23.2: Anatomy of the male reproductive system (2023)

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    By the end of this section, you will be able to:

    • Describe the structure and function of the organs of the male reproductive system.
    • Describe the structure and function of sperm.
    • Explain the events during spermatogenesis that result in the development of haploid sperm from diploid cells.
    • Give the importance of testosterone for male reproductive function.

    Unique for its role in human reproduction, agamete It is a specialized sex cell with 23 chromosomes, half the number of cells in the body. During fertilization, the chromosomes of a male gamete, calledsperm (or sperm) fuse with the chromosomes into a single female gamete, called an oocyte. The function of the male reproductive system is to produce sperm and transfer them to the female reproductive system. Structures of the male reproductive system include the testicles, epididymis, penis, and the ducts and glands that produce and transmit semen (Fig. 23.2.1). Sperm leave the scrotum through the vas deferens, which is wrapped in the spermatic cord. The spermatic cord is made up of the spermatic cord, the testicular artery, the autonomic nerve, the lymphatic vessels, and the testicular venous plexus. The seminal vesicles and the prostate add fluid to the sperm to form semen. The paired testicles play a key role in this process, producing sperm and androgens, hormones that support male reproductive physiology. In humans, the most important male androgen is testosterone. Several additional organs and ducts support the sperm maturation process and carry sperm and other semen components to the penis, which transports them to the female reproductive tract. In this section, we will explore each of these different structures and discuss the process of sperm production and transport. The details of these male anatomical structures will be discussed below.

    23.2: Anatomy of the male reproductive system (2)


    The testicles are contained in a highly pigmented, skin-covered, muscular sac called thescrotumwhich extends from the body behind the penis (see Figure 23.2.1). This site is important for sperm production, which takes place in the testes, and is most efficient when the testes are kept 2-4°C below core body temperature.

    Hedartos muscleit forms a layer of subcutaneous muscles of the scrotum (Fig. 23.2.2). It continues internally to form the scrotal septum, the wall that divides the scrotum into two parts, each containing a testis. From the internal oblique muscle of the abdominal wall twocremator musclesthat cover each testicle like a muscular network. By contracting simultaneously, the darto and cremaster muscles can lift the testicles in cold weather (or water), drawing the testicles closer to the body and reducing the surface area of ​​the scrotum to retain heat. Alternatively, as ambient temperatures rise, the scrotum relaxes, moving the testicles away from the center of the body and increasing the surface area of ​​the scrotum, which promotes heat loss. Externally, the scrotum has a convex medial bulge on the surface called thesewing.

    23.2: Anatomy of the male reproductive system (3)


    HeIrascible (singular = testicle) are malegonad- the male reproductive organs. They produce sperm and androgens such as testosterone and are active throughout the male's reproductive period.

    The paired, oval testicles are about 4-5 cm long and are situated in the scrotum (see Figure 23.2.2). They are surrounded by two distinct layers of protective connective tissue. Directly deep to the cremaster muscle is the vaginal sheath. Externalvagina shelterit is the serosa, which has both a parietal layer and a thin visceral layer. Beneath the vagina sheath is located.White coata hard, white, dense layer of connective tissue that covers the testis. The white sheath not only covers the outer surface of the nucleus, but also penetrates it to form septa that divide the nucleus into 300 to 400 structures calledencounters. Inside the lobules, sperm develop in structures calledseminiferous tubules(Figure 23.2.3). In the seventh month of development of a male fetus, each testicle moves through the abdominal muscles to descend into the scrotal cavity. This is called "core descent." Cryptorchidism is the clinical term used when one or both testicles do not descend into the scrotum before delivery.

    well rolledseminiferous tubulesThey make up the bulk of each nucleus. They consist of developing sperm that surround the lumen, the hollow center of the tubule, from where the formed sperm are released into the duct system of the testis. In particular, from the lumen of the seminiferous tubules, spermatozoa entersimple tubules(or simple tubules), and from there to a fine network of tubules calledrepeat tests. Sperm leave the testicles and the testicle itself between the ages of 15 and 20.they will remove the leadersthat pass through the whitish pod.

