Cephalopod mantle muscle

The mantle membrane of cephalopods is multimuscular, including radiating muscles and circular muscles. The mantle is connected to the body wall on the back of the body, free on the ventral surface, and the space between the internal organs forms a mantle cavity. The funnel formed by the specialization of the foot is located at the front end of the ventral trunk of the body. It is also a muscular structure. 

The front end of the funnel is slender, and its opening points to the front end. The back end of the funnel is wide and can extend into the coat cavity. There is cartilage on both sides of the back end of the funnel. The depression and the cartilaginous process at the front end of the ventral edge of the mantle form a socket and knob to close the opening of the mantle cavity.

The mantle forms a fin on the edge of the trunk, which acts as a rudder during movement. In addition, many types of bodies form a streamlined shape, making their movement speed the fastest among aquatic invertebrates.