BMS Anatomy Lecture 7 Fall 2023 PDF

BMS Anatomy Lecture 7 Introduction to Upper Limb Compartments Arm Muscles Introduction to Anterior Forearm 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. Da...

BMS Anatomy Lecture 7 Introduction to Upper Limb Compartments Arm Muscles Introduction to Anterior Forearm 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: 207 – 211, 220 – 222 ❑ Arm Compartments  The arm is divided into anterior and posterior compartments by extensions of deep fascia called the medial and lateral intermuscular septae.  The anterior, or flexor, compartment is occupied by the flexor muscles (biceps brachii, coracobrachialis, and brachialis) and is innervated by the musculocutaneous nerve.  The posterior or extensor compartment is occupied by the extensor muscle( triceps brachii ) and is innervated by the radial nerve. The anterior compartment of the arm contains three muscles that are innervated by the musculocutaneous nerve. Biceps brachii: Ori: Short head: Coracoid process of scapula Long head: Supraglenoid tubercle of scapula Ins: Radial tuberosity and fascia of forearm via bicipital aponeurosis Fun: Coracobrachialis: Ori: Coracoid process of scapula Ins: Middle third of the medial surface of humerus Fun: Brachialis: Ori: Distal half of the anterior surface of humerus Ins: - Ulnar tuberosity - Coronoid process of ulna Fun: Posterior compartment of the arm consists of one muscle which is innervated by the radial nerve Triceps brachii: Ori: Long head: Infraglenoid tubercle Lateral head: Lateral, posterior humerus (superior to radial groove) Medial head: Posterior surface of humerus (inferior to radial groove) Ins: Olecranon process of ulna Fun: ❑ Forearm Compartments The tendons of the forearm muscles pass through the distal part of the forearm and into the hand. The radius, ulna , the interosseous membrane connecting them as well as the intermuscular septum divide the forearm into an anterior (flexor-pronator) and a posterior (extensor-supinator) compartment. All muscles of the anterior compartment are innervated by the median nerve, except one and a half muscles (FCU and medial half of the FDP), which are innervated by the ulnar nerve. All muscles of the posterior compartment are innervated by the radial nerve. ❑ Most of the flexor-pronator muscles arise from the medial epicondyle of the humerus via a common flexor tendon. The tendons of most flexor muscles pass across the anterior surface of the wrist and are held in place by the flexor retinaculum. The muscles of this compartment are divided into three layers. 1) Superficial layer: Pronator teres (PT), flexor carpi radialis (FCR), palmaris longus (PL), flexor carpi ulnaris (FCU) 2) Intermediate layer: Flexor digitorum superficialis (FDS) 3) Deep layer including: Flexor digitorum profundus (FDP), flexor pollicis longus (FPL), and pronator quadratus (PQ). ❑ All of these muscles are innervated by the median nerve, except one and half muscles (FCU and medial half of the FDP), which are innervated by the ulnar nerve. Muscles and Nerves of the Upper Limb Muscles of the Anterior forearm: Superficial Layer: Pronator Teres Flexor Carpi radialis Palmaris Longus Flexor Carpi ulnaris SUPERFICIAL LAYER: PRIMARY ACTIONS: If the tendons cross the wrist = FLEX wrist If the tendons cross the phalangeal joints = FLEX digits Pronation of forearm Intermediate Layer: Flexor Digitorum Superficialis Deep Layer: Flexor Pollicis longus Flexor Digitorum Profundus Pronator Quadratus Anterior, Right side DEEP LAYER: The extensor-supinator muscles of the forearm are organized anatomically into superficial and deep layers. The superficial layer includes: 1. 2. 3. 4. 5. 6. 7. Brachioradialis (BR) Extensor carpi radialis longus (ECRL) Extensor carpi radialis brevis (ECRB) Extensor digitorum (ED) Extensor digiti minimi (Edm) Extensor carpi ulnaris (ECU) Anconeus The deep layer includes: 8. Supinator 9. Abductor pollicis longus (APL) 10. Extensor pollicis brevis (EPB) 11. Extensor pollicis longus (EPL) 12. Extensor indicis (EI)  The most superficial extensor muscles originate from the lateral epicondyle of the humerus via a common extensor tendon. However, the deep muscles in this region mainly arise from the posterior ulna, radius and interosseous membrane.  All extensor muscles are innervated by the radial nerve. (The brachioradialis muscle in this group is also innervated by the radial nerve; however, it is a flexor of the forearm). Posterior, Right side Muscles and Nerves of the Upper Limb Muscles of the Posterior forearm: DEEP LAYER: SUPERFICIAL LAYER: PRIMARY ACTIONS: Supination of forearm If the muscle crosses the wrist = EXTENSION of wrist If the muscle crosses the digits = EXTENSION of digits Muscles and Nerves of the Upper Limb Muscles of the Posterior forearm: Superficial Layer: Brachioradialis Distal humerus to distal radius Anterolateral forearm muscle Functions: Flexion of elbow in “mid-pronation” Beer drinking muscle! Nerve innervation: Radial nerve Lateral Muscles and Nerves of the Upper Limb Muscles that perform Elbow Flexion: Flexion with Supination = Biceps = Musculocutaneous nerve Flexion with pronation = Brachialis = Musculocutaneous nerve Flexion in mid-pronation = Brachioradialis = Radial nerve ❑ Retinacula ❖ The forearm (antebrachial) fascia invests the forearm muscles. This fascia thickens posteriorly over the distal ends of the radius and ulna to form a transverse band, the extensor retinaculum, which retains the extensor tendons in position. ❖ This fascia also forms an anterior thickening, the flexor retinaculum, which converts the anterior concavity of the carpus (wrist bones) into a carpal tunnel through which the flexor tendons and median nerve pass. ❖ The retinacula prevent bowstringing of the tendons when the hand flexed or hyperextended at the wrist joint. ❖ As the extensor tendons pass over the dorsum of the wrist they are invested by synovial sheaths which reduce friction between the extensor tendons and the bones.