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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 -
Seminars in Interventional Radiology Dec 2011The pelvic course of the ureter with its close proximity to the iliac artery, pelvic viscera, and other structures predispose to fistula formation. Surgical management...
The pelvic course of the ureter with its close proximity to the iliac artery, pelvic viscera, and other structures predispose to fistula formation. Surgical management of lower urinary tract fistulas is difficult and often ineffective. Nonvascular lower urinary tract fistulas can be managed by urinary diversion with percutaneous nephrostomy to allow for fistula healing. If this fails, ureteral embolization can be very effective; however, this should be preceded by careful evaluation and discussion with the patient as this intervention results in irreversible ureteral occlusion necessitating a diverting nephrostomy catheter indefinitely. A ureteroarterial fistula is a distinct entity compared with nonvascular fistulas with a different approach to management; it can be managed by exclusion of the fistula by endovascular placement of a stent graft across the arterial component of the fistula.
PubMed: 23204637
DOI: 10.1055/s-0031-1296081