Anatomy and physiology of the male genitourinary system. male reproductive system
The male reproductive system includes the scrotum, testicles, seminal ducts, gonads, and penis. These organs work together to produce sperm, male gametes, and other components of sperm. These organs also work together to carry sperm out of the body and into the vagina, where it will help fertilize the egg to produce offspring… [Read below]
[Start from above] … Scrotum
The scrotum is a burso-like organ made of skin and muscle where the testes are located. It is located lower than the penis in the pubic region. The scrotum consists of 2 testis sacs located side by side. The smooth muscles that make up the scrotum allow them to regulate the distance between the testes and the rest of the body. When the testicles become too warm to support spermatogenesis, the scrotum relaxes to move the testicles away from heat sources. Conversely, the scrotum moves closer to the body with the testicles when the temperature drops below the ideal range for spermatogenesis.
testicles
The 2 testes, also known as the testicles, are the male gonads responsible for the production of sperm and testosterone. The testicles are ellipsoidal glandular organs about 4 to 5 cm long and 3 cm in diameter. Each testis resides inside its own sac on one side of the scrotum and is connected to the abdomen by the funiculus and cremaster muscle. Internally, the testicles are divided into small compartments known as lobules. Each lobule contains a section of seminiferous tubules lined with epithelial cells. These epithelial cells contain many stem cells that divide and form sperm through the process of spermatogenesis.
Appendages
The epididymis is a sperm storage area that wraps around the superior and posterior margins of the testicles. The appendage consists of several long, thin tubes that are tightly coiled into a small mass. Spermatozoa are produced in the testicles and pass into the adnexa to mature before being passed through the male reproductive organs. The length of the appendage delays the release of spermatozoa and gives them time to mature.
spermatic cord and vas deferens
In the scrotum, a pair of spermatic cords connects the testes to the abdominal cavity. The spermatic cords contain the vas deferens along with the nerves, veins, arteries, and lymphatics that support the function of the testes.
The vas deferens is a muscular tube that carries semen from the epididymis into the abdominal cavity to the ejaculatory canal. The vas deferens is wider in diameter than the epididymis and uses its internal space to store mature sperm. The smooth muscles of the walls of the vas deferens are used to move sperm to the ejaculatory duct through the peristalsis.
seminal vesicles
The seminal vesicles are a pair of lumpy exocrine glands that store and produce some of the liquid semen. The seminal vesicles are about 5 cm long and are located behind the bladder closer to the rectum. The fluid in the seminal vesicles contains proteins and phlegm and has an alkaline pH to help sperm survive the acidic environment of the vagina. The liquid also contains fructose to feed the sperm cells so they survive long enough to fertilize an egg.
Ejaculatory canal
The vas deferens passes through the prostate and joins the urethra at a structure known as the ejaculatory duct. The ejaculatory canal also contains canals from the seminal vesicles. During ejaculation, the ejaculatory canal opens and expels semen and secretions from the seminal vesicles into the urethra.
Urethra
Sperm travels from the ejaculatory canal to the outside of the body through the urethra, a 20 to 25 cm long muscular tube. The urethra passes through the prostate and ends at the external opening of the urethra, located at the end of the penis. Urine exiting the body, from the bladder, passes through the urethra.
The walnut-sized prostate gland borders the lower end of the bladder and surrounds the urethra. The prostate produces most of the fluid, which is semen. This liquid is milky white in color and contains enzymes, proteins and other chemicals to support and protect sperm during ejaculation. The prostate also contains smooth muscle tissue that can contract to prevent the flow of urine or semen.
cooper glands
Cooper's glands, also known as bulbourethral glands, are a pair of pea-sized exocrine glands located below the prostate and up to the anus. Cooper's glands secrete a thin, alkaline fluid into the urethra, which lubricates the urethra and neutralizes acid from the urine that remains in the urethra after urination. This fluid enters the urethra during sexual arousal prior to ejaculation to prepare the urethra for the flow of semen.
Penis
The penis is the male external sex organ located above the scrotum and below the navel. The penis is roughly cylindrical and contains the urethra and the external opening of the urethra. Large pockets of erectile tissue in the penis allow it to fill with blood and become erect. Excitation of the penis leads to its increase in size. The function of the penis is to deliver semen to the vagina during intercourse. In addition to its reproductive function, the penis also allows urine to pass through the urethra to the outside of the body.
