<prompt> Invertor of foot:GastrocnemiusTibialis posteriorPeroneus tertiusPeroneus longus  <response>: Ans. b Tibialis posterior Ref. BDC Vol. II 4thpg. -156 Tibialis anterior and Tibialis posterior are principal invertors of foot. Peroneus longus and Peroneus brevis are principal evertors of foot.TIBIALIS POSTERIOROriginPosterior aspect of interosseous membrane, superior 23 of medial posterior surface of fibula, superior aspect of posterior surface of tibia, and from intermuscular and deep transverse septum.Insertion Splits into two slips after passing inferior to plantar calcaneonavicular ligament Superficial slip inserts on the tuberosity of the navicular bone and sometimes medial cuneiform. Deeper slips insert on plantar surfaces of metatarsals 2-4 and second cuneiform.Actions Principal invertor of foot,0 Adducts foot, Plantar flexes ankle, and Helps to supinate the foot.InnervationTibial nerve L4, L5.Arterial SupplyMuscular branches of sural, peroneal and posterior tibial arteries. 