Pelvic Skeleton Anatomy Quiz

Pelvic Skeleton Anatomy

• The pelvic skeleton is composed of two hip bones (ossa coxae), the sacrum, and the coccyx.

Pelvic Regions

• The pelvis is divided into two regions:
  • False Pelvis (Greater Pelvis): The wider, superior region, often considered part of the abdominal cavity.
  • True Pelvis (Lesser Pelvis): The narrower, inferior region, containing the pelvic cavity.
• Pelvic Inlet: The opening at the top of the true pelvis, formed by the pelvic brim.
• Pelvic Cavity: Enclosed by the true pelvis, it houses the bladder, reproductive organs, and rectum.

Hip Bone (Os Coxae)

• The os coxae is formed by the fusion of three bones:
  • Ilium: The superior portion.
  • Ischium: The posteroinferior portion.
  • Pubis: The anteroinferior portion.
• These bones meet at the acetabulum, the socket for the head of the femur, forming the hip joint.

Ilium

• Iliac Crest: A prominent ridge along the top of the ilium, level with the L4 vertebra and aortic bifurcation.
  • Useful landmark for lumbar punctures (spinal cord ends above this level).
• Anterior Superior Iliac Spine (ASIS): A palpable bony projection on the ilium.
  • The inguinal ligament attaches here, extending to the pubic tubercle.
  • The femoral artery runs midway between the ASIS and pubic tubercle.
• Anterior Inferior Iliac Spine (AIIS): Located inferior to the ASIS.
• Posterior Superior Iliac Spine (PSIS): Located posteriorly on the iliac crest.
• Posterior Inferior Iliac Spine (PIIS): Located inferior to the PSIS.
• Greater Sciatic Notch: A notch inferior to the PSIS, allowing passage of nerves and blood vessels.
• Iliac Fossa: A depression on the ilium's medial surface, providing attachment for the iliacus muscle.

Ischium

• Ischial Spine: A bony projection on the posteroinferior aspect of the ilium.
• Greater Sciatic Foramen: The opening above the ischial spine.
• Lesser Sciatic Foramen: The opening below the ischial spine.
• Ischial Tuberosity: A large, roughened area inferiorly on the ischium.
  • The sacrotuberous ligament connects the sacrum to the ischial tuberosity.
• Sacrospinous Ligament: Connects the sacrum to the ischial spine.
• Ischiopubic Ramus: The continuous bony structure formed by the ischium and pubis.
• Obturator Foramen: A large opening in the ischiopubic ramus, covered by a membrane except for a small canal for the obturator vessels and nerve.

Pubis

• Superior Pubic Ramus: The upper branch of the pubis.
• Inferior Pubic Ramus: The lower branch of the pubis.
• Pubic Body: The central portion of the pubis.
• Pubic Symphysis: The joint where the two pubic bones meet.
• Pubic Tubercle: A palpable projection on the pubis.

Angle of the Pelvis

• The pelvic inlet is angled approximately 50-60 degrees relative to a horizontal line.
• The ASIS and pubic tubercle are on the same vertical plane.

Sacrum and Coccyx

• The sacrum articulates with the 5th lumbar vertebra superiorly and the coccyx inferiorly.
• The sacroiliac joints connect the sacrum to the ilium on each side.
• The coccyx is a small, triangular bone at the end of the vertebral column.

Other Important Features

• Gluteal Muscles: The gluteus maximus, medius, and minimus attach to the ilium's lateral surface.
• Pelvic Walls and Floor: The pelvic cavity is bounded by the pelvic walls and the pelvic floor, formed by muscles. These structures will be discussed in a separate tutorial.