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Anatomical Science International Jul 2023The purpose of this review is to present our researches on the pelvic outlet muscles, including the pelvic floor and perineal muscles, which are responsible for urinary... (Review)
Review
The purpose of this review is to present our researches on the pelvic outlet muscles, including the pelvic floor and perineal muscles, which are responsible for urinary function, defecation, sexual function, and core stability, and to discuss the insights into the mechanism of pelvic floor stabilization based on the findings. Our studies are conducted using a combination of macroscopic examination, immunohistological analysis, 3D reconstruction, and imaging. Unlike most previous reports, this article describes not only on skeletal muscle but also on smooth muscle structures in the pelvic floor and perineum to encourage new understanding. The skeletal muscles of the pelvic outlet are continuous, which means that they share muscle bundles. They form three muscle slings that pass anterior and posterior to the anal canal, thus serving as the foundation of pelvic floor support. The smooth muscle of the pelvic outlet, in addition to forming the walls of the viscera, also extends in three dimensions. This continuous smooth muscle occupies the central region of the pelvic floor and perineum, thus revising the conventional understanding of the perineal body. At the interface between the levator ani and pelvic viscera, smooth muscle forms characteristic structures that transfer the lifting power of the levator ani to the pelvic viscera. The findings suggest new concepts of pelvic floor stabilization mechanisms, such as dynamic coordination between skeletal and smooth muscles. These two types of muscles possibly coordinate the direction and force of muscle contraction with each other.
Topics: Pelvic Floor; Perineum; Muscle, Skeletal; Muscle, Smooth; Anal Canal
PubMed: 36961619
DOI: 10.1007/s12565-023-00717-7 -
American Journal of Obstetrics and... Jan 2020Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal... (Review)
Review
Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal birth canal. The precise frequency of obstructed labor is difficult to estimate because of the widespread use of cesarean delivery for indications other than proven cephalopelvic disproportion, but it has been estimated that at least 1 million mothers per year are affected by this disorder worldwide. Why is the fit between the fetus and the maternal pelvis so tight? Why did evolution not lead to a greater safety margin, as in other primates? Here we review current research and suggest new hypotheses on the evolution of human childbirth and pelvic morphology. In 1960, Washburn suggested that this obstetrical dilemma arose because the human pelvis is an evolutionary compromise between two functions, bipedal gait and childbirth. However, recent biomechanical and kinematic studies indicate that pelvic width does not considerably affect the efficiency of bipedal gait and thus is unlikely to have constrained the evolution of a wider birth canal. Instead, bipedalism may have primarily constrained the flexibility of the pubic symphysis during pregnancy, which opens much wider in most mammals with large fetuses than in humans. We argue that the birth canal is mainly constrained by the trade-off between 2 pregnancy-related functions: while a narrow pelvis is disadvantageous for childbirth, it offers better support for the weight exerted by the viscera and the large human fetus during the long gestation period. We discuss the implications of this hypothesis for understanding pelvic floor dysfunction. Furthermore, we propose that selection for a narrow pelvis has also acted in males because of the role of pelvic floor musculature in erectile function. Finally, we review the cliff-edge model of obstetric selection to explain why evolution cannot completely eliminate cephalopelvic disproportion. This model also predicts that the regular application of life-saving cesarean delivery has evolutionarily increased rates of cephalopelvic disproportion already. We address how evolutionary models contribute to understanding and decision making in obstetrics and gynecology as well as in devising health care policies.
Topics: Animals; Biological Evolution; Cephalopelvic Disproportion; Cesarean Section; Female; Gait; Hominidae; Humans; Parturition; Pelvic Bones; Pelvimetry; Pelvis; Pregnancy; Pubic Symphysis; Selection, Genetic
PubMed: 31251927
DOI: 10.1016/j.ajog.2019.06.043 -
Diagnostic and Interventional Imaging Nov 2017Endometriosis is a common gynecological disorder defined by the presence of endometrial tissue outside the uterus. It is the most common cause of chronic pelvic pain and... (Review)
Review
Endometriosis is a common gynecological disorder defined by the presence of endometrial tissue outside the uterus. It is the most common cause of chronic pelvic pain and typically affects the ovaries, uterine ligaments, peritoneum, tubes, rectovaginal septum and bladder. It may, however, be found at various extrapelvic sites, including the perineum, liver, pancreas, lung or even the central nervous system, and in such cases, diagnosis may be quite challenging. Even though definitive diagnosis requires laparoscopy, preoperative identification of endometriosis is important not only to differentiate it from other diseases with similar clinical presentations but also, for accurate presurgical mapping, since complete removal of all endometriotic foci is critical for the effective treatment of the patient's symptoms. Ultrasound is performed initially, but magnetic resonance imaging (MRI) is increasingly being used, particularly when sonographic findings are unclear, when deep pelvic endometriosis is suspected or when surgery is planned, as it provides better contrast resolution and a larger field of view compared to ultrasound. In this article, we will discuss distinctive MRI appearances of endometriotic foci and we will review common and uncommon locations of endometriosis within the body, in an attempt to familiarize radiologists with its wide spectrum of manifestations.
Topics: Abdominal Wall; Adnexa Uteri; Cell Transformation, Neoplastic; Diagnosis, Differential; Endometriosis; Female; Gastrointestinal Diseases; Humans; Magnetic Resonance Imaging; Nervous System Diseases; Pelvis; Peritoneum; Thoracic Diseases; Urinary Bladder Diseases; Uterus; Viscera
PubMed: 28652096
DOI: 10.1016/j.diii.2017.05.009