The testis (from the Greek word orchis) is the male gland important for both reproductive (exocrine) and endocrine functions.
Initially, it begins as an undifferentiated gonad in the retroperitoneal area. Transcription of the SRY gene (testis-determining factor region) on the Y chromosome ultimately leads to sex differentiation. Without the SRY gene, the gonad would develop into an ovary. As the fetus develops, the functioning testis produces the male hormone testosterone to allow development of male genitalia. Over the last 3 months’ gestation, the testis must course its way down from its original retroperitoneal position to its final destination in the scrotum. During its journey, it must pass through the peritoneum, abdominal wall via the inguinal canal, and into the scrotal pouch.
An image depicting the testes and epididymis can be seen below.
Male reproductive organs, sagittal section.