The Human Semen

Abstract

• Physical properties

• Composition

• Fructolysis

• Coagulation and liquefaction

Human semen is a protein-rich body fluid produced by the male reproductive organs. It is a complex cell suspension in a fluid containing an array of heterogeneous substances produced by different male reproductive glands like the testis, epididymis, seminal vesicles, prostate, Cowper’s gland (bulbourethral) and glands of Littre (periurethral glands). Its main function is to act as a buffered, nutrient-rich medium which transports the sperm through the male reproductive tract into the female reproductive tract.

During coitus, a heterogeneous ejaculate is deposited in the female tract. This is because the accessory sex glands discharge their secretions by contracting in an organ-specific sequence during emission/ejaculation. This ensures that the various components of semen are delivered in sequential order. The order of secretion and the relative contribution of each gland are listed in Table 11.1. The initial secretion, known as preejaculate, comprises of secretions from the Cowper’s and Littre glands. This mucinous secretion lubricates the urethra and neutralizes any traces of residual acidic urine. The next fraction results from the simultaneous contractions of the epididymis and prostate. It contains the maximum concentration of sperm along with epididymal and prostatic secretions. The final and largest fraction of the ejaculate is contributed by the seminal vesicles.

Two fates exist for the semen components that remain in the male tract after ejaculation: (i) passive resorption by surrounding tissue or (ii) expulsion during urination (Prins and Lindgren 2015).