages of 1st to 7th ribs
I: lateral lip of intertubular (bicipital) groove of the humerus
What are the actions of the pectoralis major?
Horizontal adduction
What are the origins and insertions of the latissimus dorsi?
O: SP’s of T7-L5
Crest of ilium & sacrum
Lowest four ribs (via thoracolumbar fascia)
I: Floor of the intertubercular groove of the humerus
What nerve innervates the latissimus dorsi?
Thoracodorsal
What actions does the latissimus dorsi perform?
Internal rotation, adduction, and extension of the arm
What are the origins and insertions of the deltoid muscle?
O: lateral clavicle (anterior fibers)
acromion (lateral fibers)
Spine of the scapula (posterior fibers)
I: Deltoid tuberosity of humerus
What nerve innervates the deltoid?
Axillary
What are the origins and insertions of the subscapularis?
O: Subscapular fossa
I: lesser tubercle of the humerus
What nerve innervates the subscapularis?
Upper and lower subscapularis
What are the origins and insertions of the Supraspinatus?
O: Supraspinous fossa
I: Greater tubercle of humerus
What nerve innervates the supraspinatus?
Suprascapular nerve
What are the origins and insertions of the infraspinatus?
O: infraspinous fossa
I: Greater tubercle of humerus
What nerve innervates the infraspinatus?
Suprascapular nerve
What are the origins and insertions of the Teres minor?
O: The superior lateral border of scapula
I: Greater tubercle of humerus
What nerve innervates the teres minor?
Axillary nerve
What are the origins and insertions of the teres major?
O: The inferior lateral border of the scapula
I: Medial lip of intertubercular (bicipital) sulcus (groove) of humerus
What nerve innervates the teres major?
Upper and lower subscapular nerve
What muscles are included in the rotator cuff?
1) Supraspinatus
2) Infraspinatus
3) Teres minor
4) Subscapularis
What is the roll of the rotator cuff?
Strengthen the shoulder capsule all around except inferiorly.
In which direction it is most common to dislocate the humerus?
Downward direction
Review axillary spaces:
