Question

describe its origin, insertion, and main function of the deltoid muscle  

flexion of the elbow. Which muscle is the prime mover? Which muscle is the antagonist, and which is the synergist for that particular movement?

Answer 1

Origin:

Origin of deltoid takes place from 3 different regions:

1. Anterior fibres-from lateral 1/3rd of clavicle.
2. Medial fibres- acromion process of scapula
3. Posterior fibres-spine of scapula

Insertion:

Insertion of deltoid takes place on the lateral surface of humerus on deltoid tuberosity.

Action:

Anterior fibres-flexion of arm,medial rotation

Medial fibres-abduction of arm

Posterior fibres- extension of arm,lateral rotation.

Flexion of elbow:

​​​​​​main muscle- brachialis

Synergist muscle- biceps brachii

Antagonist muscle- triceps brachii