Opponens pollicis
- Inserts on the lateral side of the first metacarpal
- Provides thumb opposition.
Hand - Thenar & Adductor
Bones
Radius
Ulna
Hand
Key Points:
- The muscles of the thenar and adductor compartments of the hand act on digit 1, the thumb.
- Adduction of the digits moves them towards the midline (digit 3).
- Abduction of the digits moves them away from it.
Thenar Compartment
- Each thenar muscle originates on the flexor retinaculum and trapezium.
- Inserts on the lateral side of the first metacarpal
- Provides thumb opposition.
- Inserts on base of proximal phalanx of the thumb
- Flexes the thumb.
- In addition to arising from the flexor retinaculum and trapezium, also originates on the scaphoid.
- Inserts on the lateral side of the base of the proximal phalanx,
- Abducts the thumb away from the plane of the palm.
- Abductor pollicis brevis also assists opponens pollicis in the early stages of opposition.
Adductor compartment
Adductor pollicis, which has two heads:
- Oblique head originates on the bases of the 2nd and 3rd metacarpals and the capitate
- Oblique head inserts on the medial side of the base of the proximal phalanx of the thumb;
- Transverse head originates on the anterior surface of the third metacarpal;
- Transverse head inserts with the oblique head on digit 1.
- Together, the oblique and transverse heads adduct the thumb.