The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis.
The coccyx, commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates since Nacholapithecus, the coccyx is the remnant of a vestigial tail. In animals with bony tails, it is known as tailhead or dock, in bird anatomy as tailfan. It comprises three to five separate or fused coccygeal vertebrae below the sacrum, attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between the sacrum and the coccyx.
The sacrum, 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.
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.
Coccydynia is a medical term meaning pain in the coccyx or tailbone area, often brought on by a fall onto the coccyx or by persistent irritation usually from sitting.
The coccygeus muscle or ischiococcygeus is a muscle of the pelvic floor located posterior to levator ani and anterior to the sacrospinous ligament.
The external anal sphincter is an oval tube of skeletal muscle fibers. Distally, it is adherent to the skin surrounding the margin of the anus. It exhibits a resting state of tonical contraction and also contracts during the bulbospongiosus reflex.
A nerve plexus is a plexus of intersecting nerves. A nerve plexus is composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels. There are five spinal nerve plexuses, except in the thoracic region, as well as other forms of autonomic plexuses, many of which are a part of the enteric nervous system. The nerves that arise from the plexuses have both sensory and motor functions. These functions include muscle contraction, the maintenance of body coordination and control, and the reaction to sensations such as heat, cold, pain, and pressure. There are several plexuses in the body, including:
In human anatomy, the sacral plexus is a nerve plexus which provides motor and sensory nerves for the posterior thigh, most of the lower leg and foot, and part of the pelvis. It is part of the lumbosacral plexus and emerges from the lumbar vertebrae and sacral vertebrae (L4-S4). A sacral plexopathy is a disorder affecting the nerves of the sacral plexus, usually caused by trauma, nerve compression, vascular disease, or infection. Symptoms may include pain, loss of motor control, and sensory deficits.
The anococcygeal nerve is a sensory nerve of the pelvis that arises from the coccygeal plexus. It pierces the coccygeus muscle and the sacrotuberous ligament to supply a small area of skin between the coccyx and anus, as well as the sacrococcygeal joint. The number of anococcygeal nerves varies between one and three.
The perforating cutaneous nerve is a cutaneous nerve of the sacral plexus that provides sensory innervation to the skin of the buttocks.
The sacrotuberous ligament is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends.
The pelvic portion of each sympathetic trunk is situated in front of the sacrum, medial to the anterior sacral foramina. It consists of four or five small sacral ganglia, connected together by interganglionic cords, and continuous above with the abdominal portion. Below, the two pelvic sympathetic trunks converge, and end on the front of the coccyx in a small ganglion, the ganglion impar, also known as azygos or ganglion of Walther.
The anococcygeal body is a fibrous median raphe in the floor of the pelvis, which extends between the coccyx and the margin of the anus. It is composed of fibers of the levator ani muscle that unite with the muscle of the opposite side, muscle fibres from external anal sphincter, and fibrous connective tissue.
The sacrococcygeal symphysis is an amphiarthrodial joint, formed between the oval surface at the apex of the sacrum, and the base of the coccyx.
The anterior sacrococcygeal ligament or ventral sacrococcygeal ligament consists of a few irregular fibers, which descend from the anterior surface of the sacrum to the front of the coccyx, blending with the periosteum.
The anal triangle is the posterior part of the perineum. It contains the anus in mammals.
Coccygectomy is a surgical procedure in which the coccyx or tailbone is removed. It is considered a required treatment for sacrococcygeal teratoma and other germ cell tumors arising from the coccyx. Coccygectomy is the treatment of last resort for coccydynia which has failed to respond to nonsurgical treatment. Non surgical treatments include use of seat cushions, external or internal manipulation and massage of the coccyx and the attached muscles, medications given by local injections under fluoroscopic guidance, and medications by mouth.
A coccyx fracture is a fracture of the coccyx, commonly called a broken tailbone or ‘puzzle fracture.’
