Biceps

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Biceps brachii
1120 Muscles that Move the Forearm Humerus Flex Sin.png
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.
Details
Pronunciation /ˈbaɪsɛpsˈbreɪkiaɪ/
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) [1]
Actions
Antagonist Triceps brachii muscle
Identifiers
Latin musculus biceps brachii
TA98 A04.6.02.013
TA2 2464
Anatomical terms of muscle

The biceps or biceps brachii (Latin : musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join to form a single muscle belly which is attached to the upper forearm. While the biceps crosses both the shoulder and elbow joints, its main function is at the elbow where it flexes and supinates the forearm. Both these movements are used when opening a bottle with a corkscrew: first biceps screws in the cork (supination), then it pulls the cork out (flexion). [2]

Contents

Structure

Location of biceps. Two different colors represent two different bundles which compose biceps. .mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{} Short head Long head Biceps brachii muscle06.png
Location of biceps. Two different colors represent two different bundles which compose biceps.
  Short head
  Long head
Attachment to the radial tuberosity and Bursa bicipitoradialis. Braus 1921 194.png
Attachment to the radial tuberosity and Bursa bicipitoradialis.

The biceps is one of three muscles in the anterior compartment of the upper arm, along with the brachialis muscle and the coracobrachialis muscle, with which the biceps shares a nerve supply. [1] The biceps muscle has two heads, the short head and the long head, distinguished according to their origin at the coracoid process and supraglenoid tubercle of the scapula, respectively. [1] From its origin on the glenoid, the long head remains tendinous as it passes through the shoulder joint and through the intertubercular groove of the humerus. [2] Extending from its origin on the coracoid, the tendon of the short head runs adjacent to the tendon of the coracobrachialis. Unlike the other muscles in the anterior compartment of the arm, the biceps muscle crosses two joints, the shoulder joint and the elbow joint.

Both heads of the biceps join in the middle upper arm to form a single muscle mass, usually near the insertion of the deltoid, to form a common muscle belly; [3] although several anatomic studies have demonstrated that the muscle bellies remain distinct structures without confluent fibers. [4] [5] As the muscle extends distally, the two heads rotate 90 degrees externally before inserting onto the radial tuberosity. The short head inserts distally on the tuberosity while the long head inserts proximally closer to the apex of the tuberosity. [4] The bicipital aponeurosis, also called the lacertus fibrosus, is a thick fascial band that organizes close to the musculotendinous junction of the biceps and radiates over and inserts onto the ulnar part of the antebrachial fascia. [6]

The tendon that attaches to the radial tuberosity is partially or completely surrounded by a bursa, the bicipitoradial bursa, which ensures frictionless motion between the biceps tendon and the proximal radius during pronation and supination of the forearm. [7]

Two muscles lie underneath the biceps brachii. These are the coracobrachialis muscle, which like the biceps attaches to the coracoid process of the scapula, and the brachialis muscle which connects to the ulna and along the mid-shaft of the humerus. Besides those, the brachioradialis muscle is adjacent to the biceps and also inserts on the radius bone, though more distally.

Variation

Traditionally described as a two-headed muscle, biceps brachii is one of the most variable muscles of the human body and has a third head arising from the humerus in 10% of cases (normal variation)—most commonly originating near the insertion of the coracobrachialis and joining the short head—but four, five, and even seven supernumerary heads have been reported in rare cases. [8]

One study found a higher than expected number of female cadavers with a third head of biceps brachii, equal incidence between sides of the body, and uniform innervation by musculocutaneous nerve. [9]

The distal biceps tendons are completely separated in 40% and bifurcated in 25% of cases. [10] [5]

Nerve supply

The biceps shares its nerve supply with the other two muscles of the anterior compartment. The muscles are supplied by the musculocutaneous nerve. Fibers of the fifth, sixth and seventh cervical nerves make up the components of the musculocutaneous nerve which supply the biceps. [1]

Blood supply

The blood supply of the biceps is the brachial artery. The distal tendon of the biceps can be useful for palpating the brachial pulse, as the artery runs medial to the tendon in the cubital fossa.

Function

Arm flex pronate.jpg
Arm flex supinate.jpg
Flexed arm in the pronated position (left); with the biceps partially contracted and in a supinated position with the biceps more fully contracted, approaching minimum length (right.)

