Alec Titan
The human elbow is a complex joint that allows for significant motion and function, primarily in the form of extension and flexion. Many muscles of the upper and lower arm either cross or attach to at least one component of the elbow joint, making it the second most commonly injured joint in sports-related injuries. These muscles are responsible for the secondary stabilisation of the joint and can be broadly grouped into the flexor and extensor groups of the forearm.
| Characteristics | Values |
|---|---|
| Muscles that cross the elbow | Biceps Brachii, Brachialis, Brachioradialis, Triceps Brachii, Anconeus, Supinator, Pronator Teres, Flexor Carpi Radialis, Flexor Carpi Ulnaris, Palmaris Longus, Flexor Digitorum Superficialis, Extensor Carpi Radialis Longus, Extensor Carpi Radialis Brevis, Extensor Digitorum |
| Function | Elbow flexion, elbow extension, supination, pronation, stabilisation, protection against varus and valgus forces |
| Nerves | Musculocutaneous nerve, Radial nerve, Lateral antebrachial cutaneous nerve, Medial antebrachial cutaneous nerve |
Explore related products
What You'll Learn
Triceps Brachii
The triceps brachii is a large, thick muscle on the dorsal part of the upper arm, often appearing in the shape of a horseshoe on the posterior aspect of the arm. It is the only constituent of the posterior muscle group of the arm, spanning almost the entire length of the humerus. The triceps brachii is composed of three heads: a long head, a lateral head, and a medial head. The tendons of these three heads have different origins, but they converge into a single tendon distally, attaching to the proximal portion of the olecranon process (the bony prominence of the elbow) located on the upper portion of the ulna.
The long head originates from the infraglenoid tubercle of the scapula, while the lateral and medial heads originate from the humerus. The long head is unique in that it attaches to the scapula, which allows it to extend the elbow and also play a small role in the glenohumeral or shoulder joint. With the arm adducted, the triceps muscle acts to hold the head of the humerus in the glenoid cavity, helping to prevent any displacement of the humerus. The long head also assists with the extension and adduction of the arm at the shoulder joint. The lateral head is active during forearm extension at the elbow joint when the forearm is supinated or pronated. The medial head of the triceps courses adjacent to the biceps brachii muscle anteriorly, and the space between them forms the medial bicipital groove, which provides a passageway for the brachial artery and median and ulnar nerves.
The triceps brachii is primarily responsible for the extension of the forearm at the elbow joint, opposing the action of flexors such as the biceps brachii. It works together with the anconeus muscle to increase the angle between the humerus and the ulna and radius, straightening the arm until the olecranon locks into the olecranon fossa of the humerus at full extension. The triceps brachii is innervated by the radial nerve, which gives off separate branches for each head. The C6 root value of the radial nerve innervates the lateral head, the C7 root value innervates the long head, and the C8 root value supplies the medial head. The muscle receives its arterial supply from the deep brachial artery, a branch of the brachial artery, and is also supplied by ulnar collateral arteries. The venous drainage is provided by the brachial vein, which runs alongside the deep brachial artery.
Axillary nerve damage can impact the long head of the triceps brachii, and distal triceps ruptures, although uncommon, typically occur due to a fall on an outstretched hand or a direct blow to the triceps tendon.
Arthritis and Muscle Tone: What's the Abnormal Link?
You may want to see also
Explore related products
Anconeus
The anconeus is a small, triangular muscle located at the elbow, attaching the humerus and ulna. It is considered a continuation of the triceps brachii muscle, with the two muscles often being partially or completely blended together. The anconeus originates at the distal end of the humerus near the elbow and inserts at the olecranon of the ulna, along the proximal third of the posterior face of the ulna.
The anconeus is supplied by a motor branch of the radial nerve, which arises at the radial sulcus of the humerus and continues through the medial head of the triceps. It is also supplied by the recurrent interosseous branch of the posterior interosseous artery. The skin over the anconeus is supplied by the T1 spinal nerve.
Functionally, the anconeus acts as an extensor of the forearm, working together with the triceps brachii to increase the angle between the humerus and the ulna and radius, straightening the arm. It also provides support for the dorsal joint capsule and the ulna, helping to prevent damage during hyperextension.
The anconeus muscle can be easily palpated just lateral to the olecranon process of the ulna, especially during pronation and supination movements. An anatomical variation of the anconeus, known as the anconeus epitrochlearis muscle, is found in about one-third of all humans. This variation can cause a compression of the ulnar nerve, resulting in numbness and pain in the elbow, known as cubital tunnel syndrome.
Muscle Hernia: Can It Heal Itself?
You may want to see also
Explore related products
Supinator
The supinator is a broad muscle in the superior and posterior compartment of the forearm. It is a spiral muscle that curves or wraps around the upper third of the radius, connecting it with the ulna. The supinator muscle has a broad origin from the ulna and humerus. The two layers of fibres originate in common from the supinator crest of the ulna, the lateral epicondyle of the humerus, the radial collateral ligament, and the annular radial ligament. The supinator muscle consists of two planes or layers of fibres, between which passes the deep branch of the radial nerve. The superficial layer of fibres has a tendinous origin and surrounds the upper part of the radius. The deeper layer of fibres encircles the neck of the radius above the radial tuberosity.
