coccygis

The coccygis, commonly known as the coccyx or tailbone, is the small terminal part of the human vertebral column. In many anatomical texts the Latin term coccygis is used to refer to this bone. It represents the vestigial tail in humans and usually consists of three to five rudimentary vertebrae that fuse in adulthood.

Location and connections: The coccygis sits at the base of the spine, just below the sacrum. It articulates with the sacrum at the sacrococcygeal joint, a junction that allows only limited movement. The coccyx is connected by ligaments such as the anterior and posterior sacrococcygeal ligaments and by the anococcygeal structures to surrounding tissues. It also serves as an anchor point for several muscles and pelvic floor elements.

Structure and variation: The exact number of coccygeal vertebrae varies among individuals, typically ranging from three to five. Variations can include fusion of adjacent segments or atypical counts, and sometimes partial fusion occurs during development or aging.

Function: The coccygis provides minor structural support and acts as an attachment site for muscles, ligaments, and connective tissues of the pelvic floor. Its role in weight distribution is modest, especially when a person is seated, where the coccyx helps to bear part of the body's load in combination with surrounding tissues.

Clinical relevance: Coccydynia is pain localized to the coccygeal region and is often related to trauma, falls, prolonged sitting, or childbirth. Management is usually conservative, including cushions, nonsteroidal anti-inflammatory drugs, physical therapy, and, in some cases, injections. Surgical removal is rare.

Evolution: The coccygis is the remnant of a tail in evolutionary terms; in many animals the coccygeal region remains longer and more pronounced.