The biceps works across three joints. [11] 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. [12] In more detail, the actions are, by joint: [13]

Motor units in the lateral portion of the long head of the biceps are preferentially activated during elbow flexion, while motor units in the medial portion[ clarification needed ] are preferentially activated during forearm supination. [17]

The biceps are usually attributed as representative of strength within a variety of worldwide cultures.[ citation needed ]

Clinical significance

The Preacher curl, also known as the Scott Curl, is a popular exercise for biceps PreacherBenchBicepsCurl.JPG
The Preacher curl, also known as the Scott Curl, is a popular exercise for biceps

The proximal tendons of the biceps brachii are commonly involved in pathological processes and are a frequent cause of anterior shoulder pain. [18] Disorders of the distal biceps brachii tendon include insertional tendonitis and partial or complete tears of the tendon. Partial tears are usually characterized by pain and enlargement and abnormal contour of the tendon. [19] Complete tears occur as avulsion of the tendinous portion of the biceps away from its insertion on the tuberosity of the radius, and is often accompanied by a palpable, audible "pop" and immediate pain and soft tissue swelling. [20]

A soft-tissue mass is sometimes encountered in the anterior aspect of the arm, the so-called Reverse Popeye deformity, which paradoxically leads to a decreased strength during flexion of the elbow and supination of the forearm. [21]

Tendon rupture

Panoramic ultrasonography of a proximal biceps tendon rupture. Top image shows the contralateral normal side, and lower image shows a retracted muscle, with a hematoma filling out the proximal space. Panoramic ultrasonography of biceps tendon rupture - Annotated.jpg
Panoramic ultrasonography of a proximal biceps tendon rupture. Top image shows the contralateral normal side, and lower image shows a retracted muscle, with a hematoma filling out the proximal space.

Tears of the biceps brachii may occur during athletic activities, however avulsion injuries of the distal biceps tendon are frequently occupational in nature and sustained during forceful, eccentric contraction of the biceps muscle while lifting. [20]

Treatment of a biceps tear depends on the severity of the injury. In most cases, the muscle will heal over time with no corrective surgery. Applying cold pressure and using anti-inflammatory medications will ease pain and reduce swelling. More severe injuries require surgery and post-op physical therapy to regain strength and functionality in the muscle. Corrective surgeries of this nature are typically reserved for elite athletes who rely on a complete recovery. [22]

Training

The biceps can be strengthened using weight and resistance training. Examples of well known biceps exercises are the chin-up and biceps curl.

Etymology and grammar

The biceps brachii muscle is the one that gave all muscles their name: it comes from the Latin musculus, "little mouse", because the appearance of the flexed biceps resembles the back of a mouse. The same phenomenon occurred in Greek, in which μῦς, mȳs, means both "mouse" and "muscle".[ citation needed ]

The term biceps brachii is a Latin phrase meaning "two-headed [muscle] of the arm", in reference to the fact that the muscle consists of two bundles of muscle, each with its own origin, sharing a common insertion point near the elbow joint. The proper plural form of the Latin adjective biceps is bicipites, [23] a form not in general English use. Instead, biceps is used in both singular and plural (i.e., when referring to both arms).

The English form bicep, attested from 1939, is a back formation derived from misinterpreting the s of biceps as the English plural marker -s. [24] [25]

Adriaan van den Spiegel called the biceps a Pisciculus) [26] due to its fusiform shape, which is why in the Italian-language medical literature it is sometimes called il pescetto, "the small fish".

History

Leonardo da Vinci expressed the original idea of the biceps acting as a supinator in a series of annotated drawings made between 1505 and 1510; in which the principle of the biceps as a supinator, as well as its role as a flexor to the elbow were devised. However, this function remained undiscovered by the medical community as da Vinci was not regarded as a teacher of anatomy, nor were his results publicly released. It was not until 1713 that this movement was re-discovered by William Cheselden and subsequently recorded for the medical community. It was rewritten several times by different authors wishing to present information to different audiences. The most notable recent expansion upon Cheselden's recordings was written by Guillaume Duchenne in 1867, in a journal named Physiology of Motion. It remains one of the major references on supination action of the biceps brachii. [ citation needed ]

Other species

Neanderthals

In Neanderthals, the radial bicipital tuberosities were larger than in modern humans, which suggests they were probably able to use their biceps for supination over a wider range of pronation-supination. It is possible that they relied more on their biceps for forceful supination without the assistance of the supinator muscle like in modern humans, and thus that they used a different movement when throwing. [27]

Horses

In the horse, the biceps' function is to extend the shoulder and flex the elbow. It is composed of two short-fibred heads separated longitudinally by a thick internal tendon which stretches from the origin on the supraglenoid tubercle to the insertion on the medial radial tuberosity. This tendon can withstand very large forces when the biceps is stretched. From this internal tendon a strip of tendon, the lacertus fibrosus, connects the muscle with the extensor carpi radialis  -- an important feature in the horse's stay apparatus (through which the horse can rest and sleep whilst standing.) [28]

Related Research Articles

<span class="mw-page-title-main">Arm</span> Proximal part of the free upper limb between the shoulder and the elbow

In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint and the elbow joint. The distal part of the upper limb between the elbow and the radiocarpal joint is known as the forearm or "lower" arm, and the extremity beyond the wrist is the hand.

