Forearm Flashcards
(39 cards)
Muscles in the posterior compartment of the forearm perform which movement?
How does this differ to muscles in the anterior compartment?
Posterior compartment contains extensor muscles
They produce extension at the wrist and fingers
Anterior compartment contains flexor muscles
Brachioradialis flexes the elbow. At which forearm position is it most effective?
Neutral position
Imagine a soldiers arms as he marches
What is the function of brachioradialis?
In which forearm position does it merely assist in this function?
Brachioradialis flexes the elbow
In the supinated position (soup, please) brachioradialis only assists flexion. It is less effective than in the neutral position.
Brachioradialis:
Origin?
Insertion?
Origin- proximal aspect of the lateral supracondylar ridge of the humerus
Insertion- next to the radial styloid process (distal)
How many muscles are in the superficial compartment of the posterior forearm?
Name them.
7
(Lateral) Brachioradialis Extensor carpi radialus longus Extensor carpi radialis brevis Extensor digitorum digitorum Extensor digiti minimi Extensor carpi ulnaris Anconeus
Extensor carpi radialus longus Extensor carpi radialis brevis Extensor carpi ulnaris Which muscles are these? What is their common origin? What does carpi mean?
All superficial muscles of the posterior compartment
Insert onto the metacarpals of the hand
metacarpals link the carpals (wrist bones) to the phalanges (finger bones)
Carpi means wrist
All muscles of the posterior compartment are innervated by which nerve?
Radial nerve
What is the common extensor origin? (for some superfical muscles)
Lateral epicondyle
Which of the 7 superfical extensor muscles do not originate at the lateral epicondyle?
Lateral epicondyle = common extensor origin
Brachioradialis, extensor carpi radialis longus and anconeus do not originate here
Extensor carpi radialis longus shares the same origin as which other superficial posterior muscle?
What is the origin?
Brachioradialis
Both originate from the lateral side of the supracondylar ridge of the humerus
Which other movement at the wrist do extensor carpi radialis longus (ECRL) and brevis (ECRB) perform?
How are they able to do this?
Abduction
Due to position on the radial side of the forearm
Where do ECRL and ECRB insert?
How does their innervation differ?
Longus- dorsal (posterior) surface of the base of the 2nd metatarsal bone
(thumb is 1st)
Brevis- dorsal (posterior) surface of the base of the 3rd metatarsal bone
Both innervated by the radial nerve
ECRB innervated by the deep branch of the radial nerve (nerve branches into superficial and deep).
There are 2 ‘extensor digitorum…’ muscles in the body.
What are their full names and different locations?
Extensor digitorum longus = foot
Extensor digitorum (communis) = superficial compartment of the posterior forearm
What and where is the radial groove?
Shallow depression for the radial nerve and deep brachial artery
In the center of the lateral border of the humerus
The radial nerve emerges from the radial groove on which side of the arm?
It emerges 5cm beneath which tuberosity?
Lateral side (radial)
The deltoid tuberosity (where deltoid muscle inserts)
Describe the anatomical course of the radial nerve, beginning at the radial groove
- Radial nerve emerges from the radial groove on the lateral side of the arm.
- Gives off muscular branches to the brachioradialis and extensor carpi radialis longus
(plus a small supply to the brachialis) - Pierces the lateral intermuscular septum to enter the anterior compartment
- Travels through the cubital fossa anterior to the lateral epicondyle of the humerus
- Divides within the cubital fossa to give the superficial and deep branches
- Superfical branch (sensory) innervates dorsal surface of the lateral 3.5 digits (begin at thumb)
- Deep branch innervates extensor carpi radialis brevis and supinator muscles
- Deep branch exits cubital fossa posteriorly between 2 heads of the supinator and enters the posterior compartment of the forearm. Now called the posterior interosseous nerve
- Innervates all remaining muscles of the posterior forearm (superficial and deep).
When does the radial nerve become the posterior interosseous nerve?
When it enters the posterior compartment of the forearm (after passing between the 2 heads of the supinator)
Where does the extensor digitorum originate and insert?
Common extensor origin (lateral epicondyle of humerus)
Splits into 4 tendons and inserts into the extensor hoods of the 4 fingers
Why can’t you fully extend the middle finger if your other fingers are flexed?
(finger flexion points downwards/ fist)
The 4 tendons of digitorum longus are linked (on the dorsal surface) by juncturae tendinum (fibrous bands).
Thus the finger is tethered to its flexed counterparts.
How many muscles are in the superficial posterior compartment of the forearm?
The posterior interosseus nerve innervates which muscles of the superficial posterior compartment?
How are the other muscles innervated?
7 superficial muscles
The medial 3:
Extensor digitorum
Extensor digiti minimi
Extensor ulnaris
- Radial nerve innervates brachoradialis and extensor carpus radialis longus.
- Deep radial nerve innervates extensor carpi radialis brevis.
Role of the extensor digitorum muscle?
Main extensor of the fingers
Extends at the metacarpophalangeal and interphalangeal joints
Where does extensor digiti minimi insert?
What is its role?
Inserts into the extensor hood of the little finger (ulnar/ medial side)
Extends the little finger and assists in wrist extension
Which superficial posterior muscle has 2 heads?
Where do they originate and insert?
Extensor carpi ulnaris
- Humeral head originates at common extensor origin (lateral epicondyle of humerus)
- Ulnar head originates at the olecranon process of the ulnar
- Both insert at the base of the fifth metacarpal
Function of extensor carpi ulnaris?
Extends the wrist
Adducts the wrist (due to position on the ulnar side)