    interstitial cells(also know asKomórki square) produce testosterone and are located between the seminiferous tubules (Fig. 23.2.4). There are six different types of cells within the seminiferous tubules. Among them are the support cells, the so-calledsupport cells, as well as five types of developing sperm, the so-calledreproductive cells. Germ cell development occurs from the basement membrane, at the periphery of the tubule, toward the lumen. Let's take a closer look at these cell types.

    sertoli cells

    Surrounded by all stages of sperm development, they are elongated, branched.sertoli cells(Figure 23.2.4). Sertoli cells are a type of supporting cells called supporting cells or sustenocytes that are usually found in epithelial tissue. Sertoli cells secrete signaling molecules that promote sperm production and can control whether reproductive cells live or die. Sertoli cells (also known as nurse cells) produce an androgen-binding protein. This is necessary for testosterone to really have an effect on sperm development. These cells also produce inhibin, which then goes to the anterior pituitary gland to regulate sperm production. They physically extend around the germ cells from the peripheral basement membrane of the seminiferous tubules to the lumen. Tight connections are formed between these supporting cells.blood testis barrier, which prevents blood-borne substances from entering reproductive cells and, at the same time, prevents developing reproductive cell surface antigens from entering the bloodstream and triggering an autoimmune response.

    Germ cells

    less mature cells.spermatogonias (singular = sperm), lines the basement membrane within the tubules. Spermatogonia are testicular stem cells, which means that they continue to differentiate into different cell types throughout their adult lives. Spermatogonia divide to producebasicIsecondary spermatocyte, Sospermatids, which eventually produce formed sperm. The process that begins with spermatogonia and ends with sperm production is calledspermatogenesis.


    As already mentioned, spermatogenesis occurs in the seminiferous tubules, which make up the majority of each testis (Fig. 23.2.3). This process begins during puberty, after which sperm are produced throughout a man's life. A production cycle, from the spermatogonia to the formed spermatozoa, lasts about 64 days. Approximately every 16 days a new cycle begins, although this timing is not synchronous in the seminiferous tubules. Sperm count (the total number of sperm a man produces) slowly declines after age 35, and some research suggests that smoking may lower sperm count regardless of age.

    The process of spermatogenesis begins with mitosis of diploid spermatogonia in which one sperm develops into two primordial spermatocytes. Since these cells are diploid (2norte), each of them has a complete copy of the father's genetic material, that is, 46 chromosomes. After mitosis, primary spermatocytes begin two rounds of meiosis, i.e., meiosis I, which produces secondary spermatocytes, and meiosis II, which produces sperm. Mature gametes are haploid (1norte), which contains 23 chromosomes, which means that the spermatogonial daughter cells must undergo a second cell division in the process of meiosis. Figure 23.2.4). These sperm cells will continue spermiogenesis to become sperm cells, also known as sperm cells. A section of the seminiferous tubule will show cells of early spermatogenesis on the outer edge and more mature cells migrating into the lumen in the center.

    23.2: Anatomy of the male reproductive system (5)

    Two identical diploid cells are formed by spermatogonial mitosis. One of these cells remains spermatogonium and the other becomesbasicspermatocytethe next step in the process of spermatogenesis. As with mitosis, the DNA is replicated in the primary spermatocyte, and the cell divides to form two cells with identical chromosomes. each one of them issecondary spermatocyte. Now, in both secondary spermatocytes, a second round of cell division takes place, separating the pairs of chromosomes. This second meiotic division results in a total of four cells with only half as many chromosomes. Each of these new cells isspermatids. Although haploid early sperm closely resemble cells in earlier stages of spermatogenesis, they have a round shape, a central nucleus, and a large amount of cytoplasm. The calling processspermiogenesis it transforms these first spermatozoa by reducing the cytoplasm and beginning to form part of the true spermatozoon. The fifth stage of the formation of germ cells.spermor formed sperm - is the end result of this process, which occurs in the part of the tubule closest to the lumen. Finally, the sperm are released into the lumen and move along a series of ducts in the testis toward a structure called the testis.epididymisto the next stage of sperm maturation.

