BMS Anatomy Lecture 6 - Brachial Plexus and Shoulder Girdle Muscles PDF

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...

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: 1. 2. 3. 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) 2) Lateral pectoral nerve Musculocutaneous nerve Branches of the medial cord are as follows: 1) Medial pectoral nerve 2) Medial cutaneous nerve of arm 3) Medial cutaneous nerve of forearm 4) Ulnar nerve Branches of the posterior cord are as follows: 1) Upper subscapular nerve 2) Thoracodorsal nerve 3) Lower subscapular nerve 4) Axillary nerve 5) 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 side • Brachial plexus in situ: – Lateral to cervical spine (R) – Passes through scalene muscles (strong muscles of lateral neck) – Heads inferolaterally to travel underneath clavicle and enter axilla / armpit – Associated with arterial supply of upper limb • Subclavian artery 🡪 Axillary artery (as it passes under clavicle) 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” • inferior and lateral divisions • 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 lateral to medial set up ANTERIOR, Right side The Brachial Plexus ANTERIOR, 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 ANTERIOR, Right side The Brachial Plexus C5 C6 Parts of the plexus: TRUNKS C7 Superior Roots pass through scalene muscles on the lateral aspect of the Middle neck and combine to form three trunks (names are based on anatomical location in lateral neck) 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 ANTERIOR, Right side The Brachial Plexus Anterior divisions Parts of the plexus: DIVISIONS • Each trunk gives off two branches • Superior trunk 🡪 anterior and 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 Sup Mid Inf Posterior divisions DIVISIONS 5 ROOTS 🡪 3 TRUNKS 🡪 6 DIVISIONS 🡪 9 The Brachial Plexus ANTERIOR, Right side Parts of the plexus: CORDS • Medial cord 🡪 forms from anterior division of inferior trunk (medial to artery) Posterior y Posterior cord 🡪 formed from posterior divisions from all three trunks (posterior to artery) Inf ar te r • Mid CORDS Medial ry Lateral cord 🡪 forms from anterior divisions of superior and middle trunk (lateral to artery) Sup illa • Lateral Ax 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 5 ROOTS 🡪 3 TRUNKS 🡪 6 DIVISIONS 🡪 3 CORDS 🡪 5 TERMINAL BRANCHES ANTERIOR, 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. • Lateral cord = Musculocutaneous nerve • Posterior cord = Axillary and Radial nerves • Lateral and Medial cord* = Median nerve • Medial cord = Ulnar nerve L P M * 11 POLLING QUESTION 1: Based on your new knowledge, which part of the brachial plexus do you think passes through the scalene muscles in the neck? A. B. C. D. E. Roots Trunks Divisions Cords Terminal branches Brachial Plexus Animation – Video is posted on canvas! C4 Musculocutaneous nerve (C5 – C7) C5 NERVE C5 ANTERIOR LATERAL CORD SUPERIOR TRUNK POSTERIOR C6 NERVE C6 ANTERIOR C7 NERVE MIDDLE TRUNK C7 Axillary nerve (C5-C6) POSTERIOR C8 NERVE POSTERIOR CORD Radial nerve (C5 – T1) POSTERIOR INFERIOR TRUNK T1 T1 NERVE ANTERIOR MEDIAL CORD T2 Median nerve (C5 – T1) Ulnar nerve (C8-T1) 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 Nerve: Spinal accessory nerve (CN XI) UPPER FIBERS OF TRAPS: Movements of the head and neck: - extension of the head - lateral flexion of the head - contralateral rotation of the head and neck Scapulae: - elevation and upwards rotation MIDDLE FIBERS OF TRAPS: - adduction/retraction of the scapula LOWER FIBERS OF TRAPS: - abduction of scapula - helps in upper rotation - Depression of scapula *weakest part 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: - retraction - elevation of scapula Levator Scapulae Ori: TVPs of C1-C4 Ins: Medial border of scapula (above the spine of scapula) Nerve: dorsal scapular nerve N: Dorsal scapular Actions of Levator Scapula on cervical spine: - ext of neck @ spinal joints - lateral flexion of neck - rot neck (ipsilateral) On scapula: - elevate scap - downward rotation of scapula Pectoralis minor, Ori: 3rd to 5th ribs Ins: Coracoid process N: Medial pectoral Actions of Pec Minor: - protraction (ABD.) of scapula - downward rot of scapula - depression of scapula Actions on the ribs: - elevation of ribs 3-5 @ SCM and costospinal joints (during forced inhalation when scap is fixed) Subclavius, Ori: First rib Ins: Subclavian groove of the clavicle Function: - depression of clavicle @ the sternoclavicular and acromioclavicular joints N: nerve to subclavius Serratus anterior, Ori: Upper nine ribs (1-9) Ins: Anterior surface of vertebral (medial) border of scapula Fun: - portraction (ABD.) of scapula - upward rotation of the scapula 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 N: Medial and lateral pectoral Actions of Pectoralis Major : - flexion of arm (clavicle head) - ADD arm - medial rotation of arm - horizontal adduction of the arm 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 intertubercular groove of the humerus N: Thoracodorsal Actions of Latissimus Dorsi: - extension of the arm - adduction of the arm - medial rotation of the arm - anterior tilt of the pelvis (not a lot)