Coracobrachialis
Arm · Upper Limb
The coracobrachialis is a slender muscle of the medial arm, sharing its origin, the coracoid process of the scapula, with the short head of biceps. It runs down to insert on the middle third of the medial surface of the humerus. Acting across the shoulder, it flexes and adducts the arm, and it helps steady the humerus during movement. It is pierced and supplied by the musculocutaneous nerve (C5, C6, C7), a useful landmark for that nerve in the arm.
Origin, Insertion, Action & Nerve
Origin
Coracoid process of scapula
Insertion
Middle third of medial surface of humerus
Action
Flexion and adduction of arm at the shoulder
Nerve
Musculocutaneous nerve (C5, C6, C7)
Attachments explained
The Coracobrachialis is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Coracoid process of scapula
Insertion
Middle third of medial surface of humerus
Action & function
When the Coracobrachialis contracts, it produces the following movement: Flexion and adduction of arm at the shoulder.
As part of the Arm group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Coracobrachialis receives its nerve supply from the Musculocutaneous nerve (C5, C6, C7). This nerve carries fibres from spinal segment(s) C5, C6, C7.
Because a muscle can only contract when its nerve is intact, injury to the Musculocutaneous nerve or to its spinal roots (C5, C6, C7) can weaken or paralyse the Coracobrachialis, impairing the movements it normally produces (flexion and adduction of arm at the shoulder). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Coracobrachialis (the OIANS method)
Study coracobrachialis as the third musculocutaneous muscle, the smallest and highest of the anterior arm group. Its origin on the coracoid process (shared with the short head of biceps) and its insertion halfway down the medial humerus explain why it flexes and adducts the arm at the shoulder rather than acting at the elbow.
Its most distinctive feature is that the musculocutaneous nerve pierces it, making the muscle a landmark for finding that nerve. Remembering coracoid, coracobrachialis, and the piercing nerve as a linked trio makes both the muscle and its innervation easy to retrieve.
Frequently asked questions
Where is the Coracobrachialis located?
The Coracobrachialis is a muscle of the Arm group, located in the Upper Limb.
What is the origin of the Coracobrachialis?
Coracoid process of scapula
What is the insertion of the Coracobrachialis?
Middle third of medial surface of humerus
What movements does the Coracobrachialis produce?
Flexion and adduction of arm at the shoulder
What nerve supplies the Coracobrachialis?
Musculocutaneous nerve (C5, C6, C7)
Is the Coracobrachialis free to study in OIANS?
Yes. The Coracobrachialis is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Coracobrachialis
Test yourself on Upper Limb muscles with interactive quizzes and flashcards in the free OIANS app.
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