    The structure of the spermatozoon formed.

    Sperm are smaller than most cells in the body; in fact, the volume of the spermatozoon is 85,000 times smaller than the volume of the female gamete. Approximately 100 to 300 million sperm are produced each day, while women normally ovulate only one oocyte per month, as is the case with most cells in the body. The structure of the sperm indicates its function. Heheadspermatozoa contain an extremely compact haploid nucleus with very little cytoplasm (Fig. 23.2.5). These characteristics contribute to the small overall size of the sperm (the head is only 5.5 cm).METROmeters long). The construction calledacrosomait covers most of the sperm head in the form of a "cap" filled with lysosomal enzymes important in preparing sperm to participate in fertilization. Filled with very compact mitochondriahalfsperm. The ATP produced by these mitochondria will power the flagellum that extends from the neck to the middle of the neck.colasperm, allowing it to move around the entire sperm. The central band of flagella, the axial filament, forms from a centriole within the maturing sperm during the final stages of spermatogenesis.

    23.2: Anatomy of the male reproductive system (6)

    sperm transport

    To fertilize an egg, sperm must be transferred from the seminiferous tubules of the testicles, through the epididymis, and later, during ejaculation, along the penis and into the female reproductive tract.

    (Video) BIOL 20 23.1-23.2 The Male Reproductive System

    The role of the epididymis.

    From the lumen of the seminiferous tubules, immobile spermatozoa are surrounded by testicular fluid and transported toepididymis (plural = epididymis), a coiled tube attached to the testis where newly formed sperm continue to mature (see Figure 23.2.3). Although the epididymis doesn't take up much space when tightly coiled, it would be about 20 feet (6 m) long when extended. Sperm travel through the epididymal ganglia in an average of 12 days, the shortest transit time recorded in humans being one day. Sperm enter the head of the epididymis and move along it mainly as a result of contraction of the smooth muscles lining the fallopian tubes. The most mature sperm are then stored in the tail of the epididymis (last part) until ejaculation occurs.

    channel system

    During ejaculation, sperm exit the tail of the epididymis and are pushed by smooth muscle contraction into the epididymis.spermatic(also called the vas deferens). The vas deferens is a thick muscular tube connected within the scrotum to connective tissue, blood vessels, and nerves in a structure called thespermatic cord(see Figure 23.2.1 and Figure 23.2.2). Since the vas deferens is physically accessible in the scrotum, surgical sterilization can be performed to interrupt the sperm supply by cutting and sealing a small portion of the vas deferens. This procedure is calledvasectomyand is an effective form of birth control for men. While it may be possible to reverse a vasectomy, doctors consider the procedure permanent and advise men to only have it if they are sure they no longer want children.

    interactive element

    23.2: Anatomy of the male reproductive system (7)

    Watch the Vasectomy video to learn about the procedure that removes a small portion of the spermatic cord from the scrotum. This interrupts the path of sperm through the vas deferens. If sperm cannot pass through the duct because the man has had a vasectomy or has not ejaculated, what area of ​​the testicles is left?


    Answer: Sperm remain in the epididymis until they degenerate.

    From each epididymis, each vas deferens extends upward into the abdominal cavity throughcanal inguinalon the abdominal wall. From here, the vas deferens continues into the pelvic cavity and ends behind the bladder, where it widens to form an area called the papilla (meaning "flask").

    Sperm make up only 5 percent of the final volume.sperm, a thick, milky liquid secreted by a man. Most of the semen is produced by the three major accessory glands of the male reproductive system: the seminal vesicles, the prostate, and the bulbourethral glands (fig. 23.2.6).

    Seminal vesicles

    As the spermatozoa pass through the bubble of the digestive tract during ejaculation, they mix with fluid coming fromseminal vesicle(see Figure 23.2.6). The paired seminal vesicles are glands that make up about 60 percent of the volume of semen. Seminal vesicle fluid contains large amounts of fructose, which is used by sperm mitochondria to produce ATP for movement through the female reproductive system. The spermatozoa remain immobile until they mix with the secretions of the seminal glands.