Sperm
Sperm is the fluid produced by males for sexual reproduction and ejected from the body during intercourse. Sperm contains spermatozoa, the male sex gametes, along with a range of chemicals suspended in a fluid medium. The chemical makeup of semen gives it a thick, sticky texture and a slightly alkaline pH. These traits help sperm maintain reproduction by helping sperm stay in the vagina after intercourse and to neutralize the acidic environment of the vagina. In healthy adult males, semen contains about 100 million sperm per milliliter. These sperm cells fertilize the oocytes inside the female fallopian tubes.
spermatogenesis
Spermatogenesis is the process of sperm production that occurs in the testicles and appendages of adult males. Before puberty, there is no spermatogenesis due to the lack of hormonal triggers. During puberty, spermatogenesis begins when enough luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are produced. LH initiates the production of testosterone by the testicles, while FSH causes the maturation of germ cells. Testosterone stimulates stem cells in the testes, known as spermatogonia. Each diploid spermatocyte goes through the process of meiosis I and splits into 2 haploid secondary spermatocytes. Secondary spermatocytes go through meiosis II to form 4 haploid spermatids of the cell. Spermatid cells go through a process known as spermatogenesis, where they grow a flagellum and develop a sperm head structure. After spermatogenesis, the cell finally turns into spermatozoa. The spermatozoa are ejected into the appendages, where they complete their maturation and become able to move on their own.
Fertilization
Fertilization is the process by which a sperm combines with oocytes or eggs to become a fertilized zygote. The sperm released during ejaculation must first swim through the vagina and uterus into the fallopian tubes, where they can find an egg. Having collided with the egg, the sperm must penetrate the layers of the oocyte. Sperm cells contain enzymes in the acrosomal region of the head, which allows them to penetrate these layers. Once inside the oocyte, the nuclei of these cells fuse to form diploid cells known as the zygote. The zygote cell begins cell division to form an embryo.
The male reproductive organs are considered less complex than the female ones. However, they are by no means limited to externally visible genitalia. Inside the male body, there is a complex system of tubules and ducts connected to the reproductive organs.
The epididymis is the epididymis of the testis. It is a highly convoluted canal and is part of the vas deferens. The appendage is lined with connective tissue adjacent to the testis and located on the upper part of the testicle. In this channel, spermatozoa mature and acquire the ability to be fertilized.
Another part of the sperm storage and transport system is a long curved canal - the vas deferens. The seminal vesicles are connected to it: two formations located behind the bladder. They produce part of the seminal fluid, which is necessary for the movement and nutrition of spermatozoa.
An important organ for men's health is the prostate gland. The size of a chestnut, it is located below the bladder. It forms 60% of the seminal fluid necessary for the transport of spermatozoa.
It would seem that for fertilization, that is, for the ultimate goal, only one sperm is needed. But mother nature has programmed it so that every day the male body produces millions of germ cells. From the testicle, they enter the epididymis, an organ that stores and provides nutrients to mature spermatozoa. The complete process of sperm maturation, from the germ cell in the seminiferous tubule to the mature form in the vas deferens, takes approximately 74 days. Normally, in order to become a father, a man must have at least 60-70 million spermatozoa in his semen.
Men who have had this disease in the post-puberty period need to be especially attentive to their male health and carefully check the possibility of having children. Mumps damages the sperm progenitor cells in the testicles. In most cases, only one testicle is affected, however some men develop complete infertility.
Varicocele
Varicocele is the presence of varicose veins in the testicles. The development of this pathology leads to a violation of blood flow in this area. An increase in blood supply leads to an increase in temperature in the testicle. This causes a decrease in testosterone levels, which in turn disrupts sperm production.
Cryptorchidism (undescended testicle)
While the boy is in the womb, his testicles are located inside the abdominal cavity. Shortly before birth, they descend into the scrotum. If the descent of the testicle does not occur before birth, this condition in the newborn is called cryptorchidism. Usually, during the first 6 months of life, the testicles descend into the scrotum on their own. However, it must be remembered that unresolved and untreated cryptorchidism can lead to impaired fertility and other pathological conditions.
testicular cancer
If you are having difficulty conceiving, you should definitely get tested for possible testicular cancer. A malignant tumor, developing in this organ, can destroy normal testicular tissue, which will lead to infertility.
Not so long ago, the negative impact of diabetes on the quality of spermatozoa was proven. In addition, hormonal imbalance due to overweight in type II diabetes also leads to problems in childbearing.
