Forearm Anatomy PDF

XY2141. ANATOMY. MUSCLES OF THE ARM. FOREARM Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected]  LEARNING OUTCOMES ANAT.40 - Arm ANAT.40.01 - Describe and demonstrate movements of the elbow...

XY2141. ANATOMY. MUSCLES OF THE ARM. FOREARM Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected]  LEARNING OUTCOMES ANAT.40 - Arm ANAT.40.01 - Describe and demonstrate movements of the elbow joint. ANAT.40.02 - Identify the bones and bony features of the humerus, ulna and radius. ANAT.40.03 - Summarize the muscles and their actions of the arm and forearm. ANAT.40.04 - Define the boundaries and contents of the cubital fossa. ANAT.40.05 - Describe the motor and sensory innervation of the arm and forearm. ANAT.41 - Forearm ANAT.41.01 - Describe and demonstrate movements of the elbow joint. ANAT.41.02 - Identify the bones and bony features of the humerus, ulna and radius. ANAT.41.03 - Summarize the muscles and their actions of the arm and forearm. ANAT.41.04 - Define the boundaries and contents of the cubital fossa (will be mentioned in the following lecture). ANAT.41.05 - Describe the motor and sensory innervation of the arm and forearm (will be mentioned in the following lecture). ANAT.41.06 - Discuss the arterial and venous supply to the arm and forearm (will be mentioned in the following lecture) ANAT.41.07 - Review the bony components of the elbow joint and name the supporting ligaments. ANAT.41.08 - Apply your anatomical knowledge to clinical correlations associated with the arm and forearm, as discussed.  FOREARM OR ANTEBRACHIUM Forearm extends from the elbow to the wrist. Forearm contains two bones - radius and ulna, which are tied together by the thin strong fibrous membrane - interosseous membrane. Radius and ulna at both their ends articulate with each other to form the superior and inferior radio-ulnar joints. All important movements of supination and pronation of the forearm occur at these joints.  ULNA Ulna is a long bone located on the medial aspect of the forearm. It acts as a rotary axis for the radius during pronation and supination of the forearm. Parts: 1. Proximal end – is widened 2. Shaft (corpus ulnae) – body of the ulna 3. Head (caput ulnae) – distal narrow end  ULNA 1. Proximal end – is widened 1.1 Olecranon – insertion of triceps brachii and the attachment of the olecranohumeral and oblique ligaments 1.2 Coronoid process (processus coronoideus ulnae) – ventral border of the trochlear notch 1.3 Tuberosity of ulna (tuberositas ulnae) – insertion of the brachialis 1.4 Radial notch (incisura radialis) – articular fossa for the head of the radius 1.5 Trochlear notch (incisura trochlearis) – articular cavity for the trochlea of the humerus 1.6 Supinator crest (crista musculi supinatoris) – origin of the supinator muscle ULNA  ULNA 2. Shaft (corpus ulnae) – body of the ulna 2.1 Nutrient foramen (foramen nutricium) – entrance of vessels into the medullary cavity Surfaces: 2.2 Anterior surface 2.3 Posterior surface 2.4 Medial surface  ULNA Borders: 2.5 Interosseous border – attachment of the interosseous membrane of the forearm 2.6 Anterior border 2.7 Posterior border – palpable in its entire course  ULNA 3. Head (caput ulnae) – distal narrow end 3.1 Articular circumference (circumferentia articularis) – annular articular facet around the head – articular surface in the distal radio-ulnar joint 3.2 Ulnar styloid process (processus styloideus ulnae) – palpable projection on the dorsal side of the distal forearm ULNA ULNA ULNA  RADIUS Radius is a long bone located on the lateral aspect of the forearm. During pronation and supination, the radius rotates around the ulna. Parts: 1. Head of radius (caput radii) – is located on the proximal end of the bone 2. Neck (collum radii) – attachment of the articular capsule 3. Shaft (corpus radii) – body of the radius 4. Distal end – is widened  RADIUS 1. Head of radius (caput radii) – is located on the proximal end of the bone 1.1 Articular facet (fovea articularis) – articular fossa for the capitulum of the humerus 1.2 Articular circumference (circumferentia articularis) – annular articular facet around the head of the humerus – articular head of the proximal radio-ulnar joint 2. Neck (collum radii) – attachment of the articular capsule  RADIUS 3. Shaft (corpus radii) – body of the radius 3.1 Radial tuberosity (tuberositas radii) – tuberosity on the proximal part – insertion of the biceps brachii 3.2 Pronator tuberosity (tuberositas pronatoria radii) – tuberosity in the middle of the radial shaft – insertion of the pronator teres 3.3 Nutrient foramen (foramen nutricium) – entrance of vessels into the