Chapter 28 – Testis and Epididymis

Abstract An understanding of reproductive toxicity is increasingly important in drug safety assessments. Knowledge of the biology and functions of the cell types composing the testes and epididymis, and the hormonal interactions influencing them, is key to discerning the mechanisms underlying compound-related testicular and epididymal effects. This chapter reviews the anatomy, histology, development (prenatal and postnatal), and physiology of the rat testes and epididymis. The process of spermatogenesis and recognition of germ cell patterns (stages) aiding in interpretation of deleterious effects are described. Common spontaneous histopathologic changes (neoplastic and nonneoplastic) are presented, in addition to those changes often considered toxicologically relevant.