Peduncle (anatomy) of a fish where the caudal fin meets the spine. Peduncle (anatomy) A peduncle is an elongated stalk of tissue. Sessility is the state of not having a peduncle; a sessile mass or structure lacks a stalk. In medicine, a mass such as a cyst or polyp is said to be "pedunculated" if it is supported by a peduncle. There are in total three types of peduncles in the cerebellum of the human brain, known as superior cerebellar peduncle, middle cerebellar peduncle, and inferior cerebellar peduncle. Pedunculated eyes are also the defining attribute of the Stylophthalmine trait found in certain
Operculum (gastropod) shell when the soft parts of the animal are retracted. The shape of the operculum varies greatly from one family of gastropods to another. It is fairly often circular, or more or less oval in shape. In species where the operculum fits snugly, its outline corresponds exactly to the shape of the aperture of the shell and it serves to seal the entrance of the shell. Many families have opercula that are reduced in size, and which are not capable of closing the shell aperture. Opercula have sometimes been modified: in the Strombidae the operculum is claw-shaped and is used