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The coccyx (pl.: coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, [1] and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and other great apes) since Nacholapithecus (a Miocene hominoid), [2] [3] the coccyx is the remnant of a ...
It stretches from median sacral crest [3] and the free margin of the sacral hiatus [1] to the dorsal surface of the coccyx. [ 1 ] The lateral sacrococcygeal ligaments run from the lower lateral angles of the sacrum to the transverse processes of the first coccygeal vertebra to complete the foramina for the last sacral nerve . [ 1 ]
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 tailbone, at the end of the spine, has lost its original function in assisting balance and mobility, though it still serves some secondary functions, such as being an attachment point for muscles, which explains why it has not degraded further. In rare cases, congenital defect results in a short tail-like structure being present at birth ...
The number of vertebrae in a region can vary but overall the number remains the same. In a human vertebral 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.
The anococcygeal nerve is a sensory nerve of the pelvis [1] that arises from the coccygeal plexus. [2] It pierces the coccygeus muscle and the sacrotuberous ligament to supply a small area of skin between the coccyx and anus, [3] as well as the sacrococcygeal joint.
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.
In vertebrate animals that evolved to lose their tails (e.g. frogs and hominid primates), the coccyx is the homologous vestigial of the tail. While tails are primarily considered a feature of vertebrates, some invertebrates such as scorpions and springtails , as well as snails and slugs , have tail-like appendages that are also referred to as ...