The internal structure of the mussel.

Mussels do not have a very complex internal structure. The absence of a head and some digestive organs characteristic of other animals is due to anatomical features. At the base of the leg is a mouth that connects to a small esophagus that opens a passage to the stomach. A feature of mussels are unusual glands that produce strong protein formations of filamentous origin, consisting of synthesized liquid collagen, which harden and are used to attach to foreign objects – byssuses.
The leathery mantle is represented by folds of muscles and connective tissue covering the body on both sides of the cusps and fused at the back. It can change its shape and position by stretching and contracting. The shell valves are made by the outer layer of the mantle epithelium.