Deltoid Muscle

A human body is composed of more than 600 muscles, which are connected to the bones of the skeletal system and are involved in locomotion and movement.

What is Deltoid Muscle?

The deltoid muscle is defined as the large, triangular-shaped muscle, found lying over the shoulder joints or the glenohumeral joints. These muscles provide a round contour to the shoulders.

The deltoid muscle is an oval-shaped, triangular muscle positioned on the uppermost portion of the arm and at the tip of the shoulder. These muscles are attached to the skeleton at the clavicle (collarbone), humerus (upper arm bone) and scapula (shoulder blade). Contraction of these muscle results in a wide range of movement of the arm at the shoulder due to its location and the wide separation of its muscle fibres.

The deltoid muscle is named after the Greek letter delta, which is shaped like an equilateral triangle.

Also Refer: Muscles

Structure of Deltoid Muscle

The deltoid muscle is the main muscle of the shoulder. It receives its blood supply from the posterior circumflex humeral artery. It mainly consists of the posterior cord of the brachial plexus and different nerves including axillary nerves, C5 and C6 nerves.

The deltoid muscle comprises three distinct groups of fibres, each of which produces a different movement of the glenohumeral joint. These are grouped into the distinct portions commonly named as:

  • The clavicular or the anterior part.
  • The acromial or the middle part.
  • The spinal or the posterior heads.

Functions of Deltoid Muscle

The deltoid muscle is the major muscle, which functions as the initial movement of shoulder abduction.

The heads of the deltoid work together to produce abduction of the shoulder joint.

The vital function of the deltoid muscle is to the prevention of subluxation or dislocation of the head of the upper arm bone, especially while carrying a load.

This muscle mainly assists the elevation of the arm during a process called glenohumeral elevation.

It plays a major role in the movement and overall stability of the shoulder joints and upper arm.

This muscle traverses from the spine of the scapula to the lateral portion of the clavicle.

Other functions include:

  • The clavicular or the anterior part helps in flexion, abduction and internal rotation of the arm at the shoulder joint.
  • The acromial or the middle part helps in the abduction of the arm beyond the initial 15°.
  • The spinal or the posterior heads help in an extension, abduction and external rotation of the arm at the shoulder joint.

Also Refer to- Muscular System

This article concludes the brief introduction about the deltoid muscles, their structure and functions. For more information on muscles, deltoid muscles, and other related topics, keep visiting our website at BYJU’S Biology.

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