Trauma and surgery
Severe mechanical damage to the testicles disrupts the production of germ cells, which leads to the development of infertility. In addition, an injury sustained during sports or as a result of an accident can cause a rupture of the blood vessels supplying the testicles with blood. Unfortunately, surgery to correct an undescended testicle or an inguinal hernia can lead to impaired sperm production.
Anatomical anomalies
In some individuals, the fluid released during sexual intercourse does not contain spermatozoa at all. This phenomenon may be the result of obstruction or violation of the anatomical structure of the epididymis, which prevents the germ cells from mixing with seminal fluid to form sperm.
Overheat
Heating has a damaging effect on the physiological production of spermatozoa. Too much time in a hot bath can lead to an increase in testicular temperature and temporarily disrupt sperm production.
Severe stress, fatigue, or alcohol use
Overwork , anxiety and excessive alcohol consumption reduce sexual desire . But although until recently most cases of impotence were explained by psychological causes, new oral medications can improve treatment outcomes.
Wrong way of life
You can not discount the individual behavioral patterns, which can also affect fertility. For example, being overweight, eating unhealthy and unbalanced foods, combined with a sedentary lifestyle has a negative impact.
Male reproductive organs are intended for reproduction and maturation of male germ cells (spermatozoa), their excretion in the seminal fluid (sperm) and the formation of male sex hormones (androgens). The male reproductive organs are divided into internal and external. Internal male genital organs - testicles with appendages, vas deferens, seminal vesicles, prostate and bulbourethral (Cooper) glands. The external genitalia are the penis and scrotum.
Testicles, or testicles (testes; Greek orchis, seu didymis),- a paired organ located in the scrotum, in which spermatozoa multiply and mature and androgens are produced (they are glands of mixed secretion). In shape, each testicle represents an oval, laterally flattened body. The length of the testicle is 4 cm, width - 3 cm, thickness - 2 cm, weight - 20-30 g. There are medial and more convex lateral surfaces, anterior and posterior edges, upper and lower ends. Its appendage is adjacent to the posterior edge of the testicle.
Outside, the testicle is covered with a whitish dense fibrous membrane (albumen). At the posterior edge, it forms a thickening - the mediastinum, from which the partitions diverge forward, separating the substance (parenchyma) of the testicle into 250-300 lobules. In each lobule, there are 2-3 convoluted seminiferous tubules 70-80 cm long, 150-300 microns in diameter, containing spermatogenic epithelium. The total length of all tubules of one testicle is 300-400 m. In these tubules, spermatozoa are formed in adults. Near the mediastinum of the testis, the convoluted seminiferous tubules pass into the direct seminiferous tubules, and the latter, intertwining with each other in the mediastinum, form the network of the testis. In the connective tissue septa of the testis and in the tissue lying between the convoluted seminiferous tubules, there are glandular cells (interstitial, Fleydig cells) that produce androgens.
From the network of the testicle in the mediastinum, 12-15 efferent tubules begin, heading to the epididymis (epididymis) - the reservoir of spermatozoa, where they mature. In the epididymis, the head, body and tail are distinguished. The head of the epididymis is formed by 12-15 efferent tubules emerging from the testis, which, merging together, form the duct of the epididymis. The latter, strongly wriggling, reaches a length of 6-8 m, forms the body and tail of the epididymis and passes into the vas deferens.
The vas deferens (ductus deferens) right and left, tube 40-50 cm long, 3 mm in diameter, lumen diameter 0.5 mm. The wall of the duct has a considerable thickness, so it does not collapse and is easily palpable. It is a continuation of the duct of the epididymis, serves to remove sperm. From the tail of the epididymis, the duct as part of the spermatic cord rises, passes through the inguinal canal, and then descends along the side wall of the pelvis to the bottom of the bladder and approaches the base of the prostate next to the same duct on the opposite side. The final section of the vas deferens near the bladder has an expansion and forms an ampulla of the vas deferens 3-4 cm long, 1 cm in diameter. The wall of the vas deferens consists of three membranes: internal - mucous, middle - smooth muscle and external - adventitial.
