Triceps brachii muscle
Encyclopedia
The triceps brachii muscle (Latin
for "three-headed arm muscle") is the large muscle
on the back of the upper limb
of many vertebrates. It is the muscle principally responsible for extension
of the elbow joint (straightening of the arm).
, is found on the lower leg, the triceps brachii is commonly called the "triceps".
Historically, the plural form of the adjective triceps was tricipites, a form not in general use today; instead triceps is used in both singular
and plural
(i.e., when referring to both arms). The triceps also make up approximately 2/3 of the muscle mass in the arm.
of the scapula
. It extends distally anterior to the teres minor
and posterior to the teres major
.
The medial head arises distally from the groove of the radial nerve
; from the dorsal (back) surface of the humerus; from the medial intermuscular septum; and its distal part also arises from the lateral intermuscular septum. The medial head is mostly covered by the lateral and long heads, and is only visible distally on the humerus.
The lateral head arises from the dorsal surface of the humerus, lateral and proximal to the groove of the radial nerve
, from the greater tubercle
down to the region of the lateral intermuscular septum.
Each of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord. The medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units. It has been suggested that each fascicle "may be considered an independent muscle with specific functional roles."
. However, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve
in all cases.
process of the ulna
(though some research indicates that there may be more than one tendon) and to the posterior wall of the capsule of the elbow joint where bursae (cushion sacks) are often found. Parts of the common tendon radiates into the fascia of the forearm and can almost cover the anconeus
.
muscle of the elbow joint, and is an antagonist of the biceps
and brachialis muscles. It can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing. It has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both. The lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements.
With its origin on the scapula, the long head also acts on the shoulder joint and is also involved in retroversion and adduction
of the arm.
arch is frequently the origin of the long head and the tendon of latissimus dorsi
. In rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint.
Isolation movements include cable push-downs, lying triceps extensions
and arm extensions behind the back. Examples of compound elbow extension include pressing movements like the push up
, bench press
, close grip bench press (flat, incline or decline), military press
and dips
. A closer grip targets the triceps more than wider grip movements.
Static contraction movements include pullovers, straight-arm pulldowns, and bent-over lateral raises, which are also used to build the deltoids and latissimus dorsi.
Elbow extension is important to many athletic activities. As the biceps is often worked more for aesthetic purposes, this is usually a mistake for fitness training. While it is important to maintain a balance between the biceps and triceps for postural and effective movement purposes, what the balance should be and how to measure it is disputed. Pushing and pulling movements on the same plane are often used to measure this ratio.
Many mammals such as dogs, cows, and pigs have a fourth head, the "Accessory head", which lies between the Lateral and Medial heads. In humans, the Anconeus
is sometimes loosely called "the fourth head of the triceps brachii".
MR images show an explicit large fluid-filled gap between the distal triceps tendon and the olecranon with a large amount of edema in the surrounding subcutaneous tissue. The distal edges of the torn triceps tendon are frayed and have a heterogeneous signal intensity.
Partial ruptures affect mainly the middle section of the tendon above the olecranon. Rupture at the musculo-tendinous transition has been described, but is extremely rare. A forced flexion of the elbow against resistance, e.g. during a fall on the outstretched arm, is a common causing mechanism. Especially seen in athletes, triceps tendon tears can be caused by direct hits on the tendon itself or by extreme contractions for example while weightlifting. Predispositions for tendon injuries are: local injection of anabolic steroids, years of therapy with corticoids followed by a tendinitis, bursitis dorsally of the olecranon, hyperparathyroidism, chronic renal failure and Marfan’s syndrome.
The clinical diagnosis can be hindered because of pain. Hence the MRI, besides sonography, has a great clinical significance. The investigation is essential, because a complete rupture requires an immediate surgical repair.
Distortion or direct trauma can cause injuries to the muscles around the elbow. A rupture of muscular fibers leads to an intramuscular hematoma. There has no specific predilection site been found. Muscular injuries can best be depicted on T2-weighted fat suppressed MR images. They show the extent of the hematoma and the intramuscular edema, which can have a streaky or a macular arrangement. First the pathology appears signal weak and develops later on, with the development of methaemoglobin, a strong signal intensity. A subacute or chronic strain indicates the additional use of contrast agent in order to show a circumscribed enhancement at the lesion. Recommended are fat suppressed T1- and T2-weighted MR images, before and after injection of the contrast agent.
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "three-headed arm muscle") is the large muscle
Muscle
Muscle is a contractile tissue of animals 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...
on the back of the upper limb
Upper limb
The upper limb or upper extremity is the region in an animal extending from the deltoid region to the hand, including the arm, axilla and shoulder.-Definition:...
of many vertebrates. It is the muscle principally responsible for extension
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
of the elbow joint (straightening of the arm).
Terminology
It is sometimes called a three-headed muscle because there are three bundles of muscles, each of different origins, joining together at the elbow. Though a similarly named muscle, the triceps suraeTriceps surae
The triceps surae is a pair of muscles located at the calf - the gastrocnemius and the soleus...
, is found on the lower leg, the triceps brachii is commonly called the "triceps".
