Muscles of the shoulder region Flashcards
What are the two types of muscles in the shoulder?
Extrinsic & Intrinsic
Where do extrinsic muscles originate/attach in the shoulder?
Originate from the trunk and attach to the shoulder (clavicle, scapula, or humerus)
*2 groups: anterior and posterior extrinsic muscles
Where do the intrinsic muscles originate/attach in the shoulder?
Originate from the scapula and/or clavicle and attach to the humerus
Which muscles are anterior extrinsic muscles?
-Pec major
-Pec minor
-Subclavius
-Serratus anterior
Which muscles are posterior extrinsic muscles?
-Trapezius
-Latissimus dorsi
-Rhomboids
-Levator scapula
Which muscles are intrinsic muscles?
-Deltoid
-Teres major
-Rotator cuff muscles: supraspinous, infraspinatus, teres minor, sub scapularis
What are the attachments of the pectoralis major muscle?
Attaches from sternum/clavicle to the lateral lip of the bicipital groove in the humerus
What is the innervation of the pectoralis major muscle?
Lateral and medial pectoral nerves
What are the actions of the pectoralis major muscle?
Actions: extend, adduct and medially rotate the humerus AKA: handcuff position (hands behind the back, adducted and rotated)
*works together with the latissimus dorsi, teres major, and pec minor for this action
*also assists in flexion of humerus
What are the attachments for the pectoralis minor muscle?
Attaches from the coracoid process of the scapula to ribs 3-5
What is the innervation of the pectoralis minor muscle?
Medial pectoral nerve
What are the actions of the pectoralis minor muscle?
Actions: protract & depress scapula
*along with serratus anterior, stabilizes scapula against the rib cage (scapulothoracic joint is not a true joint, so the muscles do most of the anchoring here)
What is thoracic outlet syndrome (TOS)?
Poor posture, cervical rib/scalene hypertrophy, or other trauma can shorten and tighten the pec minor muscles
-will compress brachial plexus and axillary artery which are passing underneath
What are the signs/symptoms of thoracic outlet syndrome (TOS)?
Compression of the brachial plexus/axillary artery can cause:
Neurological symptoms (nerve compression)
-sensory: paresthesia, burning of upper extremity
-motor: upper extremity weakness
Vasculature symptoms (artery compression)
-cold intolerance
What is the location of the subclavius muscle?
Sits just beneath the clavicle
What is the innervation of the subclavius muscle?
Nerve to subclavius
What are the actions of the subclavius muscle?
Actions: stabilizes/depresses clavicle
*in cases of trauma (i.e. clavicle fracture) the subclavius spasms to keep the clavicle from moving/protect underlying structures (brachial plexus, arteries)
What are the attachments of the serratus anterior muscle?
Attach from the medial scapula and wrap around to anchor onto ribs 1-9
What is the innervation of the serratus anterior muscle?
Long thoracic nerve
What are the actions of the serratus anterior muscle?
Actions: protracts scapula
works with pec minor for protraction
& upward rotation of scapula
works with upper and lower trap for upward rotation - combination of these muscle movements allows the scapula to rotate up/point upward for reaching with the arm
What is long thoracic nerve palsy?
The long thoracic nerve becomes stretched or compressed, leading to impairment
-causes paralysis/weakness of serratus anterior, which this nerve innervates
What are the signs/symptoms of long thoracic nerve palsy?
paralysis and weakness of the serratus anterior muscle due to nerve damage will present as:
-“Winging of scapula” (scapula cannot stay snug against the rib cage)
-Inability to reach above shoulder height (scapula cannot properly rotate upward)
What are the regions of the trapezius?
Upper trap, mid trap, lower trap
What are the attachments of the trapezius?
Runs down the occiput, nuchal ligament and spinous process of C7-T12 and attaches to the spine of the scapula and acromion, wraps around to land on the clavicle
What is the innervation of the trapezius?
CN 11
What actions are the upper, middle, and lower trapezius responsible for?
-Upper trap/Lower trap: upward rotation of scapula
-Mid trap: retracts scapula
Which three muscles work together/combine actions to produce upward rotation of the scapula?
Serratus anterior, Upper trap, Lower trap
What are the attachments of the latissimus dorsi?
Runs down the of the lower T-spine, the thoracolumbar fascia and the iliac crest and lands on the floor of the bicipital groove of the humerus
*lands right next to the pec major attachment (has a similar function)
What is the innervation of the latissimus dorsi?
Thoracodorsal nerve
What are the actions of the latissimus dorsi?
Similar function to pec major and teres major
-extends, adducts, and medially rotates the humerus AKA handcuff position (behind the back)
Which three muscles are responsible for the handcuff position (extension, adduction, medial rotation)?
