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Structure
Beginner
8 min read

Biceps brachii

The biceps brachii sits on the front of the upper arm and crosses both the shoulder and the elbow. It flexes the elbow, but its most specific function is supination of the forearm.
3D scene
The biceps during a pull
The scene follows the arm through a pulling movement. The biceps shortens as the elbow closes, while the latissimus dorsi brings the arm toward the trunk. Without the 3D, the idea is simple: the biceps pulls the radius upward, which closes the elbow and turns the palm toward the face.
Open in the explorer

Where the biceps brachii is located

The biceps brachii forms the well-known relief on the front of the upper arm. It is thinner than it looks: beneath it lies the brachialis, deeper, which supplies a large share of the force of elbow flexion. The biceps is a biarticular muscle, meaning that it crosses both the shoulder and the elbow.

Origins

Its two heads both start on the shoulder blade, but at points far apart.
  • The long head arises from the supraglenoid tubercle, above the socket of the shoulder joint. Its tendon crosses the joint and then runs down the intertubercular groove of the humerus.
  • The short head arises from the tip of the coracoid process, a bony prominence at the front of the shoulder, which it shares with the coracobrachialis.

Insertion

The two heads merge into a single muscle belly that continues as a tendon attached to the radial tuberosity, a bump on the radius just below the elbow. A fibrous expansion, the bicipital aponeurosis, leaves that tendon and spreads into the fascia of the forearm.

Innervation and palpable landmarks

Innervation comes from the musculocutaneous nerve, from roots C5 and C6. The muscle belly can be felt over the whole front of the upper arm; its terminal tendon stands out at the crease of the elbow when the arm is flexed against a resistance.

What the biceps brachii does

Its attachment on the radius, a bone that rotates on itself, gives the biceps a function the other elbow flexors do not have.
  • Supination of the forearm: it turns the palm upward. This is its most powerful action, and it is greatest when the elbow is flexed.
  • Elbow flexion: it brings the forearm toward the upper arm, in partnership with the brachialis.
  • Shoulder flexion: a modest action, produced mainly by the short head.
Supination
Rotation of the forearm that turns the palm of the hand upward, bringing the radius back parallel to the ulna. The opposite movement is called pronation.
outward rotation of the forearm
This double function explains why the position of the hand changes how an elbow flexion feels: with the palm up, the biceps is in its most favourable configuration; with the palm down, it loses its supinator role and the brachioradialis takes a more visible share of the work.

Seeing the biceps in motion

The biceps during a pull

The scene follows the arm through a pulling movement. The biceps shortens as the elbow closes, while the latissimus dorsi brings the arm toward the trunk. Without the 3D, the idea is simple: the biceps pulls the radius upward, which closes the elbow and turns the palm toward the face.
Current step
Three parts to connect
A pull connects the hand to the pelvis through three moving parts: the humerus, the shoulder blade gliding over the ribcage, and the spine acting as the fixed point. Latissimus dorsi is the only muscle to span almost that whole path, from pelvis to arm.
Scene description
A three-dimensional diagram of the trunk seen from behind, arms raised diagonally overhead as at the start of a vertical pull. The ribcage, the spine, the pelvis, both shoulder blades, both humeri and the forearms are shown in bone tones, with a small dark sphere marking each shoulder joint. In terracotta, latissimus dorsi forms a wide fan on each side, spreading from the lower back and iliac crest and narrowing as it rises to the top of the humerus. The trapezius is split into three bands — upper towards the shoulder, middle towards the spine of the scapula, lower rising from the mid back — and biceps brachii runs along the front of the arm. A two-and-a-half-second animation brings the humeri back alongside the trunk in adduction while the shoulder blades descend and latissimus dorsi shortens. The volumes are stylised: this is a teaching diagram, not an exact anatomical reconstruction.
Visible structures
  • Latissimus dorsi
    A broad fan arising from the spinous processes of the lower thoracic and lumbar vertebrae, the thoracolumbar fascia, the iliac crest and the last three or four ribs. All its fibres converge on the bicipital groove of the humerus: it pulls the arm down, back and towards the trunk.
  • Shoulder blade
    A flat bone gliding over the back of the ribcage, with no direct joint to the spine. In a pull it depresses and rotates downwards: without that motion the humerus jams against the acromion and the range gets paid for elsewhere.
  • Trapezius
    Its three portions pull the shoulder blade in three directions: the upper elevates it, the middle draws it towards the spine, the lower depresses it. In a vertical pull, the lower portion is the direct partner of latissimus dorsi.
  • Biceps brachii
    Two heads arising from the scapula and inserting on the radial tuberosity. It flexes the elbow and supinates the forearm: in a pull it shortens the distance between hand and shoulder while latissimus dorsi moves the arm.
  • Insertion on the humerus
    The tendon of latissimus dorsi attaches in the floor of the bicipital groove, at the very top of the humerus. A wide origin across the whole lower back and a narrow insertion high on the arm: that convergence is what gives the muscle its fan shape.
Guided steps
  • 1/5
    A pull connects the hand to the pelvis through three moving parts: the humerus, the shoulder blade gliding over the ribcage, and the spine acting as the fixed point. Latissimus dorsi is the only muscle to span almost that whole path, from pelvis to arm.
  • 2/5
    Latissimus dorsi anchors across almost the whole lower back: the lower thoracic and lumbar spinous processes, the thoracolumbar fascia, the iliac crest and the lowest ribs. That origin surface is what gives it its strength, and why a pull is felt all the way down to the pelvis.
  • 3/5
    All those fibres converge into a flat tendon attached in the floor of the bicipital groove of the humerus. Wide below, narrow above: the pull concentrates on a single point of the arm, which makes it strongly directional — downwards and backwards.
  • 4/5
    The humeri leave the overhead position and adduct back alongside the trunk while the shoulder blades depress and rotate downwards. Latissimus dorsi shortens, the lower trapezius holds the blade down and the elbow bends: arm motion and shoulder-blade motion cannot be separated.
  • 5/5
    The lower trapezius depresses the shoulder blade, the middle trapezius draws it towards the spine, and biceps brachii flexes the elbow to bring the hand closer to the shoulder. A pull is never an isolated back exercise: it is coordination between arm, shoulder blade and spine.
Model licence · Z-Anatomy et BodyParts3D — CC-BY-SA 4.0

