By Oba Mike
Unlike other systems, the reproductive system is different in males and females both structurally and functionally.
Study of the male reproductive system and the diseases that affect it is termed Urology.
Organs of the Male Reproductive System
The organs are grouped into:
1. Testis (main sex gland)
2. Ducts (epididymis, vas deferens, ejaculatory duct and urethra)
3. Accessory sex glands (seminal vesicle, prostate, and bulbourethral gland)
5. Supporting structures (scrotum, penis, and spermatic cord).
The organs can also be grouped into external and internal genitalia. The scrotum, penis and urethral opening are the external genitals. The rest are internal genitals.
Functions of the Male Reproductive System
1. The testis (plural testes) produce sperm and the male sex hormone testosterone.
2. The ducts transport, store and assist in maturation of sperm.
3. The accessory sex glands secrete fluid that aid sperm motility, viability and survival.
4. The penis is a copulatory organ. It contains the urethra, a passageway for ejaculation of semen and excretion of urine.
5. The scrotum surrounds the testes and provides a suitable temperature for sperm production.
Scrotum
The scrotum is a supporting structure for the testes. It consist of loose skin and underlying subcutaneous layer that hangs from the root of the penis.
Externally, the scrotum looks like a pouch of skin. It is separated into two lateral portions by a median ridge called raphe.
Internally, it is divided into two sacs by the scrotal septum. Each sac, contains a single testis. The scrotal septum is composed of a smooth muscle called dartos muscle. The scrotal tissue surrounding each testis also has a skeletal muscle called cremaster muscle. Contraction and relaxation of both cremaster and dartos muscles regulates the temperature of the testes. Note that normal sperm production requires a temperature that is 2-3°C below body temperature. Hence, in response to cold temperature, the cremaster and dartos muscles contract. Contraction of the cremaster muscle moves the testes closer to the body, where they can absorb heat. Contraction of the dartos muscle causes the scrotum to become tight (wrinkled in appearance) thereby reducing heat loss. Exposure to warmth reverses these actions.
Testes
The testes or testicles, are oval glands located in the scrotum. Each testis measures about 5cm long and 2.3cm wide with a mass of 10-15 grammes.
A serous membrane called tunica vaginalis partially covers and protects the testes. Internal to the tunica vaginalis is a white fibrous capsule composed of dense irregular connective tissue called tunica albuginea.
The tunica albuginea forms extensions (septa) that project inward to divide the testis into compartments called lobules.
There are about 200-300 lobules in each testis. Each lobule contains 1-4 tightly coiled tubules called seminiferous tubules where sperm production takes place through a process called spermatogenesis.
The seminiferous tubules contain two types of cells:
i. Spermatogenic cells (sperm forming cells).
ii. Sertoli or sustentacular cells (sperm supporting cells).
The spaces between the seminiferous tubules are called interstitial spaces. Within these spaces are cells called Interstitial cells of Leydig or simply Leydig cells. These cells are responsible for the secretion of testosterone, the male sex hormone or androgen. Testosterone promotes the development of masculine characteristics. It also promotes a man's libido (sexual drive).
Ducts of the testis.
Each testis has a series of ducts that convey the produced sperm cells towards the epididymis.
From the lumen of the seminiferous tubules, pressure generated by fluid secreted by sertoli cells, pushes sperm into short ducts called straight tubules. Various straight tubules join to form a network called rete testis. From the rete testis, sperm moves into coiled tubes called efferent ductules where they finally discharge into the epididymis.
Epididymis
The epididymis is a comma-shaped organ. It is an extremely long structure but highly coiled making it just 4cm long. It will measure about 6 metres long if it were uncoiled.
Each epididymis has a head, body and tail. The head is the largest superior portion that connects with the efferent ducts of the testes, the body is the narrow midpoint while the tail is the smaller inferior portion that connects with the ductus (vas) deferens.
The epididymis is lined with pseudostratified columnar epithelium that contains sterocilia (a kind of microvilli). The sterocilia aids in the reabsorption of degenerated sperm.
Functionally, the epididymis is the site for sperm maturation, the process b which sperm acquire motility and ability to fertilize an ovum. It takes about 14days for a sperm to be fully mature. The epididymis also propel sperm into the ductus (vas) derens during sexual arousal. Any unused sperm is eventually reabsorbed.
