Retinaculum \Ret`i*nac"u*lum\, n.; pl. Retinacula. [L., a
   holdfast, a band. See Retain.]
   1. (Anat.)
      (a) A connecting band; a fraenum; as, the retinacula of
          the ileocaecal and ileocolic valves.
      (b) One of the annular ligaments which hold the tendons
          close to the bones at the larger joints, as at the
          wrist and ankle.
          [1913 Webster]

   2. (Zool.) One of the retractor muscles of the proboscis of
      certain worms.
      [1913 Webster]

   3. (Bot.) A small gland or process to which bodies are
      attached; as, the glandular retinacula to which the
      pollinia of orchids are attached, or the hooks which
      support the seeds in many acanthaceous plants.
      [1913 Webster]