Underarm

m. Extensor Carpi Radialis Longus and Brevis

*Longus* Ursprung: Distala 1/3 av margo lateralis humeri, septum intermusculare. Fäste: Basis ossis metacarpalis 2. Funktion: Radialdeviation (abduktion) och vristextension i art. radiocarpea. Innervation: N. radialis (C6-C7) *Brevis* Ursprung: *Epicondylus lateralis humeri*. Fäste: Basis ossis metacarpalis 3. Funktion: Radialdeviation (abduktion) och vristextension i art. radiocarpea. Innervation: N. radialis (C7-C8).

M. Pronator Quadratus

A square shaped muscle, found deep to the tendons of the FDP and FPL. Ursprung: Distala 1/4 av ulnas framsida. Fäste: Distala 1/4 av radius framsida. Funktion: Pronation och sammanbindning av underarmens ben. Innervation: N. medianus (C8-T1).

m. Flexor digitorum superficialis

Attachments: It has two heads - one originates from the medial epicondyle of the humerus, the other from the radius. The muscle splits into four tendons at the wrist, which travel through the carpal tunnel, and attaches to the middle phalanges of the four fingers. Actions: Flexes the metacarpophalangeal joints and proximal interphalangeal joints at the 4 fingers, and flexes at the wrist. Innervation: Median nerve.

m. Pronator teres

Attachments: It has two origins, one from the medial epicondyle, and the other from the coronoid process of the ulna. Fäste: Lateralytan av radius, ungefär mitt på benet. Funktion: Pronation och flexion i underarmen. Innervation: N. medianus (C6-C7).

M. Flexor Carpi Ulnaris

Attachments: Originates from the medial epicondyle with the other superficial flexors. It also has a long origin from the ulna. It passes into the wrist, and attaches to the pisiform carpal bone. Actions: Flexion and adduction at the wrist. Innervation: Ulnar nerve.

M. Flexor Digitorum Profundus

Attachments: Originates from the ulna and associated interosseous membrane. At the wrist, it splits into four tendons, that pass through the carpal tunnel and attach to the distal phalanges of the four fingers. Actions: It is the only muscle that can flex the distal interphalangeal joints of the fingers. It also flexes at metacarpophalangeal joints and at the wrist. Innervation: The medial half (acts on the little and ring fingers) is innervated by the ulnar nerve. The lateral half (acts on the middle and index fingers) is innervated by the anterior interosseous branch of the median nerve.

Intermediate Compartment anterior forearm

The flexor digitorum superficialis is the only muscle of the intermediate compartment. It can sometimes be classed as a superficial muscle, but in most cadavers it lies between the deep and superficial muscle layers.

Posterior forearm

The muscles in the posterior compartment of the forearm are commonly known as the extensor muscles. The general function of these muscles is to *produce extension at the wrist and fingers*. *They are all innervated by the radial nerve*. Anatomically, the muscles in this compartment can be divided into two layers; deep and superficial. These two layers are separated by a layer of fascia.

Superficial muscles of posterior forearm

The superficial layer of the posterior forearm contains seven muscles. Four of these muscles - extensor carpi radialis brevis, extensor digitorum, extensor carpi ulnaris and extensor digiti minimi share a common tendinous origin at the lateral epicondyle.

Superficial Anterior Compartment

The superficial muscles in the anterior compartment are the flexor carpi ulnaris, palmaris longus, flexor carpi radialis and pronator teres. They all originate from a common tendon, which arises from the medial epicondyle of the humerus.

Deep Muscles of the posterior forearm

There are five muscles in the deep compartment of the posterior forearm - the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis. With the exception of the supinator, these muscles act on the thumb and the index finger.

