In
human anatomyHuman anatomy, which, with physiology and biochemistry, is a complementary basic medical science is primarily the scientific study of the morphology of the adult human body. Anatomy is subdivided into gross anatomy and microscopic anatomy...
, the
biceps brachii (simply "biceps" in common parlance) is a
muscleMuscle is the contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
located on the upper
armIn anatomy, an arm is one of the upper limbs of an animal. The term arm can also be used for analogous structures, such as one of the paired upper limbs of a four-legged animal, or the arms of cephalopods....
. The biceps has several functions, the most important being to rotate the forearm (
supinationSupination is a position of either the forearm or foot; in the forearm when the palm faces anteriorly, or faces up . Supination in the foot occurs when a person appears "bow-legged" with their weight supported primarily on the anterior of their feetThe hand is supine in the anatomical position...
) and to flex the
elbowThe elbow is the region surrounding the elbow-joint—the ginglymus or hinge joint in the middle of the arm. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm....
.
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
pluralPlural, commonly abbreviated pl., is a grammatical number, typically referring to more than one of the referent in the real world. In the English language, singular and plural are the only grammatical numbers.-English:...
form of the Latin
adjectiveIn grammar, an adjective is a word whose main syntactic role is to modify a noun or pronoun, giving more information about the noun or pronoun's referent...
biceps is
bicipites, a form not in general English use.
In
human anatomyHuman anatomy, which, with physiology and biochemistry, is a complementary basic medical science is primarily the scientific study of the morphology of the adult human body. Anatomy is subdivided into gross anatomy and microscopic anatomy...
, the
biceps brachii (simply "biceps" in common parlance) is a
muscleMuscle is the contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
located on the upper
armIn anatomy, an arm is one of the upper limbs of an animal. The term arm can also be used for analogous structures, such as one of the paired upper limbs of a four-legged animal, or the arms of cephalopods....
. The biceps has several functions, the most important being to rotate the forearm (
supinationSupination is a position of either the forearm or foot; in the forearm when the palm faces anteriorly, or faces up . Supination in the foot occurs when a person appears "bow-legged" with their weight supported primarily on the anterior of their feetThe hand is supine in the anatomical position...
) and to flex the
elbowThe elbow is the region surrounding the elbow-joint—the ginglymus or hinge joint in the middle of the arm. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm....
.
Terminology
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
pluralPlural, commonly abbreviated pl., is a grammatical number, typically referring to more than one of the referent in the real world. In the English language, singular and plural are the only grammatical numbers.-English:...
form of the Latin
adjectiveIn grammar, an adjective is a word whose main syntactic role is to modify a noun or pronoun, giving more information about the noun or pronoun's referent...
biceps is
bicipites, a form not in general English use. Instead,
biceps is used in both
singularIn linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....
and plural (i.e., when referring to both arms). The form
, although common even in professional contexts, is considered incorrect. The error may originate from a mistaken belief that
biceps is a plural noun (rather than an adjective in the singular), since English typically forms its plurals by the addition of the letter
s to the end of a noun.
Anatomy
Proximally, the
short head of the biceps attaches to (originates from) the coracoid process of the
scapulaIn anatomy, the scapula, omo , or shoulder blade, is the bone that connects the humerus with the clavicle ....
. The
tendonA tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fascia as they are all made of collagen except that ligaments join one bone to another bone, and fascia connect muscles to other...
of the
long head passes along the intertubercular groove of the humerus into the
joint capsuleAn articular capsule is an envelope surrounding a synovial joint.-Layers:Each capsule consists of two layers:* an outer layer composed of avascular white fibrous tissue...
at the head of the humerus, and attaches to the scapula at the
supraglenoid tubercleThe supraglenoid tubercle is a region of the scapula to which the long head of the biceps brachii muscle attaches.-External links:...
.
Distally, biceps attaches to (inserts into) the
radial tuberosityBeneath the neck of the radius, on the medial side, is an eminence, the radial tuberosity; its surface is divided into:* a posterior, rough portion, for the insertion of the tendon of the biceps brachii....
. Because the ulnar and radial bones can rotate about each other the biceps can powerfully supinate the forearm. The biceps also connects with the fascia of the medial side of the forearm via the
bicipital aponeurosisThe bicipital aponeurosis is a broad aponeurosis of the biceps brachii which is located in the cubital fossa of the elbow and separates superficial from deep structures in much of the fossa....
