Testis – Tutorial
Please read Unit 12 – Introduction to Male Reproductive System Tissues prior to completing the activities in this chapter.
Introduction to the Testes
The testes (testicles) are a pair of male gonads that serve to produce sperm (male gametes) and secrete sex hormones known as androgens, the most important of which is testosterone. Each testis is oval-shaped and approximately 2 inches (5 cm) long and 1 inch (2.5cm) thick. The testes are suspended within the scrotum, a skin-walled pouch that hangs below the perineum just posterior to the base of the penis and anterior to the anus. Sperm produced by the testes are stored in and eventually exit the body through a system of passageways that lead to the urethra. The urethra in a male extends from the urinary bladder to the tip of the penis and propels sperm from the body in a liquid mixture known as semen during ejaculation. Testosterone produced by the testes exits the testes and scrotum via the pampiniform venous plexus in the inguinal canal and eventually enters the general circulation via the testicular vein.
Each testis is surrounded by a fibrous connective tissue capsule known as the tunica albuginea. Internally, each testis is divided by connective tissue septa into hundreds of lobules containing tightly coiled seminiferous tubules which carry out sperm production (spermatogenesis). Sperm and fluid within the lumen of seminiferous tubules eventually exit the testis via a series of larger passageways known as rete testis and efferent ductules that connect to the epididymis.
The walls of seminiferous tubules are lined with a germinal epithelium several cell layers thick. The germinal epithelium of seminiferous tubules is where spermatogenesis occurs by the process of meiosis. As germinal cells undergo meiosis and differentiate into sperm, they gradually migrate from the basal region of the germinal epithelium toward the lumen. Fully formed sperm are released into the lumen of the tubule and are eventually transported out of the testis via efferent ductules to the epididymis. The spaces between the highly coiled seminiferous tubules are occupied by areolar tissue, blood vessels, and large endocrine cells known as interstitial cells (Leydig cells) that secrete testosterone.
Tutorial: Use the image slider below to learn more about the structure and characteristics of the testes.
Microscopy: Use the image slider below to learn how to use a microscope to study a testis on a microscope slide.
