Describe the attachments of the interossei and lumbricales to the extensor mechanism. How do these attachments enable these muscles to contribute to interphalangeal (IP) extension?

What will be an ideal response?

ANS:
The "proximal" interossei (each metacarpophalangeal [MCP] abductor has a proximal attachment) attach to the hood of the extensor mechanism, and the "distal" interossei attach to the lateral bands. (All interossei have distal attachments except the first dorsal and AbDM). While the proximal interossei can generate some tension on the extensor mechanism through a pull on the hood, the primary contribution of the interossei to IP extension is through pull of the distal attachments on the lateral bands. The lumbricales each attach to a lateral band (radial) of each extensor mechanism, attaching more distally than any interossei, making the lumbricales better IP extensors.