The epididymis is a component of the mammalian male reproductive system. A narrow, coiled tube connecting each testicle to the corresponding vas deferens, the epididymis serves as a transportation tract and storage site for sperm. Male gametes are immature and incapable of egg fertilization when they leave the testes, but as sperm travel the length of the epididymis they mature, becoming capable of motility and achieving fertility. The maturation process is not completed, however, unless the reproductive cells enter the reproductive tract of a female.

Three basic sections of the epididymis are generally identified: the caput (head), corpus (body), and cauda (tail). The diameter of the epididymis increases as it proceeds from the caput to the cauda region. Internally the epididymis is lined with columnar epithelial cells and prominent microvilli. Inflammation of the structure, known as epididymitis, may occur if an infection of the bladder or urethra spreads. Symptoms of epididymitis often include testicular pain and swelling, fever, and painful urination or intercourse.

In the digital image above, a rat epididymis tissue section is presented that was labeled with the fluorophore Texas Red conjugated to wheat germ agglutinin, a fluorescent lectin that selectively binds to sialic acid residues. Wheat germ agglutinin conjugates are often used as probes for the Golgi network in mammalian tissues and cells. The sample was also stained with Alexa Fluor 488 conjugated to phalloidin and Hoechst 33342, which target filamentous actin and nuclear DNA, respectively. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.

Labeling Epididymis Tissue with Fluorescent Probes Conjugated to Phallotoxins and Lectins - Inflammation of one or both of the epididymides, known as epididymitis, may occur due to an infection of the bladder or urethra that spreads or due to various noninfectious causes, such as the use of certain medications. Among the most common infectious organisms that give rise to epididymitis are Escherichia coli, Chlamydia trachomatis, and Neisseria gonorrhoeae. Symptoms of the condition often include testicular pain and swelling, fever, and painful urination or intercourse.

Rat Epididymis Tissue Section Triple Stained for F-Actin, Sialic Acid Residues, and DNA - When sperm are released from the lower segment of the epididymis, they are packed very densely. Due to this fact, the gametes are unable to swim. Their movement instead involves the peristalsis of layers of muscle located within the vas deferens, the main duct that extends between the epididymis and the ejaculatory duct. Prior to reaching the ejaculatory duct, various fluids are added to the male gametes.