medullary cavity, points proximally  RADIUS Surfaces: 3.4 Anterior surface 3.5 Posterior surface 3.6 Lateral surface Borders: 3.7 Interosseous border – attachment of the interosseous membrane of the forearm 3.8 Anterior border 3.9 Posterior border  RADIUS 4. Distal end – is widened 4.1 Radial styloid process (processus styloideus radii) – palpable projection on the dorsal side of the distal forearm 4.2 Suprastyloid crest (crista suprastyloidea) – insertion of the brachioradialis 4.3 Grooves for tendons of extensors (sulci tendinum musculorum extensorum) – grooves for the tendons of the extensor muscles  RADIUS 4.4 Dorsal tubercle of Lister (tuberculum dorsale) – most prominent tubercle between the grooves for the extensor tendons 4.5 Ulnar notch (incisura ulnaris) – articular fossa of the distal radio-ulnar joint 4.6 Carpal articular surface (facies articularis carpalis) – articular fossa for articulation with the scaphoid and lunate RADIUS RADIUS RADIUS  ELBOW JOINT – ARTICULATIO CUBITI Elbow joint is a compound synovial joint made up of three bones - humerus, ulna, and radius, articulating in three separate simple joints. It is a biaxial joint that allows flexion and extension and, in cooperation with the distal radio-ulnar joint, pronation and supination.  JOINTS COMPRISING THE ELBOW JOINT 1. Humero-ulnar joint (a. humeroulnaris) 1.1 Shape: trochlear 2. Humeroradial joint (a. humeroradialis) 2.1 Shape: ball-and-socket 3. Proximal radio-ulnar joint (a. radioulnaris proximalis) 3.1 Shape: pivot  JOINTS COMPRISING THE ELBOW JOINT 1. Humero-ulnar joint 1.2 Articular head: trochlea of the humerus 1.3 Articular fossa: trochlear notch of the ulna 2. Humeroradial joint 2.2 Articular head: capitullum of the humerus 2.3 Articular fossa: articular facet of the head of the radius 3. Proximal radio-ulnar joint 3.2 Articular head: articular circumference of the head of the radius 3.3 Articular fossa: radial notch of the ulna  COMMON PARTS OF THE ELBOW JOINT 4. Capsule: attaches to the humerus inferior to the epicondyles, to the neck of the radius and to the ulna on the borders of its articular surface 4.1 Sacciform recess – a pouch within the articular capsule located over the neck of the radius.  LIGAMENTS OF THE ELBOW JOINT 5.1 Ulnar collateral ligament (l. collaterale ulnare) – a triangular ligament on the medial side of the elbow 5.2 Radial collateral ligament (l. collaterale radiale) – is located on the lateral side of the elbow 5.3 Annular ligament of radius (l. anulare radii) – attaches to the ulna – encircles the head of the radius  LIGAMENTS OF THE ELBOW JOINT Accessory ligament: 6.1 Subtendinous bursa of triceps brachii (bursa subtendinea musculi tricipitis brachii) – in the place of the olecranon  MOVEMENTS THE ELBOW JOINT 7.1 Flexion: 0–145° 7.2 Extension: 0–5° hyperextension up to 10° is physiological in females due to a smaller sized olecranon 7.3 Pronation: 0–90° – radius is crossed over the ulna 7.4 Supination: 0– 90° – radius and ulna are parallel 8. Neutral position: is in mild flexion and pronation TYPE OF MOVEMENTS  MUSCLES OF THE ARM – MUSCULI BRACHII Muscles around the humerus can be divided into: Anterior group Posterior group. These muscles act on the shoulder and elbow joints. Anterior group consists of flexors of the shoulder and elbow joints and is innervated by the musculocutaneous nerve. Posterior group consists of extensors of the shoulder and elbow joints and is innervated by the radial nerve.  MUSCLES OF THE ARM – MUSCULI BRACHII 1. Anterior (flexor) group 1.1 Biceps brachii (m. biceps brachii) 1.2 Coracobrachialis (m. coracobrachialis) 1.3 Brachialis (m. brachialis) 2. Posterior (extensor) group 2.1 Triceps brachii (m. triceps brachii) 2.2 Anconeus (m. anconeus) Cubitus is a Latin term for elbow. Ancon is a Greek term for elbow.  MUSCLES OF THE ARM – MUSCULI BRACHII Biceps brachii (m. biceps brachii) - is comprised of a long and short head Origin: 1. Short head (caput breve): scapula – coracoid process 2. Long head (caput longum): scapula – supraglenoid tubercle Insertion: radius – radial tuberosity, medial side of the forearm – antebrachial fascia via the bicipital aponeurosis (lacertus fibrosus) Lacerta is a Latin term for lizard.  