What is the innervation of the biceps Brachii?

What is the innervation of the biceps Brachii?/Biceps Brachii Muscles is a large, thick muscle on the ventral portion of the upper arm. The muscle is composed of a short head (caput breve) and a long head (caput longum).  The short head originates from the tip of the coracoid process, and the long head originates from the supraglenoid tubercle (tuberculum supraglenoidale) of the glenoid/scapula. Both heads course distally and become a confluent muscle belly before tapering across the anterior aspect of the elbow, eventually inserting on the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis.   The antagonist of the biceps muscle is the triceps brachii muscle.

The biceps brachii is a prominent muscle on the front side of the upper arm. It originates in two places: the coracoid process, a protrusion of the scapula (shoulder blade); and the upper glenoid cavity, the hollow for the shoulder joint. The tendon of this muscle is attached to the inner protrusion near the head of the radius, a bone of the forearm. The biceps brachii bends the forearm toward the upper arm and is thus used in lifting and pulling movements. It also supinates the forearm (turns the palm forward or upward). The size of the biceps brachii is a conventional symbol of bodily strength.

Anatomy of Biceps Brachii Muscle

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The biceps is a two-headed muscle and is one of the chief flexors of the forearm. Here is the left side, seen from the front.
Pronunciation bsɛpsˈbrki
Origin Short head: coracoid process of the scapula.
Long head: supraglenoid tubercle
Insertion Radial tuberosity and bicipital aponeurosis into deep fascia on medial part of forearm
Artery Brachial artery
Nerve Musculocutaneous nerve (C5–C7)
  • Flexes elbow
  • flexes and abducts shoulder [1]
  • supinates radioulnar joint in the forearm[1]
Antagonist Triceps brachii muscle
Latin musculus biceps brachii
TA A04.6.02.013
FMA 37670
Anatomical terms of muscle

Key facts
Origin Long head – supraglenoid tubercle of the scapula
Short head – apex of the coracoid process of the scapula
Insertion Radial tuberosity of the radius

Deep fascia of forearm (insertion of the bicipital aponeurosis)

Innervation Musculocutaneous nerve (C5- C6)
Function Flexion and supination of the forearm at the elbow joint, weak flexor of the arm at the glenohumeral joint

 The flexors of the shoulder

Muscle Nerve Spinal nerve root
Coracobrachialis Musculocutaneous C5, C6
Pectoralis major Pectoral C5–C8
Deltoid (anterior portion) Axillary C5 (C6)
Subscapularis Subscapular C5–C8
Biceps brachii Musculocutaneous C5, C6



Biceps Conditions

  • Biceps strain – A pulled biceps results from overstretching and tearing some of the biceps muscle fibers and/or tendons. Pain and sometimes swelling are the usual symptoms.
  • Proximal biceps tendon rupture – This is when one of the two biceps tendons in the shoulder is torn away from the bone. Sudden shoulder pain and an odd-shaped bulge in the biceps are symptoms.
  • Distal biceps tendon rupture – A tear of the biceps tendon at the forearm is unusual. Sudden pain over the front of the elbow and forearm weakness are symptoms.
  • Proximal biceps tendinitis (tendonitis) – Repeated use of the biceps or problems in the shoulder can irritate the proximal biceps tendon. Pain in the shoulder and biceps is the main symptom.
  • Biceps contracture – The biceps become permanently contracted, with the elbow bent. Biceps contracture may occur after a severe stroke.

The function of Biceps Brachii Muscle

The biceps work across three joints.[rx] The most important of these functions is to supinate the forearm and flex the elbow. Besides, the long head of biceps prevents the upward displacement of the head of the humerus.[11] In more detail, the actions are, by joint:[rx]

  • Proximal radioulnar joint of the elbow – The biceps brachii function as a powerful supinator of the forearm, i.e. it turns the palm upwards. This action, which is aided by the supinator muscle, requires the humeroulnar joint of the elbow to be at least partially flexed. If the humeroulnar joint, is fully extended, supination is then primarily carried out by the supinator muscle. The biceps is a particularly powerful supinator of the forearm due to the distal attachment of the muscle at the radial tuberosity, on the opposite side of the bone from the supinator muscle. When flexed, the biceps effectively pull the radius back into its neutral supinated position in concert with the supinator muscle.[rx]
  • The humeroulnar joint of the elbow – The biceps brachii also functions as an important flexor of the forearm, particularly when the forearm is supinated.[rx] Functionally, this action is performed when lifting an object, such as a bag of groceries or when performing a biceps curl. When the forearm is in pronation (the palm faces the ground), the brachialis, brachioradialis, and supinator function to flex the forearm, with minimal contribution from the biceps brachii. It is also important to note that regardless of forearm position, (supinated, pronated, or neutral) the force exerted by the biceps brachii remains the same; however, the brachioradialis has a much greater change in exertion depending on a position than the biceps during concentric contractions. That is, the biceps can only exert so much force, and as forearm position changes, other muscles must compensate.[rx]
  • Glenohumeral joint (shoulder joint) – Several weaker functions occur at the glenohumeral joint. The biceps brachii weakly assists in forwarding flexion of the shoulder joint (bringing the arm forward and upwards). It may also contribute to abduction (bringing the arm out to the side) when the arm is externally (or laterally) rotated. The short head of the biceps brachii also assists with horizontal adduction (bringing the arm across the body) when the arm is internally (or medially) rotated. Finally, the short head of the biceps brachii, due to its attachment to the scapula (or shoulder blade), assists with stabilization of the shoulder joint when a heavyweight is carried in the arm. The tendon of the long head of the biceps also assists in holding the head of the humerus in the glenoid cavity.[rx]

