Pelvis
Basin-shaped skeleton connecting trunk to lower limbs.
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The pelvis is the lower part of the anatomical trunk, situated between the abdomen and the thighs, and includes the bony pelvis, pelvic cavity, pelvic floor, and perineum. It serves as a basin-shaped ring of bones connecting the vertebral column to the femora, bearing the weight of the upper body and providing attachments for muscles of locomotion and posture.
Lore & Background
The pelvic skeleton is formed posteriorly by the sacrum and coccyx, and laterally and anteriorly by a pair of hip bones. Each hip bone consists of three sections—ilium, ischium, and pubis—which are separate during childhood and fuse during puberty. The pelvic cavity, enclosed by the bony pelvis, primarily contains reproductive organs and the rectum, with the pelvic floor assisting in supporting abdominal organs.
Anatomical Boundaries & Regional Position
The pelvis is defined as the anatomical region spanning from the pelvic inlet down to the pelvic diaphragm. It sits directly below the abdomen, which extends to the pelvic brim or pelvic inlet, and above the perineum, the zone located between the sex organs and the anus. In the broader topographical classification of the human body, the pelvis and perineum together form one of seven major regional groupings, alongside the head and neck, upper limb, thorax, abdomen, back, and lower limb.
The lower limb, defined as everything below the inguinal ligament, connects to the pelvic region at the hip joint. The back region, encompassing the spine, vertebrae, sacrum, coccyx, and intervertebral disks, also interfaces structurally with the pelvic framework. This regional framework allows anatomists and medical students to approach the body in a structured, topographical manner, studying structures by bodily region rather than solely by organ system, a method that aligns with modern pedagogical approaches to teaching human anatomy.
Reader's Guide
The pelvis is critical for both bipedal locomotion and childbirth, creating an evolutionary conflict known as the obstetrical dilemma. The female pelvis is larger, broader, and lighter than the male pelvis, with a wider inlet and outlet to accommodate childbirth, while the male pelvis is taller, narrower, and more compact for efficient walking.
Differences include the subpubic angle (acute in males, obtuse in females), the shape of the inlet, and the orientation of the acetabula, which affect gait. The pelvic floor has conflicting functions: closing the pelvic and abdominal cavities while controlling openings for the rectum and urogenital organs. The pelvic skeleton is strong and rigid compared to the shoulder girdle, transferring weight from the axial skeleton to the lower limbs.
Frequently Asked Questions
What exactly is the pelvis?
The pelvis is the lower section of the torso positioned between the abdominal region and the upper legs. It forms a ring-like bony structure that links the spine down to the thigh bones.
What are the main functions of the pelvis?
It acts as a weight-bearing platform that transfers the load from the upper body down through the legs. It also shields the internal organs housed within its cavity and, in females, provides the passage for delivery of a baby.
Which structures are considered part of the pelvis?
The pelvic region encompasses the bony ring, the internal cavity containing organs, the muscular pelvic floor, and the perineal area. Together these components create a supportive and protective framework.
How does the pelvis connect the trunk to the lower limbs?
It serves as the anatomical bridge where the vertebral column meets the femurs, forming a stable ring that anchors both. Muscles involved in walking, standing, and posture attach directly to its surfaces.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Pelvis (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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