**2. Functional anatomy**

Pelvic floor support includes:


## **2.1. Bony pelvis**

The support mechanism of Pelvic floor is provided by the complex and dynamic interactions of the muscles and connective tissues attachments within the bony pelvis. The bony pelvis provides fixed attachment to pelvic soft tissues and it consists of the two hip bones which made up of illium, ischium and pubis, anteriorly fused with each other at pubic symphysis and the sacrum posteriorly. The pelvis has divided into the false (or greater) pelvis and the true (or lesser) pelvis by the iliopectineal line, coursing along the superior edge of the superior pubic ramus, and circumferentially forms the pelvic brim. Within the true pelvis are the sacrotuberous and sacrospinous ligaments, contribute significant stability of the pelvis. The lesser pelvis is the narrower continuation of the greater pelvis inferiorly and its inferior pelvic outlet is closed by the pelvic floor.

#### **2.2. Muscular support**

#### *2.2.1. Levator ani*

post-hysterectomy vaginal cuff, small bowel, or rectum) into the vagina [4]. These pathological changes are due to loss of structural support to pelvic organs resulting in an impact on women's quality of life. They arise because of injury and deterioration of the muscles,

Despite the high prevalence of POP, current treatment options remain suboptimal and do not address the underlying mechanisms of disease. Therefore, without improving our understanding of the pathophysiology of POP, treatment options and prevention of recurrence of POP would be limited. It is important to understand the pelvic floor support and the risk factors leading to POP. This chapter would include a review of pelvic floor support and the

**2.** Subperitoneal connective tissue retinaculum and the broad ligament, including smooth

The support mechanism of Pelvic floor is provided by the complex and dynamic interactions of the muscles and connective tissues attachments within the bony pelvis. The bony pelvis provides fixed attachment to pelvic soft tissues and it consists of the two hip bones which made up of illium, ischium and pubis, anteriorly fused with each other at pubic symphysis and the sacrum posteriorly. The pelvis has divided into the false (or greater) pelvis and the true (or lesser) pelvis by the iliopectineal line, coursing along the superior edge of the superior pubic ramus, and circumferentially forms the pelvic brim. Within the true pelvis are the sacrotuberous and sacrospinous ligaments, contribute significant stability of the pelvis. The lesser pelvis is the narrower continuation of the greater pelvis inferiorly and its inferior pelvic

nerves, and connective tissue that support the pelvic floor and its contents.

pathophysiology of POP.

**2. Functional anatomy**

Pelvic floor support includes:

muscle component and round ligament.

**3.** Cardinal and uterosacral ligaments complex.

**4.** Para vaginal attachments of the vaginal sulci to the arcus tendineus.

**5.** Urogenital diaphragm, including the pubourethrovaginal ligaments.

**1.** Bony pelvis.

6 Pelvic Floor Disorders

**6.** Pelvic diaphragm.

**8.** Perineal body.

**2.1. Bony pelvis**

**7.** Fascia of denonvilliers.

outlet is closed by the pelvic floor.

Levator ani muscles form the pelvic diaphragm, which provide the firm tissue support of the pelvic floor. These muscles are attached to the inner surface of the true pelvis form the muscular floor of the pelvis. Three components of the levator ani muscles recognized are pubococcygeus, iliococcygeus and puborectalis [5]. The **pubococcygeus**, also known as pubovisceralis muscle, arises from the anterior portion of the arcus tendineus and the back of the body of the pubis and is inserted with other parts of levator ani as anococcygeal raphe which forms a hiatus or levator plate. Pubovisceralis is further divided into pubovaginalis, puboanalis, and puboperinealis muscles [6]. The fibers attached to the perineal body are puboperinealis and draw this structure toward the pubic symphysis. The fibers attached to the anus at the intersphincteric groove between the internal and external anal sphincter are puboanalis. It elevates the anus and along with the rest of the pubococcygeus and puborectalis fibers keep the urogenital hiatus closed. Pubovaginalis refers to the medial fibers of pubococcygeus that attach to the lateral walls of the vagina.

The iliococcygeus arises from the arcus tendineus of the levator ani to the ischial spine and inserted into anococcygeal raphe. The puborectalis fibers of the levator ani (LA) muscle arises on lowest portion of pubic symphysis. It passes downward and backward on either side of vagina and fuses behind the rectum and form U-shaped muscular sling encircling the junction between the rectum and anus.

#### *2.2.2. Coccygeus muscle*

It forms the most posterior division of levator ani, arises from ischial spine and inserted into coccyx and lower sacrum. The piriformis and obturator internus form the posterolateral pelvic walls. The piriformis arises from the anterior and lateral surface of the sacrum and leaves the pelvis through the greater sciatic foramen, inserted to the greater trochanter of the femur. The obturator internus muscle arises from the ilium and ischium pelvic surfaces. It leaves the pelvis through the lesser sciatic foramen and inserted to the greater trochanter of the femur. The piriformis and obturator internus function as an external hip rotator.

