Appendix testis (Hydatid of Morgagni)

The development of testis starts in very early fetal life with the first 'kidney'- the pronephros, which does not function. The second kidney appears in the fourth week, as the pronephros is degenerating, and is the mesonephros with its mesonephros duct. This mesonephros also degenerates, but the mesonephric duct persists (the Wolffian duct), which in male persists and develops into the epididymis, vas deferens, ejaculatory ducts and seminal vesicles. In females this Wolffian duct degenerates, but the paramesonephric ducts (Mullerian ducts) grow and develop into the female genital tract. The Mullerian ducts do not persist in the male( due to the secretion of Mullerian inhibiting substance), apart from the most cranial end which persists as the appendix testis (hydatid of Morgagni) on the upper pole of testis.