Surgical Anatomy Of Pelvic Diaphragm

The Levator Ani and Coccygeus muscles are two of the main muscle groups that make up the pelvic diaphragm, a funnel-shaped fibromuscular structure that serves as the essential framework for the pelvic organs. The Pubococcygeus, Puborectalis, and Iliococcygeus muscles make up the majority of the Levator Ani muscles, although the Coccygeus muscle is also referred to as the Ischiococcygeus muscle.

Two unnamed bones plus the sacrum, which the coccyx is linked to, make up the human pelvis. The sacral promontory and the upper surface of the pubic bones correspond to the entrance of the pelvic canal.

The female true pelvis differs from the male true pelvis in several ways, including being shallower, having straighter sides, having a wider angle between the pubic rami at the symphysis, and having a larger pelvic outlet. The exit, on the other hand, is defined by the pubic arch, ischial spines, sacrotuberous ligaments, and the coccyx.

This area between the entrance and exit is referred to as the true pelvis. Four general classifications can be used to categorize the morphology of the female bony pelvis: gynecoid, anthropoid, android, and platypelloid.  In females, the uterus, tubes, ovaries, and vagina are housed in the pelvis.

Some important ligaments come from the lateral aspect of the pelvis.  The ischial spine and the ischial tuberosity are joined.
The sacrotuberous ligament extends from the ischial tuberosity.  The Sacrospinous ligament originates from the lateral portion of the ligament.  The pubic bone's superior and inferior aspects are the starting points of the obturator internus muscle, which passes behind it before entering.  The Ani muscle originates from a continuous white line that extends from the posterior aspect of the pelvic bone to the Ischial spine.

Pelvic Diaphragm (lateral view)

The site of muscle attachment is the levator plate. The Ano-coccygeal raphe region is primarily referred to as the "levator plate."

Pubococcygeus Muscle

The Pubococcygeus muscle originates from the inner surface of the pubic bones and extends to attach medially to the distal lateral vagina, or perineal body. The perineal body is a fibromuscular structure situated between the anus and the vagina/testicles.

The deep, transverse perineal muscle clings to the sides of the ischiopubic rami. Since several pelvic floor components meet the perineum at this structure, it is referred to as the central tendon of the pelvis.) and Anthus. Certain fibers cling to the coccyx, while others are linked to the anus.

The pubovisceral muscle is another name for the Pubococcygeus muscle.  The pubococcygeus muscle can be separated into sections based on where it attaches to the visceral tissue. For example, it may attach to the pubovaginalis, puboperinealis, or puboanalysis regions.

Puborectalis Muscle

It is thought to be different from the Pubococcygeus muscle.
This muscle originates from the public bone's inner surface, which is located lateral to the Pubococcygeus muscle.
In addition, it joins forces with its companion to encircle the rectum in a U-shaped sling.  The anorectal junction is pulled forward by the puborectalis muscle, which aids in controlling feces.

Iliococcygeus Muscle

 It inserts into the midline Ano-coccygeal raphe and coccyx from the posterior part of the arcus tendinous levator ani and the ischial spine.  The lateral coccyx and pelvic viscera are supported by the Iliococcygeus muscle as its main job.

Coccygeus Muscle

This muscle's origins are in the sacrospinous ligament and the ischium spine; it then attaches or inserts into the lower sacrum segment and coccyx.  In women who are standing straight, the rectum and vaginal axis rest nearly horizontally over the levator plate.  The weight of the pelvic contents is the force that pushes downward from above or the abdominal pelvic cavity.

Innervation Of Pelvic Diaphragm 

In the case of innervation of the pelvic diaphragm to the Levator Ani, there is a separate nerve that arises from the S3 and S4 and occasionally with S5 segments.  There are segments of the sacral spinal nerve in front of the Piriformis muscle.

The levator ani complex and the coccygeus muscle are innervated.  The nerve that supplies the levator ani travels via the upper side of the pelvic diaphragm.  The inferior rectal nerves, a branch of the Pudendal nerve, may contribute to some of the Puborectalis' fibers.

The inferior rectal nerve (derived from the pudendal nerve - S3, S4), the levator ani (branches of S4), and the coccygeal plexus are all connected to the pubococcygeus muscle invertedly.

Puborectalis innervation extends to the levator ani nerve, encompassing S4 branches and the pudendal nerve branch (S2-4).  The inferior rectal nerve (from the pudendal nerve - S3, S4), the coccygeal plexus, and the branches of S4 are involved in the innervation of the iliococcygeus muscle. The anterior rami of S4 and S5 are involved in the innervation of the coccygeus muscle.

Also Read: Puerperium: Understanding the Postpartum Period

Applied Anatomy

 The rectum and vagina remain closed due to the regular tone of the levator ani muscles.  They prevent pelvic organ prolapse and support the pelvic organs.  Birthing and pelvic operations can injure the nerve that supplies the Levator Ani.

De Lancey's Level of Vaginal Supports 

 Delancey's three levels of pelvic support:  The cardinal and uterosacral ligaments are seen at the first level.  The pubocervical and rectovaginal fascia are provided by the parapodium on the second level. The urethra and the superficial transverse perineal muscle are visible at the third level.  An epical level of vaginal support, also known as Level 1 support, will be present at the epics of the vagina.

Support for the middle portion of the vagina is also known as Level 2 support, or mid-level vaginal support.

LEVEL I: The cardinal-uterosacral complex is involved.
LEVEL II: The arcus tendinous fascia pelvis is where the anterior and posterior fibromuscular layer attachments are laterally linked.

Inside the pelvic fascia is the arcus tendinous fasciae pelvis, a fibrous tissue extending around 10 centimeters.  It is situated laterally in the peritoneum and medially in the obturator internus muscle. The attachments of the endopelvic connective tissue are received by this fascia tendinous fasciae pelvis.

LEVEL III: The perineal membrane and perineal body, together with the connective tissue and muscle attachments that go with them, are all included.  Support for all three vaginal support levels is offered by Levator Ani.

Prolapse of the uterus (uterocervical descent) or vaginal vault may result from disruption of the level I support.  Disruption of level II and Ill supports increases the risk of prolapse of the anterior and posterior vaginal walls.

Also Read: Surgical Anatomy Of Vulva And Perineum

What are Delancey's Three Levels of Pelvic Support?

Delancey's three levels of pelvic support are as follows: the pubocervical and rectovaginal fascia as part of the paracolpium is shown on the second level, together with the uterosacral ligament and the cardinal ligament.  The urethra and the superficial transverse perineal muscle are visible on the third level.

How Pubococcygeus Muscle Is Divided On The Basis Of Attachment To The Visceral Structure?

The pubovaginalis component, puboperinealis portion, and puboanalysis area are just a few examples of the visceral structures to which the pubococcygeus muscle might be attached.

What Is The Primary Function Of The Iliococcygeus Muscle? 

The iliococcygeus muscle's primary job is to support the lateral coccyx and pelvic viscera.

Also Read: From HPO Axis To Ovulation

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