VH Dissector: Upper Limb: Posterior Arm & Forearm
VH Dissector: Upper Limb: Posterior Arm & Forearm
Embedded Files
Extensor Arm
Extensor Arm
The posterior compartment of the arm is also known as the extensor compartment of the arm. There are two muscles that reside in the posterior compartment of the arm. The only one of significance is the triceps brachii muscle which covers the entire posterior aspect of the arm.
Add the Anconeus muscle. Is the small muscle that is associated with the triceps at the elbow.
Origin - the lateral epicondyle of the humerus.
Insertion - the lateral side of the olecranon process and an adjacent part of the body of the ulna.
Innervation - the Radial nerve.
Action - There is much debate over the true function of this small muscle. Some anatomists argue it aids in elbow extension and others say it simply aids in the stability of the lateral aspect of the elbow joint. There is also speculation that it helps control valgus force at the elbow during extension movements. One can also speculate it may help to pull the joint capsule (which is redundant) out of the joint during flexion so as to not pinch the capsule in the joint.
Blood supply - the Profunda Brachii artery.
The Triceps Brachii is the muscle that covers the entire posterior aspect of the arm. The triceps, as the name implies, has three heads of origin; lateral head, long head, and medial head.
Add the Lateral Head of the Triceps Brachii muscle.
Origin of the lateral head - from the posterior surface of the humerus lateral to the radial groove and from the intermuscular septum. The lateral head and the long head merge to form the superficial portion of the triceps brachii muscle.
Add the Medial Head of the Triceps Brachii muscle.
Origin of the medial head - from the entire posterior surface of the humerus, inferior to the radial groove and from the medial and lateral intermuscular septum, inferior from where the radial nerve passes through the septum. It merges with the deep aspects of the long and lateral heads.
Add the Long Head of the Triceps Brachii muscle.
Origin of the long head - is a strong tendon on the infraglenoid tubercle of the scapula. It passes downwards between teres minor and teres major and separates the quadrangular space from the triangular space. This is the only part of the triceps to cross the shoulder joint.
Add the The entire Triceps Brachii muscle.
Insertion - a strong uniformed tendon which inserts on the olecranon process of the ulna.
Innervation - radial nerve.
Action - functions as a powerful elbow extensor and may contribute, weakly, to shoulder extension.
Blood supply - Profunda Brachii artery
Radial Nerve of the Arm
Radial Nerve of the Arm
Add the Radial nerve which is a direct continuation of the posterior cord of the brachial plexus
Add the Brachial artery The radial nerve enters the arm posterior to the brachial artery, medial to the humerus, and anterior to the long head of the triceps
The Radial nerve passes inferolaterally with the Profunda Brachii around the body of the humerus, the nerve pierces the lateral intermuscular septum and continues between the brachialis and brachioradialis muscles to the lateral epicondyle of the humerus, where it divides into deep and superficial branches.
The Radial nerve then continues between the Brachioradialis muscle to the lateral epicondyle of the humerus, where it divides into deep and superficial branches
Extensor Muscles of the Forearm
Extensor Muscles of the Forearm
The eleven muscles in the posterior aspect of the forearm are classified as extensors. They can be organized into functional groups as follows: muscles that extend the hand at the wrist (extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris); muscles that extend the fingers (extensor digitorum, extensor indicis, and extensor digiti minimi); and muscles that extend or abduct the thumb (abductor pollicis longus, extensor pollicis longus, and extensor pollicis brevis). They can also be organized into superficial and deep groups.
Deep Extensor Muscles
Deep Extensor Muscles
Remove the Brachioradialis and add the Supinator muscle.
Origin - Lateral epicondyle of the humerus, radial/lateral collateral ligament, annular ligament, and supinator crest of the ulna
Insertion - Lateral, posterior, and anterior surfaces of the proximal 1/3 of the radius
Innervation - Deep Branch Radial Nerve
Action - Supination of the forearm
Blood supply - Radial and posterior interosseous arteries.
Add the Extensor Indicis muscle.
Origin - Posterior surface of the ulna and the interosseous membrane
Insertion - Extensor hood of the index finger (2nd digit)
Innervation - Posterior Interosseous Nerve from the deep branch of the radial nerve
Action - Extends index finger and may aid in hand extension
Blood supply - Radial and posterior interosseous arteries
Add the Abductor Pollicis Longus muscle.
Origin - osterior surfaces of both the radius and ulna and interosseous membrane
Insertion - radial side of base of the first metacarpal and on trapezoid bone
Innervation - Posterior Interosseous Nerve from the deep branch of the radial nerve
Action - abducts the thumb and assists in wrist flexion; extends thumb at the carpometacarpal joint
Blood supply - Radial and posterior interosseous arteries.
Add the Extensor Pollicis Brevis muscle.
