Hobbies And Interests
Overall shape
Phylum members share a basic body outline that is flattened along both its length and its width. Flatworms are not segmented, like more complicated worm species such as earthworms. They have three fundamental cell layers: an outer epidermis, a middle layer and a distinct lining of the gut. The worms lack a body cavity, although they do have organs for breathing and digestion.
Digestion and Excretion
Flatworms have simple, muscular mouths near one end of their bodies that they use to suck in food. They may have a branched gut, spreading throughout the body. This system absorbs nutrients directly into the body's cells. Flatworms do not have anuses; once nutrients have been extracted from the food, the waste is expelled through the mouth.
Nervous System
Platyhelminthes have very simple nervous systems. Sensory cells are concentrated near the worm's front end, a structure known scientifically as cephalization. Phil Myers, of the University of Michigan's Museum of Zoology, explains that this structure in flatworms takes the form of a pair of nerve cells and a ladderlike set of sensory nerves down the length of the body. These sensory cells are specialized, detecting light, balance, water movement and smells.
Musculature
The three-layer structure of flatworms is known scientifically as a triploblastic. Muscle fibers are distributed throughout the body's mass of organ and sensory cells. These muscle fibers are not striated, which means that they are not made up of parallel bundles, like the skeletal muscles of more complex creatures. Layers of muscle control movement in some flatworms, but some move by secreting slime trails.