Biceps Brachii Muscle Tests

  • Physical examination – By examining and palpating (feeling) the biceps while it is moved into various positions, a health care provider collects clues to possible biceps conditions.
  • Speed’s test – A person holds her arm out with her elbow slightly bent and her palm up, while the health care provider presses downward on the arm. Pain in a specific area of the shoulder during Speed’s test suggests biceps tendinitis.
  • Ferguson’s test – A person bends the elbow 90 degrees (at a right angle) while gripping hands with the health care professional, who applies pressure to the arm. Pain in a specific shoulder area during the test suggests biceps tendinitis.
  • Computed tomography (CT scan) – A CT scanner takes multiple X-rays, and a computer compiles them into images of the interior of the biceps and nearby structures.
  • Magnetic resonance imaging (MRI scan) – An MRI scanner uses a high-powered magnet and a computer to create highly detailed images of the biceps and surrounding structures.
  • Biceps ultrasound – A device placed on the surface of the skin bounces high-frequency sound waves off structures in the biceps. The signals are converted into images on a video screen, allowing health care providers to see structures inside the body. Biceps ultrasound may help identify biceps tendon problems.

Biceps Treatments

  • PRICE therapy – Protecting, Resting, applying Ice, Compression (such as wrapping the area with an elastic bandage), and Elevation are enough treatment for most biceps strains.
  • Pain relievers – Over-the-counter pain medicines like Motrin (ibuprofen), Aleve (naproxen), and Tylenol (acetaminophen) may help relieve mild biceps pain. Severe biceps pain may require prescription pain relievers.
  • Physical therapy – A stretching and exercise program supervised by a physical therapist can improve recovery from some biceps injuries.
  • Biceps surgery – Surgery is occasionally recommended for biceps injuries. In people with severe biceps tendinitis and/or tendon tears or ruptures, surgery may be beneficial.
  • Biceps tenodesis – Biceps surgery to cut the biceps tendon where it attaches to the shoulder, and reattach it to the arm bone (humerus). Biceps tenodesis can relieve pain and inflammation from biceps tendinitis.
  • Biceps tenotomy – A surgeon severs an injured biceps tendon in the shoulder, to prevent ongoing pain and inflammation. The surgery relieves pain, but may result in some biceps weakness.


Proximal biceps (LHBT) surgical considerations:

In the setting of advanced tendinopathy affecting the LHBT, and in the setting of persistent, debilitating symptoms despite exhausting all nonoperative treatment options, two common procedures can be performed.

Biceps tenotomy 

Arthroscopic inspection of the tendon allows for the estimation of the relative percentage of the LHB tendon that is compromised.  A popular classification system utilized for the intra-operative grade corresponding to the degree of LHB tendon macroscopic pathology is the Lafosse grading scale:

  • Grade 0: Normal tendon
  • Grade 1: Minor lesion (partial, localized areas of tendon erosion/fraying, focal areas affect <50% of the tendon width)
  • Grade 2: Major lesion (extensive tendon loss, compromising >50% of the tendon width)

Some surgeons solely debride the tendon in the setting of a <25%-50% tendinous compromise.  Arthroscopic biceps tenotomy is performed by releasing the tendon as close as possible to the superior labrum.  As long as the tendon is free from intimate soft tissue adhesions to surrounding structures, the tendon should retract distally toward the bicipital groove.  If adhesions are present, all efforts should be made to mobilize the tendon in order to allow for retraction following the tenotomy.  In cases where the LHB tendon is particularly hypertrophic and scarred to other soft tissue structures in the joint, this serves as a potential source of postoperative pain.

Biceps tenodesis 

  • Recommended over tenotomy in the setting of LHBT instability
  • The preferred technique in younger patients, athletes, laborers, and those patients specifically concerned with postoperative cosmetic (“popeye”) deformity
  • Optimizes the length-tension relationship of the biceps muscle; mitigates the postoperative risk of muscle atrophy, fatigue, and cramping


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