Musculus deltoideus
A thick triangular muscle on the lateral shoulder. Flexes the shoulder joint and abducts the humerus. Visible as the muscular bulge over the lateral shoulder region.
Origin: Scapular spine and caudal border of the scapula via the infraspinatus fascia
Insertion: Deltoid tuberosity of the humerus
Action: Flexes the shoulder; abducts the humerus
Innervation: Axillary nerve (C6-C7)
The deltoid is occasionally used for intramuscular injections but has a higher complication rate than the neck or gluteal regions.
The deltoid is occasionally used for intramuscular injections but has a higher complication rate than the neck or gluteal regions. Signs include: Swelling and heat at injection site; reluctance to flex the shoulder; stiff forelimb gait; possible abscess formation with draining tract.
See the Deltoideus on our interactive 3D horse model. Open 3D Model