<span class="mw-page-title-main">Humerus</span> Long bone of the upper arm

The humerus is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes. The body is cylindrical in its upper portion, and more prismatic below. The lower extremity consists of 2 epicondyles, 2 processes, and 3 fossae. As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons.

<span class="mw-page-title-main">Brachioradialis</span> Muscle of the upper limb

The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way of the brachioradialis tendon, and to the lateral supracondylar ridge of the humerus.

<span class="mw-page-title-main">Brachialis muscle</span> Flexor muscle in the upper arm

The brachialis is a muscle in the upper arm that flexes the elbow. It lies beneath the biceps brachii, and makes up part of the floor of the region known as the cubital fossa. It originates from the anterior aspect of the distal humerus; it inserts onto the tuberosity of the ulna. It is innervated by the musculocutaneous nerve, and commonly also receives additional innervation from the radial nerve. The brachialis is the prime mover of elbow flexion generating about 50% more power than the biceps.

<span class="mw-page-title-main">Wrist drop</span> Medical condition

Wrist drop is a medical condition in which the wrist and the fingers cannot extend at the metacarpophalangeal joints. The wrist remains partially flexed due to an opposing action of flexor muscles of the forearm. As a result, the extensor muscles in the posterior compartment remain paralyzed.

<span class="mw-page-title-main">Radius (bone)</span> One of the two long bones of the forearm

The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is longer than the radius, but the radius is thicker. The radius is a long bone, prism-shaped and slightly curved longitudinally.

<span class="mw-page-title-main">Upper limb</span> Consists of the arm, forearm, and hand

The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the shoulder, arm, elbow, forearm, wrist and hand, and is primarily used for climbing, lifting and manipulating objects. In anatomy, just as arm refers to the upper arm, leg refers to the lower leg.

Bicep curls are a group of weight training exercises in which a person bends their arm towards their body at the elbow in order to make their biceps stronger.

<span class="mw-page-title-main">Musculocutaneous nerve</span> Nerve in the arm

The musculocutaneous nerve is a mixed branch of the lateral cord of the brachial plexus derived from cervical spinal nerves C5-C7. It arises opposite the lower border of the pectoralis major. It provides motor innervation to the muscles of the anterior compartment of the arm: the coracobrachialis, biceps brachii, and brachialis. It provides sensory innervation to the lateral forearm. It courses through the anterior part of the arm, terminating 2 cm above elbow; after passing the lateral edge of the tendon of biceps brachii it is becomes known as the lateral cutaneous nerve of the forearm.

<span class="mw-page-title-main">Triceps</span> Muscle on the back of the upper arm

The triceps, or triceps brachii, is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally responsible for extension of the elbow joint.

<span class="mw-page-title-main">Cubital fossa</span> The human elbow pit

The cubital fossa, antecubital fossa, chelidon, or inside of elbow is the area on the anterior side of the upper part between the arm and forearm of a human or other hominid animals. It lies anteriorly to the elbow (antecubital) when in standard anatomical position. The cubital fossa is a triangular area having three borders.

<span class="mw-page-title-main">Shoulder joint</span> Synovial ball and socket joint in the shoulder

The shoulder joint is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint. It involves an articulation between the glenoid fossa of the scapula and the head of the humerus. Due to the very loose joint capsule ,that gives a limited interface of the humerus and scapula, it is the most mobile joint of the human body.

<span class="mw-page-title-main">Coracobrachialis muscle</span> Muscle of the upper arm

The coracobrachialis muscle muscle in the upper medial part of the arm. It is located within the anterior compartment of the arm. It originates from the coracoid process of the scapula; it inserts onto the middle of the medial aspect of the body of the humerus. It is innervated by the musculocutaneous nerve. It acts to adduct and flex the arm.

The pronator teres is a muscle that, along with the pronator quadratus, serves to pronate the forearm. It has two origins, at the medial humeral supracondylar ridge and the medial side of the coronoid process of the ulna and inserts near the middle of the radius.

<span class="mw-page-title-main">Supinator muscle</span> Muscle of the forearm in humans

In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.

