Abnormal sperm morphology Abnormal sperm tail morphology 2014-06-09T10:50:50Z A structural abnormality of the sperm tail. The ultrastructure of the mammalian flagellum is highly conserved and is structurally divided into four major parts: the connecting piece, the mid piece, the principal piece, and the end piece. The axoneme extends from the remnant of the centriole attached to the implantation fossa of the nucleus and is the core structure along the length of the sperm tail. Defective sperm flagella are the principal cause of sperm motility disorders. Sperm tail anomaly UMLS:C4022699 HP:0012868