The coccygeus (ischiococcygeus) is a triangular muscle located on each side of the pelvis. It originates from the ischium and inserts in the coccyx and sacrum. It closes the back part of the outlet of the pelvis. The coccygeus muscle is innervated by the third and fourth sacral nerves. This muscle raises and supports the coccyx. Research Coccygeus
The coccyx (or 'tailbone') is composed of three to five rudimentary vertebrae. Often, the first of these coccygeal vertebrae is separate, while the remainder are fused together. The articulation between the coccygeal vertebrae and the sacrum allow some flexibility in the coccyx, which is particularly beneficial in taking the stresses of sitting and falling. The coccyx is extremely susceptible to shock fracture, as might be induced from a fall. Furthermore, since a number of nerve pathways pass near this area, damage to the coccyx threatens damage to the nerves of the lower body. The juncture of the first coccygeal vertebra with the sacrum occurs at the lower facet of the sacrum. Research Coccyx
The gluteus maximus is the most powerful and largest muscle in the body. It is a thick, fleshy, quadrilateral muscle that forms the major volume of the buttock. It originates from the ilium and the posterior surface of the sacrum and coccyx, descends downward and outward from its origin and wraps around the outer back corner of the pelvis to insert in the iliotibial band and the gluteal ridge of the femur. It connects the ilium, sacrum, and coccyx to the femur by tissues of the thigh. The gluteus maximus is innervated by the inferior gluteal nerve and supplied by the inferior and superior gluteal arteries. This muscle consists of coarse muscle fibres that powerfully extend the thigh at the hip joint and moves it away from the body, as when walking or running. It is also used to raise the body from a sitting position. Research Gluteus Maximus
The levator ani-coccygeus originates from the back of the pubis and inserts in the sides of the lower part of the sacrum and coccyx. This muscle draws the anus upward in defecation. It is innervated by the fourth sacral nerve. Research Levator Ani-coccygeus
The levator ani-iliococcygeus is the posterior part of the levator ani muscle. It originates from the back of the pubis and inserts in the sides of the lower part of the sacrum and coccyx. This muscle supports pelvic organs. It is innervated by the fourth sacral nerve. Research Levator Ani-iliococcygeus
The levator ani-puborectalis originates from the back of the pubis, passes around the anus and inserts in the sides of the lower part of the sacrum and coccyx. This muscle relaxes during defecation. It is innervated by the fourth sacral nerve. Research Levator Ani-puborectalis
The rectogeus (rectococcygeus) muscle lies near the coccygeus muscle on each side of the pelvis. The
rectogeus muscle consists of two bands of plain muscular tissue which extend from the second and third vertebrae of the coccyx and descend to the posterior wall of the analcanal. Research Rectogeus
The sacrum is the portion of the vertebral column between the lumbarvertebrae and the structures of the coccyx. It is composed of five vertebrae which are fused together to form a single bone structure. The sacrum features a mediancrest which is made of the fused spinous processes of its component vertebrae. Beneath this crest is the sacral canal, a tunnel which runs lengthwise from the top of the sacrum to a hiatus (opening) near the bottom. Four pairs of sacral foramina pierce the sacrum, flanking the medial line, where the intermediate sacral crests are formed by the fused articular processes of the component vertebrae. To the outside of the intermediate sacral crests are the lateral crests, formed by the fused transverse processes of the component vertebrae. In the sacrum, therefore, unlike the upper vertebrae in the spine, the intertransverse ligaments have been replaced by fusion of these processes together. The crests are not represented on the pelvic surface of the sacrum, though the sacral foramina are evident. Research Sacrum
The sphincter ani externus is a sphincter muscle that surrounds and together with the spincter ani internus, close the anus. It is attached to the coccyx and to the central tendon of the perineum. Research Sphincter Ani Externus
The spinous process is a projection of bone from the arch of almost every vertebra toward the posterior. This projection is located at the apex of the arch and bordered on the arch by the laminae. It is the series of these processes which is visible as the bumps beneath the skin on the back. The spinous process serves as an anchor point for ligaments which help control the flexibility of the spine. The vertebrae feature different types of spinous processes. Typical cervical vertebrae have bifid spinous processes, with the exception of the atlas which has no spinous process. Thoracic vertebrae generally have a single tubercle, and point downward as well as back. The lumbarvertebrae feature spinous processes which are rectangular or hatchet-shaped and have a section which points back and one which points down. The spinous processes of the sacrum and coccyx are generally fused together, to form a ridge called, in the sacrum, the sacral crest. Often, the coccygeal vertebrae (fused or not) show no evidence of any ridge, crest, or
spinous process. Research Spinous Process
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Coccygeus
