Ans. a (Thenar).Deep thenar space infection occurs in the potential space between the palmar aponeurosis and the fascia overlying adductor policis, which contains not only the flexor pollicis longus tendon plus the neurovascular (NV) bundles to the thumb, but also the NV bundle on the radial side of the index plus the flexor tendons of the index. Therefore, a deep thenar space infection can involve both the thumb and the index finger.The pollical sheath extends distally almost to its insertion, and that part of the common sheath for the little finger usually does likewise. The ring, middle, and index fingers are provided with digital sheaths that usually extend proximally no further than the necks of their metacarpal bones, leaving a gap of 1 to 3 cm below the common sheath. Hence infection of the synovial sheaths of the thumb or little finger may spread along tendon sheaths readily into the palm and even into the forearm.Also remember:Hypothenar musclesMuscle Origin Insertion InnervationActionAbductor digiti minimi Pisiform}Medial side of}} Abducts little fingerFlexor digiti minimi brevis}Hooks of hamate}proximal phalanxDeep branch of ulnarFlexes little fingerOpponens digiti minimi Front of 5th metacarpal Draws 5th metacarpal forwardPalmaris brevis Medial border of palmar aponeurosis Skin on medial side of hand Superficialbranch of ulnarDeepens hollow of palm & protects ulnar nerve & arteryThenar MusclesMuscles Origin Insertion InnervationActionAbductor pollicis brevis}Flexor ratinaculum}Lateral sesamoid &} Abducts thumb Flexes thumbFlexor pollicis brevis}& tubercle of trapezium}base of proximal phalanx}Recurrent branch of medianRotates 1st metacarpalOpponens pollicis Lateral side of 1st metacarpal- mediallyAdductor pollicis Capitate, trapezoid, base of 2nd metacarpal {oblique head) & front of 3rd metacarpal (transverse head) Medial sesamoid & base of proximal phalanx Deep branch of ulnarAdducts thumb