Biceps brachii vs Deltoid

Property	Biceps brachii	Deltoid
Latin Name	Musculus biceps brachii	Musculus deltoideus
Type	Muscle	Muscle
Body System	Muscular	Muscular
Body Region	Upper Arm	Shoulder
Function	Primary supinator of the forearm and powerful flexor of the elbow. Also assists in shoulder flexion. The long head assists in shoulder joint stabilization.	The primary abductor of the shoulder joint. The anterior fibers flex and medially rotate the arm. The posterior fibers extend and laterally rotate the arm. Gives the shoulder its rounded …
Clinical Significance	Biceps tendon ruptures cause a visible bulge (Popeye deformity). Bicipital tendinitis causes anterior shoulder pain. The biceps reflex tests the C5-C6 nerve roots.	Deltoid paralysis from axillary nerve injury prevents arm abduction. The deltoid is a common site for intramuscular injections. Rotator cuff tears may cause compensatory deltoid overuse.
FMA ID	37670	32521

{# Internal-link refocus: a comparison is an entry point, not a destination. Send readers (and crawl equity) to the structure, system and region pages. #}

Full structure pages

Biceps brachii

Musculus biceps brachii

A two-headed muscle of the anterior compartment of the upper arm, the biceps brachii is the primary supinator of the forearm and a powerful flexor of the elbow, also assisting in flexion of the shoulder. …

Muscular Upper Arm

Deltoid

Musculus deltoideus

Thick and triangular, the deltoid caps the shoulder joint and gives the shoulder its rounded contour. It is the primary abductor of the joint; its anterior fibers flex and medially rotate the arm, while its …

Muscular Shoulder