Biceps brachii anatomy, as the name implies, is a two-headed muscle on the anterior brachium. It has a long lateral head and a short medial head.
Origin
- long head – supraglenoid tubercle of the scapula
- short head – coracoid process
Insertion
- tuberosity of the radius
Function
- flexion of the elbow
- supination of the radio-ulnar joints
- assists in flexion of the shoulder
- assists in the abduction of the shoulder
Innervation
- musculocutaneus nerve (C5-C6)
Attachment Details
The subscapularis is woven between the upper attachments of the biceps brachii. It extends under the coracoid process to the medial lip of the bicipital groove. Often, it extends across the bicipital groove to the lateral lip of the bicipital groove, securing the tendon of the long head into the groove.
The tendon of the long head of the biceps lies in the bicipital groove between the attachments of latissimus dorsi and pectoralis major. Consequently, the pectoralis major helps secure the tendon when flexing the elbow forcefully, as when lifting suitcases or curling dumbbells. It also allows the bicipital tendon to slip between the pecs and lats when the arm is overhead as when rock climbing or doing chin-ups.
Functional Considerations
The biceps brachii is often the focus of the upper arm but is not the primary flexor of the elbow. Instead, it balances the brachialis, biceps, and brachioradialis. The brachialis is the primary mover, but without the biceps, strong flexion leads to instability and injury of the shoulder.
The biceps brachii is very active in supinating the elbow when the elbow is flexed but seems to be disabled in supination when the elbow is extended.
The bicipital aponeurosis usually wraps around the entire ulnar forearm. The aponeurosis extends off of the two heads as they attach to the tuberosity of the radius.
Anomalies, Etc.
Studies of biceps anomalies are numerous but state that the anomalies are rare. They commonly discuss extra heads of the long head that attach to the humerus. Some of them discuss the absence of a long or short head. These cases have proven useful in understanding how the biceps stabilizes the shoulder.
Clavipectoral Membrane
Pectoralis minor and subclavius are invested in the clavipectoral membrane. This fascial structure forms a sheet extending across the upper chest. This membrane ties together the upper ribs, subclavius, pectoralis minor, clavicle, and coracoid process. The upper portion is referred to as the costocoracoid membrane.
This membrane anchors to the coracoid process of the scapula. Continuing medially, it attaches superiorly to the clavicle, investing the subclavius. Next, the medial border extends along the ribs between the pectoralis minor and major. Then, the inferior border attaches to the pectoralis major. Finally, the lateral border extends along the biceps tendon, which connects it back to the coracoid process.
This membrane also covers the neurovascular bundle that feeds the upper extremity, making it an important part of Thoracic Outlet structures. You can read more about these structures in this post about the Anatomy of Thoracic Outlet Syndrome.
Related Posts
Biceps Brachii – Massage Notes
Biceps Brachii – Neuromuscular Protocol
Biceps Brachii – Self Care
Front of Elbow Pain When Carrying or Shoveling
Musculoskeletal Illustrations Video
Superficial strip of shoulder pain when reaching up
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Tony Preston has a practice in Atlanta, Georgia, where he sees clients. He has written materials and instructed classes since the mid-90s. This includes anatomy, trigger points, cranial, and neuromuscular.
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