HANDOUT FOR PELVIC FLOOR AND BOWEL CONTINENCE
PELVIC FLOOR
Pelvic Floor:





Formed by the pelvic diaphragm
Funnel-shaped
Muscular partition from the pubis to the coccyx and from lateral wall to lateral wall
Separates pelvic cavity from perineum inferiorly
Transmits urethra, vagina (in females) and anal canal
Muscles of Pelvic Floor:

The pelvic diaphragm is composed of two paired muscles
o Levator ani
o Coccygeus

Levator ani muscle
o Paired muscle
o Principal muscle of pelvic floor
o Supports pelvic contents
o Actively maintains position of pelvic viscera

Perineal body or central perineal tendon
o A fibromuscular body extending from the perineum into the urogenital hiatus
o The site of numerous muscle attachments in the perineum
o perineal body is essential for the integrity of the pelvic floor, particularly in females
o
Components of the levator ani muscle
Pubococcygeus
Is anterior part of levator ani
Main contributor to the levator ani
Arises from the posterior body of the pubic bone and anterior part of the arcus
Tendineus
Runs posteriorly to attach to the anococcygeal ligament and the coccyx
o Iliococcygeus
Posterior part of the levator ani
Is thin and poorly developed
Arises from the posterior part of the arcus tendineus and the ischial spine
Attaches to the anococcygeal raphe and the coccyx
o Puborectalis
is innermost and merges with the external anal sphincter. Unites with its partner to make a Ushaped sling around the rectum at its junction with the anus . Has a sphincter-like action by
pulling the anorectal junction forward and contributing to anal continence. It causes 120 deg

angulation of anorectum due to the pull against the pubic bones. By its action it also shuts the
lumen by apposing the post and the side walls of rectum
Pubococcygeous and iliococcygeous help to close the urogenital diaphragm by voluntary
contraction, as well as elevate, straighten, steady, and suspend the rectum. The perineal body
helps in the suspending action.
A thickened band of muscle best seen inferior to the pubococcygeus

Coccygeus muscle
o
o
o
o
Reinforces pelvic floor posteriorly
Arises from ischial spine
Inserts on lower two sacral and upper two coccygeal segments
Blends with sacrospinous ligament on its external surface

Innervation of the levator ani and coccygeus muscles
o Levator ani innervated by branches from the anterior rami of S3–S4 spinal nerves
o Puborectalis also innervated by branch of pudendal nerve (S2,3,4)
o Coccygeus supplied by branches of the anterior rami of S4–S5 spinal nerves

Functions of the levator ani
o Acting together raise the pelvic floor to increase abdominal pressure, such as when coughing,
sneezing, urinating, defecating, lifting heavy objects.
o Important in voluntary control of micturition (urinating)
o Supports pelvic viscera
o Supports head of the fetus
NOTES ON BOWEL CONTINENCE
EXTERNAL ANAL SPHINCTER:



Superficial external sphincter
Deep external sphincter – continuous with the puborectalis
Subcutaneous part with the corrugate cutis ani
INTERNAL ANAL SPHINCTER

Circular layer of rectum becomes internal anal sphincter
Continence during sleep and rest is by the continuous tonic contraction of the internal sphincter
Continence during raised intra abdominal pressure is by the levator ani and the external sphincter
The external anal sphincter and puborectalis muscles are innervated by the pudendal nerve
The levator ani receives innervation from both the internal pudendal nerve and direct branches of S3- S5
Sensory innervation to the anal canal is provided by the inferior rectal branch of the pudendal nerve
Rectum is relatively insensate, the anal canal below the dentate line is sensate.
Supportive structures for continence:
1. Perineal body