Seminal vesicle (vesicula seminalis)- a paired organ located in the pelvic cavity laterally from the ampulla of the vas deferens, above the prostate gland, behind and to the side of the bottom of the bladder. The oblong body, 5 cm long, 2 cm wide and 1 cm thick, is a gland whose secretion is mixed with semen as a nourishing and protective liquid for spermatozoa, and also for semen liquefaction. The cavity of the seminal vesicle consists of tortuous chambers containing a proteinaceous fluid that is part of the sperm. This cavity in the lower part passes into the excretory duct, which connects with the vas deferens and forms the vas deferens. Having passed through the thickness of the prostate gland, both ejaculatory ducts, right and left, open on the seminal mound into the prostatic part of the urethra.
Prostate (prostata, seu glandula prostatica)- This is an unpaired glandular-muscular organ covering the initial section of the urethra. It secretes a secret that is part of the semen and stimulates spermatozoa. The gland is located at the bottom of the small pelvis under the bladder. The mass of the prostate gland is 20-25 g. It resembles a chestnut in shape and size. With its base, the prostate gland is turned upwards to the bottom of the bladder, the top is turned down to the urogenital diaphragm. The anterior surface of the gland faces the pubic symphysis, and the posterior surface faces the rectum.
The prostate gland consists of glandular (30-40 lobules in the back and side sections) and smooth muscle tissue (anterior), which is involved in the formation of the internal (involuntary) sphincter of the male urethra. When contracting, muscle tissue contributes to the ejection of secretions from the glandular lobules and narrowing of the urethra, i.e. retention of urine in the bladder while semen passes through the urethra. The totality of all the muscular elements of the gland is the prostatic muscle involved in ejaculation.
Bulbourethral (Cooper's) gland (glandula bulbourethralis)- a paired organ the size of a pea, located in the thickness of the urogenital diaphragm (behind the membranous part of the urethra at the end of the bulb of the cavernous body of the penis). By structure, it is an alveolar-tubular gland. The excretory ducts of the glands (3-4 cm long) open into the lumen of the urethra. The bulbourethral glands secrete a viscous fluid that protects the mucous membrane of the wall of the urethra from irritation by urine.
Inflammation of the testicle - orchitis, epididymis - epididymitis, prostate gland - prostatitis.
Penis (penis, rper. phallos) - an organ that serves to remove urine and seminal fluid. There is a front thickened part - the head, the middle - the body and the back - the root. On the head of the penis is the external opening of the urethra. Between the body and the head there is a narrowing - the neck of the head. The upper anterior surface of the body of the penis is called the back. The root of the penis is attached to the pubic bones. The penis is covered with skin and consists of three cylindrical bodies: two paired of them are called the cavernous bodies, and one unpaired is called the spongy body. The urethra passes inside the spongy body, which has an extension in the head - a scaphoid fossa. All 3 bodies of the penis have a connective tissue protein membrane, from which numerous partitions (trabeculae) extend, separating the cavernous and spongy bodies into a system of interconnected cavities - caves (caverns) ) lined with endothelium. These cavities during the excited state of the penis (erection) are filled with blood, their walls straighten out, as a result of which the penis swells, increases 2-3 times in volume, becomes hard and elastic. The spongy body of the penis is thickened at the ends. The posterior thickening is called the bulb, the anterior one is called the head. The skin of the penis on the head is tightly fused with the albuginea of the spongy body, and the rest of the length is mobile and easily extensible. In the region of the neck, it forms a fold (the foreskin of the penis), which, in the form of a hood, covers the head and can be displaced. On the back surface of the glans penis, the foreskin forms a fold - the frenulum of the foreskin, which almost reaches the edge of the external opening of the urethra.
Scrotum is a musculoskeletal sac containing both testicles with appendages and the initial sections of the spermatic cords. It is located downward and behind the root of the penis, formed by protrusion of the anterior abdominal wall and consists of the same layers. A suture runs along the midline of the scrotum - from the lower surface of the penis to the anus. The skin of the scrotum is folded, thin, pigmented, extensible, covered with sparse hair, supplied with sweat and sebaceous glands. The scrotum forms a "physiological thermostat" that maintains the temperature of the testicles at a lower level (32-34 ° C) than the body temperature, which is a necessary condition for normal spermatogenesis. The wall of the scrotum consists of seven layers - 1) skin; 2) fleshy membrane - corresponds to subcutaneous tissue; forms a scrotal septum that separates the right testicle from the left; 3) external seminal fascia; 4) fascia of the muscle that lifts the testicle; 5) muscle that lifts the testicle; 6) internal seminal fascia; 7) the vaginal membrane of the testicle is serous - corresponds to the peritoneum.
