Sacrum and Coccyx

Joe Muscolino

Share This

 

  • Click here for access to the full Anatomy Glossary.
  • Right click on the image for a downloadable file of this muscle.
  • Use of this artwork requires proper credit to be given (Permission: Dr. Joe Muscolino. www.learnmuscles.com – photography by David Eliot)

    •  

    • The sacrum and coccyx are part of the spine and are located in the pelvis.
    • The sacrum articulates with:
      • the fifth lumbar vertebra superiorly, forming the lumbosacral joint.
      • the ilium of the pelvic bone laterally, forming the sacroiliac joint.
      • the coccyx inferiorly, forming the sacrococcygeal joint.

     

    NOTES:

    1. The sacrum is composed of five vertebral elements (S1-S5) that do not fully form and that fuse into one bone.
    2. The sacrum is an upside-down triangle, with the base of the sacrum at the top (superior end) and the apex of the sacrum at the bottom (inferior end).
    3. The coccyx is usually said to be composed of two-four vertebral elements that do not fully form.
    4. The coccyx does not ossify until later in adulthood.
    5. The coccyx is considered to be the evolutionary remnant of a tail.
    6. The pelvis is a transitional body part. It has both axial body bones (sacrum and coccyx) and appendicular body bones (pelvic bones) within it.
    Posterior view of the sacrum and coccyx.

    Posterior view of the sacrum and coccyx.

     

    Anterior view of the sacrum and coccyx.

    Anterior view of the sacrum and coccyx.

     

    Right lateral view of the sacrum and coccyx.

    Right lateral view of the sacrum and coccyx.

     

    Superior view of the upper surface of the sacrum.

    Superior view of the upper surface of the sacrum.