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It runs from the sacrum (the lower transverse sacral tubercles, the inferior margins sacrum and the upper coccyx [1]) to the tuberosity of the ischium. It is a remnant of part of biceps femoris muscle. The sacrotuberous ligament is attached by its broad base to the posterior superior iliac spine, the posterior sacroiliac ligaments (with which ...
The laminae of the fifth sacral vertebra, and sometimes those of the fourth, do not meet at the back, resulting in a fissure known as the sacral hiatus in the posterior wall of the sacral canal. The sacral canal is a continuation of the spinal canal and runs throughout the greater part of the sacrum. Above the sacral hiatus, it is triangular in ...
These eminences are separated by three notches: one in front, the pubic arch, formed by the convergence of the inferior rami of the ischium and pubis on either side.; The other notches, one on either side, are formed by the sacrum and coccyx behind, the ischium in front, and the ilium above; they are called the sciatic notches; in the natural state they are converted into foramina by the ...
The deep dorsal sacrococcygeal ligament (ligamentum sacrococcygeum posterius profundum) is a continuation of the posterior longitudinal ligament. [1] A flat band arising inside the sacral canal, posteriorly at the orifice of the fifth sacral segment, it descends to the dorsal surface of the coccyx under its longer fellow described below. [3]
The posterior tubercle is a rudimentary spinous process and gives attachment to the rectus capitis posterior minor muscle. The spinous process is small so as not to interfere with the movement between the atlas and the skull. On the under surface is a facet for articulation with the dens of the axis.
In humans, the sciatic nerve is formed from the L4 to S3 segments of the sacral plexus, a collection of nerve fibres that emerge from the sacral part of the spinal cord. The lumbosacral trunk from the L4 and L5 roots descends between the sacral promontory and ala, and the S1 to S3 roots emerge from the ventral sacral foramina.
The posterior divisions of the sacral nerves are small and diminish in size as they move downward; they emerge, except the last, through the posterior sacral foramina. The upper three are covered at their points of exit by the multifidus and divide into medial and lateral branches.
The posterior border of the ala of sacrum, shorter than the anterior, also presents two projections separated by a notch, the posterior superior iliac spine and the posterior inferior iliac spine. The posterior superior iliac spine serves for the attachment of the oblique portion of the posterior sacroiliac ligaments and the multifidus.