Generality
The seminal fluid, also known as sperm, is made up of spermatozoa immersed in a liquid medium called seminal plasma . The latter is essential for the maturation, metabolism and life of the spermatozoa, as well as for their survival after ejaculation (emission, at the peak of the sexual act (orgasm), of the seminal fluid through the urethra). Spermatozoa, on the other hand, represent male reproductive cells, which once released into the vagina, together with the other components of the sperm, go up the female reproductive system to fertilize the egg cell.
As soon as it is released, the seminal fluid coagulates, assuming a gelatinous consistency and a milky-white color. A few minutes later the ejaculation begins the process of dissolution of the coagulum and refluidification of the sperm, which is completed in the next 20 minutes by specific enzymes.
Sperm synthesis takes place within the seminiferous tubules of the testes (contribution of 2-5% to the total sperm volume), while the plasma is produced by the seminal vesicles (contribution of 60-70% to the spermatic volume), from the prostate ( 20/30%) and to a lesser extent by the bulb-urethral glands (<1%).
Seminal plasma components
The composition of the seminal plasma is compounded by various substances produced at the level of the epididymis, seminal vesicles and accessory glands, such as the prostate gland, located along the excretory pathway. Among these substances, which we have seen to be extremely important for guaranteeing the correct function of sperm or semen, include proteins, lipids, prostaglandins, hormones, ions, citric acid, fructose, vitamin C, a wide variety of enzymes, zinc, carnitine and many other substances.
Each of these components is assigned a specific function:
- fructose and carnitine (respectively useful as a source and energy production), for example, are important in the metabolism and motility of spermatozoa;
- several proteolytic enzymes are responsible for the already described liquefaction of the seminal coagulum;
- similarly, citric acid also intervenes in the sperm coagulation-liquefaction process;
- lipids stabilize sperm membranes, protecting them from thermal and environmental insults, and can represent an additional source of energy;
- zinc probably has a direct and indirect bactericidal function, and stabilizes sperm chromatin;
- the bicarbonates of seminal fluid have a buffering capacity, useful for neutralizing the acidity of the vaginal environment;
- the mucus increases the mobility of the spermatozoa in the female reproductive tract, creating channels inside the sperm, along which the spermatozoa themselves can advance without dispersing;
- prostaglandins are instead involved in the suppression of the female immune response against sperm from the partner (a common cause of infertility).
It is important to emphasize that some of these substances are synthesized or filtered in a specific district and as such can be used as functional diagnostic markers of a given anatomical structure. Fructose, for example, represents a very faithful index of the state of functionality of seminiferous vesicles, while citric acid is a typical marker of prostatic function. A good indicator of the epididymal function is instead represented by the concentration of carnitine in the seminal fluid.
Sperm characteristics
- Average ejaculate volume: 3/5 ml (greatly influenced also by the psychological conditions and the excitement of the subject).
- Sperm count in ejaculated sperm: 300 to 500 million.
- pH slightly alkaline: 7.2 / 8.
- Seminal fluid osmolarity: iso-osmotic.
- Color: white, opalescent.
- Taste: variable also in relation to eating habits, with sweet, salty and bitter nuances. These and other physiological characteristics of the seminal fluid (with the exception of taste ...) are evaluated in an examination, called spermiogram, which provides an indicative picture of male fertility.
- Also read: sperm smell