    The fluid, which now contains sperm and seminal vesicle secretions, then travels to associated secretions. ejaculatory tube, a short structure formed by the papilla of the digestive tract and the duct of the seminal vesicle. The paired ejaculatory ducts carry seminal fluid to the next structure, the prostate.


    As shown in Figure 23.2.6, centrally locatedprostateIt lies in front of the rectum, at the base of the bladder, surrounding the prostatic urethra (the part of the urethra that passes through the prostate). The prostate is about the size of a walnut and is made up of muscle and glandular tissue. It secretes an alkaline milky fluid into the passing seminal fluid, now called semen, which is essential for the initial coagulation and subsequent deagulation of semen after ejaculation. The temporary thickening of the semen helps to retain it in the female reproductive tract, giving sperm time to use the fructose supplied by the secretions of the seminal vesicles. When the semen regains its fluidity, more sperm can pass into the female reproductive tract.

    During puberty, the prostate often doubles in size. Around the age of 25, it gradually begins to enlarge again. This extension does not usually cause problems; however, abnormal prostatic hyperplasia or benign prostatic hyperplasia (BPH) can cause a narrowing of the urethra that passes through the center of the prostate, causing a variety of lower urinary tract symptoms, such as a frequent and intense urge to urinate , weak stream and sensation of urge to urinate. the bladder has not been completely emptied. By age 60, about 40 percent of men have some degree of BPH. By the age of 80, the number of people affected by this disease has increased by up to 80 percent. Treatment for BPH aims to relieve pressure on the urethra so urine can flow more normally. Mild to moderate symptoms are treated with medication, while severely enlarged prostate is treated with surgery, during which part of the prostate tissue is removed.

    Another common disease associated with the prostate is prostate cancer. According to the Centers for Disease Control and Prevention (CDC), prostate cancer is the second most common cancer in men. However, some forms of prostate cancer grow very slowly and therefore may never need treatment. By contrast, aggressive forms of prostate cancer metastasize to sensitive organs such as the lungs and brain. There is no link between BPH and prostate cancer, but the symptoms are similar. Prostate cancer is detected through history, blood tests, and digital rectal examination, which allows the doctor to feel the prostate and look for unusual growths. If a tumor is detected, the diagnosis of cancer is confirmed by a biopsy of the cells.

    bulbar glands

    The final addition to the semen is done together.bulbourethral glands(or Cowper's glands), which release a thick, salty fluid that lubricates the end of the urethra and vagina and helps flush the urethra of residual urine. The fluid from these accessory glands is released after sexual arousal in the male and shortly before the release of semen. This is why it is sometimes called pre-ejaculation. It should be noted that, in addition to moisturizing proteins, the bulbourethral fluid can absorb sperm already present in the urethra and thus can lead to pregnancy. Once inside the female reproductive system, the spermatozoa will travel to the unfertilized egg and undergo chemical changes, the so-calledtrainingfor fertilization of the ovum. The capacitation consists of the destabilization of the acrosome membrane of the head of the spermatozoon and a greater mobility of the tail of the spermatozoon, which makes fertilization possible.

    interactive element

    23.2: Anatomy of the male reproductive system (12)

    (Video) Full Lecture: Male Reproductive System

    Look at this videomale anatomystudy the structure of the male reproductive system and the sperm pathway that begins in the testicles and ends when the sperm leaves the penis through the urethra. Where are the spermatozoa deposited after leaving the ejaculatory duct?


    Answer: The sperm enters the prostate.


    Hepene It is the male copulatory (coitus) organ. It is flaccid for non-sexual activities like urination and swollen and rod-shaped for sexual arousal. When erect, the rigidity of the organ allows it to enter the vagina and deposit semen in the female reproductive tract (Fig. 23.2.7).

