Search results
Results from the WOW.Com Content Network
The sacrum (pl.: sacra or sacrums [1]), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1–S5) between ages 18 and 30. [2] The sacrum situates at the upper, back part of the pelvic cavity, between the two wings of the pelvis. It forms joints with four other bones.
The wing (ala) of ilium is the large expanded portion of the ilium, the bone which bounds the greater pelvis laterally. It presents for examination two surfaces—an external and an internal—a crest, and two borders—an anterior and a posterior.
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.
The linea terminalis or innominate line consists of the pubic crest, pectineal line (pecten pubis), the arcuate line, the sacral ala, and the sacral promontory. [1]It is the pelvic brim, which is the edge of the pelvic inlet.
The arcuate line marks the border between the body (corpus) and the wing (ala) of the ilium, and, running inferior, anterior, and medial from the auricular surface to the area corresponding to the acetabulum, it also indicates where weight is transferred from the sacroiliac joint to the hip joint.
The sacroiliac joint or SI joint (SIJ) is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side. The joint is strong, supporting the entire weight of the upper body.
There are five sacral vertebrae (S1–S5) which are fused in maturity, into one large bone, the sacrum, with no intervertebral discs. [18] The sacrum with the ilium forms a sacroiliac joint on each side of the pelvis , which articulates with the hips .
The sacrum is curved upon itself and placed very obliquely, its base projecting forward and forming the prominent sacrovertebral angle when articulated with the last lumbar vertebra. It is also known as the "lumbosacral angle".