The Normal Pelvic Floor Anatomy and Function
Written By Eliza Bernardi - Women’s Health Physiotherapist @ The Physiotherapy Clinic
When we talk pelvic floor, most people just think about the muscles. The pelvic floor is actually made up of both muscles AND fascia. Together the muscles and the fascia work to support the pelvic organs (bladder, uterus, and bowel) that sit in the pelvis, control our continence mechanisms and sexual function. In addition, this structure connects to the deepest layer of our abdominals and contributes to our core stability.
In order to understand the normal function of the pelvic floor muscles, we first must understand the anatomy. Some analogies may help!
The superficial layer is the outermost, and its main job is to provide CLOSURE around the anus, vagina and urethra. The muscles include ischiocavernosus, bulbospongiosus, transverse pereneii superficialis, and deep transverse pereneii. These muscles make up what is also known as the perineum.
The deep layer is made up of three muscles collectively known as levator ani (illiococcygeus, pubococcygeus, puborectalis) and coccygeus. The deep layer is attached from the front of the pubic bone, around the sides of the pelvis and into the coccyx and sacrum. You could think of this like a trampoline mat, as you “tighten” the mat, it will LIFT UP towards your head.
The role of the fascia is to connect the pelvic organs to the pelvis, provide support to the pelvic organs and suspend the organs within the pelvis.
There are three main structures that act to suspend our pelvic organs in our pelvis - the pubocervical facia that runs between the urethra/vagina, the rectovaginal fascia that runs between the vagina/bowel and lastly the uterosacral ligaments that suspend the lower part of the uterus up in the pelvis.
Taryn Hallam from Women’s Health Training Associates has a great analogy: Imagine you have a small room with a gym ball/ Swiss ball suspended, floating in the middle of the room, being held up via elastic bands into each corner. The ball represents our pelvic organs (bladder/uterus/bowel) and the elastic bands represent our connective tissue (uterosacral ligaments and endopelvic fascia). Now imagine that you walk up to the ball, and use your hands to push the ball up towards the ceiling, taking the elastic bands off the stretch -Your hands are the muscles. The muscles support the fascia that hold up our organs!
We need good integrity of the connective tissue and good function of the pelvic floor muscles to have optimal function! BOTH are important! The muscles support the connective tissue to ensure it doesn't stretch too much. Poor fascial integrity may lead to pelvic organ prolapse and incontinence.
Optimal function of a pelvic floor means the muscles have good resting tone (not too low in tone and not too high in tone). It also means the muscles move through their full range of motion, have strength, endurance and are co-ordinated with the diaphragm.
The Normal Continence and Voiding MechanismTo put it simply, to be continent of urine the pressure inside the bladder must be lower than the pressure around the urethra.
To empty our bladder, the pressure inside the bladder must be higher than the pressure around the urethra (see below).
- STORE URINE B. EMPTY URINE
But it’s not as simple as this, as there are many other factors that contribute to pressures around the urethra and bladder including: the muscular contraction / relaxation of the superficial and deep pelvic floor, the vascular supply of the tissue, and tension from the endopelvic fascia.
The Abnormal Pelvic Floor Anatomy and Function
The Pelvic floor that doesn’t work automatically
To remain continent with activities that provide some load to the urethra and anus, the pelvic floor muscles should automatically activate PRIOR to increases in intra abdominal pressure, to help with the closure around the urethra. The deep pelvic floor muscles also tug on our endopelvic fascia, pulling it firm to act like a backstop for the urethra.
Here is another analogy to aid our understanding, think of a running garden hose on the hard ground. If you step on the hose, you will stop the flow of water easily with the force from your foot. If the ground is soft, the force from your foot won’t kink the hose, but rather push the hose into a soft surface. Imagine the ground is your endopelvic facia. If the facia lacks tension, a force on the urethra, and onto the fascia, will not kink the urethra but just distort it - this leaves the urethra OPEN and incontinence may occur.
If under a force (cough, sneeze, laugh, and lift) the fascia has been pre tensioned by an optimal pelvic floor, the urethra will hit the tense facia, and the urethra will close (just like the hose did when stepped on it while on a HARD surface).
The Weak pelvic floor
At times the pelvic floor simply lacks strength. There are a numbers of reasons why the pelvic floor may have become weak, far more than just having a baby vaginally!
It is of course important to attempt to establish why the weakness has occurred as this will aid designing an optimal retraining program. Surprisingly, despite the pelvic floor being a group of small muscles with a relatively simple function, most individuals end up with a very different retraining program to meet their needs!
The hypertonic/ tight / inability to relax Pelvic Floor
As a Physio working in the women’s health space, one of the largest clientele is the hypertonic or tight pelvic floor caseload. But what is the difference between a tight and a hypertonic pelvic floor? “Tightness” comes from shortening or contracture of the connective tissues, hypertonicity is the inability of the muscle to “let go”. The pelvic floor muscles are somatic muscles, meaning they’re under our voluntary control just like our biceps and our quadriceps. For optimal function, the muscles should be able to switch ON and LET GO
There are numerous symptoms a patient might describe that may lead us to be suspicious of pelvic floor over activity and, there are many potential mechanisms as the cause. Symptoms of a non-relaxing pelvic floor may include (but are not limited to) issues with constipation and difficulty emptying bowels, voiding ( urinating) dysfunction, irritable bowel type symptoms, painful intercourse and difficulty with inserting tampons/fingers / having vaginal speculum checks, musculoskeletal symptoms such as hip and pelvic girdle pain, altered breathing patterns, urethral burning, recurrent urinary tract infection like sensations and difficulty with a vaginal birth.
The potential mechanisms behind a non-relaxing pelvic floor are varied and very individual. It is important to figure out “what came first?” There may be underlying endometriosis causing severe pain within the pelvis. There may be an underlying vulval skin disorder. There could be a history of various syndromes including irritable bowel syndrome, interstitial cystitis, overactive bladder, trauma to the pelvis from birth or other causes. It is not uncommon to have a few of the above.
A hypertonic or over active pelvic floor needs very different treatment than that of a weak or uncoordinated pelvic floor. The most important message is to never prescribe pelvic floor exercises, or use pelvic floor cues if you are unaware of how the person’s pelvic floor is functioning. Should a person have any of the symptoms described above, it is a good idea for that individual to have their pelvic floor assessed thoroughly. Once again, despite the pelvic floor being a small group of muscles with a relatively simple function, when hypertonic they can cause serious symptoms for people.
- Pelvic Floor examination - Physiotherapist palpating the muscles.
- Thanks to Peter Conlan for the photo