Muscles of the Posterior Forearm

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Questions and Answers

What is the main action of the Abductor pollicis longus?

Extends the metacarpophalangeal joint of the thumb

Adducts the carpo-metacarpal joints of the thumb

Flexes the wrist

Abducts the carpo-metacarpal joints of the thumb (correct)

Where does the Extensor pollicis longus insert?

Extensor expansion of the index finger

Base of the distal phalanx of the thumb (correct)

Base of the proximal phalanx of the thumb

Base of the metacarpal bone of the thumb

Which nerve supplies the Extensor indicis?

Ulnar nerve

Median nerve

Posterior interosseous nerve (correct)

Musculocutaneous nerve

What is the insertion point for the tendon of the Abductor pollicis longus?

Base of metacarpal bone of the thumb Signup and view all the answers

Which tendon is accompanied by the tendon of the Abductor pollicis longus?

Tendon of extensor pollicis brevis Signup and view all the answers

Which muscle's tendon extends all joints of the thumb?

Extensor pollicis longus Signup and view all the answers

What is the primary action of the Extensor pollicis brevis?

Extends the metacarpophalangeal joint of the thumb Signup and view all the answers

Which finger does the Extensor indicis primarily act on?

Index finger Signup and view all the answers

Which muscle extends the metacarpo-phalangeal and interphalangeal joints of the medial 4 fingers?

Extensor digitorum Signup and view all the answers

What is the action of the extensor carpi ulnaris?

Extends and adducts the wrist joint Signup and view all the answers

Which nerve supplies the anconeus muscle?

Posterior interosseous nerve Signup and view all the answers

What is the origin of the supinator muscle?

Lateral epicondyle of the humerus Signup and view all the answers

The extensor digiti minimi primarily functions to extend which part?

The extensor expansion of the little finger Signup and view all the answers

Which muscle helps in the extension of the wrist joint?

Extensor digitorum Signup and view all the answers

Which of the following muscles is NOT part of the deep group of the posterior compartment of the forearm?

Extensor carpi ulnaris Signup and view all the answers

What is the insertion point for the supinator muscle?

Lateral surface of the radius Signup and view all the answers

What action is primarily associated with the brachioradialis muscle?

Elbow joint flexion Signup and view all the answers

Which nerve supplies the extensor carpi radialis longus muscle?

Radial nerve Signup and view all the answers

What is the main action of the extensor digitorum muscle?

Extension of the proximal phalanx Signup and view all the answers

The insertion of the extensor carpi radialis brevis is located at which bone?

Base of the 3rd metacarpal bone Signup and view all the answers

Which muscle primarily functions to abduct the thumb?

Abductor pollicis longus Signup and view all the answers

What is the origin of the extensor carpi radialis longus muscle?

Lower 1/3 of lateral supracondylar ridge Signup and view all the answers

Which muscle is innervated by the posterior interosseous nerve?

Extensor carpi radialis brevis Signup and view all the answers

Which muscle is responsible for extending and abducting the wrist?

Extensor carpi radialis longus Signup and view all the answers

Study Notes

Muscles of the Posterior Compartment of the Forearm

The extensor group of muscles in the posterior forearm are innervated by the radial nerve and its posterior interosseous branch.
These muscles act on the digits (digitorum), thumb (pollicis), and wrist (carpi).
Superficial group muscles include: brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris and anconeus muscle.
Deep group muscles include: supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.

Brachioradialis

Origin: upper two-thirds of the lateral supracondylar ridge of the humerus.
Insertion: lateral surface of the lower end of the radius, just above the styloid process.
Nerve supply: radial nerve.
Action: 1. Position the forearm in a mid-pronation/supination position; 2. Flex the elbow joint.

Extensor Carpi Radialis Longus

Origin: lower one-third of the lateral supracondylar ridge of the humerus.
Insertion: base of the second metacarpal bone.
Nerve supply: radial nerve, running along the lateral side of the arm.
Action: extends and abducts the wrist.

Extensor Carpi Radialis Brevis

Origin: lateral epicondyle of the humerus (from the common extensor).
Insertion: base of the third metacarpal bone.
Nerve supply: posterior interosseous nerve (on the front of the elbow, before piercing the supinator).
Action: extends and abducts the wrist.

Extensor Digitorum

Origin: common extensor origin from the lateral epicondyle of the humerus.
Insertion: base of the middle and distal phalanges of the middle four fingers.
Nerve supply: posterior interosseous nerve.
Action: extends the metacarpophalangeal and interphalangeal joints of the medial 4 fingers, and helps extend the wrist.

Extensor Digiti Minimi

Origin: common extensor origin, lateral epicondyle of the humerus
Insertion: the extensor expansion of the little finger.
Nerve supply: posterior interosseous nerve
Action: Extends all joints of the little finger.

Extensor Carpi Ulnaris

Origin: common extensor origin, lateral epicondyle of humerus and the posterior border of the ulna.
Insertion: base of the fifth metacarpal bone
Nerve supply: posterior interosseous nerve.
Action: extends and adducts the wrist (pure adduction if acting with flexor carpi ulnaris).

Anconeus

Origin: lateral epicondyle of the humerus and posterior surface of the lateral ulna.
Insertion: olecranon process of the ulna and posterior surface of the proximal, upper 1/4 of the ulna.
Nerve supply: radial nerve.
Action: Extends the elbow joint.

Supinator

Origin: superficial part from the lateral epicondyle, and radial collateral ligament of the elbow, deep part from supinator crest and fossa.
Insertion: upper one-third of the lateral surface of the radius.
Nerve supply: posterior interosseous nerve.
Action: supinates the forearm.

Abductor Pollicis Longus

Origin: upper part of the posterior surface of the ulna (below anconeus), middle one-third of the posterior surface of the radius (below supinator).
Insertion: base of the first metacarpal.
Nerve Supply: posterior interosseous nerve.
Action: abducts the carpometacarpal joints of the thumb and abducts the wrist.

Extensor Pollicis Brevis

Origin: posterior surface of the radius (below supinator), interosseous membrane.
Insertion: base of the proximal phalanx of the thumb
Nerve supply: posterior interosseous nerve.
Action: extends the metacarpophalangeal joint and abducts the thumb.

Extensor Pollicis Longus

Origin: middle third of the posterior surface of the radius, interosseous membrane
Insertion: base of the distal phalanx of the thumb
Nerve supply: posterior interosseous nerve.
Action: extends the metacarpophalangeal and interphalangeal joints of the thumb and abducts the wrist.

Extensor Indicis

Origin: lower part of the back of the ulna below the extensor pollicis longus, the back of the interosseous membrane.
Insertion: the extensor expansion of the index finger (with the extensor digitorum tendon.
Nerve supply: posterior interosseous nerve.
Action: extends the index finger.

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Description

This quiz covers the extensor group of muscles located in the posterior compartment of the forearm, including their innervation, actions, and specific muscles such as brachioradialis and extensor carpi radialis longus. Gain a deeper understanding of the muscular anatomy and their functions in relation to forearm movements.