Lecture 4- Anatomy of Shoulder & Arm Muscles PDF

Lecture 4 Muscles of shoulder region &front of arm  ILOs Recognize the muscles of shoulder region & front of arm.  Identify origin and insertion of each muscle in these region. Enumerate the nerve supply of each muscle. Recall the actions of the different muscles of...

Lecture 4 Muscles of shoulder region &front of arm  ILOs Recognize the muscles of shoulder region & front of arm.  Identify origin and insertion of each muscle in these region. Enumerate the nerve supply of each muscle. Recall the actions of the different muscles of shoulder region & arm.  Muscles of shoulder region Deltoid Supraspinatus Infraspinatus Teres minor Teres major Subscapularis  Deltoid muscle Thick multipinnate muscle that covers shoulder joint forming rounded contour of the shoulder Origin: Anterior fibers: from anterior border of lateral 1/3 of clavicle Middle fibers: from lateral margin of acromion Posterior fibers: from lower lip of crest of scapular spine Insertion: deltoid tuberosity in middle of anterolateral surface of humerus. Nerve supply: Axillary nerve Action: -Anterior fibers: flexion & medial rotation of arm -Middle fibers: abduct the arm from 15 to 90 ͦ -Posterior fibers: extension & lateral rotation of arm  Supraspinatus Origin: from medial 2/3 of supraspinous fossa Insertion: into upper impression of greater tuberosity of humerus. Nerve supply: suprascapular nerve (C5,6) Action: Abduction of the arm from 0 to 15 ͦ Hepls in stabilizing the head of humerus in the glenoid  Infraspinatus Origin: from medial 2/3 of infraspinatus fossa Insertion: into middle impression on the greater tuberosity of the humerus. Nerve supply: Suprascapular nerve (C5,6) Action: Adduction and lateral rotation of the arm. Hepls in stabilizing the head of humerus in the glenoid cavity.  Teres Minor Origin: from upper 2/3 of dorsal aspect of the lateral border of scapula. Insertion: into lower impression of greater tuberosity of humerus. Nerve supply: Axillary nerve Action: -Adduction and lateral rotation of arm -Hepls in stabilizing the head of humerus in the glenoid  Teres Major Origin: from oval area on dorsal aspect of inferior angle of scapula and lower 1/3 of back of lateral border Insertion: into medial lip of biceptal groove Nerve supply: lower subscapular nerve Action: Adduction & medial rotation of arm  Subscapularis Origin: medial 2/3 of subscapular fossa Insertion: into lesser tuberosity of humerus Nerve supply: upper & lower subscapular nerves (C5,6). Action: * Adduction & medial rotation of arm * Hepls in stabilizing the head of humerus in the glenoid  Rotator cuff muscles 4 muscles are intimately adherent to capsule of shoulder joint Supra spinatous Infraspinatus Teres minor Subscapularis -They reinforce the capsule of shoulder joint -Their tone helps stabilizing the head of humerus.  Muscles of Arm 2 intermuscular septa (medial & Lateral intermuscular septa) from deep fascia attached to the humerus divide the arm into 2 compartments: Ant. Compartment: Biceps brachii, coracobrchialis & brachialis Post. Compartment: Triceps  Biceps Brachii Origin: by 2 heads -Short head: with coracobrachialis from tip of coracoid process. -Long head: by tendon from supra-glenoid tubercle of scapula. Insertion: by tendon into rough posterior part of radial tuberosity & by bicipital aponeurosis that passes downwards and medially to deep fascia of upper part of medial side of forearm  Brachialis Origin: from lower ½ of front of humerus including anteromedial, anterolateral surfaces and anterior border inbetween & front of medial and lateral intermuscular septa. Insertion: anterior surface of cronoid process of ulna. Nerve supply: -media part by muculocutaneous nerve -lateral part by radial nerve. Action: main flexor of elbow joint.  Coracobrachialis Origin: tip of coracoid process Insertion: into middle of medial border of humerus Nerve supply : Musculocutaneous nerve before peircing it. Action: weak flexor of arm Anatomical events at insertion of coracobrachialis Fascai: Medial and lateral intermuscular septa begin. Muscles: Deltoid insertion, brachialis origin & medial head of triceps origin. Nerves: -median nerve crosses the brachial artery from lateral to medial -Rddial nerve: pierces lateral intermuscular septum to reach anterior compartment of arm. -Ulnar nerve: pierces medial intermuscular septum to reach posterior compartment of arm  So, all muscles of front of arm are supplied by musculocutaneous nerve except lateral ½ of brachialis muscle which is supplied by radial nerve  Summary Muscles of shoulder region Rotator cuff muscles Muscles of front of arm: Biceps, coracobrachialis & brachialis  Questions * Which muscle does not inserted into the intertubecular groove of the upper humerus? a) pectoralis major b) pectoralis minor c) latissimus dorsi d) teres major *All are rotator cuff muscles EXCEPT…… A. Suraspinatus B. Infraspinatus C. Teres major D. Subscapularis *. …………………..is pierced by musculocutaneous nerve a. biceps b. brachialis c.coracobrachailis d. brachioradialis * Enumerate the muscular attachment of medial border of the scapula. * Mention 3 events occur at the level of insertion of coracobrachialis.  Refrences Snell, R.S. (2012): Snell Clinical anatomy by region. 9th edition. Chapter 9: Upper limb