<span class="mw-page-title-main">Fascial compartments of arm</span> Anatomical compartments

The fascial compartments of arm refers to the specific anatomical term of the compartments within the upper segment of the upper limb of the body. The upper limb is divided into two segments, the arm and the forearm. Each of these segments is further divided into two compartments which are formed by deep fascia – tough connective tissue septa (walls). Each compartment encloses specific muscles and nerves.

<span class="mw-page-title-main">Humeroulnar joint</span>

The humeroulnar joint is part of the elbow-joint. It is composed of two bones, the humerus and ulna, and is the junction between the trochlear notch of ulna and the trochlea of humerus. It is classified as a simple hinge-joint, which allows for movements of flexion, extension and circumduction. Owing to the obliquity of the trochlea of the humerus, this movement does not take place in the antero-posterior plane of the body of the humerus.

<span class="mw-page-title-main">Elbow</span> Joint between the upper and lower parts of the arm

The elbow is the region between the upper arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa, and the lateral and the medial epicondyles of the humerus. The elbow joint is a hinge joint between the arm and the forearm; more specifically between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body. The term elbow is specifically used for humans and other primates, and in other vertebrates it is not used. In those cases, forelimb plus joint is used.

Yergason's test is a special test used for orthopedic examination of the shoulder and upper arm region, specifically the biceps tendon.

<span class="mw-page-title-main">Biceps tendon rupture</span> Complete or partial rupture of a tendon of the biceps brachii muscle

A biceps tendon rupture or bicep tear is a complete or partial rupture of a tendon of the biceps brachii muscle. It can affect any of the three biceps brachii tendons - the proximal tendon of the short head of the muscle belly, the proximal tendon of the long head of the muscle belly, or the distal tendon. The characteristic finding of a biceps tendon rupture is the Popeye sign. Patients often report an audible pop at the time of injury as well as pain, bruising, and swelling. Provocative physical exam maneuvers to assess for a rupture include Ludington's test, Hook test, and the Ruland biceps squeeze test. Treatment and prognosis are highly dependent on the site of the injury described in further detail below.

