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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.
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 ...
In anatomy, extension is a movement of a joint that increases the 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 (bent) elbow. Straightening of the arm would require extension at the elbow joint.
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:
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 splenius cervicis (/ ˈ s p l iː n i ə s s ər ˈ v aɪ s ɪ s /) (also known as the splenius colli, /-ˈ k ɒ l aɪ /) is a muscle in the back of the neck.It arises by a narrow tendinous band from the spinous processes of the third to the sixth thoracic vertebrae; it is inserted, by tendinous fasciculi, into the posterior tubercles of the transverse processes of the upper two or three ...
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 the hand's midline (ray of middle finger) and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle and ring fingers. [1]
The radial nerve and its branches provide motor innervation to the dorsal arm muscles (the triceps brachii and the anconeus) and the extrinsic extensors of the wrists and hands; it also provides cutaneous sensory innervation to most of the back of the hand, except for the back of the little finger and adjacent half of the ring finger (which are ...