Atlas of Anatomy
19 Shoulder & Arm
Bones of the Upper Limb
Fig. 19.1 Skeleton of the upper limb
Right limb. The upper limb is subdivided into three regions: arm, forearm, and hand. The shoulder girdle (clavicle and scapula) joins the upper limb to the thorax at the sternoclavicular joint.
Fig. 19.2 Palpable bony prominences
Except forthe lunate and trapezoid bones, all of the bones in the upper limb are palpable to some degree through the skin and soft tissues.
Clavicle & Scapula
The shoulder girdle (clavicle and scapula) connects the bones of the upper limb to the thoracic cage. Whereas the pelvic girdle (paired hip bones) is firmly integrated into the axial skeleton (see p. 358), the shoulder girdle is extremely mobile.
Fig. 19.3 Clavicle
Right clavicle. The S-shaped clavicle is visible and palpable along its entire length (generally 12 to 15 cm). Its medial end articulates with the sternum at the sternoclavicular joint (see p. 258). Its lateral end articulates with the scapula attheacromioclavicular joint (see p. 259).
The superior transverse ligament of the scapula (see p. 259) may become ossified, transforming the scapular notch into an anomalous bony canal, the scapular foramen. This can lead to compression of the suprascapular nerve as it passes through the canal (see p. 333).
Fig. 19.4 Scapula
Right scapula. In its normal anatomical position, the scapula extends from the 2nd to the 7th rib.
Fig. 19.5 Humerus
Right humerus. The head of the humerus articulates with the scapula at theglenohumeral joint (see p. 258). Thecapitellum and trochlea of the humerus articulate with the radius and ulna, respectively, at the elbow (cubital) joint (see p. 282).
Fractures of the humerus
Anterior view. Fractures of the proximal humerus are very common and occur predominantly in older patients who sustain a fall onto the outstretched arm or directly onto the shoulder. Three main types are distinguished.
Extra-articular fractures and intra-articular fractures are often accompanied by injuries of the blood vessels that supply the humeral head (anterior and posterior circumflex humeral arteries), with an associated risk of post-traumatic avascular necrosis.
Fractures of the humeral shaft and distal humerus are frequently associated with damage to the radial nerve.
Joints of the Shoulder
Fig. 19.6 Joints of the shoulder: Overview
Right shoulder, anterior view.
Fig. 19.7 Joints of the shoulder girdle
Right side, superior view.
Fig. 19.8 Scapulothoracic joint
Right side, superior view. In all movements of the shoulder girdle, the scapula glides on a curved surface of loose connective tissue between the serratus anterior and the subscapu-laris muscles. This surface can be considered a scapulothoracic joint.
Fig. 19.9 Sternoclavicular joint
Anterior view with sternum coronally sectioned (left). Note: A fibrocartilaginous articular disk compensates for the mismatch of surfaces between the two saddle-shaped articular facets of the clavicle and manubrium sterni.
Fig. 19.10 Acromioclavicular joint
Anterior view. The acromioclavicular joint is a plane joint. Because the articulating surfaces are flat, they must be held in place by strong ligaments, greatly limiting the mobility of the joint.
Injuries of the acromioclavicular joint
A fall onto the outstretched arm or shoulder frequently causes dislocation of the acromioclavicular joint and damage to the coracoclavicular ligaments.
Joints of the Shoulder: Glenohumeral Joint
Fig. 19.11 Glenohumeral joint: Bony elements
Fig. 19.12 Radiograph of the shoulder
Fig. 19.13 Glenohumeral joint: Capsule and ligaments
Fig. 19.14 Glenohumeral joint cavity
Fig. 19.15 MRI of the shoulder
Coronal section, anterior view.
Subacromial Space & Bursae
Fig. 19.16 Subacromial space
Fig. 19.17 Subacromial bursa and glenoid cavity
Right shoulder, lateral view of sagittal section with humerus removed.
Fig. 19.18 Subacromial and subdeltoid bursae
Right shoulder, anterior view.
Anterior Muscles of the Shoulder & Arm (I)
Fig. 19.19 Anterior muscles
Right side, anterior view. Muscle origins (O) are shown in red, insertions (I) in blue.
Anterior Muscles of the Shoulder & Arm (II)
Fig. 19.20 Anterior dissection
Right arm, anterior view. Muscle origins (O) are shown in red, insertions (I) in blue.
Posterior Muscles of the Shoulder & Arm (I)
Fig. 19.21 Posterior muscles
Right side, posterior view.
Posterior Muscles of the Shoulder & Arm (II)
Fig. 19.22 Posterior dissection
Right arm, posterior view. Muscle origins (0) are shown in red, insertions (I) in blue.
Muscle Facts (I)
The actions of the three parts of the deltoid muscle depend on their relationship to the position of the humerus and its axis of motion. At less than 60 degrees, the muscles act as adductors, but at greater than 60 degrees, they act as abductors. As a result, the parts of the deltoid can act antagonistically as well as synergistically.
Fig. 19.23 Deltoid
Fig. 19.24 Rotator cuff
Right shoulder. The rotator cuff consists of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis.
Muscle Facts (II)
Fig. 19.25 Pectoralis major and coracobrachialis
Fig. 19.26 Subclavius an pectoralis minor
Right side, anterior view.
Fig. 19.27 Serratus anterior
Right lateral view.
Muscle Facts (III)
Fig. 19.28 Trapezius
Fig. 19.29 Levator scapulae with rhomboids major and minor
Right side, posterior view.
Fig. 19.30 Latissimus dorsi and teres major
Muscle Facts (IV)
The anterior and posterior muscles of the arm may be classified respectively as flexors and extensors relative to the movement of the elbow joint. Although the coracobrachialis is topographically part of the anterior compartment, it is functionally grouped with the muscles of the shoulder (see p. 274).
Fig. 19.31 Biceps brachii and brachialis
Right arm, anterior view.
Fig. 19.32 Triceps brachii and anconeus
Right arm, posterior view.