\Ret`i*nac"u*lum\, n.; pl. {Retinacula}. [L., a
holdfast, a band. See {Retain}.]
1. (Anat.)
   (a) A connecting band; a fr[ae]num; as, the retinacula of
       the ileoc[ae]cal 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.

2. (Zo["o]l) One of the retractor muscles of the proboscis of
   certain worms.

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.