With a delay in lowering the testicles from the abdominal cavity into the scrotum, both testicles (cryptorchism) or one testicle (monorchism) may be absent in it.
The human body is a complex of physiological systems (nervous, cardiovascular, respiratory, digestive, excretory, etc.) that ensure the existence of a person as an individual. Violation of any of them leads to disorders, often incompatible with life. The functions of the reproductive or reproductive system are primarily aimed at the continuation of the existence of man as a biological species. All life-supporting systems function from the moment of birth to death, the reproductive "works" only in a certain age period, corresponding to the optimal rise in physiological capabilities. This temporal conditionality is associated with biological expediency - the bearing and rearing of offspring requires significant resources of the body. Genetically, this period is programmed for the age of 18–45 years.
Reproductive function is a complex of processes that covers the differentiation and maturation of germ cells, the process of fertilization, pregnancy, childbirth, lactation and subsequent care of offspring. Interaction and regulation of these processes are provided by the system, the center of which is the neuroendocrine complex: hypothalamus - pituitary gland - gonads. The central role in the implementation of the reproductive function is played by the reproductive, or genital, organs. The reproductive organs are divided into internal and external.
The structure and age features of the male reproductive system
In men, the internal genital organs include the gonads (testicles with appendages), the vas deferens, the vas deferens, the seminal vesicles, the prostate, and the bulbourethral (Cooper) glands; to the external genital organs - the scrotum and penis (Fig. 9.2).
Fig. 9.2.
Testicle - a paired male sex gland that performs exo- and endocrine functions in the body. The testicles produce spermatozoa (external secretion) and sex hormones that influence the development of primary and secondary sexual characteristics (internal secretion). In shape, the testicle (testis) is an oval, slightly compressed laterally body, lying in the scrotum. The right testicle is larger, heavier and located higher than the left.
The testicles are formed in the abdominal cavity of the fetus and before birth (at the end of pregnancy) descend into the scrotum. The movement of the testicles occurs along the so-called inguinal canal - an anatomical formation that serves to conduct the testicles to the scrotum, and after the completion of the lowering process - to locate the vas deferens. The testicles, having passed the inguinal canal, descend to the bottom of the scrotum and are fixed there by the time the child is born. Undescended testicle (cryptorchidism) leads to a violation of its thermal regime, blood supply, trauma, which contributes to the development of dystrophic processes in it and requires medical intervention.
In a newborn, the length of the testicle is 10 mm, the weight is 0.4 g. Before puberty, the testicle grows slowly, and then its development accelerates. By the age of 14, it has a length of 20–25 mm and a mass of 2 g. At 18–20 years, its length is 38–40 mm, weight - 20 g. Later, the size and weight of the testicle increase slightly, and after 60 years, slightly decrease.
The testicle is covered with a dense connective tissue membrane, which forms a thickening at the posterior edge, called mediastinum. From the mediastinum inside the testicle, radially located connective tissue septa extend, which divide the testis into many lobules (100–300). Each lobule includes 3–4 closed convoluted seminiferous tubules, connective tissue, and interstitial Leydig cells. Leydig cells produce male sex hormones, and the spermatogenic epithelium of the seminiferous tubules produce spermatozoa, consisting of a head, neck and tail. The convoluted seminiferous tubules pass into the direct seminiferous tubules, which open into the ducts of the testicular network located in the mediastinum. In a newborn, the convoluted and straight seminiferous tubules do not have a lumen - it appears by puberty. In adolescence, the diameter of the seminiferous tubules doubles, and in adult men it triples.
The efferent tubules (15–20) emerge from the network of the testis, which, strongly wriggling, form cone-shaped structures. The combination of these structures is an appendage of the testicle, adjacent to the upper pole and the posterolateral edge of the testicle, in which the head, body, and tail are distinguished. The epididymis of a newborn is large, its length is 20 mm, its weight is 0.12 g. During the first 10 years, the epididymis grows slowly, and then its growth accelerates.
