What is the function of the Extensor Muscle?

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There are so many muscles in our body. But the basic function of all these muscles is working as flexors or extensors. Every muscle group is dedicated for working particular responsibility and their functions are very specific as well as general. So  it will be interesting to know how the extensor muscles work along with flexors to give movement to our body.


What Is the Extensor Muscle?

The forearm muscles can be categorized into two divisions or groups: - flexor/pronator group and an extensor/supinator group. The extensor/supinator group is located in forearm’s posterior compartment. The extensor muscles originate from lateral epicondyle of humerus which is also termed as extensor attachment.


What are the different extensor muscles?

The extensor muscles work in groups and are of various types. They are:

Extensor carpi radialis brevis: It is a flat yet wide and short muscle which starts from upper arm bone or the humerus and tapers down to the two third distance of arm and become a long flat tendon. It is located in between extensor digitorum and carpi radialis longus and is parallel to the radius surface. This muscle performs the function of moving the wrist joint of hand radially.

Extensor carpi radialis longus: It is a short and flat muscle originating from humerus and extending till the end of arm. At its belly, the muscle narrows to turn into flat and long tendon moving to the forearms’ upper third and reaching the radium outer edge. This muscle helps to flex elbow joint and also assists in moving of wrist and extending of arms.

Extensor carpi ulnaris: It is a superficial muscle located inside the forearm and is narrow, long and flattened. It extends further from the upper arm bone and reaches the fifth metacarpal bone present inside the little finger. Here it penetrates with the help of flat, narrow tendon. This tendon emerges three fourths down the passage to forearm. It helps in the extension of wrist.

Extensor digiti minimi: It is a tiny and slender muscle that also rises from the humerus and is placed between extensor carpi ulnaris and digitorium. It is the most important part of the little finger.

Extensor digitorum: It is a broadened, lateral group of muscles comprising of fusiform and flat belly extending from the humerus moving further into the lower half portion of the forearm. It then grows 4 tendons that penetrate the middle as well as the distal phalanges of fingers. It helps in the extension of all joint fingers and also extends the wrist.

Extensor indicis: It is situated in deep forearm and originates from the back of ulna. It grows as a tendon at the wrist and further courses along the back of hand along with extensor digitorum and finally penetrates in index finger. It assists in adduction and extension of index finger.

Extensor pollicis brewis: Together with abductor pollicis longus, the extensor pollicis brevis (thumb muscle) makes a narrow, triangular muscle form which encircles the bone of the forearm placed at the side of thumb. The extensor pollicis brevis rises from the radius back side and then penetrates in thumb’s first phalanx from the back side of the radius and inserts in the base of the first phalanx of the thumb. This muscle helps in extension of thumb and manages the rotational activities of hand. The abductor pollicis longus along with extensor pollicis brevis create oblique carpal muscle group.

Abductor pollicis longus: This muscle is placed immediately beside the extensor pollicis brevis and creates a narrow, triangular muscle that encircles the lower end of radius. It penetrates the metacarpal bone base of thumb from the palm’s back surface. This muscle helps in abduction and extension of thumb and also helps in bending of wrist.

Extensor pollicis longus: It emerges from the deep of the forearm from the ulna shaft, moves across the extensor carpi radials brevis and longus tendons and then comes down along the back side of the thumb to finally penetrate the phalanx of thumb. This muscle helps in extension of thumb and hand at wrist.


What are the functions of extensor muscles?

The main purpose of extensor muscles is to enhance the angles between the You do not have access to view this node. A good example of its working is triceps that are present on the back side of the arm and moves down below the elbow. These triceps enable the movement of lower arm away from the upper arm. Quadriceps are also group of muscles located in knee front and courses up to the knee joint due to which lower leg can move away from the upper leg. The forearm extensors are responsible for the movement of bone fingers away from the palm You do not have access to view this node.


What is Co- Contraction?

Flexors and extensors work in tandem or in compound with each other and work against the actions of the muscles that are located on the either side of the joint or even maintain stability during work. For example, whenever the bicep contracts, the tricep have to elongate or stretch and when the quadriceps is being flexed, the hamstring has too be stretched and vice versa. But when quadriceps is flexed, the hamstring action actually stabilizes the knee joint. This principle of working is termed as co-contraction.


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