What are the three heads of the biceps brachii?

October 2, 2025 •

3 min read

While the prefix 'bi' correctly indicates 'two', leading to the common understanding of a two-headed muscle, the query What are the three heads of the biceps brachii? points to a fascinating anatomical variation. The standard biceps brachii muscle is composed of the long and short heads, but some individuals are born with an extra, or supernumerary, head.

Quick Summary

The biceps brachii is anatomically defined by its two heads: the long head and the short head. In a small percentage of the population, a third humeral head is present as a congenital variation.

Key Points

Standard Anatomy: The biceps brachii typically consists of two heads, the long head and the short head.
Long Head Origin: The long head of the biceps originates from the supraglenoid tubercle of the scapula and is associated with the 'biceps peak'.
Short Head Origin: The short head originates from the coracoid process of the scapula and is associated with adding width to the biceps.
Accessory Head: A third, or supernumerary, head is an anatomical variation, not standard, and is present in a minority of the population.
Primary Function: The main functions of the biceps brachii are to flex the elbow and powerfully supinate the forearm.
Training Emphasis: While full isolation is impossible, different grip widths and arm positions can place more emphasis on either the long or short head during exercises.

The Standard Anatomy of the Biceps Brachii

The biceps brachii is a two-headed muscle in the upper arm, known for its visibility and role in arm movement. Both heads originate on the scapula and insert onto the radius in the forearm, working together to flex the elbow and supinate the forearm.

The Long Head

Located on the outer side of the arm, the long head originates from the supraglenoid tubercle of the scapula. Its tendon passes through the shoulder joint, contributing to shoulder stabilization as well as elbow flexion.

The Short Head

The short head is on the inner side of the arm, originating from the coracoid process of the scapula. It primarily contributes to elbow flexion and adds to the muscle's overall width.

The Third Head: An Anatomical Variation

The idea of a third biceps head refers to a supernumerary head, a variation present in a minority of people. This extra head typically originates from the humerus and merges with the main muscle. Its prevalence varies significantly among populations.

Origins of the Supernumerary Head

The third head most often arises from the humerus shaft, with possible origins including the anteromedial or medial borders. It generally joins the common biceps tendon.

Clinical Significance of a Third Head

A supernumerary head can sometimes have clinical relevance. It may compress nearby nerves (like the musculocutaneous or median nerves) or the brachial artery, potentially causing symptoms. Awareness of this variation is important during surgical procedures.

Function and Biomechanics of the Biceps Brachii

The biceps is crucial for upper limb function, acting on both the elbow and shoulder.

Forearm Supination

This is a key function, especially with the elbow flexed, allowing movements like turning a doorknob.

Elbow Flexion

The biceps is a strong elbow flexor, essential for bending the arm and movements like bicep curls.

Shoulder Flexion

Both heads, particularly the long head, assist in lifting the arm forward.

Comparison of Biceps Brachii Heads


Feature	Long Head	Short Head	Third/Supernumerary Head
Origin	Supraglenoid tubercle of the scapula	Coracoid process of the scapula	Typically the humerus (anteromedial, anterolateral)
Location	Lateral (outer) side of the upper arm	Medial (inner) side of the upper arm	Variable, often medial
Function	Elbow flexion, shoulder flexion, shoulder stabilization	Elbow flexion, forearm supination, adds muscle mass	Reinforces elbow flexion and supination
Variations	Tends to have higher incidence of rupture and tendinitis	Less variable in origin compared to the long head	Congenital variation, present in a minority of the population

Training for Biceps Development

Targeting specific biceps heads during training involves adjusting grip and arm position.

Emphasizing the long head: Use a closer grip and allow elbows behind the body (e.g., incline dumbbell curls).
Emphasizing the short head: Use a wider grip and keep elbows slightly forward (e.g., preacher curls).

Conclusion

The biceps brachii typically has two heads: long and short. A third, supernumerary head is a known anatomical variation, originating from the humerus and present in a minority of individuals. Understanding both standard and variant anatomy is beneficial for both healthcare professionals and those interested in fitness. For more detailed information, consult authoritative sources such as Physiopedia.

Frequently Asked Questions

No, it is not the normal anatomy. The standard biceps brachii muscle has two heads. A third, or supernumerary, head is an anatomical variation that is present in a minority of the population.

The third head is typically referred to as a 'supernumerary head' or a 'third head of the biceps brachii'. It does not have a unique, universally accepted name like the long and short heads.

The origin of the supernumerary head is most commonly from the humerus, typically from the anteromedial or anterolateral surface of the bone. It then merges with the main muscle belly or tendon.

No, you cannot train to develop a supernumerary head. It is a congenital variation, meaning it is something you are born with. If you have one, general biceps training will stimulate it along with the other two heads.

For most people, a third head has no negative effects and may even slightly increase strength. However, in some rare cases, its position can lead to compression of surrounding nerves or blood vessels, which can cause clinical symptoms.

The prevalence varies depending on the population, but studies report it is present in anywhere from 2% to over 30% of individuals. This highlights that while not standard, it is a fairly common anatomical variant.

Yes, the term still applies because 'biceps' refers to the standard, most common anatomy. The extra head is a variation of the same muscle, not a new or different muscle entirely.