Anterior compartment of the arm

There are many muscles in the forearm. In the anterior compartment, they are split into three categories; superficial, intermediate and deep. In general, muscles in the anterior compartment of the forearm perform flexion at the wrist and fingers, and pronation

Deep Compartment Anterior Forearm

There are three muscles in the deep anterior forearm; flexor digitorum profundus, flexor pollicis longus, and pronator quadratus.

m. Flexor carpi radialis

There are two other muscles in the palm that are not lumbricals or interossei and do not fit in the hypothenar or thenar compartments: Ursprung: Epicondylus medialis humeri. Fäste: Basis ossis metacarpalis 2-3. Funktion: Flexion och abduktion. Innervation: N. medianus (C6-C7)

m. Palmaris brevis

This is a small, thin muscle, found very superficially in the subcutaneous tissue of the hypothenar eminence. Attachments: Originates from the palmar aponeurosis and flexor retinaculum, attaches to the dermis of the skin on the medial margin of the hand. Actions: Wrinkles the skin of the hypothenar eminence and deepens the curvature of the hand, improving grip. Innervation: Ulnar nerve.

m. Palmaris longus

This muscle is absent in about 15% of the population. Dissection Tip: Just distal to the wrist, if you reflect back the palmaris longus, you will find the median nerve immediately underneath it Attachments: Originates from the medial epicondyle, attaches to the flexor retinaculum of the wrist. Actions: Flexion at the wrist. Innervation: Median nerve.

M. Flexor Pollicis Longus

This muscle lies laterally to the FlexorDigitorumProfundus. Attachments: Originates from the anterior surface of the radius, and surrounding interosseous membrane. Attaches to the base of the distal phalanx of the thumb. Actions: Flexes the interphalangeal joint and metacarpophalangeal joint of the thumb. Innervation: Median nerve (anterior interosseous branch).

m. Brachioradialis

Ursprung: Distala 1/3 av margo lateralis humeri. Septum intermusculare laterale. Fäste: Distalt och lateralt på radius. Funktion: Flexion i art. cubiti. Innervation: N. radialis (C5-C6). Syns bäst när armen är halft pronerad

m. Abductor pollucis longus

Ursprung: Dorsalt om membrana interossea och angränsande delar av radius och ulna. Fäste: Basis ossis metacarpalis 1. Funktion: Abduktion och extension i art. carpometacarpea pollicis. Innervation: N. radialis (C7-C8).

m. Extensor carpi ulnaris

Ursprung: Epicondylus lateralis humeri, lig. collaterale radiale och facies posterior ulnae. Fäste: Basis ossis metacarpalis 5. Funktion: Ulnardeviation (adduktion) och dorsalflexion i art. radiocarpea. Innervation: N. radialis (C7-C8).

m. extensor digitorum

Ursprung: Epicondylus lateralis humeri. Fäste: Extensoraponeurosen. Basen av 2:a-5:e fingrets falanger. Funktion: Dorsalflexion i art. radiocarpea. Extension av fingrarnas leder. Extends medial four fingers at the MCP and IP joints. Innervation: N. radialis (C6-C8).

m. extensor digitorum minimi

Ursprung: Epicondylus lateralis humeri. Fäste: Lillfingrets extensoraponeuros. Funktion: Dorsalflexion i art. radiocarpea. Extension av lillfingret. Innervation: N. radialis (C7-C8). Fotnot: The extensor digiti minimi is thought to originate from the extensor digitorum muscle. In some people, these two muscles are fused together. *Anatomically, the extensor digiti minimi lies medially to the extensor digitorum.*

m. Supinator

Ursprung: It has two heads of origin. One originates from the lateral epicondyle of the humerus, the other from the posterior surface of the ulna. Fäste: Proximala 1/3 av radius laterala sida.. Funktion: Supination i armbågen. Innervation: N. radialis (C5-C6)

m. extensor indicis proprius

Ursprung: Membrana interossea och distala delen av ulnas baksida. Fäste: Extensoraponeurosen till 2:a fingret. Indicis betyder pekfinger. Funktion: Extension av pekfingrets leder och handleden (art. radiocarpea). Innervation: N. radialis (C7-C8).

m. Extensor pollucis brevis

Ursprung: Radius baksida, membrana interossea. Fäste: Basen av tummens grundfalang, phalanx proximalis 1. Funktion: Extension i art. metacarpophalangeae pollicis. Innervation: N. radialis (C7-C8).

m. Extensor pollucis longus

Ursprung: Ulnas baksida, membrana interossea. Fäste: Basen av tummens ytterfalang, phalanx distalis 1. Funktion: Extends all joints of the thumb: carpometacarpal, metacarpophalangeal and interphalangeal Innervation: N. radialis (C7-C8).