In the region of the body of the appendage, the efferent tubules merge into the duct of the appendage, which passes into the region of the tail into vas deferens , which contains mature but immobile spermatozoa, has a diameter of about 3 mm and reaches a length of 50 cm. Its wall consists of mucous, muscular and connective tissue membranes. At the level of the lower pole of the testicle, the vas deferens turns upward and, as part of the spermatic cord, which also includes vessels, nerves, membranes and the muscle that lifts the testicle, follows the inguinal canal into the abdominal cavity. There it separates from the spermatic cord and, without passing through the peritoneum, descends into the small pelvis. Near the bottom of the bladder, the duct expands, forming an ampulla, and, having accepted the excretory ducts of the seminal vesicles, continues as ejaculatory duct. The latter passes through the prostate gland and opens into the prostatic part of the urethra.
In a child, the vas deferens is thin, its longitudinal muscle layer appears only by the age of 5. The muscle that lifts the testicle is poorly developed. The diameter of the spermatic cord in a newborn is 4.5 mm, at 15 years old - 6 mm. The spermatic cord and vas deferens grow slowly until the age of 14–15, and then their growth accelerates. Spermatozoa, mixing with the secretion of the seminal vesicles and the prostate gland, acquire the ability to move and form seminal fluid (sperm).
seminal vesicles are a paired oblong organ about 4-5 cm long, located between the bottom of the bladder and the rectum. They produce a secret that is part of the seminal fluid. The seminal vesicles of a newborn are poorly developed, with a small cavity, only 1 mm long. Up to 12–14 years old, they grow slowly, at 13–16 years old, growth accelerates, the size and cavity increase. At the same time, their position also changes. In a newborn, the seminal vesicles are located high (due to the high position of the bladder) and are covered on all sides by the peritoneum. By the age of two, they descend and lie retroperitoneally.
prostate (prostate) ) is located in the pelvic area under the bottom of the bladder. Its length in an adult man is 3 cm, weight - 18-22 g. The prostate consists of glandular and smooth muscle tissues. The glandular tissue forms lobules of the gland, the ducts of which open into the prostate part of the urethra. Prostate mass in a newborn
0.82 g, at 3 years old - 1.5 g, after 10 years there is an accelerated growth of the gland and by the age of 16 its mass reaches 8–10 g. The shape of the gland in a newborn is spherical, since the lobules are not yet expressed, it is located high, has a soft texture, glandular tissue is absent in it. By the end of the pubertal period, the internal opening of the urethra shifts to its anterior superior edge, the glandular parenchyma and prostate ducts are formed, the gland acquires a dense texture.
bulbourethral (Cooper's) gland - a paired organ the size of a pea - located in the urogenital diaphragm. Its function is to secrete a mucous secretion that promotes the movement of sperm through the urethra. Its excretory duct is very thin, 3-4 cm long, opens into the lumen of the urethra.
Scrotum is a receptacle for testicles and appendages. In a healthy man, it is reduced due to the presence in its walls of muscle cells - myocytes. The scrotum is like a "physiological thermostat" that maintains the temperature of the testicles at a lower level than the body temperature. This is a necessary condition for the normal development of spermatozoa. In a newborn, the scrotum is small in size, its intensive growth is observed during puberty.
Penis has a head, neck, body and root. The head is the thickened end of the penis, on which the external opening of the urethra opens. Between the head and the body of the penis there is a narrowed part - the neck. The root of the penis is attached to the pubic bones. The penis consists of three cavernous bodies, two of which are called the cavernous bodies of the penis, the third - the spongy body of the urethra (the urethra passes through it). The anterior part of the spongy body is thickened and forms the head of the penis. Each cavernous body is covered on the outside with a dense connective tissue membrane, and inside it has a spongy structure: thanks to numerous partitions, small cavities (“caves”) are formed, which fill with blood during intercourse, the penis swells and comes into a state of erection. The length of the penis in a newborn is 2-2.5 cm, the foreskin is long and completely covers its head (phimosis). In children of the first years of life, the state of phimosis is physiological, however, with a pronounced narrowing, swelling of the foreskin can be noted, leading to difficulty urinating. A whitish sebaceous substance (smegma) accumulates under the foreskin, produced by glands located on the glans penis. If personal hygiene is not followed and infection is added, smegma decomposes, causing inflammation of the head and foreskin.
Before puberty, the penis grows slowly, and then its growth accelerates.
Spermatogenesis - the process of development of male germ cells, ending with the formation of spermatozoa. Spermatogenesis begins under the influence of sex hormones during the puberty of a teenager and then proceeds continuously, and in most men - almost until the end of life.
