Q31 Deltoid

Question 1

Briefly describe this muscle giving its position and arrangement

Answer 1

Course thick triangular muscle which caps and surrounds the shoulder joint and gives the shoulder its rounded contour. Functionally it has 3 parts anterior fibres, middle (multipennate) fibres, and posterior fibres.

Question 2

State the attachments of this muscle

Answer 2

Proximal attachment is for the anterior fibres the anterior border and upper surface of the lateral third of the clavicle, the middle fibres lateral margin of the acromion process and the posterior fibres attach to the lower lip of the crest of the spine of the scapular.
Distal attachments The Deltoid tuberosity on the lateral surface of the shaft of the humerus

Question 3

List the actions of this muscle

Answer 3

Actions of deltoid are: Middle fibres abduction of the arm (only after initiation by supraspinatus), the anterior fibres flex and medially rotate the humerus and the posterior fibres extend and laterally rotate the humerus.