The movements it takes part in

The biceps accompanies every pulling movement. In the vertical pull, it flexes the elbow while the latissimus dorsi draws the arm down. In the horizontal pull, it works the same way, with a contribution that depends on the grip used.
It is also involved in everyday carrying tasks, where its supination function serves to orient the hand before flexion even begins.

Synergists

  • The brachialis, lying beneath the biceps, is the most consistent flexor of the elbow because its attachment on the ulna makes it indifferent to rotation of the forearm.
  • The brachioradialis contributes to flexion, especially when the forearm is in an intermediate position.
  • The latissimus dorsi and the trapezius create the shoulder and shoulder blade movement that makes the pull possible.

Antagonists

  • The triceps brachii and the anconeus extend the elbow.
  • The pronator teres and the pronator quadratus produce pronation, the opposite action to supination.

What the 3D model simplifies

Limit
A muscle rarely on its own
The scene puts the biceps in the foreground, whereas elbow flexion is shared work. The brachialis, lying deep, is not visible but takes part in every repetition; crediting the movement entirely to the biceps is a simplification.
The biceps is also a muscle with marked anatomical variation. A supernumerary head is described in part of the population, and the length of the muscle belly relative to the tendon changes clearly from person to person. The model shows the most common arrangement, not an individual anatomy.

Sources

Key sources

  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
Put it into practice in Shapier

See the biceps curl exercise

Performing the biceps curl step by step is done in Shapier; Body Lab only explains why this elbow flexion movement recruits the biceps.
See the biceps curl exercise
Body Lab explains; Shapier lets you act and track.

Check my understanding

What is the most specific action of the biceps brachii?
Which muscles supply the force of an elbow flexion?
What changes when an elbow flexion is done with the palm down?
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Read next

  • Forearm muscles
    The forearm muscles drive the wrist and fingers from a distance, through long tendons. They carry grip strength, which often gives out before the large muscles do.
    With a 3D scene
  • Latissimus dorsi
    The latissimus dorsi is the broadest muscle of the back. It links the pelvis and the spine to the humerus, and draws the arm down and backward in every pulling movement.
    With a 3D scene
  • Triceps brachii
    The triceps brachii fills the whole back of the upper arm and extends the elbow. Its long head also crosses the shoulder, which changes its length depending on the position of the arm.
    With a 3D scene

Where to go next

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Trust and method

Author
equipe-editoriale-shapier
Editorial review
Thanh Chau
Scientific review
Pending
Published on
August 2, 2026
Reviewed on August 2, 2026
Next review due August 2, 2027
Limits of this page
  • The brachialis, lying beneath the biceps and the main flexor of the elbow, does not appear distinctly in the 3D scene.
  • The path of the long head tendon in the groove of the humerus is drawn schematically, without the sheath or the capsule that surround it.
  • Anatomical variation is common for this muscle, in particular a third head found in part of the population.
Sources
  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
Educational content. Body Lab does not diagnose and does not replace professional advice.
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