References

  1. 1 2 3 4 5 6 7 8 Bogart BI, Ort VH (2007). Elsevier's integrated anatomy and embryology. Philadelphia, Pa.: Elsevier Saunders. pp. 262–267. ISBN   978-1-4160-3165-9.
  2. 1 2 Lippert LS (2006). Clinical kinesiology and anatomy (4th ed.). Philadelphia: F. A. Davis Company. pp.  126–7. ISBN   978-0-8036-1243-3.
  3. ↑ "Google Scholar". scholar.google.com. Retrieved August 21, 2024.
  4. 1 2 Athwal GS, Steinmann SP, Rispoli DM (October 2007). "The distal biceps tendon: footprint and relevant clinical anatomy". The Journal of Hand Surgery. 32 (8): 1225–9. doi:10.1016/j.jhsa.2007.05.027. PMID   17923307.
  5. 1 2 Eames MH, Bain GI, Fogg QA, van Riet RP (May 2007). "Distal biceps tendon anatomy: a cadaveric study". The Journal of Bone and Joint Surgery. American Volume. 89 (5): 1044–9. doi:10.2106/JBJS.D.02992. PMID   17473142.
  6. ↑ Platzer W (2004). Color Atlas of Human Anatomy. Vol. 1: Locomotor System (5th ed.). Thieme. p. 154. ISBN   978-1-58890-159-0.
  7. ↑ Kegels L, Van Oyen J, Siemons W, Verdonk R (June 2006). "Bicipitoradial bursitis. A case report" (PDF). Acta Orthopaedica Belgica. 72 (3): 362–5. PMID   16889153.
  8. ↑ Poudel PP, Bhattarai C (June 2009). "Study on the supernumerary heads of biceps brachii muscle in Nepalese". Nepal Medical College Journal. 11 (2): 96–8. PMID   19968147. S2CID   9963394.
  9. ↑ Schwerdtfeger, Luke A.; Pascoe, Michael A.; Clapp, Tod (September 2018). "High incidence of a third head of biceps brachii in females". Translational Research in Anatomy. 12: 25–27. doi: 10.1016/j.tria.2018.08.001 .
  10. ↑ Dirim B, Brouha SS, Pretterklieber ML, Wolff KS, Frank A, Pathria MN, Chung CB (December 2008). "Terminal bifurcation of the biceps brachii muscle and tendon: anatomic considerations and clinical implications". AJR. American Journal of Roentgenology. 191 (6): W248-55. doi:10.2214/AJR.08.1048. PMID   19020211.
  11. ↑ "Biceps Brachii". ExRx.net. Retrieved January 16, 2017.
  12. ↑ Krishna G (2010). "8 - Arm". BD Chaurasia's Human Anatomy (Regional and Applied Dissection and Clinical) Volume 1 - Upper limb and thorax (Fifth ed.). India: CBS Publishers and Distributors Pvt Ltd. p. 88. ISBN   978-81-239-1863-1.
  13. ↑ Simons DG, Travell JG, Simons LS (1999). "30: Biceps Brachii Muscle". In Eric Johnson (ed.). Travell & Simons' Myofascial Pain and Dysfunction (2nd ed.). Baltimore, Maryland: Williams and Wilkins. pp.  648–659. ISBN   978-0-683-08363-7.
  14. 1 2 Saladin K (2015). Anatomy and Physiology: The Unity of Form and Function. New York, NY: McGraw-Hill Education. ISBN   978-0-07-340371-7.
  15. ↑ Kleiber T, Kunz L, Disselhorst-Klug C (January 1, 2015). "Muscular coordination of biceps brachii and brachioradialis in elbow flexion with respect to hand position". Frontiers in Physiology. 6: 215. doi: 10.3389/fphys.2015.00215 . PMC   4526813 . PMID   26300781.
  16. ↑ Hermann Braus, Curt Elze: Musculus biceps brachii. In: Anatomie des Menschen. Ein Lehrbuch für Studierende und Ärzte. Erster Band. Bewegungsapparat. 3. Auflage. Julius Springer, Berlin 1954. Digitalisat der Universität Heidelberg. S. 298-301.
  17. ↑ ter Haar Romeny, B.M.; Denier van der Gon, J.J.; Gielen, C.C.A.M. (September 1984). "Relation between location of a motor unit in the human biceps brachii and its critical firing levels for different tasks". Experimental Neurology. 85 (3): 631–650. doi:10.1016/0014-4886(84)90036-0. hdl: 1874/23877 . ISSN   0014-4886. PMID   6468581. S2CID   36705348.
  18. ↑ Frost A, Zafar MS, Maffulli N (April 2009). "Tenotomy versus tenodesis in the management of pathologic lesions of the tendon of the long head of the biceps brachii". The American Journal of Sports Medicine. 37 (4): 828–33. doi:10.1177/0363546508322179. PMID   18762669. S2CID   35918574.
  19. ↑ Chew ML, Giuffrè BM (2005). "Disorders of the distal biceps brachii tendon". Radiographics. 25 (5): 1227–37. doi:10.1148/rg.255045160. PMID   16160108.
  20. 1 2 Miller MD, Thompson SR, DeLee J, Drez D (2015). DeLee & Drez's orthopaedic sports medicine : principles and practice (Fourth ed.). Philadelphia, PA. ISBN   978-1-4557-4376-6. OCLC   880421005.{{cite book}}: CS1 maint: location missing publisher (link)
  21. ↑ Arend CF. Ultrasound of the Shoulder. Master Medical Books, 2013. Free chapter on ultrasound evaluation of biceps tendon tears available at ShoulderUS.com
  22. ↑ "Bicep tear - Muscular Injuries". Sports Medicine Information.
  23. ↑ "biceps". Latin Declension - Wiktionary. Retrieved October 31, 2020.
  24. ↑ "Bicep". Dictionary and Thesaurus — Merriam-Webster Online. Retrieved December 22, 2010.
  25. ↑ Zwicky A (July 30, 2008). "The dangers of satire". Language Log. Retrieved December 22, 2010.
  26. ↑ Joseph Hyrtl: Muskeln. Anatomische Bedingung eines dreiköpfigen Biceps. In: Handbuch der Topographischen Anatomie. Band II. Braumüller, Wien 1865. S. 353–354.
  27. ↑ Churchill SE, Rhodes JA (2009). "The Evolution of the Human Capacity for 'Killing at a Distance': The Human Fossil Evidence for the Evolution of Projectile Weaponry". In Hublin JJ, Richards MP (eds.). The evolution of hominin diets: integrating approaches to the study of Palaeolithic subsistence. Springer Science + Business Media. p. 208. ISBN   978-1-4020-9698-3.
  28. ↑ Watson JC, Wilson AM (January 2007). "Muscle architecture of biceps brachii, triceps brachii and supraspinatus in the horse". Journal of Anatomy. 210 (1): 32–40. doi:10.1111/j.1469-7580.2006.00669.x. PMC   2100266 . PMID   17229281.
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