Origin - Posterior surface of the radius and interosseous membrane
Insertion - Base of the proximal phalanx of the thumb
Innervation - Posterior Interosseous Nerve from deep branch of radial nerve
Action - Extends thumb, may aid in wrist extension
Blood supply - Radial and posterior interosseous arteries.
Add the Extensor Pollicis Longus muscle.
Origin - Posterior shaft (middle 1/3) of the ulna and interosseous membrane
Insertion - Base of the distal phalanx of the thumb
Innervation - Posterior Interosseous Nerve from deep branch of radial nerve
Action - Extends thumb, may aid in wrist extension
Blood supply - Radial and posterior interosseous arteries.
Superficial Extensor Muscles
Superficial Extensor Muscles
Add the Extensor Digiti Minimi muscle.
Origin - Lateral epicondyle of the humerus
Insertion - Dorsal digital expansion of the 5th metacarpal
Innervation - Posterior Interosseous Nerve from the deep branch of the radial nerve
Action - Extends the little finger and the hand
Blood supply - Radial and posterior interosseous arteries.
Add the Extensor Carpi Ulnaris muscle.
Origin - Lateral epicondyle of the humerus and posterior border of ulna
Insertion - Medial side of the base of the 5th metacarpal
Innervation - Posterior Interosseous Nerve from the deep branch of the radial nerve
Action - Ulnar deviation and extension of wrist
Blood supply - Radial and posterior interosseous arteries.
Add the Extensor Digitorum muscle.
Origin - Lateral epicondyle of the humerus
Insertion - Dorsal aspect of the middle and distal phalanges of the four fingers
Innervation - Posterior Interosseous Nerve from the deep branch of the radial nerve
Action - Extends the fingers and the hand
Blood supply - Radial and posterior interosseous arteries.
Add the Extensor Carpi Radialis Brevis muscle.
Origin - Lateral epicondyle of the humerus
Insertion - Dorsal surface of the base of the 3rd metacarpal
Innervation - Deep Radial Nerve
Action - Radial deviation and wrist extension
Blood supply - Radial and posterior interosseous arteries.
Add the Extensor Carpi Radialis Longus muscle.
Origin - Distal lateral 1/3rd of the supracondylar ridge of humerus
Insertion - Dorsal surface of the base of the 2nd metacarpal
Innervation - Radial Nerve
Action - Radial deviation and wrist extension
Blood supply - Radial and posterior interosseous arteries.
Add the Brachioradialis muscle.
Origin - Proximal 2/3rds of lateral supracondylar ridge of humerus
Insertion - Lateral aspect of the base of the styloid process of the radius
Innervation - Radial Nerve
Action - Flexes the forearm when forearm is semi-pronated
Blood supply - Radial and posterior interosseous arteries.
Anatomical Snuff Box
Anatomical Snuff Box
The tendons of the abductor pollicis longus and extensor pollicis brevis bound the anatomical snuff box anteriorly, and the tendon of the extensor pollicis longus bounds it posteriorly. The radial artery crosses the floor of the snuff box. The scaphoid and trapezium can be felt in the floor of the anatomical snuff box and the radial styloid process can be palpated proximally.
Identify your anatomical snuff box and palpate the structures identified above.
Nerves of the Posterior Forearm
Nerves of the Posterior Forearm
The nerves of the posterior forearm are small and are not deliniated on this 3D cadaver.
Deep Branch of the radial nerve supplies the extensor carpi radialis brevis and the supinator muscles. When the deep branch of the radial nerve emerges from the supinator muscle and enters the posterior compartment of the forearm it is called the posterior interosseous nerve. It lies on the interosseous membrane where it is accompanied by the posterior interosseous artery. The posterior interosseous nerve supplies the extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, extensor indicies and the three thumb muscles.
Superficial Branch – continuation of the radial nerve. It passes deep to the brachioradialis muscle then at the wrist divides into four or five digital nerves. The distribution of the superficial branch of the radial nerve is cutaneous and articular. It supplies the lateral two-thirds of the dorsal surface of the hand and the dorsal surface of the lateral 2-3 ½ proximal phalanges.
Arteries of the Posterior Forearm
Arteries of the Posterior Forearm
The posterior aspect of the forearm and the hand is supplied by the posterior interosseous artery which arises from the common interosseous branch of the ulnar artery. The posterior interosseous artery passes through the interosseous membrane to the posterior aspect of the forearm.
As it reaches the posterior aspect of the wrist, the posterior interosseous artery ends by anastomosing with the termination of the anterior interosseous artery and the dorsal carpal arch. (Niether of these are visable on the 3D cadaver)
Credits:
Credits:
VH Dissector steps modified for Drexel Dissector by Dr. Haviva Goldman from original website activity created by Jeffrey Fahl, MD, Kyle Petersen, PhD, Richard Drake, PhD, Alesha Petitt, MA, Claira Ralston, MS and Kim Price, MA and modified by Jeffrey Fahl, MD, Michael Smith, PhD, Albany Medical College.
Page updated
Google Sites
Report abuse