Anatomy of the Sacrum and Coccyx

Sacral foramina

-4 pairs of foramina -Provide passageways for the sacral nerves through both the anterior and posterior sides of the sacrum *SACRUM*

Superior articular processes

-Articulate with the inferior articular processes of L5 and form the lumbo-sacral junction -Laterally, the right and left borders articulate with the ilium and form the sacro iliac (SI) joints *SACRUM*

sacrum

-Base is wide with the apex pointed downward Presents left and right borders which articulate with the innominate bones -Posterior surface is rough and uneven for muscle attachment -Anterior surface is relatively smooth

sacrum

-Composed of 5 sacral segments, fused in adults -Only bony anatomy considered to be part of both the axial and appendicular skeleton -Shorter in females than in males -Shaped like an inverted triangle

sacrum

-Directly inferior to the lumbar spine -Between the 2 innominate bones, forming the posterior aspect of the pelvic cavity

Coccyx

-Directly inferior to the sacrum -Presents a triangular shape

coccyx

-Three to five vertebrae that fuse into one segment in the adult -The superior articulating processes on the superior aspect of the coccyx articulates with the inferior segment of the sacrum to form the sacro-coccygeal articulation -There are 4 segments in the child that fuse into 1 segment in the adult

Ala

Broad, expanded portion of the upper sacral segment

sacrum

Formed by the fusion of the five sacral vertebral segments into a curved, triangular bone.

Vertebral foramen

Forms a descending tunnel called the sacral canal *SACRUM*

The inferior aspect of the sacrum and the superior aspect of the coccyx.

What forms the sacraococcygeal articulation?

The coccyx

What is the most inferior portion of the spinal column?

An inverted triangle

What is the shape of the sacrum?

It is formed of five fused segments

Why is the sacrum considered atypical?