MSK Muscles of the pectoral and shoulder region Flashcards
Name the muscles of the pectoral region
Pectoralis major
Pectoralis minor
Serratus anterior
What are the attachments and actions of the pectoralis major?
Fan shaped muscle:
The clavicular head attaches to the clavicle
The sternocostal head attaches to the sternum and ribs
Both heads attach to the intertubecular groove of humerus
Actions:
Adduct and medial rotate humerus at shoulder
Clavicular head also performs flexion
What is the innervation of pec major and minor?
Pec major - medial and lateral pectoral nerves
Pec minor - medial pectoral nerve
(derived from brachial plexus)
What are the attachments and actions of the pectoralis minor?
Triangular shaped muscle:
Originates from ribs 3-5
Attach to coracoid process of scapula (forms a bridge where vessels pass underneath to reach arm)
Actions:
Depresses the shoulder
What are the attachments and actions of the serratus anterior?
Consists of several strips:
Originates from ribs 2-8
Attach to costal surface of medial border of scapula
Actions:
Holds scapula against ribcage
Rotates scapula so arm can abduct over 90 degrees
What is the innervation of serratus anterior?
Long thoracic nerve
What is the difference between extrinsic and intrinsic shoulder muscles?
Extrinsic - originate from torso and attach to shoulder bones, located at the back
Intrinsic - originate from scapula or clavicle and attach to humerus
Name deep and superficial extrinsic shoulder muscles
Superficial:
- trapezius
- latissimus dorsi
Deep:
- levator scapulae
- rhomboid major
- rhomboid minor
What are the attachments and actions of the trapezius?
Broad, flat, triangular muscle:
Originates from skull and spinous processes of C7-T12
Attaches to clavicle, acromion and scapula spine
Actions:
Upper fibres elevate scapula and rotate it during arm abd
Lower fibres retract scapula and pull it inferiorly
What is the innervation of the trapezius and how would you test this?
Innervated by accessory nerve
Also proprioreceptor fibres from C3-4
Surgeries such as lymph node biopsy or cannulation to jugular vein can cause trauma to the accessory nerve
To test the nerve the patient is asked to shrug
What are the attachments and actions of the latissimus dorsi?
Broad origin from spinous processes of T6-12, iliac crest, inferior 3 ribs
Attaches to intertubecular groove of humerus
Actions:
Extends, adducts and medial rotates upper limb
What is the innervation of the latissimus dorsi?
Thoracodorsal nerve
What are the attachments and actions of the levator scapulae?
Small strap-like muscle:
Originated from transverse processes of C1-4
Attaches to medial border of scapula
Actions:
Elevates scapula
What is the innervation of the levator scapulae?
Dorsal scapular nerve
What are the attachments and actions of the rhomboid major?
Originated from spinous processes of T2-5
Attaches to medial border of scapula
Actions:
Retracts and rotates scapula
What are the attachments and actions of the rhomboid minor?
Originates from spinous processes of C7-T1
Attaches to medial border of scapula
Actions:
Retracts and rotates scapula
What is the innervation of rhomboid major and minor?
Dorsal scapular nerve
Name the intrinsic shoulder muscles
Teres major
Deltoid
Rotator cuff muscles: Subscapularis Supraspinatus Infraspinator Teres minor
What are the attachments and actions of the deltoid?
Originates from spine of scapula and clavicle
Attaches to deltoid tuberosity of humerus
Actions:
Anterior fibres flex arm
Posterior fibres extend arm
Middle fibres are major abductor of arm (takes over from supraspinatus which does the first 15 degrees)
What is the innervation of the deltoid?
Axillary nerve
What are the attachments and actions of teres major?
Forms inferior border of quadrangular space
Originates from posterior surface of scapula
Attaches to intertubecular groove of humerus
Actions:
Adducts and medially rotates arm
What is the innervation of teres major?
Lower subscapular nerve
What is the collective function of the rotator cuff muscles?
They originate from the scapula and attach to the humeral head
Their resting tone acts to pull the humeral head into the glenoid fossa, giving the joint a lot of stability
What are the attachments and actions of supraspinatus?
Originates from supraspinous fossa and attaches to greater tubercle
Actions:
Abducts arm 0-15 degrees
Assists deltoid for 15-90 degrees
What are the attachments and actions of infraspinatus?
Originates from infraspinous fossa and attaches to greater tubercle
Actions:
Laterally rotates arm
What are the attachments and actions of subscapularis?
Originates from sub scapular fossa and attaches to less tubercle
Actions:
Medially rotates arm
What are the attachments and actions of teres minor?
Originates from lateral border of scapula and attaches to greater tubercle
Actions:
Laterally rotates arm
What is the innervation of the rotator cuff muscles?
Supra/infraspinatus - suprascapular nerve
Subscapularis - upper and lower sub scapular nerves
Teres minor - axillary nerve
What is the cause and treatment of rotator cuff tendonitis?
Inflammation of the rotator cuff tendons due to repetitive use of the shoulder
Supraspinatus tendon most affected because it rubs over the coerce-acromial arch during abduction, causing inflammation
Rest, analgesia (pain relief), physiotherapy
More severe - steroid injections, surgery
