The transport function of the vas deferens and the body's hormone regulation axis
**A continuous stream of tireless vas deferens**
In Aksu region of Xinjiang, a beautiful love story about a spring in the Tianshan Mountains is told:
Legend has it that in the land of Kucha, there was a spring inhabited by a beautiful fairy named Princess Spring. The local tribal leader was a handsome prince, wielding a bow and arrow. One day, Princess Spring was admiring the scenery from a mountaintop when she suddenly saw a group of hunters galloping across the grasslands below. They rode across the vast plains, and the leader of the hunters was the prince. Princess Spring and the prince fell in love at first sight on the boundless grasslands. However, the Desert King also loved Princess Spring, and he constantly interfered, eventually abducting her. From then on, the spring dried up, the vegetation in Kucha withered, and the crops died. The prince overcame all difficulties, devised a plan to defeat the Desert King, and rescued Princess Spring. Thousands of years have passed, and to this day, the spring still lovingly nourishes the tall pine trees with its clear waters, sustaining youthful life.
In fact, within a man's body, there is a place like this spring, continuously nourishing life and flowing ceaselessly for the purpose of procreation. The vas deferens in a man is like a perpetually flowing spring, always in motion for the continuation of life.
The vas deferens is a continuous section of the epididymal duct, originating at the tail of the epididymis and terminating in the ejaculatory duct. It is 40–60 cm long and approximately 3 mm in diameter, divided into three parts. The vas deferens is capable of autonomous rhythmic contraction. It serves as the passageway for transporting sperm from the epididymis to the prostatic urethra. Sperm are produced in the testes and, with the aid of contraction of the seminiferous tubules, enter the efferent ducts of the testes. Here, the movement of cilia on the ductal skin propels the sperm into the epididymis, where they undergo functional maturation. The walls of the epididymal tail and the vas deferens have thick muscle fibers. During ejaculation, the vas deferens contracts in a coordinated manner, allowing sperm to pass through and enter the prostatic urethra.
The vas deferens is the only passageway for transporting sperm, characterized by thick walls and a small lumen. Without the vas deferens, sperm cannot be ejaculated through the penis, and fertilization cannot occur. The vas deferens is a key area in male family planning surgery. Male sterilization involves ligating both vas deferens, preventing mature sperm from being transported out, thus achieving sterilization. After sterilization, the vas deferens can be surgically reconnected, restoring male fertility.
The vas deferens is an important organ for ejaculation and should be avoided by touching it. The vas deferens consists of two long, thin tubes, one on each side, each approximately 40 centimeters long. One end connects to the epididymal duct, and the other end merges with the seminal vesicle duct to form the ejaculatory duct, which opens into the posterior urethra. The vas deferens also stores a portion of mature sperm. Under the influence of norepinephrine released by the sympathetic nervous system, the smooth muscles of the epididymal tail, vas deferens, and ejaculatory duct undergo coordinated, rhythmic, and strong contractions, propelling the fluid and sperm from the epididymal tail and vas deferens into the posterior urethra. The fluid from the vas deferens flows directly into the posterior urethra through the ejaculatory duct, bypassing the seminal vesicle. Under sympathetic nerve control, the smooth muscles of the seminal vesicle undergo 6-10 peristaltic contractions, expelling their secretions into the posterior urethra. The seminal vesicle fluid contains almost no sperm, and its expulsion helps flush sperm from the urethra. Sympathetic nerve excitation also causes contraction of the prostate smooth muscle. This process promotes the discharge of prostatic fluid, and the bladder sphincter also contracts, allowing semen to be discharged into the posterior urethra. Through a series of reflex actions and coordinated contractions of the perineal muscles, the semen is discharged into the anterior urethra, completing the entire ejaculation process.
The vas deferens extends from the epididymis to the neck of the seminal vesicle, directly connecting with the epididymal duct, and is the final duct for the expulsion of the testis. It originates at the tail of the epididymis, ascends along the posterior border of the testis medially, passes through the external inguinal ring, passes through the inguinal canal to the level of the internal inguinal ring, and terminates at the ejaculatory duct. It is a muscular canal with thick walls and a narrow lumen. The wall consists of three layers: mucosa, muscle layer, and adventitia. The vas deferens can undergo voluntary rhythmic contractions, with the contraction frequency gradually increasing from the proximal end (epididymis) to the distal end. The strong rhythmic contractions during ejaculation are caused by the synchronous release of large amounts of norepinephrine from the sympathetic nervous system.
Vasectomy is a type of vasectomy. The vas deferens is relatively superficial and can be fixed through the skin. Infiltration anesthesia is then performed on both sides of the scrotum in areas with sparse blood vessels. The skin is incised, the vas deferens is extracted and freed, and cut slightly away from the epididymis, removing approximately 0.8 cm. The two ends are ligated and buried. After confirming there is no bleeding, the skin is sutured. This procedure is simple and safe. As long as aseptic techniques and surgical procedures are strictly followed, and the procedure is performed carefully, complications are extremely rare. If complications do occur, they can be effectively resolved with timely detection and appropriate treatment.