Historically, the plural form of the adjective triceps was tricipites, a form not in general use today; instead triceps is used in both singular
Grammatical number
In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....
and plural
Plural
In linguistics, plurality or [a] plural is a concept of quantity representing a value of more-than-one. Typically applied to nouns, a plural word or marker is used to distinguish a value other than the default quantity of a noun, which is typically one...
(i.e., when referring to both arms). The triceps also make up approximately 2/3 of the muscle mass in the arm.
Origins
The long head arises from the infraglenoid tubercleInfraglenoid tubercle
The infraglenoid tubercle is the part of the scapula to which the long head of the triceps brachii attaches.-External links: - "Axillary Region: Scapula "...
of the scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
. It extends distally anterior to the teres minor
Teres minor muscle
The teres minor is a narrow, elongated muscle of the rotator cuff.-Origin:It arises from the dorsal surface of the axillary border of the scapula for the upper two-thirds of its extent, and from two aponeurotic laminæ, one of which separates it from the infraspinatus muscle, the other from the...
and posterior to the teres major
Teres major muscle
The teres major muscle is a muscle of the upper limb and one of six scapulohumeral muscles. It is a thick but somewhat flattened muscle, innervated by the lower subscapular nerve .-Origin and insertion:...
.
The medial head arises distally from the groove of the radial nerve
Radial sulcus
The radial sulcus is a broad but shallow oblique depression for the radial nerve and deep brachial artery. It is located on the center of the lateral border of the humerus bone....
; from the dorsal (back) surface of the humerus; from the medial intermuscular septum; and its distal part also arises from the lateral intermuscular septum. The medial head is mostly covered by the lateral and long heads, and is only visible distally on the humerus.
The lateral head arises from the dorsal surface of the humerus, lateral and proximal to the groove of the radial nerve
Radial sulcus
The radial sulcus is a broad but shallow oblique depression for the radial nerve and deep brachial artery. It is located on the center of the lateral border of the humerus bone....
, from the greater tubercle
Greater tubercle
The greater tubercle of the humerus is situated lateral to the head of the humerus and posteriolateral to the lesser tubercle.Its upper surface is rounded and marked by three flat impressions....
down to the region of the lateral intermuscular septum.
Each of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord. The medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units. It has been suggested that each fascicle "may be considered an independent muscle with specific functional roles."
Innervation
All three heads of the triceps brachii are classically believed to be innervated by the radial nerveRadial nerve
The radial nerve is a nerve in the human body that supplies the upper limb. It supplies the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.It...
. However, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve
Axillary nerve
The axillary nerve or the circumflex nerve is a nerve of the human body, that comes off the of the brachial plexus at the level of the axilla and carries nerve fibers from C5 and C6...
in all cases.
Insertion
The fibers converge to a single tendon to insert onto the olecranonOlecranon
The olecranon is a large, thick, curved bony eminence of the forearm that projects behind the elbow.It is situated at the upper end of the ulna, one of the two bones in the forearm...
process of the ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
(though some research indicates that there may be more than one tendon) and to the posterior wall of the capsule of the elbow joint where bursae (cushion sacks) are often found. Parts of the common tendon radiates into the fascia of the forearm and can almost cover the anconeus
Anconeus muscle
The anconeus muscle is a small muscle on the posterior aspect of the elbow joint.Some consider anconeus to be a continuation of the triceps brachii muscle...
.
Actions
The triceps is an extensorExtension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
muscle of the elbow joint, and is an antagonist of the biceps
Biceps
Biceps may refer to:*Biceps brachii muscle, a muscle located on the inside of the upper arm*Biceps femoris muscle, one of the hamstring muscles of the back of each thigh*Biceps , a point in a metrical pattern...
and brachialis muscles. It can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing. It has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both. The lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements.
With its origin on the scapula, the long head also acts on the shoulder joint and is also involved in retroversion and adduction
Adduction
Adduction is a movement which brings a part of the anatomy closer to the middle sagittal plane of the body. It is opposed to abduction.-Upper limb:* of arm at shoulder ** Subscapularis** Teres major** Pectoralis major** Infraspinatus...
of the arm.
Variants
A tendinousTendon
A 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 fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
arch is frequently the origin of the long head and the tendon of latissimus dorsi
Latissimus dorsi muscle
The latissimus dorsi , meaning 'broadest muscle of the back' , is the larger, flat, dorso-lateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.The latissimus dorsi is responsible for extension,...
. In rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint.
Training
The triceps can be worked through either isolation or compound elbow extension movements, and can contract statically to keep the arm straightened against resistance.Isolation movements include cable push-downs, lying triceps extensions
Lying triceps extensions
Lying triceps extensions, also known as skull crushers and French extensions, are a strength exercise used in many different forms of weight lifting. Lying triceps extensions are one of the most stimulating exercises to the entire triceps muscle group in the upper arm. It works the triceps from...
and arm extensions behind the back. Examples of compound elbow extension include pressing movements like the push up
Push Up
This article is about the single. For the body exercise, see Push-upPush Up is a single by British group Freestylers, featuring Theo, released in 2004. It was a hit mainly in Belgium and Australia, as well as the Netherlands....
