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The triceps, or triceps brachii, is a large muscle on the back of the upper limb of many vertebrates. It is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. The triceps brachii is a three-headed muscle, with the three heads being the medial, lateral, and long head. The triceps is the only constituent of the posterior muscle group of the arm, spanning almost the entire length of the humerus.
| Characteristics | Values |
|---|---|
| Definition | Any muscle with three heads, or points of origin, particularly the large extensor along the back of the upper arm in humans |
| Location | Upper arm, between the shoulder joint and elbow joint |
| Function | Extension of the forearm at the elbow joint |
| Parts | The medial, lateral, and long head |
| Innervation | The four branches of the radial nerve (C7, C8) |
| Blood Supply | Branches of the deep brachial artery |
| Reflex | Used to test the function of the nerves of the arm (spinal nerves C6 and C7) |
| Rupture | Rare, typically occurs in anabolic steroid users |
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What You'll Learn
Triceps brachii is a three-headed muscle
The triceps, or triceps brachii, is a three-headed muscle of the arm. The name comes from the Latin for "three-headed muscle of the arm" (tri = three, cep = head). It is a large muscle on the back of the upper limb of many vertebrates. It is the only constituent of the posterior muscle group of the arm, spanning almost the entire length of the humerus.
The three heads of the triceps brachii are the medial, lateral, and long head. All three heads cross the elbow joint, but the long head also crosses the shoulder joint. The triceps muscle contracts when the elbow is straightened and expands when the elbow is bent. The long head gets a further contraction when the arm is behind the torso due to how it crosses the shoulder joint. The long head arises from the infraglenoid tubercle of the scapula, which is a rough area at the inferior margin of the glenoid fossa. The medial head arises proximally in the humerus, just inferior to the groove of the radial nerve, and from the dorsal (back) surface of the humerus. The lateral head originates from a narrow, linear ridge on the posterior surface of the humerus, just superior to the radial groove.
The triceps brachii is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. Its main function is the extension of the forearm at the elbow joint. The long head also contributes to the extension and adduction of the arm at the shoulder joint. With its origin on the scapula, the long head also acts on the shoulder joint and is involved in retroversion and adduction of the arm. It helps stabilise the shoulder joint at the top of the humerus.
The triceps brachii can be trained in a variety of ways, including isolation and compound elbow extension movements. It can also be contracted statically to keep the arm straightened against resistance.
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Triceps brachii is an extensor muscle of the elbow joint
The triceps brachii is a large muscle on the back of the upper limb of many vertebrates, including humans. It is a three-headed muscle, with the Latin name 'triceps' meaning 'three-headed'. The three heads are the medial, lateral, and long head. The triceps brachii is the only constituent of the posterior muscle group of the arm, and it spans almost the entire length of the humerus.
The triceps brachii is an extensor muscle of the elbow joint. It is the muscle principally responsible for the extension of the forearm at the elbow joint (straightening of the arm). The triceps brachii contracts when the elbow is straightened and expands when the elbow is bent. The long head gets a further contraction when the arm is behind the torso due to how it crosses the shoulder joint. The triceps brachii 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, such as when writing.
The triceps brachii originates just below the socket of the scapula (shoulder blade) and at two distinct areas of the humerus, the bone of the upper arm. It extends downward and inserts on (attaches to) the upper part of the ulna, in the forearm. The medial head arises proximally in the humerus, just inferior to the groove of the radial nerve, while the lateral head originates from a narrow, linear ridge on the posterior surface of the humerus, just superior to the radial groove. The long head arises from the infraglenoid tubercle of the scapula, which is a rough area at the inferior margin of the glenoid fossa.
The triceps brachii is supplied with oxygen and nutrients from the branches of the deep brachial artery. The triceps brachii is innervated by the radial nerve. However, some studies have found that in around 14% of individuals, the long head of the triceps brachii is innervated by the axillary nerve, and in 3% it receives dual innervation from both the radial nerve and the axillary nerve.
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Triceps brachii is an antagonist of the biceps and brachialis muscles
The triceps brachii is a large muscle on the back of the upper arm in humans and other vertebrates. It is a three-headed muscle, with a long, lateral, and medial head. All three heads cross the elbow joint, while the long head also crosses the shoulder joint. The triceps brachii is the only constituent of the posterior muscle group of the arm, and it is the functional antagonist of the biceps and brachialis muscles.
The primary function of the triceps is the extension of the forearm upon the elbow joint, which is the opposite of the action performed by the biceps brachii. The triceps brachii contracts when the elbow is straightened and expands when the elbow is bent. The long head of the triceps brachii gets an additional contraction when the arm is behind the torso due to how it crosses the shoulder joint. This further contraction of the long head contributes to the extension and adduction of the arm at the shoulder joint.
