Welcome back to this session for the anatomy of the thoracic and the upper limb. Here is the thoracic cage. The first rib attaches to the manubrium and it is hidden behind the clavicle. The second rib is the highest rib that can be identified by palpation. The Xiphoid process is cartilaginous in the early life and it gradually ossified by the time of middle age. Sternum gets anchored to the ribs to the T1 to T12, but the T8 to T12 are not attached directly to it. For the muscles of the thoracic cage, the pectoralis major is thick, it's fan-shaped and it has a clavicular part, a sternocostal part and the abdominal part. It inserts into the greater tubercle of the humerus. Underneath this, the pectoralis minor, and it's relatively thin and it's triangular. For the serratus anterior, is a fan-shaped muscle. It is easy to palpate which is located between the pectoralis major and the latissimus dorsi. The scapula protraction and the scapula upward rotation are performed by the serratus anterior. This is also a scapular stabilizer. There are intercostal muscles within the thoracic cage. There are 11 pairs of external intercostals. The thoracic volume can be increased by elevating the ribs. The internal intercostals have the opposite direction to the external intercostals. It decreases the thoracic volume. The contraction of innermost intercostal will decrease the thoracic volume. The upper limb, from proximal to distal, is formed by the shoulder girdle, the upper arm, the elbow and forearm, and most distally the wrist, hand and fingers. There are three bones within the shoulder region. The scapula, which can be known also as the shoulder blade. The clavicle, also known as the collarbone. The humerus is the upper arm. The scapula is the back of the shoulder girdle. It is a triangular bone and has three processes, the acromion, spine of scapula and the coracoid process. For the clavicle, it articulates with the sternum and acromion. The humerus has a head, neck and the greater and lesser tubercles. The shoulder joints include the sternoclavicular joint (SCJ), the scapulothoracic joint (STJ), the acromioclavicular joint (ACJ) and the glenohumeral joint (GHJ). The sternoclavicular joint connects the clavicle and the sternum and it is a saddle joint. The scapulothoracic joint connects the scapula and thoracic cage. It is not a true anatomical joint. The acromioclavicular joint is the distal end of the clavicle and acromion of the scapula. It is a plain synovial joint and allows the scapula to have the additional range of rotation on the thorax. The transmission of force is from the upper extremity to the clavicle. The glenohumeral joint is a synovial joint. It's in conjunction with the pectoral girdle, humerus head and glenoid cavity of the scapula. It is the most mobile joint. The ligaments in the shoulder girdle, include the acromioclavicular ligament and the coracoclavicular ligament, connect the clavicle to the scapula. The coracohumeral ligament and the glenohumeral ligament connect the scapula to the humerus. The coracoid process and acromion are connected by the coracoacromial ligament. The glenohumeral joint involves both the dynamic stabilizers and the static stabilizers. The dynamic stabilizers include the muscles and tendons. The most well known ones are the rotator cuff muscles which controls the movement of the humeral head within the glenoid fossa. The periscapular muscles are the serratus anterior, levator scapula, pectoralis minor, rhomboids and trapezius. The muscles help to avoid any misalignment. This is the surface anatomy of the shoulder, which includes the landmarks, clavicle, acromion, ACJ and the coracoid process. For the muscles in the shoulder and arm, the deltoid has the anterior, posterior and the middle part. The anterior part is responsible for the flexion and internal rotation. The posterior is responsible for the extension and external rotation. The middle part is responsible for abduction. The pectoralis major is over the shoulder joint and it’s responsible for adduction, internal rotation, flexion and extension. The biceps brachii has two heads, the short head and the long head. It's responsible for the flexion and the supination of forearm at the elbow joint. Trapezius is in a superior, middle and inferior part. The superior part is responsible for the extension of the head and neck and the lateral flexion of the head and neck. From the middle part, it draws scapular medially and inferior part draws the scapular inferomedially. Triceps have the long head, the medial head and the lateral head. It is responsible for the elbow extension and shoulder extension and adduction. Latissimus dorsi is responsible for the shoulder internal rotation, adduction and extension. It helps in respiration as well. Rotator cuff is formed by four muscles, the supraspinatus muscle, which helps for the abduction of the arm; the infraspinatus muscle helps external rotation of the arm along with the teres minor; and subscapularis muscle is responsible for the internal rotation of the arm. Elbow joint is a synovial joint. It's also a hinge joint. It is the articulation between three bones - the humerus, radius and ulna. The joint is responsible for the movement includes the flexion and extension of the elbow, along with the pronation and supination of the forearm. There are three joints, the ulnohumeral joint, radiocapitellar joint and the proximal radioulnar joint. The ulnohumeral joint, which is circled in pink in the diagram, is called the humeroulnar joint. It's between the trochlea of the humerus and trochlear notch of the ulna. The radiocapitellar joint is circled in green. It is also called the humeroradial joint, it’s the rotation between the