Scapular Region

Scapular Region

Question 1. Give the origin, insertion, nerve supply and actions of the deltoid muscle.
Answer.

The deltoid is a three-in-one muscle. It is a strong triangular muscle covering the shoulder like a hood. It is responsible for the rounded contour of the shoulder.

Deltoid Muscle Origin

Anterior unipennate part:

From the anterior border and upper surface of the lateral one-third of the clavicle.

scapular region anatomy

Intermediate multipennate part:

From the lateral border of the acromion process of the scapula.

Deltoid muscle anatomy

Posterior unipennate part:

From the lower lip of the crest of the spine of the scapula.

Deltoid Muscle  Insertion

In the V-shaped deltoid tuberosity on the lateral aspect of the shaft of the humerus.

Deltoid Muscle  Nerve Supply

Axillary/circumflex nerve.

Deltoid Muscle  Actions

Deltoid origin and insertion

• Lateral (acromial) fibres cause abduction of the shoulder joint from 15° to 90°.
• Anterior (clavicular) fibres cause medial rotation and flexion of the shoulder joint.
• Posterior (spinous) fibres cause lateral rotation and extension of the shoulder joint (i.e. they draw the arm backwards and rotate the humerus laterally).