4 muscles 2 paired, 2 unpaired
Superficial transverse perinei, deep transverse perinei (paired)
Arching fibers of the puborectalis around the rectum+fibers of bulbospongiosus (unpaired)
2. Anorectal angle
3. Rectal ampulla
4. Mucosal valves
Neural organization of anorectal sphincters:
 Somatic from S2,3,4 (pudendal nerve) to the external anal sphincter
 Sympathetic from L2,3,4 (superior hypogastric plexus)
 Parasympathetic S2-4 (nervi erigentis also called pelvic splanchnic nerves) to the internal anal sphincter
PELVIC PLEXUS- formed by sympathetic and parasympathetic nerves


hypogastric plexus (by branches from the sacral part of the sympathetic chain)- sympathetic
pelvic splanchnic nerves (also called nervi erigentes) - parasympathetic
Pudendal nerve supplies to all 3 muscles of levator ani
Nervi erigentis or pelvic splanchnic nerves or pelvic nerves - parasympathetic
 -distal most nerve fibers relay on to the ganglia of Auerbach's plexus
 -Sensory reflex of rectal distention
Presacral sympathetic nerves - Motor to involuntary internal sphincter
Physiologic coordination- responsible for continence:
Sensory reflex + motor reflex + unique rectal contractions
Fine control over defecation reflex
Mucosa contains
- Nerve endings for pain
- Meissner's corpuscles for touch
- Krause end organs for pressure
- Pacinian corpuscles for friction
- The relaxation of internal sphincter allows the contents to come in contact with the above sensory
receptors
- They are able to discriminate air vs solid fecal matter
- The relaxation of external sphincter will occur if air is leading the flow – if one wants.
Motor reflex involves:
 Tonic contraction of the internal anal sphincter
 Reflex contraction of the levator ani and external sphincter
DEFECATION REFLEX
Initiation by voluntary abdominal contraction, gastrocolic reflex, colonic reflex, direct rectal mucosal stimulation,
rectal distention
1. Filling and distention of lower rectum
Fecal material passes to rectum by the longitudinal muscular contraction.
When there is distension in the sigmoid colon and rectum, the internal sphincter relaxes at the same time as
the external sphincter contracts.
This allows some of the fecal contents to enter the anal canal and be sampled by its sensitive epithelium to
determine if its solid, liquid or gas.
2. Increase rectal pressure
If the individual decides to continue with defecation, the intrarectal pressure increases on straining. Added
pressure from abdominal straining or Valsalva maneuver aids defecation. Straining requires intact
innervation of the lower thoracic cord T6-T12.
The intraabdominal pressure should be sufficient to overcome the external sphincter which relaxes with the
pelvic floor that causing the rectum to straighten up reducing the rectal angle. This increase in
intraabdominal pressure forces stool into the rectum with relaxation of the extenal anal sphincter allowing
defecation.
3. Stimulation of receptors in the pelvic floor – desire to defecate –relaxation of the internal
sphincter
2 alternatives:
1. If not voluntarily inhibited, the external sphincter also relaxes resulting to defecation. Fecal matter
stimulate the anal canal further relaxing the external anal sphincter.
2. No social opportunity, contraction of external anal sphincter and puborectalis occurs, the rectum
relaxes and the urge to defecate passes—accommodation or adaptation of the rectum.
If the individual decides not to continue with defecation, the rectum relaxes further to allow accommodation of
the contents which further stimulates the external sphincter to contract, the rectum relaxes and the urge
to defecate passes—accommodation or adaptation of the rectum
HOLDING – Puborectalis, external and internal sphincters contract
INITIATION – puborectalis and external anal sphincter relax, levator ani, abdominal and diaphragm contract
COMPLETION – internal and external anal sphincters relax, rectum contracts
Upper motor neuron lesion- damage above the defecation reflex center in the sacral cord
Results to:
1. Abnormal storage of feces
2. Inability to recognize urge and distinguish contents
3. External sphincter dyssynergia
Lower motor neuron lesion – damage within the reflex defecation center
Results to:
1. Fecal retention
2. Oozing of stool through the flaccid sphincter
3. Sensory and motor pathways are disrupted so the patient is unaware of urge to defecate and unable to
exercise voluntary external anal sphincter
Assessment is through the bulbocavernosus reflex and the anal relfex to determine UMN or LMN lesions.
The bulbocavernosus reflex is a palpable or visible contraction of the anal sphincter when pressure is applied to
the glans penis or clitoris.
When contraction is present, (+) result. This indicates that the reflex activity of the sacral cord is intact and
therefore the SCI is an UMN lesion. Should be tested soon after SCI, before the spinal shock passes.
The anal reflex is a visible contraction of the anal sphincter in response to a pinprick. A positive response
indicates an UMN lesion.