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The deep layer of the precursor extensor mass is known to be phylogenetically unstable and is undergoing evolution as high variability is seen in non-human primates. [5] [8] [9] [10] In humans, anomalous or additional muscles can be seen in small portion of population. Anomalous muscles in human extensor compartment are listed as follow:
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 ...
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.
It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm. Together the flexor pollicis longus, pronator quadratus, and flexor digitorum profundus form the deep layer of ventral forearm muscles. [2] The muscle is named from Latin 'deep bender of the fingers'.
The extensor digitorum muscle (also known as extensor digitorum communis) [2] 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. [3]
In human anatomy, the extensor pollicis brevis (EPB) is a skeletal muscle on the dorsal side of the forearm. It lies on the medial side of, and is closely connected with, the abductor pollicis longus. The extensor pollicis brevis belongs to the deep group of the posterior fascial compartment of the forearm.
Split tendons of the muscle inserting on both ulnar and the radial side of the common extensor digitorum was also reported. [2] Anomalous hand extensors including the extensor medii proprius and the extensor indicis et medii communis are often seen as variations of the extensor indicis [2] due to the shared characteristics and embryonic origin. [8]
The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles allow for flexion , extension , adduction , abduction and opposition of the thumb . The muscles acting on the thumb can be divided into two groups: The extrinsic hand muscles, with their muscle bellies located in the forearm, and the intrinsic hand ...