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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 joint locks (or rather becomes close packed) on one side as weight is transferred from one leg to the other, and through the pelvis the body weight is transmitted from the sacrum to the hip bone. The motions of the sacroiliac joint Anterior innominate tilt of both hip bones on the sacrum (where the left and right move as a unit) Posterior ...
Movements in the joint are restricted to flexion and extension. These essentially passive movements occurs during defecation and labour. When movements in the sacrum increase the anteroposterior diameter of the pelvic outlet, movements in the sacrococcygeal joint can further increase this diameter. [2]
It consists of numerous fasciculi, which pass between the bones in various directions. The upper part ( short posterior sacroiliac ligament ) is nearly horizontal in direction, and pass from the first and second transverse tubercles on the back of the sacrum to the tuberosity of the ilium .
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
3D medical animation still shot of human skull. The axial skeleton is the core part of the endoskeleton made of the bones of the head and trunk of vertebrates.In the human skeleton, it consists of 80 bones and is composed of the skull (28 bones, including the cranium, mandible and the middle ear ossicles), the vertebral column (26 bones, including vertebrae, sacrum and coccyx), the rib cage ...
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.
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 ...