We are moving into the Muscles of Thumb! Guess what there are EIGHT of them! 4 long and 4 short! We'll be starting with the long muscles of the thumb..
Starting with: Flexor Pollicis Longus - one of four LONG thumb muscles.
Flexor: meaning that it probably performs the muscle action of flexion ;)
Pollicis: latin word for thumb
Longus: usually indicates that there is a short version of this muscle (for example , yes! there IS a Flexor Pollicis Brevis ('brevis' = short, small, or brief)
Did you know that this muscle that curls our thumb starts all the way up at the elbow? Then it ends at almost the tip of your thumb!
Official Attachment Points:
Origin: medial epicondyle of the humerus, (that bump on inside of elbow) the coranoid process of the ulna (bump on one of two forearm bones, just below elbow) << some text does not include these first two points), the interosseus membrane (connective tissue that stretches between the two forearm bones: radius and ulna) and the anterior surface of the radius.
Insertion: base of the phalanx of the thumb
flexion of the thumb athe CMC, MCP, and IP joints*
*CMC = Carpo-Meta-Carpal joint
MCP = Meta-Carpal-Phalangeal joint
IP = Inter-Phalangeal joint (The thumb is the only digit with just an interphalangeal joint. The fingers have two joints, there is a proximal and distal IP joint remember?) In this case the flexion is happening at the IP joint of the thumb :)