The process of sperm maturation occurs inside the convoluted seminiferous tubules and lasts an average of 74 days. On the inner wall of the tubules are spermatogonia (the earliest, first cells of spermatogenesis), containing a double set of chromosomes. After a series of successive divisions, in which the number of chromosomes in each cell is halved, and after a long phase of differentiation, spermatogonia turn into spermatozoa. This happens by gradual stretching of the cell, changing and elongating its shape, as a result of which the cell nucleus forms the head of the spermatozoon, and the membrane and cytoplasm form the neck and tail. Each spermatozoon carries a half set of chromosomes, which, when combined with a female germ cell, will give a complete set necessary for the development of the embryo. After that, mature spermatozoa enter the lumen of the testicular tubule and further into the epididymis, where they are accumulated and excreted from the body during ejaculation. 1 ml of semen contains up to 100 million spermatozoa.
A mature, normal human spermatozoon consists of a head, neck, body, and tail, or flagellum, which ends in a thin terminal filament (Fig. 9.3). The total length of the spermatozoon is about 50–60 µm (head 5–6 µm, neck and body 6–7 µm, and tail 40–50 µm). In the head is the nucleus, which carries the paternal hereditary material. At its anterior end is the acrosome, which ensures the penetration of the sperm through the membranes of the female egg. Mitochondria and spiral filaments are located in the neck and body, which are the source of the motor activity of the spermatozoon. An axial filament (axoneme) departs from the neck through the body and tail, surrounded by a sheath, under which 8–10 smaller filaments are located around the axial filament - fibrils that perform motor or skeletal functions in the cell. Motility is the most characteristic property of the spermatozoon and is carried out with the help of uniform blows of the tail by rotating around its own axis in a clockwise direction. The duration of the existence of the sperm in the vagina reaches 2.5 hours, in the cervix - 48 hours or more. Normally, the spermatozoon always moves against the flow of fluid, which allows it to move up at a speed of 3 mm / min along the female genital tract until it meets the egg.
Includes internal and external genitalia.
Internal male reproductive organs.
These include: testicles with appendages, vas deferens and ejaculatory ducts, seminal glands, prostate and bulbourethral glands.
Testicle,testis ,or testis,- steam male gland weighing 20-30 g the testicles are both glands of external and internal secretion. The testicles are located in a special container - moshonke, with the left lower than the right. They are laid in the abdominal cavity, and by the time of birth they descend into the inguinal canal, dragging the peritoneum with them. An undescended testicle is called monorchism, undescended testicles - cryptorchidism. The testicles are separated from each other by a septum and surrounded by membranes. The length of the testicle is on average 4 cm, width - 3 cm, thickness - 2 cm. The testicle is oval in shape, of a dense consistency and somewhat flattened from the sides. It distinguishes two surfaces: more convex outer and inner, as well as twothe edges: front and back. Secreted in the testicle upper and lower ends (poles).
The peritoneum forms a closed serous cavity around the testicle. Under serous shell the other shell of the testicle is located - protein, under which is parenchymatesticles. On the inner surface of the posterior edge of the testicle, the albuginea forms a thickening - mediastinum testicles, from which dense connective tissue extends into the thickness of the organ partitions testicles, dividing the gland into numerous (from 250 to 300) pyramidal slices, facing their tops to the mediastinum of the testis, and the bases - to the albumin. In each lobule pass 2-3 convoluted seminal ductca, 60-90 mm long, surrounded by loose connective tissue with a large number of blood vessels. From the inside, the walls of the convoluted seminiferous tubules are lined with a special multilayer spermtogenic epithelium in which the formation of male germ cells occurs - spermatozoa. This process is called stolematogenesis.
spermatozoa
These are mobile cells, about 70 microns long. The speed of their movement through the tubules is about 3.5 mm per minute.
They move towards the egg, which is due to chemotaxis. The life expectancy and fertilizing ability of human spermatozoa ranges from several hours to two days.
The spermatozoon has a nucleus, cytoplasm with its organelles and a cell membrane. The spermatozoon has a rounded head and thin long tail. The head contains a nucleus, in front of which is a structure called acrosome. The acrosome has a set of enzymes that are able to dissolve the egg cell membrane during fertilization. With underdevelopment or absence of the acrosome, the spermatozoon is not able to penetrate the egg and fertilize it.