capitulum of the humerus and the radial head. Both joints give the elbow the hinge-like properties. The proximal radioulnar joint is a pivot joint. It allows the rotational movement of the radius on ulna, hence leading to the pronation and supination of forearm. In the elbow, we have the radial collateral ligament. It is on the lateral side of the elbow and extends from the lateral epicondyle and blends with the annular ligament. The ulnar collateral ligament is on the medial side of the joint. It's from the medial epicondyle to the coronoid process and the olecranon of the ulna. There's the annular ligament which holds the radius and ulna together at the proximal articulation. This is the surface anatomy of the elbow joint. Important structures include the biceps tendon, the medial and the lateral epicondyle and the olecranon. For the muscles of the elbow in the upper arm, there are the biceps, which is the ventral portion of the upper arm. It's composed of a short head and long head. The long head is located on the lateral side of the biceps brachii while the short head is located on the medial side. They works across three joints and is able to generate movements in the glenohumeral, elbow and the radioulnar joints. The triceps, which is a dorsal part of the upper arm and its main function is for the extension of the elbow joint. In the forearm, the anterior compartment of the forearm includes superficially - the flexor carpi ulnaris, the palmaris longus, the flexor carpi radialis and the pronator teres. In the intermediate layer, there's a flexor digitorum superficialis. For the deep layer, we will cover it in the wrist session as well later. It includes the flexor pollicis longus, the flexor digitorum profundus and the pronator quadratus. In the posterior compartment of the forearm, there are the extensor muscles. The function of these muscles is to produce extension at the wrist and fingers. The superficial layer includes the extensor carpi radialis longus, the extensor carpi radialis brevis, the extensor digitorum, the extensor carpi ulnaris, the extensor digiti minimi, the brachioradialis and anconeus. The deep layer includes the supinator, the abductor pollicis longus, the extensor pollicis brevis, the extensor pollicis longus and the extensor indicis. For the bones of the hand and wrist, there are 27 bones in total. 8 of them are carpals, 5 metacarpals and 14 phalanges. The five distal phalanges are in yellow; the four intermediate phalanges are in orange; and the five proximal phalanges are in green. There are two rows in carpals. The proximal carpals include the scaphoid, lunate, triquetrum and the pisiform. Distal carpals includes trapezium, trapezoid, capitate and hamate. For the wrist joint, the carpometacarpal joint (CMCJ) are five joints in the wrist that articulate with the distal row of the carpal bones and the proximal bases of the five metacarpal bones. The CMC of the thumb or the first CMC, also known as the trapeziometacarpal joint (TMC), differs significantly from the other four CMCs. The metacarpophalangeal joint (MCPJ) is the collection of condyloid joints. It connects the metacarpus and the palm of the hand to the fingers. There are five separate metacarpophalangeal joints, connect each metacarpal bone to the corresponding proximal phalanx of each finger. The interphalangeal joint (IPJ) is a synovial hinge joint. It spans between the proximal, middle and distal phalanges of the hand. Its function is to permit fine motor movements in the digits. This is the overview of the muscles of the hand and wrist. These are the ligaments in the wrist. The capsule is continuous with the midcarpal joint and is strengthened by the numerous ligaments. This includes the palmer and a dorsal radiocarpal ligaments and the ulnar and radial collateral ligaments. We come to the major arteries of the upper limb. For the upper arm, this includes the brachial artery. It is a continuation of the axillary artery pass the lower border of the terrace major. It’s distal to the teres major, descends (down) the arm, moves through the cubital fossa, underneath the bicipital aponeurosis and finally it is terminated by bifurcating into the radial and ulnar arteries. In forearm, the radial artery supplies the posterolateral aspect of the forearm and forms anastomotic networks surrounding elbow joint and the carpal bones. The radial pulse can be palpated in a distal forearm. The ulnar artery supplies the anteromedial aspect of the forearm and it forms the anastomotic networks surrounding the elbow joint. For the major nerves of the upper limb, the axillary nerve froms the brachial plexus and provides sensory of the “regimental badge” area. It also provides the motor functions of the deltoid and the teres minor muscles. The median nerve provides the motor functions for the muscles of the anterior compartment of forearm, the thenar muscles and the lateral two lumbricals of the hand. It provides the sensation for the lateral three and a half digits of the hand. For the radial nerve, it's from all roots of the brachial plexus. It spirals down in radial groove of the humerus. It provides the motor functions of the triceps brachii muscles and extensor muscles of forearm. And for the sensory, it supplies the posterior forearm and the dorsal surface of the hand. The ulnar nerve provides motor functions for the intrinsic muscles of the hand and the two muscles in the anterior forearm. It also supplies the sensory of the little finger and part of the ring finger and the medial palmar area. These are the important common sports injuries in the upper limb region includes shoulder dislocation, SLAP lesion, fracture clavicle, tennis elbow, fracture wrist and the skier thumb.