    23.2: Anatomy of the male reproductive system (13)

    The shaft of the penis surrounds the urethra (fig. 23.2.7). The shaft consists of three columnar chambers of erectile tissue that extend along the entire length of the shaft. Each of the two larger side chambers is calledcorpora cavernosa(plural = corpus cavernosum). Together they make up the bulk of the penis. He spongy bodywhich can be felt as a raised ridge on the erect penis, is a smaller chamber that surrounds the spongy urethra, or penis. the end of the penisglans penis, has a high concentration of nerve endings, which makes the skin very sensitive, which affects the probability of ejaculation (see Figure 23.2.7). The skin of the shaft extends downward over the glans and forms a collar calledforeskin (or foreskin). The foreskin also contains a dense cluster of nerve endings that moisturize and protect the sensitive skin of the glans penis. A surgical procedure called circumcision, which is often performed for religious or social reasons, involves the removal of the foreskin, usually within a few days of birth.

    Both sexual arousal and REM sleep (during which dreams occur) can trigger an erection. Penile erection is the result of vasoconstriction, which is swelling of the tissues due to more arterial blood flowing into the penis than out of the veins. During sexual arousal, nitric oxide (NO) is released from nerve endings close to the blood vessels in the corpora cavernosa and spongiosum. The release of NO activates a signaling pathway that causes the smooth muscles surrounding the penile arteries to relax, causing them to dilate. This dilation increases the amount of blood that can enter the penis and causes the endothelial cells in the walls of the penile arteries to also secrete NO and perpetuate vasodilation. The rapid increase in blood volume fills the erectile chambers, and the increased pressure in the filled chambers compresses the thin-walled penile veins, preventing venous drainage from the penis. The result of increased blood flow to the penis and decreased return of blood from the penis is an erection. Depending on the flaccidity of the penis, it can increase slightly or significantly in size during erection, with the average length of the erect penis being about 15 cm.


    The male reproductive system.

    Erectile dysfunction (ED) is a condition in which a man has difficulty starting or maintaining an erection. The combined incidence of minimal, moderate, and complete erectile dysfunction is approximately 40 percent in men by the age of 40 and reaches almost 70 percent by the age of 70. In addition to aging, erectile dysfunction has been linked to diabetes, vascular disease, mental disorders, prostate disorders, the use of certain medications, such as certain antidepressants, and testicular problems that result in low testosterone levels. These physical and emotional conditions can cause interruptions in the vasodilation pathway and result in the inability to achieve an erection.

    Let us remember that the release of NO causes the relaxation of the smooth muscles that surround the arteries of the penis, which causes the dilation of the vessels necessary for erection. To reverse the vasodilation process, an enzyme called phosphodiesterase (PDE) breaks down a key component of the NO signaling pathway called cGMP. There are several different forms of this enzyme and PDE type 5 is the type of PDE found in penile tissues. Researchers have discovered that inhibition of PDE5 increases blood flow and allows vasodilation of the penis.

    The PDE and vasodilation signaling pathway is found in vessels in other parts of the body. In the 1990s, clinical trials began with a PDE5 inhibitor called sildenafil to treat high blood pressure and angina (chest pain caused by poor blood flow through the heart). The study found that the drug was not effective in treating heart disease; however, many men have experienced erections and priapism (an erection that lasts longer than 4 hours). For this reason, a clinical trial was initiated to investigate the ability of sildenafil to promote erections in men suffering from erectile dysfunction. In 1998, the FDA approved a drug marketed as Viagra®. Since the drug's approval, sildenafil and similar PDE inhibitors now generate sales of more than $1 billion a year and are reported to be effective in treating 70 to 85 percent of dysfunction cases. erectile. Importantly, men with health problems, especially those with heart disease who take nitrates, should either avoid Viagra or talk to their doctor to find out if they are eligible to take the drug, as deaths have been reported among those at risk.


