Seminiferous tubules
It is in the seminiferous tubules that sperm are produced. While we do not intend to describe this structure in detail, it is important to understand some basic principles. The image below shows a semiferous tubule in the center. Within the seminiferous tubules are located the developing sperm and their precursors. They are surrounded by Sertoli cells that are also known as nurse cells as they support the development of sperm, in a process called spermatogenesis. Sertoli cells produce estrogen which surprisingly can be quite high in stallions. Between adjacent seminiferous tubules are the Leydig cells and the smallest blood vessels, capillaries. The Leydig cells produce the androgen, testosterone. Testosterone is the major hormone produced by the testis and it controls sperm production as well as male behavior.
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