MedCourseFinder

Structure

Pelvis

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The bony pelvis is a ring formed by the two hip bones, the sacrum and the coccyx. It transmits the weight of the trunk to the lower limbs, protects the pelvic viscera and provides attachment for muscles and the birth canal.

Terminologia Anatomica (Latin): Pelvis; Cingulum pelvicum · Open in the 3D atlas

Location

It lies at the inferior end of the trunk, articulating with the fifth lumbar vertebra above (lumbosacral joint) and with the femora below at the hip joints. The pelvic brim divides the false (greater) pelvis from the true (lesser) pelvis.

Structure

Each hip bone fuses from the ilium, ischium and pubis at the acetabulum (the triradiate cartilage ossifies in adolescence). The two pubic bones meet at the pubic symphysis, and the sacroiliac joints with strong ligaments (sacrotuberous, sacrospinous) stabilise the ring. Female pelvis: wider, rounder inlet, wider subpubic angle; male pelvis: narrower, heart-shaped inlet, narrower subpubic angle.

Blood supply

The pelvic bones are supplied mainly by branches of the internal iliac artery (iliolumbar, lateral sacral, superior gluteal, obturator) with contributions from the median sacral artery and the circumflex iliac vessels. The rich venous plexuses explain major bleeding in pelvic fractures.

Innervation

Periosteum and joints are supplied by adjacent nerves: lumbosacral plexus branches (obturator, superior gluteal, femoral), sacral nerve roots and the pudendal nerve. The sacroiliac joint receives L4-S3 fibres (levels vary between authors).

Function

The pelvis bears and transfers body weight (sacrum to acetabula), shields the bladder, rectum and reproductive organs, anchors the muscles of the trunk and lower limb, and in females forms the bony birth canal.

Clinical correlations

Pelvic ring fractures usually occur at two sites because of the ring structure, and can cause haemorrhage and injury to the bladder, urethra and lumbosacral nerves; unstable injuries are emergencies. Acetabular fractures may accompany hip dislocation. Pelvic dimensions (obstetric conjugate, outlet) matter in childbirth.

Common exam points

  • Hip bone = ilium + ischium + pubis, meeting at the acetabulum.
  • True pelvis lies below the pelvic brim (sacral promontory, arcuate and pectineal lines, pubic crest); false pelvis lies above.
  • Female pelvis: wider inlet and subpubic angle; male: heart-shaped inlet, narrower angle.
  • Pelvic ring fractures: two breaks are usual; look for haemorrhage and urethral or bladder injury.
  • Sacroiliac joint stability depends on the posterior sacroiliac, sacrotuberous and sacrospinous ligaments.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Netter FH. Atlas of Human Anatomy. Elsevier — Tier 3 (textbook)

References are listed only where the article cites them. See the sources page for the full policy. How sources are chosen and credited

Back to the index