The following precautions should be taken after vasectomy:
1. Pay attention to bleeding. If bleeding is found on the gauze strip within 24 hours after vasectomy, you should immediately consult a doctor for examination and timely treatment.
2. After a vasectomy, patients should remain in the hospital for observation for 1-2 hours. If no abnormalities are observed, they can go home. It is best to travel by car or walk slowly, and avoid cycling. After returning home, it is important to rest more and avoid excessive activity to prevent pain and hematoma. Depending on the nature of your work, you may need to rest for 7-14 days after the surgery.
3. Be careful not to remove the gauze from the incision site, and do not touch the wound with your hands. Do not bathe before the incision heals after vasectomy to prevent infection. For some more sensitive individuals, a T-bandage or towel can be used to support the scrotum for about a week to prevent pain.
4. The scrotal skin has a strong healing ability; if no sutures were made or subcutaneous sutures were used, the sutures do not need to be removed. If only one suture was made to the skin, it can be removed 4-5 days after vasectomy.
5. Sexual activity should be avoided for two weeks after vasectomy.
6. It is important to note that after a vasectomy, many live sperm may remain in the distal end of the vas deferens and the ampulla of the vas deferens.
**Human hormones play a crucial role in reproduction.**
The Song Dynasty poet Hong Zikui once wrote a seven-character quatrain about landscapes titled "White Crane Temple," which reads:
"The cleft-lipped well should be a thousand feet deep, the bald-topped cedar tree should be a hundred spans in circumference. The crane has gone and no one is heard laying eggs, while countless wasps return to gather nectar."
The "bald-headed fir" in the poem inevitably evokes images of a cold winter, with the north wind howling. The bare tree, like a bald old man, sways in the biting northwest wind, emitting a sharp, piercing whistle... But then, the poem introduces countless wasps returning from gathering nectar. It seems this can't be winter, so the bald tree isn't an old man, but perhaps a young and strong youth!
The saying "extremely intelligent" is not without basis. According to a large number of studies, the vast majority of bald people are intelligent. Their spatial recognition ability and mathematical talent are closely related. Therefore, those who are prone to hair loss and baldness have far higher talents in mathematics and other fields than the average man.
In addition, male baldness indicates that the man has high levels of male hormones or that his body is more sensitive to male hormones, and that he has a stronger libido than normal people.
Research has shown that baldness, a phenomenon that men often avoid, is closely related to male endocrine function. The endocrine regulation of male reproductive function is achieved through the hypothalamus-pituitary-testicular axis. The main pathway of this axis involves the hypothalamus secreting gonadotropin-releasing hormone (GnRH), which travels through the portal vein to the anterior pituitary gland, stimulating it to secrete gonadotropins-luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Under the influence of these gonadotropins, testicular cells secrete androgens, with testosterone being the primary regulator, acting on target cells to trigger a series of biological effects.
Normal reproductive function is regulated not only by the gonadal axis but also by neurotransmitters at various levels of the central nervous system. Central nervous systems outside the hypothalamus, such as the amygdala, hippocampus, and midbrain, participate in the regulation of reproductive function. These external central nervous systems influence human reproductive function. Decreased serum testosterone levels in men experiencing mental stress or serious illness indicate that the function of the cerebral cortex has a significant impact on reproductive endocrine regulation. The information from central neurotransmitters to the hypothalamus represents the influence of various environmental factors, such as the external environment (temperature, light), stress states (pain, fear, and psychological factors), and internal rhythms (daily, monthly, and seasonal cycles). External environmental factors converge on the hypothalamus, influencing or regulating the function of the hypothalamus-pituitary-testicular axis. Simultaneously, hormones secreted by the testes also reach the hypothalamus and pituitary gland via the bloodstream to exert regulatory effects, and pituitary gonadotropins also act on the hypothalamus, a process known as feedback regulation. High concentrations of androgens in the blood can feedback-inhibit the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). At the same time, testosterone can also inhibit the hypothalamus's responsiveness in secreting gonadotropin-releasing hormone.
The hypothalamus, located at the base of the brain, plays a crucial role in reproductive endocrine regulation. The nerve cells in the hypothalamus have a dual function: they are both nerve cells, capable of receiving brain regulation and triggering nerve impulses, and endocrine cells, converting incoming nerve signals into hormonal information. Therefore, they are also known as neuroendocrine cells.
The hypothalamus secretes gonadotropin-releasing hormone (GnRH), primarily synthesized by neuroendocrine cells located in the medial basal region of the hypothalamus. After synthesis, it is released into the pituitary portal system, reaching the distal anterior pituitary gland and stimulating the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The half-life of GnRH after entering the bloodstream is very short, only 2-4 minutes. The main function of GnRH secreted by the hypothalamus is to promote the synthesis and release of gonadotropins-luteinizing hormone (LH) and follicle-stimulating hormone (FSH). After reaching the pituitary gland via the portal system, GnRH stimulates the synthesis and release of these two gonadotropins. LH and FSH are secreted into the blood in a transient manner. The metabolic rate of LH in the blood is faster than that of FSH; therefore, a single blood concentration measurement may not accurately reflect the concentrations of LH and FSH in clinical practice.