The triceps brachii also plays a role in creating anatomical spaces that are traversed by neurovascular structures. This makes the triceps brachii an important surgical landmark. Additionally, the triceps muscle can be used to test the function of the nerves of the arm through the triceps reflex. This reflex tests spinal nerves C6 and C7, predominantly C7.
The triceps brachii is innervated by the radial nerve, with some studies indicating that the long head may be innervated by the axillary nerve in some individuals. The muscle is supplied with oxygen and nutrients from the branches of the deep brachial artery. Ruptures of the triceps muscle are rare and typically only occur in anabolic steroid users.
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Triceps ruptures are rare and caused by anabolic steroid use
The triceps is a large muscle on the back of the upper arm in humans. It is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. The triceps is also called the triceps brachii, which in Latin means "three-headed muscle of the arm". This is because it consists of three parts: the medial, lateral, and long head. All three heads cross the elbow joint, but the long head also crosses the shoulder joint.
Triceps ruptures are rare but can occur in anabolic steroid users. Anabolic steroids are known to have detrimental effects on the mechanical properties of connective tissue, which can lead to tendon ruptures. In fact, anabolic steroid abuse by weightlifters is the most common predisposing factor for triceps tendon ruptures. Triceps tendon ruptures can also result from traumatic incidents or chronic overuse causing degenerative changes to the insertion. However, it is important to note that ruptures of the triceps mechanism are uncommon injuries that have been recognised with increasing frequency in recent years.
Triceps tendon ruptures typically occur in weightlifters or athletes who place high demands on their musculoskeletal structures. The injury is often accompanied by fractures of the radial head and must be actively evaluated in the presence of such a fracture. The patient is usually unable to extend their arm against gravity, and swelling and bruising may be observed. A hinged splint can be used after triceps repair to allow for early controlled motion.
The diagnosis of triceps tendon ruptures can be challenging, and the initial diagnosis is often missed. Ultrasound or magnetic resonance imaging (MRI) can be used to confirm the diagnosis, with MRI being the gold standard to evaluate the size and extension of the tear. Early diagnosis is crucial as it increases the chance of a direct repair. Operative treatment with direct repair is usually indicated for full-thickness or large partial-thickness tears. Triceps tendon repair surgery has been performed on military personnel and athletes, with uniformly good to excellent results if recognised and treated early.
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Triceps brachii is an important surgical landmark
The triceps is a large muscle on the back of the upper arm in humans. It is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. The triceps muscle has three points of origin, or heads: the medial, lateral, and long head. All three heads converge to form a single tendon, which attaches to the ulna. The triceps brachii is the specific term for the triceps muscle.
The triceps brachii is an important surgical landmark. This is because, besides movement, the triceps brachii also plays a role in creating anatomical spaces which are traversed by neurovascular structures. The quadrangular space, for example, is bordered by the subscapularis and teres minor superiorly, the teres major inferiorly, the long head of the triceps medially, and the surgical neck of the humerus laterally. This space allows the axillary nerve and the posterior circumflex humeral artery and vein to pass from the axillary region to the posterior region of the shoulder.
The triceps brachii is also important in surgery because it is a common site for ruptures, which usually only occur in anabolic steroid users. Distal triceps ruptures are also uncommon. The injury typically occurs due to either a fall on an outstretched hand or a direct blow to the triceps tendon. The patient presents after a painful popping sensation with pain and swelling over the posterior elbow with the inability to extend the elbow against resistance. Surgical consideration for a partial rupture is controversial, but it is necessary for a complete rupture. If the rupture is chronic, then along with surgical repair, remodeling is also indicated.
The triceps brachii is also used as a landmark in the triceps deep tendon reflex examination. The triceps tendon, olecranon, and triceps muscle are all used as landmarks in this examination.
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Frequently asked questions
The triceps brachii is a large muscle on the back of the upper limb of many vertebrates. It is composed of three heads: the medial, lateral, and long head. All three heads cross the elbow joint, but the long head also crosses the shoulder joint.
The triceps muscle contracts when the elbow is straightened and expands when the elbow is bent. The long head gets a further contraction when the arm is behind the torso. It is the muscle responsible for the extension of the elbow joint (straightening of the arm).
The triceps brachii is made of concentric layers of mesodermal cells formed with cranial to caudal progression. They organise in somites, which appear at a frequency of about three pairs a day. By the fifth week of embryogenesis, there are 42 to 44 pairs of somites.
