Detailed explanation of the fertilization process, the mechanisms of infertility caused by andrological diseases, and the physiological changes in male infertility.

Fertilization is the process by which sperm and egg fuse to form a zygote. In humans, the site of fertilization is the ampulla of the fallopian tube. Through sexual intercourse, sperm is ejaculated into the female reproductive tract, travels up the fallopian tube, and meets the egg from the ovary. The sperm penetrates the zona pellucida of the egg, and fertilization begins. The fertilization process takes approximately 24 hours. For successful fertilization, the following conditions must be met: ① The male has normal sexual function and can ejaculate normally. ② The male has a sufficient number of sperm with normal morphology and function, and a suitable fluid environment for sperm motility. ③ The female can produce normal, mature eggs, and the fallopian tubes are patent. ④ Normal sexual intercourse occurs around the time of the female's ovulation to ensure that the sperm and egg have the opportunity to meet.

While it's widely known that urological diseases can lead to infertility, men tend to focus on adjusting factors like diet and environment for prevention. Consequently, many men don't prioritize public awareness of urological health, resulting in these diseases going undetected and untreated. When infertility sets in, they often resort to desperate measures and unproven treatments.

In fact, andrological diseases are a major cause of infertility. In infertility clinics, patients diagnosed with andrological diseases commonly include prostatitis, seminal vesiculitis, and varicocele. These andrological diseases can cause oligospermia, asthenospermia, and necrospermia, which can impair male fertility and lead to infertility.

Why do urological diseases lead to infertility? First, let's understand the main steps of male reproduction. Through neuroendocrine regulation of the male reproductive system, the testes begin producing sperm. The sperm then mature in the epididymis. During ejaculation, the sperm mixes with seminal fluid secreted by the seminal vesicles and prostate gland to form semen. Finally, the semen successfully enters the female body and fertilizes an egg. If a man suffers from a urological disease, any of these steps may be affected, leading to infertility.

However, there are also patients in clinical practice with similar conditions like varicocele who have successfully fathered children without treatment. However, we cannot deny the harm this disease can cause to male fertility. Andrologists state that varicocele can cause an increase in testicular temperature, leading to a decrease in sperm count and motility. Furthermore, the testicles of men with varicocele are highly susceptible to toxins, which can completely impair their spermatogenic function. Therefore, the harm varicocele poses to male fertility is not insignificant.

In addition, sexual dysfunction, a condition that men dread, is also a cause of infertility. Common sexual dysfunctions include premature ejaculation, erectile dysfunction, and ejaculatory dysfunction. Erectile dysfunction prevents the penis from penile penetration, preventing sperm from meeting the egg and causing infertility. Ejaculatory dysfunction prevents the man from ejaculating during intercourse, or from ejaculating inside the woman's body, also leading to infertility.

In conclusion, andrological diseases are closely related to infertility. Therefore, understanding andrological diseases can effectively prevent infertility. It is also important to remember that andrological diseases, like other physiological illnesses, are not something to be ashamed of. Patients should not avoid seeking medical attention but should promptly consult a reputable hospital for examination and treatment.

Based on the location of physiological changes, they can be divided into: physiological changes caused by pre-testicular factors, such as endocrine diseases, hypothalamic tumors, pituitary tumors, hyperprolactinemia, etc.; physiological changes caused by testicular factors, such as varicocele, cryptorchidism, orchitis, congenital hereditary diseases, etc.; and physiological changes caused by post-testicular factors, such as reproductive tract obstruction, epididymitis, ejaculatory dysfunction, etc.

Specifically, this can be manifested in the following aspects:

(1) Spermatogenic dysfunction: refers to reproductive disorders caused by primary hypogonadism due to lesions of the seminiferous tubules or interstitial tissue of the testes. Conditions such as congenital testicular hypoplasia, Klinefelter syndrome, cryptorchidism, varicocele, testicular trauma, testicular inflammation, and testicular torsion leading to atrophy can all cause spermatogenic dysfunction. Hypothalamic and pituitary dysfunction, radioactive substances, and spermatogenic inhibitors can also affect sperm production and maturation.

(2) Obstruction of the vas deferens: The epididymis, vas deferens and ejaculatory duct are the channels through which sperm are transported. If these channels are blocked, sperm cannot pass through and infertility will result. Common causes of obstruction include congenital absence or atresia of the vas deferens, gonorrhea, tuberculosis and other reproductive tract inflammations.

(3) Abnormal semen: Abnormalities in the quantity and quality of semen can affect fertility.

(4) Immune factors: Infertility is caused by the production of antisperm antibodies in the male body, which catastrophically kill sperm in the reproductive tract. This is an autoimmune infertility. Antisperm antibodies can be produced in the human body when there is damage, infection, obstruction of the reproductive tract, the effects of certain drugs, local heating and cooling of the testes, or congenital genetic factors.

(5) Accessory gland abnormalities: Abnormalities in prostate and seminal vesicle function can both cause infertility.

(1) Cryptorchidism: The testis remains stuck in one place during its descent and fails to descend into the scrotum, or the testis is ectopic. Examination may reveal scrotal hypoplasia, absence of one or both testes, and the undescended testis can usually be felt at the base of the scrotum, inguinal canal, femoral triangle, or internal ring. Unilateral cryptorchidism generally only reduces fertility, while bilateral cryptorchidism leads to infertility.

(2) Anorchia: True anorchia is very rare. The main manifestations are the absence of puberty and the absence of development of secondary sexual characteristics. The patient has a castrated appearance and personality, and the sex hormone levels are abnormal in laboratory tests.

(3) Congenital penile developmental abnormalities: Congenital penile abnormalities that can lead to male infertility include concealed penis or absence of penis, micropenis, ectopic penis, etc. Concealed penis or absence of penis clinically manifests as lack of erection and inability to have sexual intercourse; patients with micropenis (length less than 5cm) often have testicular abnormalities and other endocrine diseases, which affect normal sexual intercourse or even if they can have normal sexual intercourse, they are unable to have fertility due to low sperm count; ectopic penis is commonly a posterior penis of the scrotum, and is often accompanied by urethral malformations, which lead to infertility due to impaired sexual function.

(4) Congenital urethral abnormalities: usually including epispadias and hypospadias. These malformations can often affect sexual intercourse and prevent sperm from entering the female reproductive tract, resulting in infertility.