We've got 2 short thumb muscles left – let’s wrap up this hand and do
the last two together!
One thing these two short thumb muscles have in common is that they are both "Brevis" :
Brevis meaning short – a strong hint that there is a
similar, longer version of this
muscle (ahem, see long muscles of the
thumb -or- 'big brothers:
Let's begin!
Abductor Pollicis
Brevis (3 or 4 short thumb muscles)
Abductor: this muscle abducts; performs the muscle action of
abduction
Pollicis: referring to the thumb
Brevis : meaning short
Muscle Attachment Points
Origin: Flexor Retinaculum (band of connective tissue inside the wrist) trapezium & scaphoid
tubercles (carpal (wrist) bones near the thumb)
Insertion: Base of the proximal phalange of the thumb
(about where thumb meets wrist ;)
Muscles Action (s):
a)
Abducts the thumb (at the carpo-metacarpal &
meta-carpo-phalangeal joints - see a picture of these joints below!)
b)
Assists in opposition of the thumb (see
previous post: Opponens Pollicis for action)
above: thumb abduction
Flexor Pollicis Brevis
(4 of 4 short muscles of the thumb)
Flexor: can perform muscle action of flexion
Pollicis: referring to the thumb
Brevis: meaning short
Muscle Attachment Points :
Origin: this muscle has two different origins or 'heads' one deeper than the other:
Superficial
Head: Flexor Retinaculum
Deep Head: Trapezium,
trapezoid and capitate (carpal/wrist bones*)
Insertion: Base of
the proximal phalange of the thumb (same insertion as Abductor Pollicis Brevis -above!)
*will have to someday do a post on the carpal bones – there
are eight of them that make up the wrist!))
Muscle Action (s) :
above: flexion of the thumb
a)
Flexes the thumb (at the carpo-metacarpal and
metacarpophalangeal joints)
b)
Assists in
opposition of the thumb (see previous post: Opponens Pollicis for action)
Both these short thumb muscles assist in opposition of thumb. See last weeks post Opponens Pollicis for a visual of opposition!
Okay wow! It only took over a YEAR but Muscle Monday has made it through the head,neck, shoulders, down the arms and hands - we're back in the Torso - next week!
