The Biceps Brachii
By : Fahad Al-BakThe Naming
/BY-seps BRAY-key-eye/
From the name we can understand that it consists of two heads [bi- meaning two], [cep = head], also we get that it’s located over the arm [brachium means the arm].
From the name we can understand that it consists of two heads [bi- meaning two], [cep = head], also we get that it’s located over the arm [brachium means the arm].
General
-The Biceps Brachii is one of the three muscles in the anterior compartment of the arm, it is the most superficial of the three and even though it is in the anterior compartment, it does not come in contact with the humerus. It is thick and quite bit large and it can be easily noticed in the surface anatomy. It belongs to the Muscles of the Elbow and Radioulnar Joints as while.
-The BB crosses 3 joints and effect their movement, and they are the:
1-Glenohumeral.
2-Elbow.
3-Radio-ulnar joints.
-The BB crosses 3 joints and effect their movement, and they are the:
1-Glenohumeral.
2-Elbow.
3-Radio-ulnar joints.
Surface anatomy of the BB
The Agonist & Antagonist
In an antagonistic muscle pair as one muscle contracts the other muscle relaxes or lengthens. The muscle that is contracting is called the agonist and the muscle that is relaxing or lengthening is called the antagonist.
One way to remember which muscle is the agonist – it's the one that's in 'agony' when you are doing the movement as it is the one that is doing all the work.
The Biceps Brachii and Triceps Brachii are agonist and antagonist, where when the Biceps Brachii is flexed the Triceps Brachii is relaxed and vice versa.
One way to remember which muscle is the agonist – it's the one that's in 'agony' when you are doing the movement as it is the one that is doing all the work.
The Biceps Brachii and Triceps Brachii are agonist and antagonist, where when the Biceps Brachii is flexed the Triceps Brachii is relaxed and vice versa.
The Supply
-The Biceps Brachii has a nerve supply from Musculocutaneous n.
-The blood supply comes from the muscular branches of the Brachial Artery (the continuation of the Axillary Artery)
and the Anterior Circumflex Humeral Artery (a branch of the Axillary Artery).
-The blood supply comes from the muscular branches of the Brachial Artery (the continuation of the Axillary Artery)
and the Anterior Circumflex Humeral Artery (a branch of the Axillary Artery).
Nerve and Blood Supply of the Biceps Brachii
Origin & Insertion
Origins (The immoveable part):
Biceps Brachii tendons originate from the scapula processes.
-As the short head originates from the apex of the coracoid process of the scapula, the short head passes anterior to the head and shaft of the humerus and fuses with the long head around the middle of the humerus.
-For the long head of the Biceps Brachii, it arises from the supraglenoid tubercle of the scapula, and descend lateral to the short head. On the surgical head of the humerus it passes through the cavity of the glenohumeral joint, the rounded tendon of the long head of the
biceps continue to be surrounded by synovial membrane
as it cross in the intertubercular sulcus of the humerus.
A wide band surround the bicipital tendon of the long head that goes from the lesser to the greater tubercle of the humerus, it is known as transverse humeral ligament and it covers the intertubercular groove thus making it a channel, this ligament holds the long head in the intertubercular groove.
Insertion (The Action Center): -
The Biceps Brachii attach distally to the radial tuberosity by the biceps tendon while the bicipital aponeurosis which is a triangular membranous band that goes from the biceps tendon around the Cubital Fossa and combine with the antebrachial (deep) fascia that covers the flexor muscles in the medial side of the forearm, the aponeurosis gives protection to the Cubital Fossa, aside to that it helps relief stress on the biceps tendon throughout pronation and supination of the forearm. The aponeurosis attaches in an indirect manner to the subcutaneous border of the ulna, it can be felt in the proximal part around the Brachial artery and Median nerve as it passes them obliquely.
Biceps Brachii tendons originate from the scapula processes.
-As the short head originates from the apex of the coracoid process of the scapula, the short head passes anterior to the head and shaft of the humerus and fuses with the long head around the middle of the humerus.
-For the long head of the Biceps Brachii, it arises from the supraglenoid tubercle of the scapula, and descend lateral to the short head. On the surgical head of the humerus it passes through the cavity of the glenohumeral joint, the rounded tendon of the long head of the
biceps continue to be surrounded by synovial membrane
as it cross in the intertubercular sulcus of the humerus.
A wide band surround the bicipital tendon of the long head that goes from the lesser to the greater tubercle of the humerus, it is known as transverse humeral ligament and it covers the intertubercular groove thus making it a channel, this ligament holds the long head in the intertubercular groove.
Insertion (The Action Center): -
The Biceps Brachii attach distally to the radial tuberosity by the biceps tendon while the bicipital aponeurosis which is a triangular membranous band that goes from the biceps tendon around the Cubital Fossa and combine with the antebrachial (deep) fascia that covers the flexor muscles in the medial side of the forearm, the aponeurosis gives protection to the Cubital Fossa, aside to that it helps relief stress on the biceps tendon throughout pronation and supination of the forearm. The aponeurosis attaches in an indirect manner to the subcutaneous border of the ulna, it can be felt in the proximal part around the Brachial artery and Median nerve as it passes them obliquely.
