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 arm, forearm and hand, and is primarily used for climbing, lifting and manipulating objects.
The extensor digiti minimi is a slender muscle of the forearm, placed on the ulnar side of the extensor digitorum communis, with which it is generally connected.
The extensor digitorum muscle is a muscle of the posterior forearm present in humans and other animals. It extends the medial four digits of the hand. Extensor digitorum is innervated by the posterior interosseous nerve, which is a branch of the radial nerve.
In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from hand's midline and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle and ring fingers.
In human anatomy, the abductor digiti minimi is a skeletal muscle situated on the ulnar border of the palm of the hand. It forms the ulnar border of the palm and its spindle-like shape defines the hypothenar eminence of the palm together with the skin, connective tissue, and fat surrounding it. Its main function is to pull the little finger away from the other fingers.
In human anatomy, the extensor indicis [proprius] is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it extends.
Within each osseo-aponeurotic canal, the tendons of the flexor digitorum superficialis and flexor digitorum profundus are connected to each other, and to the phalanges, by slender, tendinous bands, called vincula tendina.
The extensor retinaculum is a thickened portion of the antebrachial fascia that holds the tendons of the extensor muscles in place. It is located on the back of the forearm, just proximal to the hand. It is continuous with the palmar carpal ligament.
The posterior compartment of the forearm contains twelve muscles which primarily extend the wrist and digits. It is separated from the anterior compartment by the interosseous membrane between the radius and ulna.
The muscles of the hand are the skeletal muscles responsible for the movement of the hand and fingers. The muscles of the hand can be subdivided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm. The intrinsic group are the smaller muscles located within the hand itself. The muscles of the hand are innervated by the radial, median, and ulnar nerves from the brachial plexus.
Extensor digitorum brevis manus is an extra or accessory muscle on the backside (dorsum) of the hand. It was first described by Albinus in 1758. The muscles lies in the fourth extensor compartment of the wrist, and is relatively rare. It has a prevalence of 4% in the general population according to a meta-analysis. This muscle is commonly misdiagnosed as a ganglion cyst, synovial nodule or cyst.
The mucous sheaths of the tendons on the back of the wrist are protective coverings for tendons in the wrist. Between the dorsal carpal ligament and the bones six compartments are formed for the passage of tendons, each compartment having a separate mucous sheath. One is found in each of the following positions:
- on the lateral side of the radial styloid process, for the tendons of the Abductor pollicis longus and Extensor pollicis brevis;
- behind the styloid process, for the tendons of the Extensores carpi radialis longus and brevis;
- about the middle of the dorsal surface of the radius, for the tendon of the Extensor pollicis longus;
- to the medial side of the latter, for the tendons of the Extensor digitorum communis and Extensor indicis proprius;
- opposite the interval between the radius and ulna, for the Extensor digiti quinti proprius;
- between the head and styloid process of the ulna, for the tendon of the Extensor carpi ulnaris.
The extrinsic extensor muscles of the hand are located in the back of the forearm and have long tendons connecting them to bones in the hand, where they exert their action. Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand. They include the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis (EI).
Lister's tubercle or dorsal tubercle of radius is a bony prominence located at the distal end of the radius. It is palpable on the dorsum of the wrist.
The extensor indicis et medii communis is a rare anatomical variant in the extensor compartment of forearm. This additional muscle lies in the deep extensor layer next to the extensor indicis proprius and the extensor pollicis longus. The characteristics of this anomalous muscle resemble those of the extensor indicis proprius, with split tendons to the index and the middle finger. This muscle can also be considered as a variation of the aberrant extensor medii proprius.
In human anatomy, juncturae tendinum or connexus intertendinei refers to the connective tissues that link the tendons of the extensor digitorum communis, and sometimes, to the tendon of the extensor digiti minimi. Juncturae tendinum are located on the dorsal aspect of the hand in the first, second and third inter-metacarpal spaces proximal to the metacarpophalangeal joint.
Palmaris profundus is a rare anatomical variant in the anterior compartment of forearm. It was first described in 1908. It is usually found incidentally in cadaveric dissection or surgery.
In human anatomy, the extensor pollicis et indicis communis is an aberrant muscle in the posterior compartment of forearm. It was first described in 1863. The muscle has a prevalence from 0.5% to 4%.
Linburg–Comstock variation is an occasional tendinous connection between the flexor pollicis longus and the flexor digitorum profundus of the index, the middle finger or both. It is found in around 21% of the population. It is an anatomical variation in human, which may be viewed as a pathology if causes symptoms. It was recognised as early as the 1800s, but was first described by Linburg and Comstock in 1979.
Extensor indicis proprius (EIP) and extensor medii proprius (EMP)