    Testosterone, an androgen, is a steroid hormone produced byKomórki square. The alternative term Leydig cells, or interstitial cells, reflects their location between the seminiferous tubules of the testes. In male embryos, testosterone is secreted by Leydig cells in the seventh week of development, reaching maximum levels in the second trimester of pregnancy. This early release of testosterone results in the anatomical differentiation of the male genitalia. Testosterone levels are low in childhood. They intensify during puberty, activating characteristic physical changes and initiating spermatogenesis.

    Testosterone Functions

    The constant presence of testosterone is necessary for the proper functioning of the male reproductive system, and the Leydig cells produce between 6 and 7 mg of testosterone per day. Testicular steroidogenesis (production of androgens, including testosterone) results in testosterone levels in the testes 100 times higher than in the circulation. Maintaining normal testosterone levels promotes spermatogenesis, while low testosterone levels can lead to infertility. In addition to intratesticular secretion, testosterone is also released into the systemic circulation and plays an important role in muscle development, bone growth, development of secondary sexual characteristics, and maintenance of libido (sexual desire) in both men and women. women. In women, the ovaries secrete small amounts of testosterone, although most of it is converted to estradiol. The adrenal glands also secrete a small amount of testosterone in both sexes.

    testosterone control

    Regulation of testosterone levels throughout the body is critical to male reproductive function. The regulation of testosterone production by Leydig cells begins outside of the testicles. The brain's hypothalamus and pituitary gland integrate external and internal signals to control the synthesis and secretion of testosterone. The regulation starts inhypothalamus. The pulsatile release of a hormone calledgonadotropin-releasing hormone (GnRH)from the hypothalamus stimulates the secretion of hormonal hormones from the pituitary gland. binding of GnRH to its receptors inanterior pituitary glandthe gland stimulates the release of two gonadotropins:luteinizing hormone (LH)Ifollicle stimulating hormone (FSH). These two hormones are essential for reproductive function in both men and women. In men, FSH binds primarily to Sertoli cells in the seminiferous tubules, promoting spermatogenesis. FSH also stimulates Sertoli cells to produce hormones called inhibins, which act to inhibit the release of FSH from the pituitary gland, thus reducing testosterone secretion. These polypeptide hormones are directly related to Sertoli cell function and sperm count; Inhibin can be used as a marker of spermatogenic activity. In men, LH binds to receptors on the Leydig cells in the testicles and increases testosterone production. See chapters 15.3 and 15.8 of the Endocrine System for additional details.

    Aging and...

    The male reproductive system.

    A decrease in Leydig cell activity may occur in men between the ages of 40 and 50. The resulting reduction in circulating testosterone levels can lead to symptoms of andropause, also known as male menopause. Although the reduction in the use of sex steroids in men resembles menopause in women, there are no clear signs, such as amenorrhea, that indicate the onset of andropause. Instead, men report feeling tired, reduced muscle mass, depression, anxiety, irritability, loss of libido, and insomnia. Decreased spermatogenesis resulting in reduced fertility has also been reported, and sexual dysfunction may also be associated with andropause symptoms.

    While some researchers believe that some aspects of andropause are difficult to eliminate beyond the general aging process, testosterone replacement therapy is sometimes prescribed to alleviate some symptoms. Recent studies have shown the benefits of androgen replacement therapy in the treatment of new depressive symptoms in older men; however, other studies caution against testosterone replacement in the long-term treatment of andropause symptoms, showing that high doses can significantly increase the risk of heart disease and prostate cancer.

    (Video) Reproductive System Male

    Concept review

    Gametes are reproductive cells that come together to form offspring. Organs called gonads produce gametes along with hormones that regulate human reproduction. The male gametes are called sperm. Spermatogenesis, or sperm production, takes place in the seminiferous tubules, which make up the majority of the testicles. The scrotum is the muscular sac that holds the testicles outside of the body cavity.