.
Two additional muscles lie underneath the biceps brachii. These are the
coracobrachialis muscleThe Coracobrachialis is the smallest of the three muscles that attach to the coracoid process of the scapula. It is situated at the upper and medial part of the arm....
, which like the biceps attaches to the coracoid process of the scapula, and the
brachialis muscleThe brachialis is a muscle in the upper arm that flexes the elbow joint. It lies just deep of the biceps brachii, and is a synergist that assists the biceps brachii in flexing at the elbow...
which connects to the
ulnaThe ulna is a long bone, prismatic in form. In anatomical position the ulna is placed at the medial side of the forearm closest to the body, parallel with the radius on both arms.-Articulations:The ulna articulates with:...
and along the mid-shaft of the
humerusThe humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
.
Functions
The biceps is tri-articulate, meaning that it works across three joints. The most important of these functions are to supinate the forearm and flex the elbow.
These joints and the associated actions are listed as follows in order of importance:
- Proximal radioulnar joint - Contrary to popular belief, the biceps brachii is not the most powerful flexor of the forearm, a role which actually belongs to the deeper brachialis muscle. The biceps brachii functions primarily as a powerful supinator of the forearm (turns the palm upwards). This action, which is aided by the supinator muscle, requires the elbow to be at least partially flexed. If the elbow, or humeroulnar joint
The humeroulnar joint, is part of the elbow-joint or the Olecron Joint, between the ulna and humerus bones is the simple hinge-joint, which allows for movements of flexion, extension and circumduction...
, is fully extended, supination is then primarily carried out by the supinator muscle.
- Humeroulnar joint
The humeroulnar joint, is part of the elbow-joint or the Olecron Joint, between the ulna and humerus bones is the simple hinge-joint, which allows for movements of flexion, extension and circumduction...
(Elbow) - The biceps brachii also functions as an important flexor of the forearm, particularly when the forearm is supinated. Functionally, this action is performed when lifting an object, such as a bag of groceries or when performing a biceps curlThe biceps curl is any of a number of weight training exercises which target the biceps brachii muscle in order to develop one or more of the following attributes:* size* definition* strength* stamina...
. When the forearm is in pronationIn anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...
(the palm faces the ground), the brachialis, brachioradialisBrachioradialis is a muscle of the forearm that acts to flex the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm; for this reason it is also called "the beer drinker muscle." It is attached to the distal styloid process of the...
, and supinator function to flex the forearm, with minimal contribution from the biceps brachii.
- Glenohumeral joint
The glenohumeral joint, commonly known as the shoulder joint, is a multiaxial synovial ball and socket joint and involves articulation between the glenoid fossa of the scapula and the head of the humerus .-Movements:...
(Shoulder) - Several weaker functions occur at the glenohumeral, or shoulder, joint. The biceps brachii weakly assists in forward flexion of the shoulder joint (bringing the arm forward and upwards). It may also contribute to abductionAbduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:The coming together of two bones attached by a joint laterally* of arm at shoulder...
(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 adductionAdduction is a movement which brings a limb — arm or leg — closer to the sagittal plane of the body. It is opposed to abduction.This term is also used in reference to the operation of the muscle in anatomy or musculature.-Upper limb:* of arm at shoulder...
(bringing the arm across the body) when the arm is internally (or medially) rotated. Finally, the long head of the biceps brachii, due to its attachment to the scapulaIn anatomy, the scapula, omo , or shoulder blade, is the bone that connects the humerus with the clavicle ....
(or shoulder blade), assists with stabilization of the shoulder joint when a heavy weight is carried in the arm.
Training
The biceps can be strengthened using
weightWeight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the force of gravity to oppose the force generated by muscle through concentric or eccentric contraction...
and
resistance trainingResistance training has two different, sometimes confused meanings: a broader meaning that refers to any training that uses a resistance to the force of muscular contraction , and elastic or hydraulic resistance, which refers to a specific type of strength training that uses elastic or hydraulic...
. An example of a well known biceps exercise is the simple
biceps curlThe biceps curl is any of a number of weight training exercises which target the biceps brachii muscle in order to develop one or more of the following attributes:* size* definition* strength* stamina...
.