ABSTRACT
There has been a mushrooming of basic and applied knowledge in this field, in the last 20 years, that has been marked by a number of reviews and books on the subject (1-5). The striated muscles to be considered are specialized in function, and they form groups of muscle on opposite sides of the body, which are subject to functional coordination that allows them to work together as a functional group. Within this overall concept there remain areas of muscle that are specialized for different tasks-the puborectalis or the fibers of levator ani that loop behind the urethra are examples-and one of the clear conclusions of the last decade or so has been that subdivisions of the muscle of the pelvic floor exhibit some functional differences. There are clear differences, for example, between the urethral sphincter, the associated paraurethral muscles, and the muscle fibers of the major part of levator ani. These differences extend to the histological and biochemical properties of the muscle fibers, the pattern and source of innervation, the reflex behavior, and the role in voluntary control of the lower urinary tract.