, bench press
Bench press
The bench press is an exercise of the upper body. For bodybuilding purposes, it is used to stimulate the pectorals, deltoids, and triceps. While on his or her back, the person performing the bench press lowers a weight to the level of the chest, then pushes it back up until the arm is straight...
, close grip bench press (flat, incline or decline), military press
Military press
The military press is a variation of the overhead press weight training exercise using very strict form.The military press targets the deltoid muscles in the shoulders as well as the triceps...
and dips
Dip (exercise)
The dip is an exercise used in strength training. Normal, shoulder-width dips primarily train the triceps, with major synergists being the anterior deltoid, the pectoralis muscles , and the rhomboid muscles of the back...
. A closer grip targets the triceps more than wider grip movements.
Static contraction movements include pullovers, straight-arm pulldowns, and bent-over lateral raises, which are also used to build the deltoids and latissimus dorsi.
Elbow extension is important to many athletic activities. As the biceps is often worked more for aesthetic purposes, this is usually a mistake for fitness training. While it is important to maintain a balance between the biceps and triceps for postural and effective movement purposes, what the balance should be and how to measure it is disputed. Pushing and pulling movements on the same plane are often used to measure this ratio.
Evolutionary variation
In the horse, 84%, 15%, and 3% of the total muscle weight correspond to the long, lateral, and medial heads, respectively.Many mammals such as dogs, cows, and pigs have a fourth head, the "Accessory head", which lies between the Lateral and Medial heads. In humans, the Anconeus
Anconeus muscle
The anconeus muscle is a small muscle on the posterior aspect of the elbow joint.Some consider anconeus to be a continuation of the triceps brachii muscle...
is sometimes loosely called "the fourth head of the triceps brachii".
Imaging
Injuries of the distal triceps tendon are rare. Beyer et al. found a higher rate of partial tears in contrast to Beletani et al. who described full thickness tears as more common. Children and adults are affected. Tendinous injuries are typically found in the area of the olecranon insertion. Full thickness tears mostly include a bony avulsion.MR images show an explicit large fluid-filled gap between the distal triceps tendon and the olecranon with a large amount of edema in the surrounding subcutaneous tissue. The distal edges of the torn triceps tendon are frayed and have a heterogeneous signal intensity.
Partial ruptures affect mainly the middle section of the tendon above the olecranon. Rupture at the musculo-tendinous transition has been described, but is extremely rare. A forced flexion of the elbow against resistance, e.g. during a fall on the outstretched arm, is a common causing mechanism. Especially seen in athletes, triceps tendon tears can be caused by direct hits on the tendon itself or by extreme contractions for example while weightlifting. Predispositions for tendon injuries are: local injection of anabolic steroids, years of therapy with corticoids followed by a tendinitis, bursitis dorsally of the olecranon, hyperparathyroidism, chronic renal failure and Marfan’s syndrome.
The clinical diagnosis can be hindered because of pain. Hence the MRI, besides sonography, has a great clinical significance. The investigation is essential, because a complete rupture requires an immediate surgical repair.
Magnetic Resonance Imaging
Recommended are T2-weighted fat suppressed axial and sagittal planes.It has to be added that the sagittal plane is at an eventual “postero-lateral rotary instability”, for example after dislocation, a good choice to illustrate the centering of the radius head or changes at the olecranon and the tripecs tendon. All tendons of the elbow are hypointense, except the triceps tendon. It shows, just like the quadriceps tendon at the area of the distal thigh, signal increased stripes in between two collagen bundles. Those are fatty inter-positions and should not be misinterpreted as tears.Patella cubiti, os supratrochleare dorsale
Small sesamoid bones in the triceps tendon (patellae cubitalis) are very rare, and their genesis remains unclear. Whether if a trauma in the patients history or an ossification disorder of the olecranon apophysis is the root cause, remains unclear and is still academically discussed. More common is an ossicle, 1-2 cm large, ventral to the triceps tendon in the subsynovial fat tissue or even intraarticular in the fossa olecrani. A so-called os supratrochleare dorsalis. Large ossicles could lead to an extension deficit. This variety of the norm is to distinguish from an olecranon fracture, because fractures at that area are often combined with a dehiscence, respectively, a dislocation of an osseous fragment due to traction of the triceps muscle.Distortion or direct trauma can cause injuries to the muscles around the elbow. A rupture of muscular fibers leads to an intramuscular hematoma. There has no specific predilection site been found. Muscular injuries can best be depicted on T2-weighted fat suppressed MR images. They show the extent of the hematoma and the intramuscular edema, which can have a streaky or a macular arrangement. First the pathology appears signal weak and develops later on, with the development of methaemoglobin, a strong signal intensity. A subacute or chronic strain indicates the additional use of contrast agent in order to show a circumscribed enhancement at the lesion. Recommended are fat suppressed T1- and T2-weighted MR images, before and after injection of the contrast agent.
Additional images
External links
- Photo at Ithaca CollegeIthaca CollegeIthaca College is a private college located on the South Hill of Ithaca, New York. The school was founded by William Egbert in 1892 as a conservatory of music. The college has a strong liberal arts core, but also offers several pre-professional programs and some graduate programs. The college is...
