The pelvic viscera (bladder, rectum, pelvic genital organs and terminal part of the urethra) reside within the pelvic cavity (or the true pelvis). This cavity is located within the lesser part of the pelvis, beneath the pelvic brim. A number of muscles help make up the walls of the cavity - the lateral walls include the obturator internus and the piriformis muscle, with the latter also forming the posterior wall.
In this article, we shall look at the anatomy of the muscles that make up the inferior lining of the cavity - the pelvic floor muscles. The pelvic floor is also known as the pelvic diaphragm. We shall look at the individual roles of these muscles, their innervation and blood supply, and any clinical correlations.
The pelvic floor is a funnel-shaped structure. It attaches to the walls of the lesser pelvis, separating the pelvic cavity from the perineum inferiorly (region which includes the genitalia and anus). In order to allow for urination and defecation, there are a few gaps in the pelvic floor. There are two ‘holes’ that have significance: the urogenital hiatus, an anteriorly situated gap which allows passage of the urethra and the vagina in females; and the rectal hiatus, a centrally positioned gap which allows passage of the anal canal.
Between the urogenital hiatus and the anal canal lies a fibrous node known as the perineal body, which joins the pelvic floor to the perineum (described further here).
The roles of the pelvic floor muscles are: to support the abdominopelvic viscera through their tonic contraction; to offer resistance to increases in intra-pelvic/abdominal pressure during activities such as coughing or lifting heavy objects; and to maintain urinary and faecal continence, as the muscle fibres have a sphincter action on the rectum and urethra, which relax to allow urination and defecation.
When learning about the muscles of the pelvic floor, it is important to keep in mind its funnel-shaped structure. There are three main components of the pelvic floor: the levator ani muscles, the coccygeus muscle, and the fascia coverings of the muscles.
The levator ani is a broad sheet of muscle. It is composed of three separate paired muscles; pubococcygeus, puborectalis and iliococcygeus.
The puborectalis is the most important of the levator ani group for maintaining faecal continence. It originates from the posterior surface of the pubis and forms a U-shaped sling around the anal canal, attaching to the pubis on the contralateral side. Its action is to provide a tonic contraction that bends the anal canal anteriorly, creating the anorectal angle which contributes to faecal continence. It is voluntarily inhibited during defecation.
Muscle is innervated by the nerve to levator ani and the pudendal nerve. Some of its fibres (pre-rectal fibres) form another U-shaped sling that flank the urethra in the male and the urethra and vagina in the female (in some textbooks they appear as pubovaginalis or sphincter urethrae / vaginae). These fibres are very important in preserving urinary continence, especially during abrupt increase of the intra-abdominal pressure i.e. during sneezing.
The pubococcygeus forms the bulk of the levator ani complex. It is located between the puborectalis and iliococcygeus within the pelvic floor.
Its attachments and actions are less clear than the other components, but it is believed to be involved in maintaining balance within the pelvis as well as providing support for the organs within the pelvic cavity.
Innervation of the pubococcygeus is provided by the nerve to levator ani and the pudendal nerve.
The iliococcygeus is the most posteriorly situated component of the levator ani complex. It originates from the ischial spine and inserts onto the coccyx and the anococcygeal raphe.
It functions to provide support to the posterior aspect of the pelvis, as well as offering stability to the terminal part of the rectum.
Innervation of the iliococcygeus is provided by the nerve to levator ani and the pudendal nerve.
The coccygeus muscle is also known as the ischiococcygeus muscle. It originates from the ischial spine, and runs horizontally across the pelvic floor to insert onto the coccyx.
It functions mainly to provide support to the posterior pelvic wall, and some textbooks highlight its role in keeping the anal canal elevated and closed.
Innervation is provided by the sacral plexus, specifically the fourth and fifth sacral nerves.
The levator ani muscles are surrounded by fascia which form two separate planes - the endopelvic fascia and the parietal pelvic fascia.
In conclusion, the pelvic floor muscles are a complex network of muscles, fascia, and gaps which work together to form a supportive and dynamic structure for the abdominopelvic viscera, offering resistance to increases in intra-pelvic/abdominal pressure, and maintaining urinary and faecal continence.
The pelvic floor is a group of muscles located in the lower region of the abdomen. It consists of two 'holes' that have special significance- the Urogenital Hiatus and the Rectal Hiatus. The Urogenital Hiatus is located in an anterior position, and it allows the passage of the urethra, as well as the vagina in females. The Rectal Hiatus is located centrally, and it allows the passage of the anal canal. In between the two 'holes' is a fibrous node known as the Perineal Body, which connects the pelvic floor to the perineum.
The pelvic floor muscles have several roles in the body. They provide support to the abdominopelvic viscera by maintaining a tonic contraction. They also help to resist increases in intra-pelvic or abdominal pressure during activities like coughing or lifting heavy objects. Furthermore, they have a sphincter action on the rectum and urethra, allowing them to relax to facilitate urination and defecation.
Pelvic floor dysfunction is a range of signs and symptoms that are associated with abnormal functioning of the pelvic floor muscles. In women, the pelvic floor muscles provide support to the urethra, vagina, and anal canal. When these muscles weaken, it can lead to a loss of structural support for these organs, which may present as urinary incontinence, faecal incontinence, genitourinary prolapse, pelvic pain, or sexual dysfunction.