Short head origin
Long Head Origin
Bicipital Aponeurosis
Biceps Brachii insertion
Morphology (Tricipital Biceps Brachii)
Around 10% of the population have third head for the BB, it originated from the anterior investing fascia of the brachialis muscle, after arising from the brachialis fascia, the third head traversed deep to the tendon of biceps to finally blend with it.
Motion & Action
(Flexion & Supination of the forearm, Adduction & Abduction of the arm)
Although it achieves flexing and contrary to popular belief the BB isn’t the main flexor of the forearm, The brachialis is the main flexor; however, the Biceps Brachii is a strong flexor for the elbow and weak flexor for the shoulder, aside of that it works in the supination action of the forearm and has abduction movement in the arm at the shoulder joint.
The BB effectiveness depend upon the position of the forearm; when the elbow is just extended the BB acts as flexor and when the elbow starts to reach 90° and the forearm is supinator that’s where the Biceps Brachii acts as the main flexor and shows a lot of power against resistance; however, when the elbow is fixed at 90° and the forearm is pronated, the BB barely operates as a flexor when the forearm is pronated, even against resistance but acts as the main supinator (most powerful), In the semi-prone position, it is active only against resistance, aside to that, the BB has an abduction and adduction movement in the shoulder where the long head achieves abduction of the arm (away from the trunk), while the short head does the adduction of the arm.
Examples : -
-When reaching ones right shoulder with the right hand (that’s an example of flexing via using the Biceps Brachii).
-When trying to start the car engine or tightening a screw (that’s an example of supination via using the Biceps Brachii).
Although it achieves flexing and contrary to popular belief the BB isn’t the main flexor of the forearm, The brachialis is the main flexor; however, the Biceps Brachii is a strong flexor for the elbow and weak flexor for the shoulder, aside of that it works in the supination action of the forearm and has abduction movement in the arm at the shoulder joint.
The BB effectiveness depend upon the position of the forearm; when the elbow is just extended the BB acts as flexor and when the elbow starts to reach 90° and the forearm is supinator that’s where the Biceps Brachii acts as the main flexor and shows a lot of power against resistance; however, when the elbow is fixed at 90° and the forearm is pronated, the BB barely operates as a flexor when the forearm is pronated, even against resistance but acts as the main supinator (most powerful), In the semi-prone position, it is active only against resistance, aside to that, the BB has an abduction and adduction movement in the shoulder where the long head achieves abduction of the arm (away from the trunk), while the short head does the adduction of the arm.
Examples : -
-When reaching ones right shoulder with the right hand (that’s an example of flexing via using the Biceps Brachii).
-When trying to start the car engine or tightening a screw (that’s an example of supination via using the Biceps Brachii).
Supinating the forearm (the yellow tendon shows the movement)
Flexing of the forearm (the yellow tendon shows the movement)
In The Field Notes
- Testing The Biceps Brachii : -
Flex the elbow joint and supinate the forearm, if a bulge is formed on the anterior aspect of the arm, then the Biceps Brachii is functioning properly.
In physical examination, the biceps play an important role. It provides an orientation for the palpation of the brachial artery. Hereby the artery is pushed with the fingertips against the humerus in the medial bicipital groove. Furthermore, it serves as a reference muscle for the nerve roots C5 and C6. In this exam the biceps reflex is tested by striking the insertion tendon with a hammer and thus activating a contraction of the muscle.
- The bicipital groove of the humerus is named the bicipital groove, because the long head of the biceps brachii courses through it. (The bicipital groove of the humerus is also known as the intertubercular groove, because it is located between the two tubercles of the humerus.)
- The proximal attachment of the short head of the biceps brachii blends with the proximal attachment of the coracobrachialis at the coracoid process of the scapula.
- The bicipital aponeurosis is also known as the lacertus fibrosis.
Flex the elbow joint and supinate the forearm, if a bulge is formed on the anterior aspect of the arm, then the Biceps Brachii is functioning properly.
In physical examination, the biceps play an important role. It provides an orientation for the palpation of the brachial artery. Hereby the artery is pushed with the fingertips against the humerus in the medial bicipital groove. Furthermore, it serves as a reference muscle for the nerve roots C5 and C6. In this exam the biceps reflex is tested by striking the insertion tendon with a hammer and thus activating a contraction of the muscle.
- The bicipital groove of the humerus is named the bicipital groove, because the long head of the biceps brachii courses through it. (The bicipital groove of the humerus is also known as the intertubercular groove, because it is located between the two tubercles of the humerus.)
- The proximal attachment of the short head of the biceps brachii blends with the proximal attachment of the coracobrachialis at the coracoid process of the scapula.
- The bicipital aponeurosis is also known as the lacertus fibrosis.
Clinical Notes
Biceps & Biceps Tendon Injuries: -
- Biceps Tendonitis (Tendinitis) : It is the micro tear in one or more of the BB, occur due to overuse of the muscle especially with athletes, also it can happen because of a sudden, serious load to the tendon.
