Forearm Extensor Aspect Flashcards
Role of muscles on back of forearm
They serve largely to extend the fingers and thumb either during release of a grip or prior to making a grasp
wrist extensors role
particularly important in making a fist and in facilitating the power grip
front of the forearm muscles of the posterior compartment can be divided into different groups depending on…
Depth
How many extensor muscle groups and what are they
2 Groups: Superficial and Deep
What are the superficial muscles of the front forearm muscles and Where do they arise from/go to
- role
Two of the superficial muscles brachioradialis (BR) and extensor carpi radialis longus (ECRL) arise from the lateral supracondylar line of the humerus and pass in front of the elbow, thereby actually flexing it.
What other muscles also come from the common extensor tendon
Extensor carpi radialis brevis, (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM) and extensor carpi ulnaris (ECU) arise from the lateral epicondyle by way of the common extensor tendon, and ECU also has a significant aponeurotic attachment to the posterior border of the ulna. Technically Anconeus (A) also belongs to this grou
What makes up the deep group and where do they arise from
supinator, abductor pollicis longus (APL), extensor pollicis longus (EPL) and brevis (EPB), and extensor indicis (EI) arise from various parts of the ulna, interosseous membrane and radius
Supinator inserts where… to… and is aided by…
Supinator (SuP) inserts in the antero-lateral aspect of the radius to remove the forearm from pronation, aided by that part of biceps brachii that inserts into the radial tuberosity on the radius.
o = lateral epicondyle
Defining characteristic of the extensor compoartment
All muscles of the extensor compartment are innervated by the radial nerve.
Long tendons of the extensor muscle pass through how many tunnels and where
The long tendons of the extensor muscles pass through 6 or 7 tunnels under the extensor retinaculum which is slightly proximal to the wrist.
Summary of the functional classification of extensor muscles
Group:
Number in group:
Muscles involved:
Location:
*Role for last group instead
Group: Act upon wrist
3 in group
- ECRL (extensor carpi radialis longus)
- ECRB (Extensor carpi radialis brevis)
- ECU (extensor carpi ulnaris)
Location:
ECRL: base of 2nd metacarpal
ECRB:base of 3rd metacarpal
ECUbase of 5th metacarpal
Group: Act on thumb
3 in group
- APL (supinator, abductor pollicis longus)
- EPB (extensor pollicis brevis)
- EPL (extensor pollicis longus)
Location:
APL: base of 1st metacarpal
EPB: base of proximal phalanx
EPL: base of distal phalanx
Group: Extend fingers:
3 in group
- ED (extensor digitorum)
-EI (extensor indicis)
-EDM (extensor digiti minimi)
Location:
all attach to Dorsal Digital Exapansion Hood (DDEH) of appropriate digit(s)
Group: Act upon forearm only *dont extend onto the wrist or hand)
3 in group
-Anconeus
- Brachioradialis
-Supinator
Role:
-Anconeus (Extend elbow
- Brachioradialis (Flex elbow)
-Supinator (Supinates forearm (along with biceps)
Tip for remembering group muscles
Those that act on wrist all have CARPI in name
Those that act on thumb all have POLLICIS in name
Nerve Supply to forearm muscles
- Name of nerve
- Number of muscles
- Name of muscles
- Forearm compartment (aka role)
- Median (ALL anterior forearm muscles except FCU)
6.5 muscles
PT, FCR, PL, FDS, FPL, PQ and Lateral half of FDP
- Flex and pro - Ulnar
1.5 muscles
FCU & Med. half FDP
Flex/Pro - Radial (ALL posterior muscles)
12 muscles
- Superficial = BR, A, ECRL, ECRB, ED, EDM, ECU
- Deep = EI, EPL, APL, EPB, SuP
Ext/Sup
radial nerve innverates all …
All muscles of the extensor compartment are innervated by the radial nerve.
All except brachioradialis and ECRL by its deep (interosseous) branch. The superficial branch is entirely cutaneous (unless it supplies ECRB ).
Cutaneous innervation is by…
Cutaneous innervation is by the medial cutaneous nerve of the forearm (from the medial cord of brachial plexus) medially
the lateral cutaneous nerve of the forearm (terminal portion of musculocutaneous nerve from the lateral cord) laterally
the posterior cutaneous nerve of the forearm (a branch of the radial) posteriorly.
Blood supply to the back of the forearm is by…
the posterior interosseous artery (a branch of the common interosseus off the ulnar artery) except distally where the anterior interosseus artery passes back through a gap in the interosseus membrane to either augment or often replace the supply from the posterior interosseus artery.
Name the 7 Superficial extensor
muscles of the forearm and locate them on diagram
- Brachioradialis
- Anconeus
- Extensor carpi ulnaris
- Extensor digiti minimi
5.Extensor digitorum - Extensor carpi radialis longus
- Extensor carpi radialis brevis
Insertion points for Superficial extensor
muscles
- Brachioradialis
-base of radial styloid
process - Anconeus
- Back of ulna - Extensor digiti minimi
- DDEH of little finger
4.Extensor digitorum
- DDEH of all four fingers
- Extensor carpi radialis longus
- Base of 2nd metacarpal - Extensor carpi radialis brevis
-Base of 3rd metacarpal - Extensor carpi ulnaris
- Base of 5th metacarpal
What carpi muscles are flexors and what ones are extenders?
Flexors:
FCR, FCU, ECU
Extendors
ECRL
ECRB
Lecture slide
5 Deep extensor muscles of the forearm and their insertion points
- Supinator
(Deep head)
- Crest just beside radial notch - Supinator (superifical head)
- lateral epicondyle - Extensor pollicis longus
- base distal phalanx - Extensor pollicis brevis
- base prox. phalanx - Abductor pollicis longus
- base 1st metacarpal - Extensor indicis
- DDEH
Where does raidal nerve sit in relative to Supinator heads
Nerve divides into 2 as approaches sipunator heads. Deep part goes between the two heads of supinator
Superifical branch does not go between the 2 heads.
Superior view of the cross section through the right forearm
Lecture Slide
Label the different areas of the radial branch
- radial nerve
- Deep branch
3.Posterior interosseous nerve - Superifical branch
Label the complete diagram of the forearm (Full nerve supply with what muscle is being innervated)
*colourful diagram
**Just need to know that back of forearm is innervated by radial nerve
Need to know what part of radial nerve is innervating it (muscles)
Radial Nerve innervates:
- Triceps
- Brachioradialis
- ECRL
Deep Branch
- ECRB
-Supinator
Posterior interosseous nerve
- ED
-EDM
- ECU
-Abductor polloicies longus
-Extensor pollicies longus
- EI
- EPB
Superifical branch
- Cutaneous only supplying dorsal surace of hand
What muscle from the anterior forearm has the same origin as the superifical muscles in extensor compartment
Pronator teres origin is supracondylar ridge of humerus
Same as the Origin for Brach, Aconeurosis and ECRL
what blood supplies the deep muscles of forearm
anterior interossei artery = supplies all the anterior muscles of forearm. runs with anterior interosseous
nerve along interosseous membrane between flexor policis longus & flexor digitorum profundus
Blood supply to the back of the forearm is by the posterior interosseous artery (a branch of the common interosseus off the ulnar artery)
