The microscopic world of prostate and seminal vesicle structure and spermatogenesis

The prostate is a firm, flat, chestnut-shaped organ. It measures 4 cm × 3 cm × 2 cm and weighs approximately 20 grams. Located below the bladder neck, it is composed of glandular tissue, smooth muscle, and connective tissue. Glandular tissue accounts for about half of the prostate. The size of the prostate increases with sexual development, generally starting to grow rapidly from age 16, reaching its peak at age 24, and then gradually regressing in old age. Prostate development often occurs concurrently with testicular development. The secretions of the prostate are alkaline and are part of semen, which is beneficial for sperm survival.

The seminal vesicle, also known as the seminal vesicle gland, is located above and behind the prostate gland. It is a cone-shaped sac, about 5 cm long and 2 cm wide, with one on each side. It is a pair of curved tubes with blind ends on the outer side.

The lower inner end of the seminal vesicle contains small excretory ducts that join the ampulla of the vas deferens to form the ejaculatory ducts. Like the prostate gland, the seminal vesicle is a major organ for producing seminal fluid. Most of the fructose in semen is secreted by the seminal vesicle, providing energy for sperm and aiding in sperm motility.

This is the basic physiological structure and characteristics of the male reproductive system. Understanding these allows us to recognize the unique characteristics of male diseases and thus take relevant prevention and treatment measures. The male "sexual axis" should be the hypothalamus-pituitary-testis axis. When the male neuroendocrine system is imbalanced, it will affect the production of reproductive cells.

**The “Exquisite” Hall of Life's Creation**

In 2003, the South Korean film *Silmido* told a classic tale of a hero's tragic end. The commander's choice between love and law was particularly gripping and unforgettable! However, what left the deepest impression was a film review:

"Silmido" tells the story of how 31 sperm cells were masturbated by the state. These sperm cells faced only two paths: either die silently in the scrotum, which resembled a prison cell, like a real protein, or compete fiercely for the single egg, perhaps even giving birth to a new life.

Of course, all 31 sperm chose the latter without hesitation. How many times in life can one take such a gamble?

Tragically, despite their immense effort and unimaginable grueling training-mastering the skill of navigating the vas deferens to its ultimate goal-on the day of release, during their frenzied advance, they discover they've fallen into a state of masturbation...

As we all know, a man's sperm is very precious, so what kind of life state do these precious sperm actually have?

Sperm is a highly differentiated cell. Under a light microscope, it can be divided into a head and a tail. Under an electron microscope, the tail can be further divided into four parts: the neck, midpiece, main segment, and terminal segment. Human sperm resembles a tadpole and is about 60 micrometers long. The sperm head is generally flattened and oval, mainly composed of a highly condensed nucleus containing chromosomes and other substances. The anterior two-thirds of the nucleus is covered by the acrosome, a specialized lysosome containing various hydrolytic enzymes such as proteases, hyaluronidase, corona radiata penetrating enzyme, and acid phosphatase. These enzymes are released during fertilization to hydrolyze the corona radiata and zona pellucida on the surface of the egg, assisting the sperm in entering the egg cell. The acrosome is a rather unstable part, easily degenerating and detaching from the head. The neck is the connecting region between the head and tail. The midpiece connects the neck and the main segment and contains a large number of mitochondria. Mitochondria contain a large number of oxidases, whose main function is to produce energy to power sperm motility. The main segment, also known as the flagellum, is the longest part of the sperm tail and is about 55 micrometers long. It is the sperm's motility apparatus. The terminal segment is very short. Sperm movement is mainly propelled forward by the whip-like undulations of the tail.

Sperm heads contain chromosomes, which in turn contain a large number of genes. A gene is a segment of nucleotides located at a specific position on a chromosome that encodes a protein with a specific function. Genes carry genetic information and are the basic structural and functional units of heredity. Genes express the genetic information they carry by directing protein synthesis, thereby controlling the phenotypic expression of an organism.

Simply put, each chromosome is like a set of building blocks, and genes are the individual blocks, each with a unique function and capable of being combined with each other. Different gene sequences and arrangements create different human characteristics, just like how building blocks can be assembled into various shapes.

Genes transmit hereditary information to the next generation, causing offspring to exhibit traits similar to their parents. Humans have approximately tens of thousands of genes, storing all the information about the processes of conception, growth, and death. Through replication, expression, and repair, they complete vital physiological processes such as reproduction, cell division, and protein synthesis. All life phenomena-birth, growth, disease, aging, and death-are related to genes. They are also the intrinsic factors determining human health.

Normal male spermatogonia have a chromosome configuration of 44+XY. Through processes such as meiosis, the resulting sperm cells have half the number of chromosomes. A single spermatogonia undergoes multiple mitotic divisions, eventually producing many spermatids, no two of which are identical. During the first meiotic division, the 23 pairs of chromosomes in the primary spermatocyte are randomly assigned to secondary spermatocytes in a 2^2^3 combination, resulting in 888,608 different chromosome combinations. Furthermore, each chromosome contains many genes, and these genes may exchange segments, forming new genetic relationships. Therefore, each sperm cell possesses unique genetic information, which is the physiological basis for the complex heredity and variation observed in humans.

Male sperm carries two chromosome configurations: 22+X or 22+Y. These two chromosomes, when combined with a female egg, will result in either a girl or a boy, respectively.

The Y chromosome is not only involved in male differentiation but also directly affects spermatogenesis. Abnormalities in the structure or function of the Y chromosome can lead to impaired sperm production, causing azoospermia or oligospermia. This condition is usually caused by congenital genetic factors.

Maintaining normal spermatogenesis also requires the coordinated action of sex hormones, primarily follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone. If a man's hormone secretion is abnormal, such as insufficient secretion of gonadotropin-releasing hormone (GnRH), LH, and FSH from the hypothalamus due to various reasons, he will be unable to produce a normal quantity and function of sperm.

These effects stem from an individual's living environment and can be eliminated by changing lifestyle habits and habits.

1. Temperature: The temperature inside the scrotum is about 3°C ​​lower than that in the abdominal cavity. This temperature is suitable for sperm production; excessively high temperatures will inhibit sperm production. During a man's reproductive years, especially when planning to have children, he should avoid wearing tight clothing, reduce bathing methods that raise scrotal temperature such as hot baths and saunas, and also avoid work and lifestyle habits that raise scrotal temperature, such as prolonged sitting.

2. Radiation, microwaves, malnutrition, unhealthy diet, and anticancer drugs can all inhibit spermatogenesis, hindering sperm production. Men of reproductive age should avoid exposure to radioactive and radiation-emitting substances. If radioactive or radiation-emitting substances are present in the work environment, a change of job should be made at least six months before conceiving to avoid exposure to these substances. Furthermore, men planning to have children should pay attention to a balanced diet, consuming plenty of protein-rich foods to increase the supply of substances needed for sperm synthesis. Foods containing nitrites, such as pickled foods, cottonseed oil, barbecued foods, canned foods containing environmental estrogens like bisphenol A, and excessive consumption of celery can all damage testicular spermatogenesis, reducing sperm count and quality.