Describe the function of abductor hallucis as a function of its origin, insertion, placement and path in the body.
Abductor hallucis is an intrinsic muscle of the foot in the 1st layer of the foot. It originates on the medial process of the calcaneal tuberosity and runs along the medial inferior border of the foot. The muscle belly fibers transition to tendon around the base of the 1st MT and the tendon inserts onto the medial side of the base of the 1st proximal phalanx. Because it runs on the medial plantar surface of the foot and across the MTP joint it can abduct the 1st digit at the MTP joint: contraction of the fibers will pull posteriorly and medially at the base of the 1st MTP, inducing abduction. It can flex the first digit at the MTP joint because it also runs somewhat inferiorly and across the 1st MTP joint.