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Pectoralis major
The pectoralis major is a muscle of the anterior chest wall. It is a large fan-shaped muscle,
which is composed of a sternal head and a clavicular head.
Attachments:
Clavicular head originates from the anterior surface of the medial clavicle.
Sternocostal head originates from the anterior surface of the sternum, the superior
six costal cartilages and the aponeurosis of the external oblique muscle.
The distal attachment of both heads is onto the intertubercular sulcus of the
humerus.
Function: Adduction and medial rotation of the upper limb.
Innervation: Lateral and medial pectoral nerves.
Blood supply: Pectoral branch of thoracoacromial artery, superior thoracic artery,
lateral thoracic artery.
Deltoid
The deltoid is an intrinsic muscle of the shoulder region. It is shaped like an inverted triangle
and can be divided into three parts (anterior, middle and posterior).
Attachments: Originates from the lateral third of the clavicle, the acromion and the
spine of the scapula. It attaches to the deltoid tuberosity on the lateral aspect of the
humerus.
Innervation: Axillary nerve.
Actions:
Anterior fibres – flexion and medial rotation at the shoulder
Posterior fibres – extension and lateral rotation at the shoulder
Middle fibres – abduction at the shoulder (takes over from the supraspinatus, which
abducts the first 15 degrees).
Blood supply: Anterior and posterior circumflex humeral artery.
Biceps Brachii
The biceps brachii is a muscle in the anterior compartment of the upper arm. Although the
majority of its mass is located anteriorly to the humerus, it has no attachment to the bone
itself.
Attachments: Long head originates from the supraglenoid tubercle of the scapula, and
the short head originates from the coracoid process of the scapula. Both heads insert
distally into the radial tuberosity and the fascia of the forearm via the bicipital
aponeurosis.
Function: Supination of the forearm, flexion at the elbow and shoulder.
Innervation: Musculocutaneous nerve.
Blood supply: Brachial artery.