BMS MSK Lecture 6 Fall 2023 student.pptx

BMS Anatomy Lecture 6 Introduction to Brachial Plexus​ Shoulder Girdle Muscles​ (In-Person Class)​ Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II PhD FAAA (Author), Anne M...

BMS Anatomy Lecture 6 Introduction to Brachial Plexus​ Shoulder Girdle Muscles​ (In-Person Class)​ Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II PhD FAAA (Author), Anne M. R. Agur BSc (OT) MSc PhD FAAA (Author), 9th ed.​ Upper Limb Chapter; Pages: 174 – 178, 195 – 197, Brachial Plexus Most nerves in the upper limb arise from the brachial plexus, a major nerve network supplying the upper limb; it begins in the neck and extends into the axilla. Almost all branches of the plexus arise in the axilla (after the plexus has crossed the 1st rib). The brachial plexus is formed by the union of the anterior rami of C5 – T1. The roots of the plexus usually pass through the gap between the anterior and the middle scalene muscles. In the inferior part of the neck, the roots of the brachial plexus unite to form three trunks. 1. A superior trunk, from the union of the C5 and C6 roots 2. A middle trunk, which is a continuation of the C7 root 3. An inferior trunk, from the union of the C8 and T1 roots Each trunk of the brachial plexus divides into anterior and posterior divisions as the plexus passes posterior to the clavicle. Anterior divisions of the trunks supply anterior (flexor) compartments of the upper limb, and posterior divisions of the trunks supply posterior (extensor) compartments. The divisions of the trunks form three cords of the brachial plexus: 4. 5. 6. Anterior divisions of the superior and middle trunks unite to form the lateral cord. Anterior division of the inferior trunk continues as the medial cord. Posterior divisions of all three trunks unite to form the posterior cord. The products of plexus formation are multisegmental, peripheral (named) nerves. The brachial plexus is divided into supraclavicular and infraclavicular parts by the clavicle. Four branches of the supraclavicular part of the plexus arise from the roots and trunks of the brachial plexus: 1) 2) 3) 4) Dorsal scapular nerve (from C5 root) Long thoracic nerve (from C5, 6, 7) Nerve to subclavius (From superior trunk) Suprascapular nerve (From superior trunk) Brachial Plexus (Continue) Branches of the infraclavicular part of the plexus arise from the cords of the brachial plexus and are approachable through the axilla. The medial and lateral cords of the plexus join to form the median nerve. Branches of the lateral cord are as follows: 1) Lateral pectoral nerve 2) Musculocutaneous nerve Branches of the medial cord are as follows: 3) Medial pectoral nerve 4) Medial cutaneous nerve of arm 5) Medial cutaneous nerve of forearm 6) Ulnar nerve Branches of the posterior cord are as follows: 7) Upper subscapular nerve 8) Thoracodorsal nerve 9) Lower subscapular nerve 10) Axillary nerve 11) Radial nerve In this session, we learn about the role of the major nerves in innervating the muscles of the upper limb. Later in the course, we also learn about the course and role of the nerve in innervating the skin of the upper limb. The Brachial Plexus ANTERIOR, Right sid • Brachial plexus in situ: – Lateral to cervical spine – Passes through scalene muscles (strong muscles of lateral neck) – Heads infero-laterally to travel underneath clavicle and enter axilla / armpit – Associated with arterial supply of upper limb The axilla is an anatomical region lying inferior to the shoulder joint at the junction between upper limb and thorax Bordered by Serratus anterior, Coracobrachialis, Pec major and Subscapularis muscles Contains many neurovascular structures but most notably: the terminal branches of the brachial plexus 5 The Brachial Plexus • Formation of plexus • Remember “5-3-6-3-5” • 5 ROOTS  3 TRUNKS  6 DIVISIONS  3 CORDS  5 TERMINAL BRANCHES (PERIPHERAL NERVES) “Red Trucks Drive Cats Nuts” “Real Texans Drink Cold Beer” • Arrangement of terminal branches • Remember “MARMU” • • • • • Musculocutaneous Axillary Radial Median Ulnar ANTERIOR, Right sid The Brachial Plexus ANTERIO R, Right side C5 Parts of the plexus: ROOTS C6 Anterior branches of fully formed spinal nerves that have exited the intervertebral foramen and head laterally / inferiorly away from the midline C7 C8 T1 ROOTS 5 ROOTS  7 The Brachial Plexus Parts of the plexus: TRUNKS Roots pass through scalene muscles on the lateral aspect of the neck and combine to form three trunks (names are based on anatomical location in lateral neck) C5 ANTERI OR, Right side C6 C7 Superior Middle Inferior C 8 T1 TRUNKS • C5 and C6 form Superior Trunk • C7 forms Middle