Acromial part of deltoid muscle

Origin

The acromial part of the deltoid muscle originates from the lateral margin of the acromion, where it is attached to four septa of origin.

Insertion

The acromial fibers converge with the other parts of the deltoid muscle to form a thick tendon, which inserts into the deltoid tuberosity on the middle lateral side of the humerus.

Arterial Supply

The primary blood supply to the acromial part comes from the posterior circumflex humeral artery.

Innervation

It is innervated by the axillary nerve, which arises from cervical spinal roots C5 and C6.

Actions

The acromial part is the main contributor to shoulder abduction, particularly from 15 to 90 degrees of arm elevation. Additionally, it works with the anterior and posterior parts to assist in other movements such as flexion, extension, and rotation.

Structure

This part of the deltoid has a multipennate fiber arrangement, which increases the strength of its contraction. The muscle fibers originate from four septa and converge onto three septa of insertion that are attached to the deltoid tuberosity.