-Latissimus dorsi
-Pec major
-Teres major
What are the attachments of the Rhomboids?
Run down the medial border of the scapula and attaches to the nuchal ligament and spinous processes of C7-T5
What is the innervation of the Rhomboids?
Dorsal scapular nerve
(pops out of the cervical spine, plugs into the levator scapula, and then continues on to plug into the rhomboids)
What is the action of the Rhomboids?
Retract the scapula
What are the attachments of the levator scapula muscle?
Runs down the medial border of the scapula and attaches to the TRANSVERSE PROCESSES of C1-C4
What is the innervation of the levator scapula muscle?
Dorsal scapular nerve
*same as rhomboids
What are the actions of the levator scapula muscle?
-Scapula movement: elevates scapula (while keeping the head still)
-Neck movements: lateral flex (side bend) and rotate to the same side (while keeping the shoulder still)
What four muscles make up the “rotator cuff” muscles?
-Supraspinatus
-Infraspinatus
-Teres minor
-Subscapularis
What are the attachments of the deltoid?
“Shoulder muscle”
Run on the spine of the scapula, acromion, and the clavicle and attach to the deltoid tuberosity of the humerus
What is the innervation of the deltoid
Axillary nerve (pops out and plugs into the deltoid)
What is the action of the deltoid?
Abduct the humerus (raising arm up from the side/away from body)
What are the attachments for the teres major muscle?
Attaches from the inferior angle of the scapula and attaches to the medial lip of the bicipital groove in the humerus
*right near the attachment for the lats and pec major
lats- bicipital floor
pec major- lateral lip of bicipital
What is the teres major muscle innervated by?
Lower subscapular nerve
What are the actions of the teres major muscle?
*Similar to the pec major and lats
-Extend, adduct, and medially rotate the humerus
-Works along with the pec major and lats to create the handcuff position (hands behind back)
What are the attachments of the supraspinatus?
Anchors onto the bony area of the supraspinous fossa of the scapula and continues to land on the greater tuberosity of the humerus
(Supraspinous fossa and GT of humerus)
*goes through subacromial space to get to GT (travels under acromion)
What is the innervation of the supraspinatus?
Suprascapular nerve
(from cervical spine)
The supraspinatus muscle is responsible for what actions?
Abduction of humerus (away from midline) and stabilization of humerus in the glenoid fossa (along with other rotator cuff muscles)
What are the attachments of the infraspinatus?
Anchors onto the bony area of the infraspinous fossa of the scapula and continues to land on the greater tuberosity of the humerus
(infraspinous fossa and GT of humerus)
What is the innervation of the infraspinatus?
Suprascapular nerve
What are the actions of the infraspinatus muscle?
External (lateral) rotation of the humerus and stabilization of humerus in the glenoid fossa (along with other rotator cuff muscles)
What are the attachments of the teres minor muscle?
Runs along the lateral border of the scapula and attaches to the greater tuberosity of the humerus
(lateral border of scapula and GT of humerus)
What is the innervation of the teres minor muscle?
Axillary nerve
What are the actions of the teres minor muscle?
External (lateral) rotation of the humerus and stabilization of humerus in the glenoid fossa (along with other rotator cuff muscles)
*Similar to the infraspinatous muscle actions, these muscles work together
What are the attachments of the subscapularis?
Anchors off of the subscapular fossa of the scapula (back of scapula) and attaches to the lesser tuberosity of the humerus
(Subscapular fossa and LT of humerus)
Which rotator cuff muscle is the only one of the group that anchors onto the lesser tubercle of the humerus (instead of the greater tubercle)?
Subscapularis
What is the innervation of the subscapularis?
The upper and lower subscapular nerves (coming off the brachial plexus)
What are the actions of the subscapularis?
Internal (medial) rotation of the humerus and stabilization of humerus in the glenoid fossa (along with other rotator cuff muscles)
What is torn in a rotator cuff tear?
The rotator cuff tendon that is landing on the head of the humerus
What is the most common rotator cuff tear?
Supraspinatus tendon
How many people in the US visit their doctor for rotator cuff pain?
2 million
What amount of rotator cuff tears are treated successfully with conservative treatment?
80%
What amount of rotator cuff tears are treated surgically?
20% (if tear is more significant or does not respond to conservative treatment)
*surgery is minimally invasive
What are the conservative treatments available for rotator cuff tears?
Physical therapy, activity modification, NSAIDs, steroid injections, topical agents, massage/acupuncture
What are the physical exam procedures for rotator cuff tears?
-contract it
-stretch it
-push on it
(If these provoke pain, will be consistent with a tear)
