MSB Lecture 1 2024 PDF

Posterior Compartment of the Forearm Superficial & Deep Muscle Groups Dr. Brennan DO NOT DISTRIBUTE/ANY NO RECORDING OFDISTRIBUTION...

Posterior Compartment of the Forearm Superficial & Deep Muscle Groups Dr. Brennan DO NOT DISTRIBUTE/ANY NO RECORDING OFDISTRIBUTION THIS LECTURE OF CONTENT THIS E-mail: [email protected] LECTURE CONTENT ANAT20080 Musculoskeletal Biology Lecture 13 24th October 2024. 1 Muscles of Posterior Forearm Muscles in the Posterior (Extensor) Compartment of the Forearm occur in two groups: Superficial Deep Functions: Brawa me Extensors of Wrist (3) Extensors of Digits (3) Thumb Extensors (3) Supinator (1) All muscles innervated by the radial nerve (directly or via deep branch) ANAT20080 2 Musculoskeletal 2  Muscles of Posterior Forearm Muscles in the Posterior (Extensor) Compartment of the Forearm: Superficial Group Brachioradialis Extensor Carpi Radialis Longus Extensor Carpi Radialis Brevis Extensor Digitorum Extensor Digiti Minimi Extensor Carpi Ulnaris *Anconeus ANAT20080 3 Musculoskeletal 3 Muscles of Posterior Forearm Big – Brachioradialis Chocolate - Extensor Carpi Radialis Longus Chips - Extensor Carpi Radialis Brevis Double - Extensor Digitorum Dip - Extensor Digiti Minimi Cherries - Extensor Carpi Ulnaris *Anconeus ANAT20080 4 Musculoskeletal 4 * Superficial Group ANAT20080 5 Musculoskeletal 5 Brachioradialis Brachioradialis muscle is a flexor of the forearm but is found in the posterior (extensor) compartment It is an exception to the rules: 1. That radial nerve supplies only extensor muscles 2. All flexors are located in the anterior (flexor) compartment of the forearm ANAT20080 6 Musculoskeletal 6  Brachioradialis Origin: Lateral supracondylar ridge of humerus Insertion: Styloid process of radius Innervation: Radial Nerve Action: Flexes Forearm ANAT20080 7 Musculoskeletal 7 Movements of Elbow Flexion Extension 3 B’s bend the elbow: Brachialis Biceps Brachioradialis Extension: Triceps brachii Anconeus ANAT20080 8 Musculoskeletal 8  Extensor Carpi Radialis Longus Origin: Lateral supracondylar ridge Insertion: Base of Metacarpal 2 Innervation: Radial Nerve Action: Extends and abducts hand at wrist ANAT20080 9 Musculoskeletal 9 Extensor Carpi Radialis Brevis Origin: Lateral epicondyle of humerus, Common Extensor Origin Insertion: Base of Metacarpal 3 Innervation: Radial Nerve (deep branch) Action: Extends and abducts hand at wrist ANAT20080 10 Musculoskeletal 10  Extensor Digitorum Origin: Lateral epicondyle of humerus, Common Extensor Tendon Insertion: Extensor expansion of digits 2-5 Innervation: Radial Nerve (Posterior interosseous nerve) Action: Extends digits 2-5 ANAT20080 11 Musculoskeletal 11 Extensor Digitorum Major extensor of the four fingers (index, middle, ring & little fingers) Forms four tendons each of which passes into a digit Each tendon inserts via the extensor expansion or hood into the base of the dorsal surfaces of the middle & distal phalanges. ANAT20080 12 Musculoskeletal 12  Extensor Digitorum Tendons Tendon splits into 3 strips over proximal phalanges Extensor expansion (extensor hood): Triangular-shaped connective tissue aponeurosis over proximal phalanges Insertion point for hand muscles Remember: The eXtensor eXpansion is on the proXimal phalynX ANAT20080 13 Musculoskeletal 13 Extensor Digiti Minimi Origin: Lateral epicondyle of humerus, Common Extensor Tendon Insertion: Joins extensor digitorum tendon to 5th digit by inserting into extensor expansion Innervation: Radial Nerve (Posterior interosseous nerve) Action: ANAT20080 Extends little finger Musculoskeletal 14 14  Extensor Carpi Ulnaris Origin: Lateral epicondyle of humerus, Common Extensor Tendon, Posterior border of ulna Insertion: Base of metacarpal 5 Innervation: Radial Nerve (Posterior interosseous nerve) Action: Extends and adducts hand at wrist ANAT20080 15 Musculoskeletal 15 Anconeus Origin: Lateral epicondyle of humerus Insertion: Lateral side of olecranon and upper ¼ of posterior surface ulna Innervation: Radial Nerve (Posterior interosseous nerve) Action: Extends the forearm ANAT20080 16 Musculoskeletal 16  Anconeus The anconeus is a small, triangular muscle on the posterolateral aspect of the elbow May be considered as part of either the extensor compartment of forearm or arm Partially blended with the triceps muscle Functions: Assists triceps extend the forearm Tenses the capsule of the elbow joint, preventing it being pinched during extension ANAT20080 17 Musculoskeletal 17 Superficial Group Brachioradialis Extensor Carpi Radialis Longus Extensor Carpi Radialis Brevis Extensor Digitorum Extensor Digiti Minimi Extensor Carpi Ulnaris *Anconeus ANAT20080 18 Musculoskeletal 18  Muscles of Posterior Forearm Muscles in the Posterior (Extensor) Compartment of the Forearm: Deep Group Supinator Abductor Pollicis Longus Extensor Pollicis Brevis Extensor Pollicis Longus Extensor Indicis ANAT20080 19 Musculoskeletal 19 Muscles of Posterior Forearm Syrup – Supinator And – Abductor Pollicis Longus Peanuts – Extensor Pollicis Brevis Preferably – Extensor Pollicis Longus Included – Extensor Indicis Remember Supination ‘SOUP’ carrying bowl of soup - palm facing up ANAT20080 20 Pronation ‘POUR’ pouring out contents of bowl – palm down Musculoskeletal 20  Except for the supinator muscle, all deep muscles originate from the posterior surfaces of the radius, ulna & interosseous membrane Insert into the thumb and fingers All muscles of the deep layer are innervated by the posterior interosseous nerve, the continuation of the deep branch of the radial nerve ANAT20080 21 Musculoskeletal 21 Deep Group ANAT20080 22 Musculoskeletal 22  Supinator Origin: 2 Heads Ulnar Head: Supinator Crest of Ulna Humeral Head: Lateral epicondyle of humerus, Ligaments of elbow (radial collateral & anular ligaments) Insertion: Lateral surface of upper 1/3 of radius Innervation: Radial Nerve (Posterior interosseous nerve) Action: Supinates forearm ANAT20080 23 Musculoskeletal 23 Supinator The two heads of supinator wrap around the posterior and lateral aspect of the head, neck, and proximal shaft of the radius Insertion on the lateral surface of the radius superior to the insertion of the pronator teres muscle. The supinator muscle supinates the forearm and hand. Remember Supination ‘SOUP’ carrying bowl of soup - palm facing up Pronation ‘POUR’ pouring out contents of bowl – palm down ANAT20080 24 Musculoskeletal 24  Extensor Pollicis Longus Origin: Posterior mid 1/3 surface of ulna and interosseous membrane Insertion: Base of distal phalanx of thumb Innervation: Radial Nerve (Posterior interosseous nerve) Action: Extends thumb ANAT20080 25 Musculoskeletal 25 Extensor Pollicis Longus The extensor pollicis longus muscle is held away from the other two deep muscles of the thumb by passing medially around the dorsal tubercle on the distal end of the radius. The tendon forms the medial margin of the anatomical snuffbox at the wrist. The extensor pollicis longus extends all joints of the thumb ANAT20080 26 Musculoskeletal 26  Extensor Pollicis Brevis Origin: Posterior surface of radius and interosseous membrane Insertion: Base of proximal phalanx of thumb Innervation: Radial Nerve (Posterior interosseous nerve) Action: Extends & abducts thumb Contributes to lateral border of the anatomical snuffbox ANAT20080 Musculoskeletal 27 27 Abductor Pollicis Longus Origin: Posterior surface of ulna, middle 1/3 of posterior surface radius and interosseous membrane Insertion: Base of metacarpal 1 Innervation: Radial Nerve (Posterior interosseous nerve) Action: Abducts & extends thumb. Contributes to lateral border of the anatomical snuffbox ANAT20080 Musculoskeletal 28 28  Extensor Indicis Origin: Posterior surface of distal ulna and interosseous membrane Insertion: Joins tendon of extensor digitorum to the 2nd digit inserting onto extensor expansion Innervation: Radial Nerve (Posterior interosseous nerve) Action: Extends index finger ANAT20080 29 Musculoskeletal 29 Extensor Indicis The extensor indicis muscle is an accessory extensor of the index finger. It originates distal to the extensor pollicis longus from the posterior surface of the ulna and adjacent interosseous membrane. The tendon passes into the hand and inserts into the extensor expansion (hood) of the index finger with the tendon of the extensor digitorum ANAT20080 30 Musculoskeletal 30  Deep Group Supinator Abductor Pollicis Longus Extensor Pollicis Brevis Extensor Pollicis Longus Extensor Indicis ANAT20080 31 Musculoskeletal 31 Extensor Muscles of Forearm Rule of 3 3 muscles for wrist extension Extensor carpi radialis brevis Extensor carpi radialis longus Extensor carpi ulnaris 3 muscles for finger extension Extensor digitorum (for all four fingers) Extensor indicis Extensor digiti minimi 3 muscles for thumb Extensor pollicis longus Extensor policis brevis Abductor pollicis longus ANAT20080 Musculoskeletal 32 32  Extensor Retinaculum Fibrous band holding extensor tendons to wrist From lateral border of radius to carpal bones Triquetrum & Pisiform All extensor tendons surrounded by synovial sheaths under retinaculum ANAT20080 33 Musculoskeletal 33 Anatomical Snuffbox Surface anatomy feature Triangular depression formed on lateral aspect of dorsum of hand Base of triangle located at the level of carpal bones with apex directed into thumb Obvious when thumb is extended ANAT20080 Musculoskeletal 34  Anatomical Snuffbox Borders: Medial: Extensor Pollicis Longus tendon Lateral: Extensor Pollicis Brevis tendon & Abductor Pollicis Longus tendon Floor: Scaphoid, Trapezium Contents: Radial artery Crosses the floor obliquely running deep to the extensor tendons. The radial pulse can be palpated in some individuals by placing two fingers on the proximal portion of the snuffbox. ANAT20080 Musculoskeletal 35 YouTube Playlist https://youtube.com/playlist?list=PLROCMs7AwS_mgFtpr3jY 7rMrD6vd4vKOM ANAT20080 36 Musculoskeletal 36