The tail of the spermatozoon contains contractile elements (fibril bundles) that ensure the movement of the spermatozoon. When passing through the vas deferens, liquid secretions of the gonads - seminal vesicles, prostate and bulbourethral glands - are added to the spermatozoa. As a result, a liquid medium is formed in which spermatozoa are located - this is sperm.
spermatogenesis
Spermatozoa are formed in a person during the entire active period of a man's life. The duration of development and formation of mature spermatozoa from their predecessors - spermatogonia is about 70-75 days. This process occurs in the convoluted seminiferous tubules of the testis. Initially, spermatogonia (the number in one testicle is up to 1 billion), multiply intensively and divide by mitosis. At the same time, their number is increasing. In the future, part of the spermatogonia retains the ability to divide, others divide twice more in the form of meiosis. As a result, from each such spermatogonia with a diploid (double) set of chromosomes (46), 4 spermatids. Each of the spermatids has a haploid (single) set of chromosomes (23). Spermatids gradually turn into spermatozoa
The formed spermatozoa enter the lumen of the seminiferous tubules of the testis and, together with the fluid secreted by the walls of the tubules, gradually move towards the epididymis, which also serves as a reservoir for spermatozoa. The amount of sperm produced is enormous. 1 ml of semen contains up to 100 million spermatozoa.
Between the spermatogenic epithelium of the convoluted seminiferous tubules of the testicles are located supporting cells (Sertoli cells) that perform a trophic function for it. In addition, there are special cells - endocrinocytes (Leydig cells) that produce testosterone. Spermatozoa are produced only in the convoluted seminiferous tubules of the testis. All other testicular tubules and ducts of its epididymis are vas deferens. Spermatozoa are part of the semen, the liquid part of which is formed from the secretions of the seminal glands and the prostate gland.
Coming from all the lobules of the testis, the convoluted seminiferous tubules, merging, form short direct seminiferous tubules, which flow into the testicular network. From this network leaves 12-15 efferent tubules of the testis, which pierce the albuginea and penetrate into the head of the appendage.
epididymis, located along the posterior margin of the testis. There is an extended upper part - adnexal head, passing into the middle part - appendage body, which, in turn, continues into a tapering lower part - tailepididymis. On the head of the epididymis, sometimes there is a vesicle on the leg - appendagetesticles.
In the caudal part of the appendage, its duct passes, bending, into the vas deferens.
Function of the appendage: maturation of sperm (2-3 days), until ejaculation.
spermatic cord, is a small rounded cord 15-20 cm long, located in the inguinal canal from the upper end of the testicle to the deep inguinal ring. In the composition of the spermatic cord are included : vas deferens, arteries of the vas deferens and testis, venous plexus, lymphatic vessels and nerves. All these formations envelop internal seminal fascia. Outside of her is muscle that lifts the testis, covered with the fascia of the same name. Outside, the entire spermatic cord surrounds outdoor seed fascia.
Seminiferous(vas deferens) duct,- a paired organ 40-50 cm long and about 3 mm in diameter. As part of the spermatic cord goes up to the inguinal canal. It distinguishes 4 parts:
- scrotal located behind the testicle;
- kanatikowow, passing in the composition of the spermatic cord to the superficial inguinal ring;
- inguinal- in the inguinal canal;
- pelvic the part that runs from the inguinal ring to the prostate gland.
After passing the canal, the vas deferens descends into the small pelvis to the bottom of the bladder. Near the prostate gland, its final part expands and forms ampoule seedswearing duct. In the lower part, the ampulla gradually narrows and passes into a narrow canal, which merges with the excretory duct of the seminal gland in ejaculatory duct. The latter, having passed through the wall of the prostate gland, opens into the prostatic part of the urethra. The wall of the vas deferens is composed of mucous shells with submucosal basis, muscular and adventitious shells.
Seminal (bubble) glands or seminal vesicles,vesiculae seminales - bag-shaped tubular formations about 5 cm long, forming many bends and protrusions. The glands are a secretory organ, located in the pelvic cavity behind and to the side of the bottom of the bladder, above the prostate gland. In each seminal gland, an upper expanded end is distinguished - base, middle part - body and lower narrowing the end, which passes into the excretory duct. The wall of the glands is formed by mucous, muscular and adventitial membranes. The cavity of the seminal glands consists of chambers containing protein secret. It is a viscous yellowish liquid that protects sperm from acidic vaginal contents and makes them motile. The secret also contains fructose(nutrient) and prostaglandynes(hormones).