    Spermatogenesis begins with the mitotic division of spermatogonia (stem cells) to produce primary spermatocytes, which undergo two divisions of meiosis to become secondary spermatocytes and then haploid sperm. During spermiogenesis, sperm cells are converted into spermatozoa (formed sperm). After being released from the seminiferous tubules, the sperm travel to the epididymis where they continue to mature. During ejaculation, spermatozoa exit the epididymis through the spermatic cord, the tube of the spermatic cord that exits the scrotum. The digestive tract ampulla connects to the seminal vesicle (a gland that supplies fructose and protein) at the ejaculatory duct. The fluid flows through the prostatic urethra, where secretions from the prostate are added to form semen. These secretions help sperm to pass through the urethra into the female reproductive tract. Secretions from the bulbourethral glands protect sperm and clean and lubricate the penile (spongy) urethra.

    The penis is the male copulatory organ. Columns of erectile tissue called the corpora cavernosa and corpus spongiosum fill with blood when sexual arousal triggers vasodilation of the penile blood vessels. Testosterone regulates and maintains the sexual organs and sexual desire and induces physical changes during puberty. The interaction of the testicles and the endocrine system precisely controls the production of testosterone.

    review the questions

    Q. What are the male gametes called?

    To ten

    B. sperm

    c. test

    D. testosterone


    Answer: B.

    Q. Eledig cells ________.

    A. are located between the seminiferous tubules.

    B. activate the flagella of sperm

    C. to spermatogonia

    D. secrete seminal fluid


    Answer: One

    Q. What structure is affected by a vasectomy?


    B. vas deferens

    C. the prostate

    D. epididymis


    Answer: B.

    Q. Where is the epididymis?

    (Video) 2. Male Reproductive System- Functional Anatomy

    A. in the scrotum

    B. in the testicles

    C. at the back of the bladder

    D. inside the pelvis


    Answer: One

    Q. What muscles surround the testicles?

    A. burner

    B. dartos


    D. smooth muscles



    critical thinking questions

    Q. Briefly explain why mature gametes contain only one set of chromosomes.


    A. Humans have 46 chromosomes. Meiosis is cell division that results in sperm (gametes) that contain only 23 chromosomes. A single gamete must fuse with the gamete of an individual of the opposite sex to produce a fertilized egg that has a complete set of chromosomes (46) and is the first cell of the new individual.

    Q. What special features are seen in sperm but not in somatic cells and how do these specializations work?


    A. Unlike somatic cells, spermatozoa are haploid and have 23 chromosomes. They also have very little cytoplasm. They have a head with a compact nucleus covered by an acrosome full of enzymes and a central part full of mitochondria that drive their movement. They are mobile thanks to the tail, a structure that contains flagella and that specializes in movement to find an egg to fertilize.

    Q. Name three male accessory glands and explain how each affects spermatozoa.


    A. The three accessory glands make the following contributions to semen: the seminal vesicle makes up about 60 percent of the volume of semen, and the fluid contains large amounts of fructose, which drives sperm movement; the prostate provides the necessary substances for the maturation of spermatozoa; and the bulbourethral glands produce a thick fluid that lubricates the ends of the urethra and vagina and helps flush the urethra of residual urine.

    Q. Describe how the erection of the penis is produced.


    A. During sexual arousal, nitric oxide (NO) is released from nerve endings near the blood vessels in the corpus cavernosum and corpora spongiosum. The release of NO activates a signaling pathway that causes the smooth muscles surrounding the penile arteries to relax, causing them to dilate. This dilation increases the amount of blood that can enter the penis and causes endothelial cells in the penile artery walls to secrete NO, perpetuating vasodilation. The rapid increase in blood volume fills the erectile chambers, and the increased pressure in the filled chambers compresses the thin-walled penile veins, preventing venous drainage from the penis. An erection is the result of increased blood flow to the penis and decreased return of blood from the penis.