THE UPPER LIMB (LEFT LATERAL VIEW) Bicipital aponeurosis  MUSCLES OF THE ARM – MUSCULI BRACHII Functions of the biceps brachii: at the shoulder joint: – abduction of the arm (long head) – adduction and ventral flexion of the arm (short head) at the elbow joint: – supination of a pronated forearm – flexion (only when the forearm is supinated) Innervation: musculocutaneous nerve  MUSCLES OF THE ARM – MUSCULI BRACHII 1. Coracobrachialis (m. coracobrachialis) O: scapula – coracoid process I: humerus (anteromedial surface) F: adduction and ventral flexion of the arm, returns the arm to the middle (basic) position from both external and internal rotation N: musculocutaneous nerve  MUSCLES OF THE ARM – MUSCULI BRACHII 2. Brachalis (m. brachialis) O: humerus (anterior surface) – distal half I: ulna – tuberosity of ulna F: flexion of the forearm N: musculocutaneous nerve  MUSCLES OF THE ARM – MUSCULI BRACHII 3. Triceps brachii (m. triceps brachii) - is comprised of a long medial, and lateral head O: a) Long head: scapula – infraglenoid tubercle b) Lateral head: humerus – proximal to the radial groove c) Medial head: humerus – distal to the radial groove I: ulna – olecranon F: whole muscle: extension of the forearm only the long head: adduction of an extended arm N: radial nerve (C6–C8) MUSCLES OF THE ARM – TRICEPS BRACHII  RADIAL CANAL – CANALIS NERVI RADIALIS A space located on the posterior surface of the humerus It contains the radial nerve and the deep brachial vessels. Boundaries: 1. Floor: radial groove 2. Proximally and laterally: lateral head of triceps brachii 3. Distally and medially: medial head of triceps brachii Content: 4. Radial nerve 5. Profunda brachii artery 6. Deep veins of arm  MUSCLES OF THE ARM – MUSCULI BRACHII 4. Anconeus (m. anconeus) O: humerus – lateral epicondyle, radial collateral ligament I: ulna (posterior border) – proximally up to the olecranon F: accessory extensor of the forearm, stretches the articular capsule of the elbow joint and therefore, prevents its constriction, stabilises the elbow joint during supination and pronation N: radial nerve (C7–C8)  MUSCLES OF THE FOREARM – MUSCULI ANTEBRACHII Divided into 3 groups: Anterior, Lateral, Posterior. They act on the elbow joint, wrist joint and joints of the hand. Flexors and supinators of the forearm are more dominant than the extensors and pronators. Flexors and supinators may shorten during long periods of inactivity, as occurs in bedridden patients.  MUSCLES OF THE FOREARM – MUSCULI ANTEBRACHII Anterior muscles of the forearm are divided into four layers. They are flexors and pronators of the forearm. These muscles are innervated predominantly by the median nerve, although the flexor carpi ulnaris and part of the flexor digitorum profundus are innervated by the ulnar nerve. Pronator teres, flexor carpi ulnaris and flexor digitorum superficialis each have two heads, through which nerves from the upper arm pass to the forearm.  MUSCLES OF THE FOREARM – MUSCULI ANTEBRACHII 1. Anterior (flexor) group - flexors and pronators of the forearm. 1st layer 1.1 Palmaris longus (m. palmaris longus) 1.2 Pronator teres (m. pronator teres) 1.3 Flexor carpi radialis (m. flexor carpi radialis) 1.4 Flexor carpi ulnaris (m. flexor carpi ulnaris) 2nd layer 1.5 Flexor digitorum superficialis (m. flexor digitorum superficialis) 3rd layer 1.6 Flexor digitorum profundus (m. flexor digitorum profundus) 1.7 Flexor pollicis longus (m. flexor pollicis longus) 4th layer 1.8 Pronator quadratus (m. pronator quadratus)  MUSCLES OF THE FOREARM – MUSCULI ANTEBRACHII 2. Lateral (radial) group: Superficial layer consists of three muscles, which have a common function of pronation of the flexed forearm and supination of the extended forearm. Deep layer consists of one muscle, the supinator, which is made up of two layers of fibres and acts as a supinator of the forearm. Superficial layer 2.1 Brachioradialis (m. brachioradialis) 2.2 Extensor carpi radialis longus (m. extensor carpi radialis longus) 2.3 Extensor carpi radialis brevis (m. extensor carpi radialis brevis) Deep layer 2.4 Supinator (m. supinator)  MUSCLES OF THE FOREARM – MUSCULI ANTEBRACHII Posterior group of the forearm muscles is organised into two layers. These muscles are extensors and have a common innervation by the radial nerve. Tendons of all muscles of the posterior group are covered by tendinous sheaths as they run through osteofibrous canals under the extensor retinaculum to the dorsum of the hand. Extensor carpi ulnaris has two heads.  MUSCLES OF THE FOREARM – MUSCULI ANTEBRACHII 3. Posterior (extensor) group - extensors Superficial layer 3.1 Extensor digitorum (m. extensor digitorum) 3.2 Extensor digiti minimi (m. extensor digiti minimi) 3.3 Extensor carpi ulnaris (m. extensor carpi ulnaris) Deep layer 3.4 Abductor pollicis longus (m. abductor pollicis longus) 3.5 Extensor pollicis brevis (m. extensor pollicis brevis) 3.6 Extensor pollicis longus (m. extensor pollicis longus) 3.7 Extensor indicis (m. extensor indicis)  THE ANTEBRACHIUM (FOREARM). (A) ANTERIOR VIEW. (B) POSTERIOR VIEW REFERENCES