Human Musculature

A: The biceps brachii, commonly known as the biceps, is a two-headed human musculature that lies on the upper arm between the shoulder and the elbow. Its main function is at the latter where it flexes the forearm at the elbow and supinates the forearm.

B: The sternocleidomastoid muscle, also known as sternomastoid and commonly abbreviated as SCM, is a paired human muscle in the superficial layers of the side of the neck. The primary actions of the muscle are the rotation of the head to the opposite side and flexion of the neck.

C: The teres major muscle is a muscle of the upper limb. It attaches to the scapula and the humerus and is one of the seven scapulohumeral muscles. It is positioned superior to the latissimus dorsi muscle and assists in the extension and medial rotation of the humerus.

D: The pectoralis major is a thick, fan-shaped muscle, situated at the chest (anterior) of the human body. It makes up the bulk of the chest muscles in the male and lies under the breast in the female. Underneath the pectoralis major is the pectoralis minor, a thin, triangular muscle.

E: The latissimus dorsi, is the larger, flat, dorso-lateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region. It is responsible for extension, adduction, the transverse extension is also known as horizontal abduction, flexion from an extended position, and (medial) internal rotation of the shoulder joint. It also has a synergistic role in extension and lateral flexion of the lumbar spine.

F: The serratus anterior is a muscle that originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula. It pulls the scapula forward around the thorax, which is essential for the anteversion of the arm.

G: The rectus abdominis or “abs“, is a paired muscle running vertically on each side of the anterior wall of the human abdomen. There are two parallel muscles, separated by a midline band of connective tissue called the linea alba. It is an important postural muscle, responsible for flexing the lumbar spine.

H: The external oblique muscle is the largest and the most superficial (outermost) of the three flat muscles of the lateral anterior abdomen. Its functions are to pull the chest downwards and compress the abdominal cavity, which increases the intra-abdominal pressure. It also has limited actions in both flexion and rotation of the vertebral column.