The supinator muscle is innervated by the deep branch of the radial nerve, that becomes the posterior interosseous nerve upon exiting the supinator muscle. Its nerve roots are primarily from C6, with some C5 involvement. There is also possible additional C7 innervation. The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle. This arrangement can lead to entrapment and compression of the deep part, potentially resulting in selective paralysis of the muscles served by this nerve. This nerve syndrome is known as supinator entrapment syndrome.
The main function of the supinator is to supinate the forearm. This can be done with the elbow in any position of flexion or extension. Supination is the movement that brings the hand into the supine position, facing anteriorly, with the palm up. Supinator always acts together with the biceps brachii, except when the elbow joint is extended. It is the most active muscle in forearm supination during unresisted supination, while the biceps become increasingly active with heavy loading. Supination strength decreases by 64% if the supinator is disabled.
Easing Neck Muscle Tension: Simple and Effective Techniques
You may want to see also
Explore related products
Pronator Teres
The pronator teres is a muscle located mainly in the forearm. It is a long, round muscle that is found in the superficial layer of the anterior compartment of the forearm. The pronator teres has two heads, the humeral head and the ulnar head, and two points of origin: the medial humeral supracondylar ridge and the medial side of the coronoid process of the ulna. The humeral head is larger and more superficial, while the ulnar head is deeper and joins the humeral head at an acute angle, forming one muscle belly. The ulnar head can vary in its composition, being more tendinous, muscular, or even absent in some cases.
The pronator teres is responsible for pronating the forearm, which involves rotating the forearm so that the palm faces downward or posteriorly. It works together with the pronator quadratus to pull the radius medially, causing the radial head to rotate around the proximal ulna. This pronation movement brings the hand from an upward palm position (supination) to a downward-facing palm (pronation). In addition to pronation, the pronator teres also assists in weak flexion of the elbow joint. When the elbow is flexed to a right angle, the pronator teres turns the hand so that the palm faces inferiorly.
The median nerve, which is responsible for innervating the pronator teres, typically passes between the two heads of the muscle. This positioning of the nerve makes it susceptible to compression, leading to a condition known as pronator teres syndrome. This syndrome is characterised by pain, numbness, and possibly motor dysfunction in the affected individual. Pronator teres syndrome can be treated through surgery, which aims to decompress the median nerve by releasing the superficial fascia of the pronator teres and, if necessary, performing a partial or complete resection of the tendon origin.
The pronator teres is an important muscle for athletes, especially in sporting activities that involve repetitive pronation and supination movements, such as racquet sports. It is also relevant in clinical conditions like medial epicondylitis, or golfer's elbow, where pain is experienced along the medial aspect of the elbow and is often exacerbated by forearm pronation or wrist flexion.
The Short Loin Muscle: A Tender Cut Explained
You may want to see also
Explore related products
Brachialis
The brachialis is a muscle in the upper arm that flexes the elbow. It is the primary flexor of the elbow, generating about 50% more power than the biceps. It is located in the anterior compartment of the arm, deep to the biceps brachii. The brachialis is a broad muscle, with its broadest part located in the middle rather than at either of its extremities. It is innervated by the musculocutaneous nerve and occasionally has double innervation with the radial nerve. The muscle is supplied by muscular branches of the brachial artery and the recurrent radial artery.
The brachialis originates from the anterior surface of the distal half of the humerus, near the insertion of the deltoid muscle. Its fibres converge to a thick tendon, which is inserted into the tuberosity of the ulna and the rough depression on the anterior surface of the coronoid process of the ulna. The tendon of the brachialis forms part of the floor of the cubital fossa (elbow pit). The cubital fossa is a region of the elbow that is bordered by the brachialis muscle, along with the biceps brachii and the median nerve.
The brachialis is a prime flexor of the forearm at the elbow joint. It steadies the movement of the elbow joint by relaxing at an even pace during controlled extension. This motion is used for precision movements such as carefully lowering a teacup onto a flat surface. The brachialis is also responsible for holding the elbow in a flexed position, so it is always contracting when the elbow joint is flexed.
The brachialis can be injured by repetitive forceful contractions or muscular contractions with the arm in hyperextension. This type of injury is common in climbers due to the pronation of the hand and the extended starting position. Physical activities that involve a lot of pull-ups, curls, and rope climbing can also cause brachialis muscle pain.
Understanding A-Adrenergic Signaling's Role in Muscle Glycogenolysis
You may want to see also
Frequently asked questions
There are seven major muscles that flex, extend, or rotate the forearm at the elbow. These include the triceps brachii, anconeus, supinator, pronator teres, biceps brachii, brachioradialis, and brachialis.
The triceps brachii is a long muscle that runs down the arm and is responsible for extension of the elbow joint.
The biceps brachii is a flexor muscle, responsible for supination and some elbow flexion.
The supinator muscle is responsible for supination of the forearm/elbow, rotating the radius and forearm so that the palm faces upwards.
The brachialis is the primary flexor of the elbow and is found in the upper arm between the humerus and ulna.