- Biceps Tendon Tears : When the overuse keeps on happing the tendons of the Biceps Brachii may weaken and eventually it may lead to a tear of the tendon, it may happen at the elbow, the bicep tendon most often tears during the act of lifting a heavy object (for example, a couch or a refrigerator) or at the shoulder; it can be partial or complete separation from the bone. While surgery may be needed to fix a torn tendon, in many cases people with a torn tendon can still function normally. Symptoms can be relieved using the same treatments that are used to treat tendonitis. Tears at the level of the elbow more often require operative repair.
- The tear at the proximal end : Happens almost always at the long head and thus it is still possible for the Biceps Brachii to function but not in the full capacity.
- The tear at the distal end : When happens it means a complete separation of the tendon from the bone and the muscles retracting back; it leads to weak flexing and supination of the forearm.
-Due to the close relationship between the long biceps tendon and the rotator cuff, inflammatory and degenerative processes often affect each other. Common consequences are a pulley lesion or biceps tendinitis. A pulley lesion is characterized by damage to the biceps pulley complex through which the long biceps tendon is no longer secured in the shoulder joint and thus slips out of the intertubercular sulcus.
- Biceps Tendonitis (Tendinitis) : It is the micro tear in one or more of the BB, occur due to overuse of the muscle especially with athletes, also it can happen because of a sudden, serious load to the tendon.
- Biceps Tendon Tears : When the overuse keeps on happing the tendons of the Biceps Brachii may weaken and eventually it may lead to a tear of the tendon, it may happen at the elbow, the bicep tendon most often tears during the act of lifting a heavy object (for example, a couch or a refrigerator) or at the shoulder; it can be partial or complete separation from the bone. While surgery may be needed to fix a torn tendon, in many cases people with a torn tendon can still function normally. Symptoms can be relieved using the same treatments that are used to treat tendonitis. Tears at the level of the elbow more often require operative repair.
- The tear at the proximal end : Happens almost always at the long head and thus it is still possible for the Biceps Brachii to function but not in the full capacity.
- The tear at the distal end : When happens it means a complete separation of the tendon from the bone and the muscles retracting back; it leads to weak flexing and supination of the forearm.
-Due to the close relationship between the long biceps tendon and the rotator cuff, inflammatory and degenerative processes often affect each other. Common consequences are a pulley lesion or biceps tendinitis. A pulley lesion is characterized by damage to the biceps pulley complex through which the long biceps tendon is no longer secured in the shoulder joint and thus slips out of the intertubercular sulcus.
Right distal bicipital tendon rupture
Relations
-Proximally, the biceps brachii is deep to the deltoid and deep to the distal tendon of the pectoralis major. The remainder of the biceps brachii is superficial.
-From an anterior perspective, the brachialis lies deep to the biceps brachii.
-The short head of the biceps brachii lies lateral to the coracobrachialis.
-The proximal attachment of the short head of the biceps brachii is the coracoid process of the scapula. The coracobrachialis and the pectoralis minor also attach to the coracoid process.
-The long head of the biceps brachii courses through the bicipital groove of the humerus. The long head of the biceps brachii then courses through the joint cavity of the glenohumeral joint; therefore, it is intra-articular.
-Directly medial to the belly and distal tendon of the biceps brachii are the brachial artery and the median nerve.
-The bicipital aponeurosis is superficial to the common flexor belly/tendon and does not attach into bone.
-The biceps brachii is located within the deep front arm line and involved with the superficial front arm line myofascial meridians.
-From an anterior perspective, the brachialis lies deep to the biceps brachii.
-The short head of the biceps brachii lies lateral to the coracobrachialis.
-The proximal attachment of the short head of the biceps brachii is the coracoid process of the scapula. The coracobrachialis and the pectoralis minor also attach to the coracoid process.
-The long head of the biceps brachii courses through the bicipital groove of the humerus. The long head of the biceps brachii then courses through the joint cavity of the glenohumeral joint; therefore, it is intra-articular.
-Directly medial to the belly and distal tendon of the biceps brachii are the brachial artery and the median nerve.
-The bicipital aponeurosis is superficial to the common flexor belly/tendon and does not attach into bone.
-The biceps brachii is located within the deep front arm line and involved with the superficial front arm line myofascial meridians.
Sources
- Moore - Clinically Oriented Anatomy 7th Edition (731-733).
- Joseph E Muscolino - The Muscular System Manual: The Skeletal Muscles of the Human Body
Book (254-258).
-Snell's Clinical Anatomy by Regions 10th Edition (306).
-Biceps Brachii Muscle (Short Head) -innerbody.com
-Bilateral Three-headed Biceps Brachii Muscle and its Clinical Implications -NCBI
-Biceps Tendon Injuries –Cleveland clinic
Biceps Brachii muscle -Ken Hub
- Joseph E Muscolino - The Muscular System Manual: The Skeletal Muscles of the Human Body
Book (254-258).
-Snell's Clinical Anatomy by Regions 10th Edition (306).
-Biceps Brachii Muscle (Short Head) -innerbody.com
-Bilateral Three-headed Biceps Brachii Muscle and its Clinical Implications -NCBI
-Biceps Tendon Injuries –Cleveland clinic
Biceps Brachii muscle -Ken Hub