#### **2.3. Facial support**

Endopelvic is composed of loose arrangements of collagen, elastin, and adipose tissue and condenses to form cardinal and uterosacral ligaments.

#### *2.3.1. The ATLA*

Arcus tendineous levator ani, dense connective tissue structure courses along the medial surface of the obturator internus muscle, serves as the point of origin for parts of the levator ani muscles (iliococcygeus). ATLA extends anteriorly from pubic tubercle to ischial spines posteriorly. The arcus tendineous fascia pelvis (ATFP), a thickening of fascia covering the medial aspect of the iliococcygeus muscles, extends from the inner surface of the superior pubic rami to the ischial spines. It provides lateral attachment point for the proximal rectovaginal septum and pubocervical fascia [7].

**4. Pathogenesis**

*4.1.1. Age*

**4.1. Risk factors of POP**

yearly examination [11].

*4.1.2. Pregnancy and childbirth*

tures and the anal sphincter.

partment defects [16].

pathogenesis.

*4.1.3. Raised intra-abdominal pressure*

Age has been recognized as an intrinsic factor in the development of pelvic floor dysfunction and most consensuses in favor that it has a role in the etiology of female pelvic organ prolapse (POP) [10]. With advancing age, incidence and prevalence of POP increases. The relative prevalence of POP increased by about 40% with every decade of life, as demonstrated by a cross-sectional study of 1004 women (age 18–83 years) who attended their

Pathophysiology of Pelvic Organ Prolapse http://dx.doi.org/10.5772/intechopen.76629 9

Age and POP relation is hypothesized to be secondary to numerous factors including physiologic changes of the pelvic floor components and decline in estrogen during the postmenopausal period with advance age. This hypothesis is supported by Swift et al. study showing an increase in the odds ratio for pelvic prolapse from 1.04 to 1.46 for a change in 10 years of age [11].

There are hormonal induced physiological changes that occur in pelvic floor musculature and connective tissue during pregnancy. These alterations are vital for preparing the body to adjust the pelvic floor for vaginal birth. High level progesterone affects the pelvic floor by

Changes in biomechanical properties of the vaginal wall have been studied in fibulin-5 knockout mice (Fbln5−/−) with and without prolapse [12]. He demonstrated that pregnant vaginal wall has increased distensibility, and decreased stiffness as compare to nonpregnant. The causative links between childbirth and prolapse have shown by various epidemiological and observational cohort studies [13, 14]. The pelvic structures affected by traumatic events are levator ani muscle complex, the pelvic nerves, the pelvic fascial struc-

Pregestational body mass index (BMI), BMI at term, duration of the first and second stages of labor, operative delivery, perineal lacerations, weight of the newborn and epidural analgesia are reported pregnancy related risk factors [14]. There is increased prevalence of true rectocele after vaginal childbirth as proven by many studies. Rectocele may be due to damage of the rectovaginal septum and Denonvillier's fascia in the posterior compartment [15]. Obstructed defaecation and pelvic organ prolapse are strongly associated with posterior com-

Chronically raised intra-abdominal pressure such as chronic constipation, higher body mass index (BMI), chronic cough, and repetitive heavy weight lifting seems to play a role in POP

causing smooth muscle-relaxation and antagonizes estrogen effects.

## *2.3.2. Urogenital diaphragm*

The urogenital diaphragm, a dense fibromuscular sheet is like sandwich and composed of superior and inferior fascial layers separated from one another by (compressor urethra and urethrovaginal sphincter muscles), the deep transverse perineal muscles. It attaches laterally to the ishiopubic rami and medially to the distal third of the vagina and to the perineal body. In standing position, urogenital diaphragm is almost horizontal and its fixation to perineal body contributes to the support of urethra and vesicourethral junction [5].

#### *2.3.3. Perineal body*

The perineal body is a pyramidal fibromuscular elastic structure found between the distal third of the posterior vaginal wall and the anus on a line between the ischial tuberosity. The perineal body apex is continuous with the rectovaginal septum (the fascia of Denonvilliers) and it extends 2–3 cm above the hymeneal ring.

#### *2.3.4. Cardinal and uterosacral ligaments complex*

The parametria attaches lateral to the uterus is known as the cardinal and uterosacral ligament complex. They form three dimensional complex attaching the lower uterine segment, cervix and upper vagina with sacrum and pelvic side walls. This complex maintains vaginal length and keeps the vaginal axis horizontal. The uterosacral ligament also provides suspension and assist in maintaining the position of the uterus and upper vagina over the levator plate.

Using 3D stress magnetic resonance imaging (MRI) in vivo, dynamic of the cardinal and uterosacral ligament for apical support with and without Valsalva have been explored. [8]. These imaging techniques continue to enhance our knowledge of the strain and lengthening of these structures, which in turn, may help in determining the nature and direction of apical support loss.
