Dr. Sherine Aubert describes the ischiocavernosus muscle, part of the superficial (or outermost) layer of the pelvic floor.
Ischiocavernosus is primarily a sexual muscle. It is attached to the erectile connective tissue, runs along the pubic ramus (a section of the pubis bone) and attaches to the sitz bones or ischial tuberosities (the bones you feel when you sit). Its purpose is to help create clitoral erections. This is why we can and should see a clitoral nod (think like a head nodding) during a pelvic floor contraction and opposite during pelvic floor relaxation and deep breathing.