Deltoid (Musculus deltoideus)
Educational content only — not medical advice.
Anatomy
The triangular muscle that rounds the shoulder: clavicular, acromial and spinal parts wrap the joint from all sides. The middle (acromial) part is the prime abductor of the arm between 15° and 90°.
Origin & insertion
Origin: lateral third of the clavicle, acromion and scapular spine. Insertion: deltoid tuberosity of the humeral shaft.
Action
Abducts the arm (middle part), flexes or extends the shoulder depending on the part, and stabilizes the humeral head.
Innervation
Axillary nerve (C5–C6)
Clinical notes
The axillary nerve wraps the surgical neck of the humerus — a fracture there paralyzes the muscle and flattens the shoulder contour; it is also the standard adult IM injection site.
Related structures
Educational references
FAQ
What is the role of the Deltoid?
The triangular muscle that rounds the shoulder: clavicular, acromial and spinal parts wrap the joint from all sides. The middle (acromial) part is the prime abductor of the arm between 15° and 90°.
Why is the Deltoid clinically important?
The axillary nerve wraps the surgical neck of the humerus — a fracture there paralyzes the muscle and flattens the shoulder contour; it is also the standard adult IM injection site.
Source & license
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). license details