Our wrist EXTENSOR muscles live in our forearms, more specifically,
they all hang out on the side of our arm that turns into the top/back
of our hands. Wrist EXTENSOR muscles help to lift your hand up as if to
say 'hello' ! Today we're going to talk about TWO wrist extensor
muscles :
1) Extensor Carpi Radialis BREVIS &
2) Extensor Carpi Radialis LONGUS
1) Extensor Carpi Radialis BREVIS &
2) Extensor Carpi Radialis LONGUS
Let's break down each word so it makes a bit more sense!
- EXTENSOR meaning that they extend
- CARPI meaning the carpal bones of the WRIST
(these muscles extend the wrist!)
-
RADIALIS referring to the radius bone in the arm. The radius is in line
with our thumb* - therefore these muscles extend down the thumb side of
our arm.
- BREVIS meaning SHORT & LONGUS meaning LONG ;)
Extensor Carpi Radialis Longus & Brevis ATTACHMENT POINTS:
Origin:
BOTH Extensor Carpi Radialis Longus AND Brevis attach at the same point
just above the elbow > onto the upper arm bone (the Humerus bone)
(officially "the lateral supracondylar ridge of the humerus)
(then they both extend down the radius bone...)
Insertion points:
1) Extensor Carpi Radialis BREVIS attaches at the base of the THIRD metacarpal
2) Extensor Carpi Radialis LONGUS attaches at the base of the SECOND metacarpal
METACARPAL aka "where your knuckle meets your finger"
(our thumb is considered the "first metacarpal" and so on...
*to help remember which of the two forearm bones (RADIUS or ULNA) is on which side I think "RAD dude - thumbs up!" Because the RADius is the bone that extends to the thumb (up!) side!
MUSCLE ACTIONS:
Both BREVIS and LONGUS perform the SAME THREE actions so that easy!
1) no surprise here that these two wrist extensors EXTEND THE WRIST at the radio-carpal joint > (where radius bone meets the Carpal bones of the wrist - on the Thumb side!)
2) they also ABDUCT the wrist at the radio-carpal joint
> tipping the wrist towards the Radial (thumb) side ((like if you were giving someone a "thumbs up" and then you pointed your thumb towards your face))
1) no surprise here that these two wrist extensors EXTEND THE WRIST at the radio-carpal joint > (where radius bone meets the Carpal bones of the wrist - on the Thumb side!)
2) they also ABDUCT the wrist at the radio-carpal joint
> tipping the wrist towards the Radial (thumb) side ((like if you were giving someone a "thumbs up" and then you pointed your thumb towards your face))
that was really hard to describe so if it doesn't make sense be sure to check out the video version!
3)
Surprise! These two muscles also assist in FOREARM FLEXION (aka -
bending your arm at the elbow!) Can you guess why? Remember how both
muscles CROSS the elbow joint and attach onto the Humerus (the upper arm
bone) ?
In that order : wrist extension & abduction (aka radial deviation) and forearm (elbow) flexion !
Whenever a muscle Crosses a JOINT it WILL create an
action of some sort. Extensor Carpi Radialis Brevis and Longus BOTH
cross the elbow joint and the wrist joint - creating actions of both
joints!