The causes of pelvic floor dysfunction are understood to be multifactorial and include obstetric trauma, increasing age, obesity, and chronic straining.
The pelvic floor consists of three main components- the levator ani muscles, the coccygeus muscle, and the fascia coverings of the muscles. Let's take a closer look at each of them.
The levator ani is a broad sheet of muscle that is composed of three pairs of muscles - the pubococcygeus, puborectalis, and iliococcygeus.
The puborectalis is the most important of the levator ani group, as it aids in maintaining faecal continence. It originates from the posterior surface of the pubis and forms a U-shaped sling around the anal canal, attaching to the pubis on the contralateral side. It has a tonic contraction that bends the anal canal anteriorly, which creates the anorectal angle and contributes to faecal continence. It is voluntarily inhibited during defecation and is innervated by the nerve to the levator ani and the pudendal nerve.
The pre-rectal fibres of the puborectalis muscle form another U-shaped sling that flanks the urethra in males, and the urethra and vagina in females. These fibres are essential in preserving urinary continence, particularly during abrupt increases in intra-abdominal pressure, such as when sneezing.
The pubococcygeus forms the bulk of the levator ani complex, located in between the puborectalis and iliococcygeus within the pelvic floor. It originates from the posterior surface of the pubis and blends with the contralateral muscle in the midline of the pelvic floor. Its primary actions are to offer stability and support to the abdominal and pelvic organs, and it is innervated by the nerve to the levator ani and branches of the pudendal nerve.
The iliococcygeus is a thin muscle that forms the posterolateral part of the levator ani muscle group. It originates from the ischial spines and the posterior tendinous arch of the internal obturator fascia, and inserts onto the coccyx, perineal body, and anococcygeal ligament. It also blends with the fibres of the contralateral muscle in the midline of the pelvic floor, and it helps to elevate the pelvic floor and anorectal canal. It is innervated by the nerve to the levator ani and branches of the pudendal nerve.
The coccygeus is a small triangular muscle located posterior to the levator ani muscle group. It originates from the ischial spines and inserts onto the inferior end of the sacrum and coccyx. Its actions are to provide support for the pelvic viscera and to flex the coccyx. It is innervated by the anterior rami of S4 and S5, and its blood supply is provided by the inferior vesical, inferior gluteal, and pudendal arteries.
Pelvic floor dysfunction refers to a range of signs and symptoms that are related to abnormal functioning of the pelvic floor muscles. In women, the pelvic floor muscles provide support to the urethra, vagina, and anal canal. When these muscles weaken, it can lead to a loss of structural support for these organs, which may present as urinary incontinence, faecal incontinence, genitourinary prolapse, pelvic pain, or sexual dysfunction.
The causes of pelvic floor dysfunction are understood to be multifactorial and include obstetric trauma, increasing age, obesity, and chronic straining.
It is important to note that pelvic floor dysfunction is a common issue amongst men and women, and can have a serious impact on one's quality of life. However, it is a condition that can be managed if diagnosed and treated appropriately. Pelvic floor rehabilitation is a form of treatment used by physiotherapists to relieve the symptoms associated with pelvic floor dysfunction. Such treatment can help to strengthen the pelvic floor muscles, improve bladder control, and relieve pelvic pain.
The pelvic floor is made up of a complicated network of muscles, nerves, and vessels held together by connective tissue, with many important anatomical features and functions. The pelvic floor's complex aponeurotic core is composed of several layers that contain deep, intermediate, and superficial muscles, as well as nerves and vessels, all playing an important role in its overall function. Since this structure is so essential for normal body physiology and for clinical considerations, any weakening of these muscles can result in a loss of structural support to these organs, presenting as urinary incontinence, faecal incontinence, genitourinary prolapse, pelvic pain, and sexual dysfunction.
The causes of pelvic floor dysfunction are understood to be multifactorial, and can be attributed to a number of different conditions and factors, including, but not limited to obstetric trauma, age, obesity, and chronic straining.
Obstetric trauma refers to physiological and psychological traumas that may or may not have resulted from the birth process itself. This type of trauma can result in lasting changes to the pelvic floor muscles, making them weak or over-tight, which can lead to a number of pelvic floor disorders and associated symptoms.
Age is another factor that can play a role in pelvic floor dysfunction. As people age, the pelvic floor muscles can become weaker, leading to dysfunction and its associated symptoms. Statistics show that pelvic floor disorders are more common in women aged over 40 years and post-menopausal women.
Obesity is another cause of pelvic floor dysfunction. Being overweight or obese can place increased pressure on the pelvic floor muscles, leading to weakened muscles and pelvic floor dysfunction. The National Institutes of Health (NIH) reports that obesity is twice as likely to cause stress urinary incontinence in women than in men.
Chronic straining is yet another cause of pelvic floor dysfunction. Chronic straining is when a person strains their pelvic floor muscles and their surrounding structures over a long period of time. This type of straining can lead to weakened muscles and the other associated symptoms of pelvic floor dysfunction.
Ultimately, it is important to understand the important role of the pelvic floor and how dysfunction of this complex structure can lead to a wide variety of conditions and symptoms. By understanding the causes of pelvic floor dysfunction, it is possible to take steps to prevent and manage the associated conditions. These steps may include avoiding the risk factors for pelvic floor dysfunction, such as ageing, obesity, obstetric trauma, and chronic straining; as well as engaging in activities to help strengthen the pelvic floor muscles, such as Kegel exercises.