    blood testis barrier
    tight junctions between Sertoli cells that prevent bloodborne pathogens from gaining access to later stages of spermatogenesis and prevent a potential autoimmune reaction to haploid sperm.
    bulbourethral glands
    (also Cowper's glands) glands that secrete lubricating mucus that cleanses and lubricates the urethra before and during ejaculation.
    corpora cavernosa
    one of the two columns of erectile tissue in the penis that fills with blood during erection
    spongy body
    (plural = corpora cavernosa) a column of erectile tissue in the penis that fills with blood during erection and surrounds the penile urethra on the ventral part of the penis.
    (also vas deferens) tube that carries sperm from the epididymis through the spermatic cord to the ejaculatory duct; Also called spermatic cord.
    ejaculatory tube
    Duct connecting the gastrointestinal papilla to the duct of the seminal vesicle in the prostatic urethra.
    (plural = epididymis) a coiled tubular structure where sperm begin to mature and are stored until ejaculation.
    a haploid germ cell that provides the genetic material for offspring
    glans penis
    the bulbous end of the penis that contains a large number of nerve endings
    gonadotropin-releasing hormone (GnRH)
    a hormone secreted by the hypothalamus that regulates the production of follicle-stimulating hormone and luteinizing hormone by the pituitary gland
    Reproductive organs (testicles in men and ovaries in women) that produce gametes and reproductive hormones.
    canal inguinal
    an opening in the abdominal wall that connects the testicles to the abdominal cavity
    Komórki square
    cells between the seminiferous tubules of the testis that produce testosterone; interstitial cell type
    male copulatory organ
    (also prepuce) a flap of skin that forms a collar around it and thus protects and hydrates the glans penis; also called foreskin
    a donut-shaped gland at the base of the bladder that surrounds the urethra and supplies fluid to semen during ejaculation
    External skin-muscle sac in which the testicles are located.
    Ejaculatory fluid made up of spermatozoa and secretions from the seminal vesicles, the prostate, and the bulbourethral glands.
    seminal vesicle
    Gland that produces seminal fluid from which semen is produced.
    seminiferous tubules
    Tubular structures in the testicles where spermatogenesis occurs.
    sertoli cells
    cells that support reproductive cells in the process of spermatogenesis; support cell type
    (also sperm) male gamete
    spermatic cord
    a set of nerves and blood vessels that supply the testicles; includes vas deferens
    Immature sperm formed by meiosis II of secondary spermatocytes.
    Cell resulting from the division of sperm that undergoes meiosis I and meiosis II to form spermatozoa.
    The formation of new sperm occurs in the seminiferous tubules of the testicles.
    (singular = spermatogonium) diploid precursor cells that develop into sperm
    Transformation of spermatozoa into spermatozoa during spermatogenesis.
    (singular = testis) male gonads

    Contributors and footnotes


    What is the male reproductive system with answers? ›

    The male reproductive system contains the external genitals (the penis, testes and the scrotum) and internal parts, including the prostate gland, vas deferens and urethra. A man's fertility and sexual traits depend on the normal functioning of the male reproductive system, as well as hormones released from the brain.

    What is the male reproductive structure anatomy? ›

    The male reproductive system mostly exists outside of your body. The external organs include the penis, scrotum and testicles. Internal organs include the vas deferens, prostate and urethra. The male reproductive system is responsible for sexual function and urination.

    What is the function of the male reproductive system anatomy? ›

    The function of the male reproductive system is to produce androgens such as testosterone that maintain male reproductive function and to promote spermatogenesis and transport into the female reproductive system for fertilization.

    What are the 7 parts of the male reproductive system? ›

    The male reproductive system includes the penis, scrotum, testes, epididymis, vas deferens, prostate, and seminal vesicles. The penis and the urethra are part of the urinary.

    What is the function of the reproductive system? ›

    To produce egg and sperm cells. To transport and sustain these cells. To nurture the developing offspring. To produce hormones.


    1. Reproductive System Part 1
    (Dr. Emma Petshow)
    2. Male Reproductive System
    (Owl's Eye Tube)
    3. Chapter 28 Lecture: Reproductive Systems
    (Prof. Whitehead's Biology 205: A&P 1)
    4. Ch 27 Male Reproduction #2*
    (NCA&T Biology 351)
    5. Chapter 27 Part A (Male Reproductive System)
    (Sarah Pugh)
    6. Medical Terminology- Male Reproductive System
    (Medical Education for All (M.E.A))


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