BMS MSK Lecture 6 WINTER 2024 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, The Brachial Plexus ANTERIOR, Right side 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 Subclavian artery à 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 3 The Brachial Plexus Formation of plexus Remember “5-3-6-3-5” 5 ROOTS à 3 TRUNKS à 6 DIVISIONS à 3 CORDS à 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 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 à 5 ANTERIOR, Right side The Brachial Plexus C5 C6 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) C7 Superior C 8 Middle Inferior T1 TRUNKS C5 and C6 form Superior Trunk C7 forms Middle Trunk C8 and T1 form Inferior trunk 5 ROOTS à 3 TRUNKS à 6 ANTERIOR, Right side The Brachial Plexus Anterior divisions Parts of the plexus: DIVISIONS Each trunk gives off two branches Superior trunk à anterior and posterior divisions Middle trunk à anterior and posterior divisions Inferior Trunk à anterior and posterior divisions These divisions pass underneath the clavicle as they head towards the axilla Sup Mid Inf Posterior divisions DIVISIONS 5 ROOTS à 3 TRUNKS à 6 DIVISIONS à 7 ANTERIOR, Right side The Brachial Plexus Parts of the plexus: CORDS Lateral cord à forms from anterior divisions of superior and middle trunk (lateral to artery) Posterior cord à formed from posterior divisions from all three trunks (posterior to artery) Medial cord à forms from anterior division of inferior trunk (medial to artery) Lateral Sup Mid Inf Posterior Ax illa ry ar te ry 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. CORDS Medial 5 ROOTS à 3 TRUNKS à 6 DIVISIONS à 3 CORDS à 8 The Brachial Plexus 5 ROOTS à 3 TRUNKS à 6 DIVISIONS à 3 CORDS à 5 TERMINAL BRANCHES L P 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 M * 9 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 POSTERIOR C8 NERVE T1 POSTERIOR CORD Radial nerve (C5 – T1) POSTERIOR INFERIOR TRUNK T1 NERVE ANTERIOR Axillary nerve (C5-C6) MEDIAL CORD T2 Missing from animation: Long thoracic nerve, Suprascapular nerves and cutaneous branches* Median nerve (C5 – T1) Ulnar nerve (C8-T1) Lateral Cord 11 Medial Cord 12 Medial & Lateral Cords 13 Posterior Cord 14 Trapezius is a flat, triangular muscle, covering the upper and back part of the neck and shoulders. Ori: Ø Upper Trapezius: External occipital protuberance and the medial superior nuchal line of the occipital bone, from the ligamentum nuchae, the spinous process of C7 Ø Middle Trapezius: SP of T1 to T5 Ø Lower Trapezius: SP of T6 – T12 Ins: (All three parts together) Lateral 1/3 of clavicle; acromion, Spine of scapula Nerve innervation: CN XI (Spinal Accessory Nerve UPPER FIBERS OF TRAPS: Ext. & lateral flexion of head (mostly bilateral contraction) Ext. & lateral flex. of neck Contralateral rotation of head Contralateral rotation of neck Elevation of scapula Upward rotation of scapula MIDDLE FIBERS OF TRAPS: Retraction (adduction) of scapula LOWER FIBERS OF TRAPS: Depression of scapula Upward rotation of scapula Ø Rhomboids minor Ori: SPs of C7 & T1 Ins: Medial (vertebral) border of scapula at the root of the spine Ø Rhomboids major Ori: SPs of T2-T5 Ins: Medial (vertebral) border of scapula inferior to spine Nerve innervation: Dorsal scapular nerve Actions of Rhomboids: Retraction (adduction) of scapula Elevation of scapula Downward rotation of scapula ØLevator Scapulae Ori: TPs of C1-C4 Ins: Medial border of scapulae (above the spine of scapula) Nerve innervation: Dorsal scapular nerve Actions of Levator Scapula: Extension of neck @ the spinal joints Lateral flexion of the neck@ the spinal joints Ipsilateral rotation of neck @ the spinal joints Elevation of scapula @ the scapulocostal joint Downward Rotation of Scapula @ the scapulocostal joint. Ø Pectoralis minor, Ori: 3rd to 5th ribs Ins: Coracoid process Nerve Innervation: Medial pectoral nerve Actions of Pec Minor: Protraction (ABD.) of scapula Downward Rot. of scapula Depression of scapula Elevation of ribs # 3 to 5 @sternocostal & costo-spinal joints (during forced inhalation when scapula is fixed) ØSubclavius, Ori: First rib Ins: Subclavian groove of the clavicle Action: Depression of clavicle @ the sternoclavicular & acromioclavicular Joints Nerve innervation: Nerve to subclavius ØSerratus anterior, Ori: Upper nine ribs Ins: Anterior surface of vertebral (medial) border of scapula Nerve innervation: Long thoracic nerve (C5,6,7) Actions of Serratus Anterior : Protraction (ABD.) of scapula Upward rotation of scapula Winged scapula: Injury of the long thoracic nerve produces paralysis (weakness) of the serratus anterior muscle. The patient will present with 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 ØPectoralis 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 Nerve innervation: Medial and lateral pectoral Actions of Pectoralis Major : Flexion of arm (clavicular head) Adduction of arm Medial rotation of arm Horizontal ADDuction of the arm ØLatissimus dorsi 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 Nerve innervation: Thoracodorsal nerve Actions of Latissimus Dorsi: Extension of arm Adduction of arm Medial rotation of arm Anterior tilt of the pelvis