The pelvic cavity is a region where anatomy is inseparable from function. This chapter explores how viscera, muscles, fascia, vessels, and nerves coexist in a confined space that must adapt continuously to posture, movement, bladder filling, bowel activity, sexual function, and—in many individuals—pregnancy and childbirth.

The chapter opens by defining the boundaries of the pelvic cavity, situating it between the pelvic inlet and outlet and distinguishing it clearly from the abdominal cavity above and the perineum below. The pelvic cavity is framed as a transitional zone rather than a closed chamber, with its anatomy shaped by both support and passage.

Central to this chapter is the pelvic diaphragm, formed primarily by the levator ani and coccygeus muscles. These muscles are explored as dynamic supports rather than static slings. Their role in maintaining continence, supporting pelvic organs, resisting intra-abdominal pressure, and coordinating with respiration and posture is emphasised. The anatomy explains how weakness, denervation, or injury can lead to prolapse, incontinence, and chronic pelvic pain.

The pelvic viscera are then examined in situ, with careful attention to sex-specific anatomy. The urinary bladder is explored in terms of position, support, and relationships to surrounding structures, explaining patterns of urinary dysfunction and referred pain. The rectum is examined through its curvature, fascial attachments, and relationship to the pelvic floor, providing the anatomical basis for defecatory control and anorectal pathology.

In the male pelvis, the prostate, seminal vesicles, ductus deferens, and associated structures are described in relation to the bladder, urethra, and pelvic floor. In the female pelvis, the uterus, cervix, vagina, ovaries, and uterine tubes are explored with emphasis on support mechanisms, peritoneal reflections, and clinical vulnerability during childbirth and surgery.

A significant portion of the chapter focuses on pelvic fascia, presented as an essential organising framework. Rather than being treated as background material, pelvic fascia is shown to shape organ position, create compartments, guide neurovascular pathways, and determine the spread of disease. This understanding is crucial for interpreting pelvic imaging and planning surgical approaches.

Neurovascular anatomy is integrated throughout. The autonomic innervation of pelvic organs is traced through sympathetic and parasympathetic pathways, explaining visceral pain referral, bladder and bowel control, and sexual function. The internal iliac vessels and their branches are revisited within the cavity context, reinforcing their proximity to viscera and susceptibility during pelvic procedures.

Surface anatomy and imaging correlations support spatial understanding, particularly in relation to pelvic examination, catheterisation, and operative planning. Cross-sectional anatomy reinforces the tight packing and layered relationships characteristic of the pelvic cavity.

By the end of the chapter, the pelvic cavity is understood as a functionally adaptive space, where anatomy must constantly balance support with flexibility. The chapter equips the reader to understand why pelvic disorders are often multifactorial, why symptoms overlap, and why precise anatomical knowledge is essential for safe and effective clinical care.

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