EMBRYOLOGY OF THE HUMAN VESTIGIAL TAIL

During the fifth and sixth week of gestation, the human embryo has a tail with 10-12 caudal vertebrae. The tail begins to regress by reduction in the number of vertebrae and fusion, leaving the vestigial coccyx.

The tail usually disappears by week eight of gestation, although the exact time of disappearance does vary somewhat.

The persistent tail probably arises from the most distal avertebrate remnant of the embryonic tail (1-3).

REFERENCES

1. Ledley FD. Evolution and the human tail. A case report. N Engl J Med 1982;306:1212-1215.
2. Dao AH, Netsky MG. Human tails and pseudotails. Hum Pathol 1984;15:449-453.
3. Belzberg AJ, Myles ST, Trevenen CL. The human tail and spinal dysraphism. J Pediatr Surg 1991;26:1243-1245.