Human Anatomy: Supinator Muscle and Deep Extensors

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the supinator muscle?

Stabilization of the elbow joint

Flexion of the forearm

Extension of the forearm

Slow, unopposed supination of the forearm (correct)

Which nerve passes between the fibers of the supinator muscle?

Ulnar nerve

Median nerve

Musculocutaneous nerve

Deep branch of the radial nerve (correct)

During rapid supination against resistance, which muscle acts as the prime mover?

Supinator

Biceps brachii (correct)

Triceps brachii

Brachialis

Where does the deep branch of the radial nerve emerge after penetrating the supinator muscle?

Posterior compartment of the forearm Signup and view all the answers

Which muscles are referred to as outcropping muscles of the thumb?

Abductor pollicis longus and extensor pollicis brevis Signup and view all the answers

What is the anatomical position of the abductor pollicis longus in relation to the supinator?

Distal to the supinator Signup and view all the answers

How does the deep branch of the radial nerve relate to the radial nerve in the cubital fossa?

It separates into deep and superficial branches Signup and view all the answers

What connects the posterior interosseous nerve to the posterior interosseous artery?

The supinator muscle Signup and view all the answers

What movement primarily tests the abductor pollicis longus?

Thumb abduction against resistance at the metacarpophalangeal joint Signup and view all the answers

Where can the tendon of the extensor pollicis brevis be palpated?

Lateral side of the anatomical snuff box Signup and view all the answers

What forms the floor of the anatomical snuff box?

Scaphoid and trapezium bones Signup and view all the answers

Which muscle aids in the adduction and lateral rotation of the extended thumb?

Extensor pollicis longus Signup and view all the answers

Which action tests the extensor pollicis longus?

Extension of the thumb at the interphalangeal joint Signup and view all the answers

The gap created between the long extensor tendons of the thumb is known as what?

Anatomical snuff box Signup and view all the answers

In which location can the radial artery be found?

In the anatomical snuff box Signup and view all the answers

What is the relative size and length of the extensor pollicis longus compared to the extensor pollicis brevis?

Larger and longer than EPB Signup and view all the answers

What differentiates the extensor indicis from other extensor muscles?

It allows for independent movement of the index finger Signup and view all the answers

Which muscle lies immediately medial to the extensor pollicis brevis?

Extensor pollicis longus Signup and view all the answers

Study Notes

Supinator Muscle

Located deep in the cubital fossa, forming part of its floor, alongside the brachialis.
Sheet-like muscle, spiraling medially and distally from its origin, enveloping the radius's neck and proximal shaft.
The radial nerve (deep branch) passes through its fibers, dividing it into superficial and deep parts.
Primary function: Slow, unopposed supination of the forearm, especially when extended.
The biceps brachii is the primary mover during rapid, forceful supination against resistance, when the forearm is flexed.

Deep Extensors of the Forearm

Act on the thumb (abductor pollicis longus, extensor pollicis longus, and extensor pollicis brevis) and the index finger (extensor indicis).
These muscles are deep to the superficial extensors, emerging from the forearm's lateral furrow.

Abductor Pollicis Longus (APL)

Long, fusiform muscle belly, situated distal to the supinator, closely associated with the extensor pollicis brevis.
Tendon often splits, one part potentially attaching to the trapezium instead of the base of the 1st metacarpal.
Function: Abduction of the thumb and extension of the thumb with extensor pollicis muscles.
One of the outcropping muscles, emerging at the wrist, passing deep to the extensor retinaculum.

Extensor Pollicis Brevis (EPB)

Fusiform, short extensor of the thumb, lying distal to the APL, partially covered by it.
Tendon lies parallel and medial to the APL's tendon, extending to the base of the proximal phalanx.
Function: Extends the proximal phalanx of the thumb, 1st metacarpal, and extends and abducts the hand when the thumb is fully extended
Forms part of the anatomical snuff box.

Extensor Pollicis Longus (EPL)

Larger muscle with a longer tendon than EPB, passing under the extensor retinaculum in its own tunnel.
Uses the dorsal tubercle of the radius as a trochlea to alter its line of pull to the distal phalanx.
Creates the gap between the thumb's long extensor tendons forming the anatomical snuff box.
Function:Extends the thumb at the interphalangeal joint, adducts and laterally rotates the extended thumb.

Extensor Indicis

Narrow, elongated muscle, medial to and alongside the EPL.
Function: Provides independent action to the index finger, extending it at the proximal interphalangeal joint (pointing) and extending the hand.

Anatomical Snuff Box

Triangular hollow visible on the radial aspect of the wrist when the thumb is fully extended.
Bounded by the APL and EPB tendons anteriorly, and the EPL tendon posteriorly.
Contains the radial artery, which courses through the floor (scaphoid and trapezium bones).
Radial styloid process and base of the 1st metacarpal are palpation points within the snuff box.

Testing Muscles

Testing involves abduction, extension, or specific actions of the thumb, index finger against resistance to identify possible abnormalities/issues.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the anatomy and functions of the supinator muscle and the deep extensors of the forearm. Test your knowledge on their locations, roles, and anatomical relationships. Perfect for students of human anatomy and physiology.