Anterior part of the ciliary muscles of a pigeon (HE)
The ciliary muscles are striated muscles that can be divided in three groups based on insertion and origin. This division differs according to species. In chickens and pigeons most of the ciliary muscle fibers are part of the anterior muscle.
On the micrograph above, the anterior muscle (m. ciliaris anterior) or Cramptonâ€™s muscle is shown. This muscle originates at the sclera underneath the ossicles and inserts on the internal surface of the cornea and sinus venosus sclerae. Contraction changes the curvature of the cornea.