Trunk • C8 and T1 form Inferior trunk 5 ROOTS  3 TRUNKS  8 ANTERI OR, Right side The Brachial Plexus Parts of the plexus: DIVISIONS Anterior divisions • Each trunk gives off two branches • Superior trunk  anterior and posterior divisions Sup Mid Inf Posterior divisions • Middle trunk  anterior and posterior divisions • Inferior Trunk  anterior and posterior divisions These divisions pass underneath the clavicle as they head towards the axilla DIVISIONS 5 ROOTS  3 TRUNKS  6 DIVISIONS  9 ANTERI OR, Right side The Brachial Plexus Parts of the plexus: CORDS Lateral cord  forms from anterior divisions of superior and middle trunk (lateral to artery) • Posterior cord  formed from posterior divisions from all three trunks (posterior to artery) • Medial cord  forms from anterior division of inferior trunk (medial to artery) Sup Mid Inf Posterior ar te ry • Lateral CORDS Medial Ax ill ar y Once the anterior and posterior divisions have entered the axilla, they combine together to form three cords, named by their position relative to the axillary artery. 5 ROOTS  3 TRUNKS  6 DIVISIONS  3 CORDS  10 The Brachial Plexus ANTERI OR, Right side Parts of the plexus: Terminal branches Once in the axilla and the proximal aspect of the upper limb, the three cords give rise to five major branches. These nerves continue into the upper limb to provide innervation to the muscles and skin present. 5 ROOTS  3 TRUNKS  6 DIVISIONS  3 CORDS  5 TERMINAL BRANCHES L P • Lateral cord = Musculocutaneous nerve • Posterior cord = Axillary and Radial nerves • Lateral and Medial cord* = Median nerve • Medial cord = Ulnar nerve M * 11 POLLING QUESTION 1: Based on your new knowledge, which part of the brachial plexus do you think passes through the scalene A. Roots muscles in the neck? B. C. D. E. Trunks Divisions Cords Terminal branches Brachial Plexus Animation – Video is posted on canvas! C4 C5 NERVE C5 ANTERIOR SUPERIOR TRUNK POSTERIOR C6 NERVE C6 ANTERIOR C7 NERVE C7 MIDDLE TRUNK POSTERIOR C8 NERVE T1 POSTERIOR CORD ANTERIOR Axillary nerve (C5C6) Radial nerve (C5 – T1) POSTERIOR INFERIOR TRUNK T1 NERVE T2 LATERAL CORD Musculocuta neous nerve (C5 – C7) MEDIAL CORD Median nerve (C5 – T1) Ulnar nerve (C8T1) Missing from animation: Long thoracic nerve, Suprascapular nerves and cutaneous branches * Lateral Cord 14 Medial Cord 15 Medial & Lateral Cords 16 Posterior Cord 17  Trapezius is a flat, triangular muscle, covering the upper and back part of the neck and shoulders. Ori:  Upper Trapezius: External occipital protuberance and the medial superior nuchal line of the occipital bone, from the ligamentum nuchae, the spinous process of C7  Middle Trapezius: SP of T1 to T5  Lower Trapezius: SP of T6 – T12 Ins: (All three parts together) Lateral 1/3 of clavicle; acromion, Spine of scapula Fun: N: Spinal accessory nerve (CN XI) UPPER FIBERS OF TRAPS: MIDDLE FIBERS OF TRAPS: LOWER FIBERS OF TRAPS:  Rhomboids minor Ori: SPs of C7 & T1 Ins: Medial (vertebral) border of scapula at the root of the spine  Rhomboids major Ori: SPs of T2-T5 Ins: Medial (vertebral) border of scapula inferior to spine Fun: N: Dorsal Scapular Actions of Rhomboids: Levator Scapulae Ori: TPs of C1-C4 Ins: Medial border of scapulae (above the spine of scapula) Fun: N: Dorsal scapular Actions of Levator Scapula :  Pectoralis minor, Ori: 3rd to 5th ribs Ins: Coracoid process Fun: N: Medial pectoral Actions of Pec Minor:  Subclavius, Ori: First rib Ins: Subclavian groove of the clavicle Fun: N: nerve to subclavius  Serratus anterior, Ori: Upper nine ribs Ins: Anterior surface of vertebral (medial) border of scapula Fun: N: Long thoracic nerve (C5,6,7)  Winged scapula: Paralysis of the serratus anterior, due to the injury of the long thoracic nerve, produces a “winged scapula” in which the inferior angle of the medial border of the scapula is excessively prominent. The patient is unable to do any pushing action, nor can he raise his arm above his head because the serratus anterior is unable to rotate the glenoid cavity superiorly to allow complete abduction of the arm.  Pectoralis major; Ori: - Clavicular head: - Medial half of clavicle - Sternocostal head: - Sternum - Costal cartilages of 1st to 7th ribs Ins: -Lateral lip of intertubercular (bicipital) groove of the humerus Fun: N: Medial and lateral pectoral Actions of Pectoralis Major :  Latissimus dorsi is a triangular, flat muscle, which covers the lumbar region and the lower half of the thoracic region. Ori: 1. Spinous process T7 to L5 2. Crests of ilium & sacrum 3. Lowest four ribs (via thoracolumbar fascia) Ins: Floor of the inter-tubercular groove of the humerus Fun: N: Thoracodorsal Actions of Latissimus Dorsi: