bovenste lidmaat.pdf

# Shoulder muscles and their functions This section details the origin, insertion, function, and innervation of key shoulder muscles essential for upper limb movement and stability [2](#page=2) [3](#page=3) [4](#page=4). ### 1.1 Muscles acting directly on the scapula and glenohumeral joint These muscles originate from the torso or scapula and insert onto the scapula or humerus, enabling a wide range of shoulder and arm movements [2](#page=2) [3](#page=3) [4](#page=4). #### 1.1.1 Muscles originating from the scapula or cervical vertebrae * **M. Levator scapulae**: * **Origin**: Transverse processes of C1-C4 [2](#page=2). * **Insertion**: Medial border and superior angle of the scapula [2](#page=2). * **Function**: Elevates the scapula and causes downward rotation (endorotation) [2](#page=2). * **Innervation**: Dorsal scapular nerve [2](#page=2). * **M. Supraspinatus**: * **Origin**: Supraspinous fossa [2](#page=2). * **Insertion**: Greater tubercle of the humerus [2](#page=2). * **Function**: Initiates abduction of the arm up to 90 degrees and acts as a capsular stabilizer [2](#page=2). * **Innervation**: Suprascapular nerve [2](#page=2). * **M. Infraspinatus**: * **Origin**: Infraspinous fossa [2](#page=2). * **Insertion**: Middle facet of the greater tubercle of the humerus [2](#page=2). * **Function**: External rotation of the arm [2](#page=2). * **Innervation**: Suprascapular nerve [2](#page=2). * **M. Teres Minor**: * **Origin**: Infraspinous fossa and lateral border of the scapula [2](#page=2). * **Insertion**: Inferior facet of the greater tubercle of the humerus [2](#page=2). * **Function**: External rotation of the arm [2](#page=2). * **Innervation**: Axillary nerve [2](#page=2). * **M. Teres Major**: * **Origin**: Inferior angle and lateral border of the scapula [2](#page=2). * **Insertion**: Lesser tubercle of the humerus [2](#page=2). * **Function**: Internal rotation, adduction, and extension (retroflexion) of the arm [2](#page=2). * **Innervation**: Inferior subscapular nerve [2](#page=2). * **M. Subscapularis**: * **Origin**: Subscapular fossa [3](#page=3). * **Insertion**: Lesser tubercle of the humerus [3](#page=3). * **Function**: Internal rotation of the shoulder [3](#page=3). * **Innervation**: Subscapular nerve [3](#page=3). #### 1.1.2 Muscles originating from the torso * **M. Latissimus Dorsi**: * **Origin**: Iliac crest, sacrum, spinous processes of L5-T1, T12-T7, ribs 10-12, and often the inferior angle [3](#page=3). * **Insertion**: Crest of the lesser tubercle anteriorly (medial to M. Teres Major insertion) [3](#page=3). * **Function**: Internal rotation, adduction, and extension (retroflexion) of the arm. It also acts as a climbing muscle, pulling the trunk upwards, and retracts the scapula with the trapezius and rhomboid muscles [3](#page=3). * **Innervation**: Thoracodorsal nerve [3](#page=3). * **M. Rhomboideus Major and Minor**: * **Origin**: Major: spinous processes of T2-T5. Minor: C7-T1 [3](#page=3). * **Insertion**: Medial border of the scapula; Major inserts caudal to the spine, Minor inserts cranial to the spine [3](#page=3). * **Function**: Retraction of the scapula and downward rotation, causing slight internal rotation so the glenoid cavity tilts caudally [3](#page=3). * **Innervation**: Dorsal scapular nerve [3](#page=3). * **M. Pectoralis Major**: * **Origin**: Clavicular part from the clavicle; Sternocostal part from the sternum and ribs 2-6; Abdominal part from the abdominal muscles [3](#page=3). * **Insertion**: Crest of the greater tubercle [3](#page=3). * **Function**: Horizontal adduction, internal rotation, and adduction of the arm. The clavicular part aids in anteflexion, and the abdominal part aids in adduction. It also acts as an accessory muscle of respiration [3](#page=3). * **Innervation**: Pectoral nerves [3](#page=3). * **M. Pectoralis Minor**: * **Origin**: Ribs 3-5 [4](#page=4). * **Insertion**: Coracoid process [4](#page=4). * **Function**: Anterior tilt and protraction and depression of the scapula; also an accessory muscle of respiration [4](#page=4). * **Innervation**: Medial and lateral pectoral nerves [4](#page=4). * **M. Coracobrachialis**: * **Origin**: Coracoid process [4](#page=4). * **Insertion**: Anterior and medial surface of the humerus, halfway down [4](#page=4). * **Function**: Flexion and adduction of the arm at the shoulder joint when the arm is elevated [4](#page=4). * **Innervation**: Musculocutaneous nerve [4](#page=4). * **M. Deltoideus**: * **Origin**: Clavicular part from the lateral third of the clavicle; Acromial part from the acromion; Spinal part from the inferior border of the spine of the scapula [4](#page=4). * **Insertion**: Deltoid tuberosity of the humerus [4](#page=4). * **Function**: The clavicular part aids in anteflexion and adduction; the acromial part aids in anteflexion and horizontal adduction; the spinal part aids in retroflexion and abduction [4](#page=4). * **Innervation**: Axillary nerve [4](#page=4). * **M. Serratus Anterior**: * **Origin**: Ribs 1-9 [4](#page=4). * **Insertion**: Medial border of the scapula [4](#page=4). * **Function**: Protracts and upwardly rotates the scapula. It also fixes the scapula against the ribs and acts as an accessory muscle of respiration [4](#page=4). * **Innervation**: Long thoracic nerve [4](#page=4). > **Tip:** Understanding the specific origin and insertion points is crucial for visualizing and predicting a muscle's line of pull and subsequent action. Pay close attention to how different parts of a muscle, like the deltoid or pectoralis major, have distinct functions [3](#page=3) [4](#page=4). > **Tip:** The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) are vital for shoulder joint stability and coordinated movement [2](#page=2) [3](#page=3). --- # Elbow and forearm muscles This section details the muscles responsible for the movements of the elbow and forearm, outlining their origins, insertions, functions, and innervations. ### 2.1 Posterior elbow and forearm muscles The posterior compartment of the arm and forearm primarily consists of extensors. #### 2.1.1 Triceps brachii The triceps brachii is the primary extensor of the elbow joint and is composed of three heads: * **Long head (Caput Longum):** * Origin: Infraglenoid tubercle of the scapula [5](#page=5). * Insertion: Olecranon [5](#page=5). * Function: Retroflexion and extension of the elbow [5](#page=5). * Innervation: Radial nerve [5](#page=5). * **Lateral head (Caput Laterale):** * Origin: Lateral and posterior aspect of the humerus shaft [5](#page=5). * Insertion: Olecranon [5](#page=5). * Function: Extension of the elbow [5](#page=5). * Innervation: Radial nerve [5](#page=5). * **Medial head (Caput Mediale):** * Origin: Medial and distal third of the humerus shaft [5](#page=5). * Insertion: Olecranon [5](#page=5). * Function: Extension of the elbow [5](#page=5). * Innervation: Radial nerve [5](#page=5). #### 2.1.2 Anconeus The anconeus muscle acts as a small synergist to the triceps brachii. * Origin: Lateral epicondyle of the humerus [5](#page=5). * Insertion: Distal to the olecranon on the ulna [5](#page=5). * Function: Supports the triceps brachii in extending the elbow and also acts as a joint capsule stabilizer [5](#page=5). * Innervation: Radial nerve [5](#page=5). #### 2.1.3 Extensor muscles of the wrist and digits These muscles are located in the posterior forearm and are primarily responsible for wrist and finger extension. * **Extensor carpi radialis longus:** * Origin: Lateral border of the humerus down to the lateral epicondyle [6](#page=6). * Insertion: Base of the second metacarpal [6](#page=6). * Function: Dorsiflexion and radial deviation of the wrist [6](#page=6). * Innervation: Radial nerve [6](#page=6). * **Extensor carpi radialis brevis:** * Origin: Lateral epicondyle of the humerus [6](#page=6). * Insertion: Base of the third metacarpal [6](#page=6). * Function: Dorsiflexion and active radial deviation of the wrist [6](#page=6). * Innervation: Radial nerve [6](#page=6). * **Extensor digitorum:** * Origin: Lateral epicondyle of the humerus [6](#page=6). * Insertion: Via the dorsal extensor aponeurosis to the second and third phalanges of digits 2-5 [6](#page=6). * Function: Extension of the metacarpophalangeal (MCP) joints [7](#page=7). * Innervation: Radial nerve [7](#page=7). * **Extensor digiti minimi:** * Origin: Lateral epicondyle of the humerus [7](#page=7). * Insertion: Dorsal aponeurosis of the fifth digit [7](#page=7). * Function: Dorsiflexion of the wrist and extension of the little finger [7](#page=7). * Innervation: Radial nerve [7](#page=7). * **Extensor indicis:** * Origin: Distal third of the posterior surface of the ulna [7](#page=7). * Insertion: Dorsal aponeurosis of the second digit [7](#page=7). * Function: Dorsiflexion of the wrist and extension of the index finger [7](#page=7). * Innervation: Radial nerve [7](#page=7). * **Extensor carpi ulnaris:** * Origin: Lateral epicondyle of the humerus [7](#page=7). * Insertion: Base of the fifth metacarpal [7](#page=7). * Function: Ulnar deviation with dorsiflexion of the wrist [7](#page=7). * Innervation: Radial nerve [7](#page=7). ### 2.2 Anterior elbow and forearm muscles The anterior compartment of the arm and forearm contains flexors and pronators. #### 2.2.1 Biceps brachii The biceps brachii is a major flexor of the elbow and supinator of the forearm. * **Long head (Caput Longum):** * Origin: Supraglenoid tubercle of the scapula [5](#page=5). * Insertion: Radial tuberosity and bicipital aponeurosis [6](#page=6). * Function: Flexion and supination of the elbow [6](#page=6). * Innervation: Musculocutaneous nerve [6](#page=6). * **Short head (Caput Breve):** * Origin: Coracoid process [6](#page=6). * Insertion: Lacertus fibrosus [6](#page=6). * Function: Flexion of the elbow in supination [6](#page=6). * Innervation: Musculocutaneous nerve [6](#page=6). #### 2.2.2 Brachialis The brachialis muscle is a powerful flexor of the elbow. * Origin: Ventral part of the humerus, distal portion to the deltoid tuberosity [6](#page=6). * Insertion: Tuberosity of the ulna [6](#page=6). * Function: Flexion of the elbow, particularly when the forearm is in pronation [6](#page=6). * Innervation: Musculocutaneous nerve [6](#page=6). #### 2.2.3 Flexor muscles of the wrist and digits These muscles are located in the anterior forearm and are responsible for wrist and finger flexion. * **Flexor carpi radialis:** * Origin: Medial epicondyle of the humerus [7](#page=7). * Insertion: Bases of the second and third metacarpals [7](#page=7). * Function: Weak flexion of the elbow, palmar flexion, and radial deviation of the wrist [8](#page=8). * Innervation: Median nerve [8](#page=8). * **Palmaris longus:** * Origin: Medial epicondyle of the humerus [8](#page=8). * Insertion: Palmar aponeurosis of the hand [8](#page=8). * Function: Tenses the palmar aponeurosis, flexes the wrist, and assists in finger flexion via the aponeurosis [8](#page=8). * Innervation: Median nerve [8](#page=8). * **Flexor carpi ulnaris:** * Origin: Humeral head on the medial epicondyle; Ulnar head on the olecranon and posterior border of the ulna [8](#page=8). * Insertion: Base of the fifth metacarpal, also attaching to the pisiform and hamate bones [8](#page=8). * Function: Weak flexion of the elbow, palmar flexion, and ulnar deviation of the wrist [8](#page=8). * Innervation: Ulnar nerve [8](#page=8). * **Flexor digitorum superficialis:** * Origin: Humeral head on the medial epicondyle; Ulnar head on the coronoid process of the ulna; Radial head from a line on the radius [8](#page=8). * Insertion: Middle phalanges of digits 2-5 [8](#page=8). * Function: Flexion of the MCP and proximal interphalangeal (PIP) joints of digits 2-5 [8](#page=8). * Innervation: Median nerve [8](#page=8). * **Flexor digitorum profundus:** * Origin: Anterior surface of the ulna and interosseous membrane of the forearm [8](#page=8). * Insertion: Distal phalanges of digits 2-5 [8](#page=8). * Function: Flexion of digits 2-5 at the MCP, PIP, and distal interphalangeal (DIP) joints [8](#page=8). * Innervation: Median nerve for digits 2-3, Ulnar nerve for digits 4-5 [9](#page=9). #### 2.2.4 Pronator and supinator muscles These muscles control the rotation of the forearm. * **Supinator:** * Origin: Lateral epicondyle of the humerus, supinator crest of the ulna, radial collateral ligament, and annular ligament of the radius [9](#page=9). * Insertion: Radius, between the radial tuberosity and the lateral surface of the radius [9](#page=9). * Function: Supination of the forearm [9](#page=9). * Innervation: Radial nerve [9](#page=9). * **Pronator teres:** * Origin: Humeral head on the medial epicondyle of the humerus; Ulnar head on the coronoid process of the ulna [9](#page=9). * Insertion: Lateral surface of the radius in the middle third [9](#page=9). * Function: Pronation of the forearm [9](#page=9). * Innervation: Median nerve [9](#page=9). * **Pronator quadratus:** * Origin: Distal quarter on the palmar side of the ulna [9](#page=9). * Insertion: Distal quarter on the palmar side of the radius [9](#page=9). * Function: Supports the pronator teres in pronation of the forearm [9](#page=9). * Innervation: Median nerve [9](#page=9). ### 2.3 Intrinsic muscles of the thumb These muscles are located within the hand but are crucial for thumb function, with some originating in the forearm. #### 2.3.1 Flexor pollicis longus * Origin: Ventral surface of the radius and interosseous membrane [9](#page=9). * Insertion: Base of the distal phalanx of the thumb [9](#page=9). * Function: Flexion of the interphalangeal (IP) and MCP joints of the thumb [9](#page=9). * Innervation: Anterior interosseous nerve (branch of the median nerve) [9](#page=9). #### 2.3.2 Abductor pollicis longus * Origin: Posterior surface of the ulna and posterior surface of the radius [9](#page=9). * Insertion: Base of the first metacarpal [9](#page=9). * Function: Abduction of the thumb [9](#page=9). * Innervation: Radial nerve [9](#page=9). --- # Muscles of the thumb and little finger This section details the specific muscles responsible for the intricate movements of the thumb and little finger, enabling complex actions like opposition and fine manipulation. ### 3.1 Muscles of the thumb The thumb muscles are crucial for its dexterity and ability to oppose the other digits. They are broadly categorized into extrinsic and intrinsic muscles, though this guide focuses on their origins, insertions, functions, and innervations as presented. #### 3.1.1 Extrinsic thumb muscles These muscles originate outside the thumb itself, primarily in the forearm. ##### 3.1.1.1 Flexor pollicis longus * **Origin:** Ventral surface of the radius and the interosseous membrane [9](#page=9). * **Insertion:** Base of the distal phalanx of the thumb [9](#page=9). * **Function:** Flexion of the thumb at the interphalangeal (IP) and metacarpophalangeal (MCP) joints [9](#page=9). * **Innervation:** Anterior interosseous nerve (branch of the median nerve) [9](#page=9). ##### 3.1.1.2 Abductor pollicis longus * **Origin:** Posterior surface of the ulna and posterior surface of the radius [9](#page=9). * **Passage:** Travels through the first tunnel under the flexor retinaculum [9](#page=9). * **Insertion:** Base of the first metacarpal bone [9](#page=9). * **Function:** Abduction of the thumb at the carpometacarpal (CMC) joint [10](#page=10). * **Innervation:** Radial nerve (posterior interosseous nerve) [10](#page=10). ##### 3.1.1.3 Extensor pollicis brevis * **Origin:** Posterior surface of the radius [10](#page=10). * **Passage:** Through the first tunnel [10](#page=10). * **Insertion:** Base of the proximal phalanx of the thumb [10](#page=10). * **Function:** Extension of the thumb [10](#page=10). * **Innervation:** Radial nerve (posterior interosseous nerve) [10](#page=10). ##### 3.1.1.4 Extensor pollicis longus * **Origin:** Posterior surface of the ulna [10](#page=10). * **Passage:** Ulnar to the dorsal tubercle, passing through the third tunnel under the flexor retinaculum [10](#page=10). * **Insertion:** Base of the distal phalanx of the thumb [10](#page=10). * **Function:** Extension of the thumb [10](#page=10). * **Innervation:** Radial nerve (posterior interosseous nerve) [10](#page=10). #### 3.1.2 Intrinsic thumb muscles These muscles are located within the hand, specifically in the thenar eminence. ##### 3.1.2.1 Abductor pollicis brevis * **Origin:** Flexor retinaculum, scaphoid bone, and trapezium bone [10](#page=10). * **Insertion:** Radial side of the base of the proximal phalanx of the thumb [10](#page=10). * **Function:** Abduction of the thumb at the CMC joint [10](#page=10). * **Innervation:** Median nerve [10](#page=10). ##### 3.1.2.2 Flexor pollicis brevis * **Origin:** * **Superficial head:** Flexor retinaculum [10](#page=10). * **Deep head:** Capitate bone, trapezium bone, and trapezoid bone [10](#page=10). * **Insertion:** Base of the proximal phalanx of the thumb [10](#page=10). * **Function:** Flexion of the thumb at the MCP joint [10](#page=10). * **Innervation:** * **Superficial head:** Median nerve [10](#page=10). * **Deep head:** Ulnar nerve [10](#page=10). ##### 3.1.2.3 Adductor pollicis * **Origin:** * **Oblique head:** Capitate bone and hamate bone [10](#page=10). * **Transverse head:** Palmar side of the second metacarpal bone [10](#page=10). * **Insertion:** Ulnar side of the proximal phalanx of the thumb [10](#page=10). * **Function:** Adduction of the thumb [10](#page=10). * **Innervation:** Ulnar nerve [10](#page=10). ##### 3.1.2.4 Opponens pollicis * **Origin:** Flexor retinaculum and the tubercle of the trapezium bone [11](#page=11). * **Insertion:** Radial side of the first metacarpal bone [11](#page=11). * **Function:** Opposition of the thumb [11](#page=11). * **Innervation:** Median nerve [11](#page=11). ### 3.2 Muscles of the little finger (pinky) These muscles are responsible for the fine movements and independent action of the little finger. #### 3.2.1 Abductor digiti minimi * **Origin:** Flexor retinaculum and the pisiform bone [11](#page=11). * **Insertion:** Ulnar side of the base of the proximal phalanx of the little finger [11](#page=11). * **Function:** Abduction of the little finger [11](#page=11). * **Innervation:** Ulnar nerve [11](#page=11). #### 3.2.2 Opponens digiti minimi * **Origin:** Flexor retinaculum and the hamulus of the hamate bone [11](#page=11). * **Insertion:** Ulnar side of the fifth metacarpal bone [11](#page=11). * **Function:** Opposition of the little finger [11](#page=11). * **Innervation:** Ulnar nerve [11](#page=11). #### 3.2.3 Flexor digiti minimi brevis * **Origin:** Flexor retinaculum and the hamulus of the hamate bone [11](#page=11). * **Insertion:** Base of the proximal phalanx of the little finger [11](#page=11). * **Function:** Flexion of the little finger at the MCP joint [11](#page=11). * **Innervation:** Ulnar nerve [11](#page=11). #### 3.2.4 Palmaris brevis * **Origin:** Ulnar side of the palmar aponeurosis and the flexor retinaculum [11](#page=11). * **Insertion:** Skin on the ulnar side of the hand [11](#page=11). * **Function:** Tensing the skin on the ulnar side of the hand [11](#page=11). * **Innervation:** Ulnar nerve [11](#page=11). --- # Intrinsic hand muscles The intrinsic muscles of the hand are crucial for fine motor control, enabling complex movements of the fingers and thumb. These muscles can be categorized into the lumbricals, dorsal interossei, and palmar interossei [12](#page=12). ### 4.1 Lumbrical muscles The lumbrical muscles are four small muscles that play a significant role in finger flexion and extension [12](#page=12). * **Origin:** The lumbricals originate from the four tendons of the flexor digitorum profundus muscle, specifically at the level of the metacarpals 2 through 5 [12](#page=12). * **Insertion:** Each of the four lumbrical tendons inserts onto the dorsal aponeurosis of the respective second, third, fourth, and fifth finger, proximal to the proximal interphalangeal joint [12](#page=12). * **Action:** They are responsible for flexing the metacarpophalangeal (MCP) joints while simultaneously extending the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints [12](#page=12). * **Innervation:** * The first and second lumbrical muscles are innervated by the median nerve [12](#page=12). * The third and fourth lumbrical muscles are innervated by the ulnar nerve [12](#page=12). ### 4.2 Dorsal interossei muscles The dorsal interossei are four muscles located between the metacarpal bones, primarily responsible for finger abduction and assisting in MCP flexion and IP extension [12](#page=12). * **Origin:** These muscles are bipennate, meaning they have two heads. Each head originates from the sides of the metacarpal bones that face away from each other. Specifically, they arise from the adjacent sides of the metacarpal bones [12](#page=12). * **Insertion:** * The first dorsal interosseus inserts onto the radial side of the dorsal aponeurosis of the proximal phalanx of the second finger [12](#page=12). * The second dorsal interosseus inserts onto the radial side of the dorsal aponeurosis of the proximal phalanx of the third finger [12](#page=12). * The third dorsal interosseus inserts onto the ulnar side of the dorsal aponeurosis of the proximal phalanx of the third finger [12](#page=12). * The fourth dorsal interosseus inserts onto the ulnar side of the dorsal aponeurosis of the proximal phalanx of the fourth finger [12](#page=12). * **Action:** Their primary actions are to abduct the fingers. They also contribute to the flexion of the MCP joints and the extension of the PIP and DIP joints [12](#page=12). * **Innervation:** All dorsal interossei muscles are innervated by the ulnar nerve [12](#page=12). ### 4.3 Palmar interossei muscles The palmar interossei are three muscles located on the palmar side of the metacarpals, responsible for finger adduction and assisting in MCP flexion and IP extension. They are unipennate [12](#page=12). * **Origin:** * The first palmar interosseus originates from the ulnar side of the second metacarpal bone [12](#page=12). * The second palmar interosseus originates from the radial side of the fourth metacarpal bone [12](#page=12). * The third palmar interosseus originates from the radial side of the fifth metacarpal bone [12](#page=12). * **Insertion:** These muscles insert onto the proximal phalanges and dorsal aponeuroses of the second, fourth, and fifth fingers, directing the movement towards the third finger [12](#page=12). * **Action:** Their primary action is to adduct the second, fourth, and fifth fingers, drawing them towards the midline (the third finger). They also contribute to the flexion of the MCP joints and the extension of the PIP and DIP joints [12](#page=12). * **Innervation:** All palmar interossei muscles are innervated by the ulnar nerve [12](#page=12). > **Tip:** Remember that the dorsal interossei abduct fingers away from the midline (the third finger), while the palmar interossei adduct fingers towards the midline. The lumbricals act on both flexion and extension in a coordinated manner. The innervation pattern is a key detail to memorize for clinical application. --- ## Common mistakes to avoid - Review all topics thoroughly before exams - Pay attention to formulas and key definitions - Practice with examples provided in each section - Don't memorize without understanding the underlying concepts

| Term | Definition | |------|------------| | M. Levator scapula | Originates from the transverse processes of C1-C4 and inserts on the medial border and superior angle of the scapula. Its function is to elevate and downwardly rotate the scapula. It is innervated by the Dorsal Scapulae nerve. | | M. Supraspinatus | Originates from the supraspinous fossa and inserts on the greater tubercle of the humerus. Its primary function is abduction of the arm up to 90 degrees and acts as a capsular stabilizer. It is innervated by the suprascapular nerve. | | M. Infraspinatus | Originates from the infraspinous fossa and inserts on the middle facet of the greater tubercle of the humerus. Its main function is external rotation of the shoulder. It is innervated by the suprascapular nerve. | | M. Teres Minor | Originates from the infraspinous fossa and the lateral border of the scapula, inserting on the inferior facet of the greater tubercle of the humerus. Its action is external rotation of the shoulder. It is innervated by the axillary nerve. | | M. Teres Major | Originates from the inferior angle and lateral border of the scapula, inserting on the lesser tubercle of the humerus. It functions in internal rotation, adduction, and retroflexion of the arm. It is innervated by the inferior subscapular nerve. | | M. Latissimus Dorsi | Originates from the iliac crest, sacrum, spinous processes of L5-T1, T12-T7, ribs 10-12, and sometimes the inferior angle. It inserts on the anterior crest of the lesser tubercle of the humerus. It performs internal rotation, adduction, and retroflexion of the arm, acts as a climbing muscle by pulling the trunk upwards, and retracts the scapula with the trapezius and rhomboid muscles. It is innervated by the thoracodorsal nerve. | | M. Rhomboideus Major and Minor | The Major originates from the spinous processes of T2-T5, and the Minor from C7-T1. Both insert on the medial border of the scapula, with the Major below the spine and the Minor above the spine. They retract the scapula and perform downward rotation. They are innervated by the dorsal scapular nerve. | | M. Subscapularis | Originates from the subscapular fossa and inserts on the lesser tubercle of the humerus. Its primary action is internal rotation of the shoulder. It is innervated by the subscapular nerve. | | M. Pectoralis Major | Originates from the clavicle (clavicular part), sternum and ribs 2-6 (sternocostal part), and abdominal muscles (abdominal part). It inserts on the crest of the greater tubercle. It functions in horizontal adduction, internal rotation, and acts as an accessory breathing muscle. The clavicular part assists in anteflexion, and the abdominal part in adduction. It is innervated by the pectoral nerve. | | M. Pectoralis Minor | Originates from ribs 3-5 and inserts on the coracoid process. It performs anterior tilt, protraction, and depression of the scapula, and also acts as an accessory breathing muscle. It is innervated by the medial and lateral pectoral nerves. | | M. Coracobrachialis | Originates from the coracoid process and inserts on the anterior medial surface of the humerus midway down. It assists in shoulder anteflexion and adduction of the raised arm. It is innervated by the musculocutaneous nerve. | | M. Deltoideus | Has three parts: clavicular (lateral third of clavicle), acromial (acromion), and spinal (inferior border of scapular spine). It inserts on the deltoid tuberosity of the humerus. The clavicular part assists in anteflexion and adduction; the acromial part in anteflexion and horizontal adduction; and the spinal part in retroflexion and abduction. It is innervated by the axillary nerve. | | M. Serratus Anterior | Originates from ribs 1-9 and inserts on the medial border of the scapula. It protracts and upwardly rotates the scapula, fixes it against the ribs, and acts as an accessory breathing muscle. It is innervated by the long thoracic nerve. | | M. Triceps Brachii | Composed of three heads: Long (originates from the infraglenoid tubercle of the scapula), Lateral (originates from the posterior and lateral corpus humeri), and Medial (originates from the medial and distal third of the corpus humeri). All insert on the olecranon. Its main function is extension of the elbow, with the long head also assisting in retroflexion. It is innervated by the radial nerve. | | M. Anconeus | Originates from the lateral epicondyle of the humerus and inserts distal to the olecranon on the ulna. It supports the triceps in elbow extension and acts as a capsular stabilizer. It is innervated by the radial nerve. | | M. Biceps Brachii | Has two heads: Long (originates from the supraglenoid tubercle of the scapula) and Short (originates from the coracoid process). Both insert on the radial tuberosity and the bicipital aponeurosis. It flexes the elbow and supinates the forearm. It is innervated by the musculocutaneous nerve. | | M. Brachialis | Originates from the ventral aspect of the humerus, distal to the deltoid tuberosity, and inserts on the radial tuberosity of the ulna. It is a primary flexor of the elbow, particularly with the forearm in pronation. It is innervated by the musculocutaneous nerve. | | M. Extensor Carpi Radialis Longus | Originates from the lateral border of the humerus to the lateral epicondyle and inserts on the base of the second metacarpal. It performs dorsiflexion and radial deviation of the wrist. It is innervated by the radial nerve. | | M. Extensor Carpi Radialis Brevis | Originates from the lateral epicondyle of the humerus and inserts on the base of the third metacarpal. It performs dorsiflexion and active radial deviation of the wrist. It is innervated by the radial nerve. | | M. Extensor Digitorum | Originates from the lateral epicondyle of the humerus and inserts via the dorsal extensor aponeurosis onto the second and third phalanges of digits 2-5. It extends the metacarpophalangeal (MCP) joints. It is innervated by the radial nerve. | | M. Extensor Digiti Minimi | Originates from the lateral epicondyle of the humerus and inserts on the dorsal aponeurosis of the fifth digit. It extends the little finger and contributes to wrist dorsiflexion. It is innervated by the radial nerve. | | M. Extensor Indicis | Originates from the distal third of the posterior ulna and inserts on the dorsal aponeurosis of the second digit. It extends the index finger and contributes to wrist dorsiflexion. It is innervated by the radial nerve. | | M. Extensor Carpi Ulnaris | Originates from the lateral epicondyle of the humerus and inserts on the base of the fifth metacarpal. It performs ulnar deviation and dorsiflexion of the wrist. It is innervated by the radial nerve. | | M. Flexor Carpi Radialis | Originates from the medial epicondyle of the humerus and inserts on the base of the second and third metacarpals. It performs weak flexion of the elbow and palmar flexion with radial deviation of the wrist. It is innervated by the median nerve. | | M. Flexor Palmaris Longus | Originates from the medial epicondyle of the humerus and inserts on the palmar aponeurosis of the hand. It tenses the palmar aponeurosis, acts as a flexor of the wrist, and aids in finger flexion through the aponeurosis. It is innervated by the median nerve. | | M. Flexor Carpi Ulnaris | Has a humeral head originating from the medial epicondyle and fascia antebrachii, and an ulnar head originating from the olecranon and posterior border of the ulna. It inserts on the base of the fifth metacarpal, also attaching to the pisiform and hamate bones. It performs weak flexion of the elbow and palmar flexion with ulnar deviation of the wrist. It is innervated by the ulnar nerve. | | M. Flexor Digitorum Superficialis | Has humeral, ulnar, and radial heads originating from the medial epicondyle, coronoid process of the ulna, and a oblique line from the radial tuberosity to the pronator teres tuberosity, respectively. It inserts on the middle phalanges of digits 2-5. It flexes the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of digits 2-5. It is innervated by the median nerve. | | M. Flexor Digitorum Profundus | Originates from the anterior surface of the ulna and the interosseous membrane of the forearm, inserting on the distal phalanges of digits 2-5. It flexes digits 2-5 at the MCP, PIP, and DIP joints. Digits 2-3 are innervated by the median nerve, and digits 4-5 by the ulnar nerve. | | M. Supinator | Originates from the lateral epicondyle of the humerus, the supinator crest of the ulna, and the radial collateral ligament and annular ligament of the radius. It inserts on the radius between the radial tuberosity and the lateral surface of the radius. Its primary function is supination of the forearm. It is innervated by the radial nerve. | | M. Pronator Teres | Has a humeral head originating from the medial epicondyle of the humerus and an ulnar head from the coronoid process of the ulna. It inserts on the middle third of the lateral surface of the radius. It pronates the forearm. It is innervated by the median nerve. | | M. Pronator Quadratus | Originates from the distal quarter of the palmar side of the ulna and inserts on the distal quarter of the palmar side of the radius. It supports the action of the pronator teres. It is innervated by the median nerve. | | M. Flexor Pollicis Longus | Originates from the ventral surface of the radius and the interosseous membrane, inserting on the base of the distal phalanx of the thumb. It flexes the interphalangeal (IP) and metacarpophalangeal (MCP) joints of the thumb. It is innervated by the anterior interosseous nerve (median nerve). | | M. Abductor Pollicis Longus | Originates from the posterior surface of the ulna and radius. It passes through the first dorsal tunnel and inserts on the base of the first metacarpal. It abducts the thumb at the carpometacarpal (CMC) joint. It is innervated by the posterior interosseous nerve (radial nerve). | | M. Extensor Pollicis Brevis | Originates from the posterior surface of the radius and passes through the first dorsal tunnel, inserting on the base of the proximal phalanx of the thumb. It extends the thumb. It is innervated by the posterior interosseous nerve (radial nerve). | | M. Extensor Pollicis Longus | Originates from the posterior surface of the ulna, ulnar to the dorsal tubercle, passing through the third dorsal tunnel, and inserts on the base of the distal phalanx of the thumb. It extends the thumb. It is innervated by the posterior interosseous nerve (radial nerve). | | M. Abductor Pollicis Brevis | Originates from the flexor retinaculum, scaphoid, and trapezium bones, inserting on the radial side of the base of the proximal phalanx of the thumb. It abducts the thumb at the CMC joint. It is innervated by the median nerve. | | M. Flexor Pollicis Brevis | Has a superficial head originating from the flexor retinaculum and a deep head originating from the capitate, trapezium, and trapezoid bones. Both insert on the base of the proximal phalanx of the thumb. It flexes the MCP joint of the thumb. The superficial head is innervated by the median nerve, and the deep head by the ulnar nerve. | | M. Adductor Pollicis | Has an oblique head originating from the capitate and hamate bones and a transverse head originating from the palmar side of the second metacarpal. It inserts on the ulnar side of the proximal phalanx of the thumb. It adducts the thumb. It is innervated by the ulnar nerve. | | M. Opponens Pollicis | Originates from the flexor retinaculum and the tubercle of the trapezium bone, inserting on the radial side of the first metacarpal. It opposes the thumb. It is innervated by the median nerve. | | M. Abductor Digiti Minimi | Originates from the flexor retinaculum and the pisiform bone, inserting on the ulnar side of the base of the proximal phalanx of the little finger. It abducts the little finger. It is innervated by the ulnar nerve. | | M. Opponens Digiti Minimi | Originates from the flexor retinaculum and the hamulus of the hamate bone, inserting on the ulnar side of the fifth metacarpal. It opposes the little finger. It is innervated by the ulnar nerve. | | M. Flexor Digiti Minimi Brevis | Originates from the flexor retinaculum and the hamulus of the hamate bone, inserting on the base of the proximal phalanx. It flexes the MCP joint of the little finger. It is innervated by the ulnar nerve. | | M. Palmaris Brevis | Originates from the ulnar side of the palmar aponeurosis and the flexor retinaculum, inserting on the skin of the ulnar side of the hand. It tightens the skin on the ulnar side of the hand. It is innervated by the ulnar nerve. | | Mm. Lumbricales | Originate from the four tendons of the Flexor Digitorum Profundus (at the level of metacarpals 2-5) and insert on the dorsal aponeurosis of the respective second, third, fourth, and fifth fingers. They flex the MCP joints and extend the PIP and DIP joints. Lumbricals 1 and 2 are innervated by the median nerve, and lumbricals 3 and 4 by the ulnar nerve. | | Mm. Interossei Dorsales | Are bipennate muscles, each originating from the adjacent sides of the metacarpal bones. They insert on the dorsal aponeurosis of the proximal phalanges. Dorsal Interossei I inserts on the radial side of the proximal phalanx of the second finger, II on the radial side of the third finger, III on the ulnar side of the third finger, and IV on the ulnar side of the fourth finger. They abduct the fingers, flex the MCP joints, and extend the PIP and DIP joints. They are innervated by the ulnar nerve. | | Mm. Interossei Palmares | Are unipennate muscles. I originates from the ulnar side of the second metacarpal, II from the radial side of the fourth metacarpal, and III from the radial side of the fifth metacarpal. They insert on the proximal phalanx and dorsal aponeuroses of the second, fourth, and fifth fingers, respectively, converging towards the third finger. They adduct the second, fourth, and fifth fingers towards the third finger, flex the MCP joints, and extend the PIP and DIP joints. They are innervated by the ulnar nerve. |