Ductus (vas) deferens (2)
The ductus or vas deferens begins where the tail of the epididymis becomes less convoluted. It is about 45cm long and passes into the pelvic cavity through the spermatic cord. The Vas deferens is also lined by pseudostratified columnar epithelium.
Functionally, the ductus deferens conveys sperm during sexual arousal from the epididymis towards the urethra. It also stores sperm for several months reabsorbs unused sperm.
Ejaculatory duct (2)
The ejaculatory duct is 2cm long and is formed by the union of the duct from the seminal vesicle and the end of the ductus deferens (please view pics while reading).
It passes through the prostate gland and connects with the prostatic urethra.
Functionally, the ejaculatory duct ejects sperm and seminal vesicle secretions into the urethra.
Urethra
The male urethra is urogenital (shared by both reproductive and urinary systems). It serves as a common passageway for both semen and urine. It is about 20cm and passes through three structures; prostate, deep muscles of the perineum and the penis. Due to this, it is divided into 3 parts:
i. Prostatic urethra (2-3cm) which is the part that passes through the prostate.
ii. Membranous urethra (1cm) passes through the deep perineal muscles.
iii. Penile (spongy) urethra which is about 15-18cm and passes through the penis.
The reproductive function of the urethra is to convey sperm to the exterior (probably the vagina).
Accessory Sex Glands
The accessory sex glands secrete most of the liquid portion of semen. Note that semen consist of sperm cells and secretions from the accessory glands. The accessory sex glands include the seminal vesicles, prostate and bulbourethral (cowper's ) glands.
Seminal vesicle (2)
The seminal vesicle is a pouch-like structure about 5cm long. It secretes an alkaline fluid that contains fructose, prostaglandins and clotting proteins.
The alkalinity helps to neutralize the acidic environment of the male uretha and the female reproductive tract that otherwise, would inactivate and kill sperm.
The fructose is used for energy (ATP) production by sperm.
Prostaglandins contribute to sperm motility and viability.
Note that seminal vesicle secretion makes up 60% of semen.
Prostate (1)
The prostate gland is a doughnut-shaped gland about the size of a golf ball. It slowly increases in size from birth to puberty. It then expands rapidly untill about age 30 where it maintains a stable size untill about age 45, where further enlargement may occur. If not managed properly, the enlargement poses serious health threat in men.
Functionally, the prostate secretes a milky slightly acidic fluid. This fluid gives semen its milky appearance.
The secretion contains citric acid used for ATP generation.
The secretion also contain substances that helps in coagulation of semen and subsequent breaking of the clot.
Bulbourethral gland (2)
Also call Cowpers's gland, it is about the size of a pea.
During sexual arousal, this gland secrete an alkaline fluid into the urethra that protects the passing sperm by neutralizing acids from urine in the urethra. They also secrete mucus that lubricates the end of the penis and lining of the urethra, decreasing the number of sperm damage during ejaculation. Some males usually release a drop or two of this mucus following sexual arousal and erection. This droplet do not contain sperm cells.
Penis
The penis helps in copulation. It contains the urethra making it a passageway for the ejaculation of sperm and excretion of urine.
Structurally, the penis is cylindrical and consist of body, glans penis and a root.
Body: The body of the penis is composed of three masses of erectile tissues. These include:
Two copora cavernosa
One corpus spongiosum
These tissues contain blood sinuses (spaces) that are filled with blood following sexual arousal leading to erection (enlargement of penis).
Glans penis: This is formed by the enlarged distal end of the corpus spongiosum. It forms a round margin called corona. The external urethral orifice emerges from the glans penis. In an uncircumcised male, the glan penis is covered by the prepuce or foreskin.
Root: The root of the penis is the attached proximal portion of the penis. The weight of the penis is supported by two ; The fundiform ligament and the suspensory ligament.
Spermatic cord
The spermatic cord is a supporting structure that ascends out of the scrotum. It contains the vas deferens and the vessels that supply and drain the testes. Such vessels like testicular artery, testicular vein, autonomic nerves, and lymphatic vessels.
Note that testosterone produced by the testes is carried into general circulation by the testicular veins.
The spermatic cord passes through the inguinal canal which is an oblique passageway in the anterior abdominal wall.
The term varicocele refers to a swelling in the scrotum due to dilation of the veins that drains the testes. It usually resolves on its own.
Erection
Erection is the enlargement of the penis following sexual stimulation (which can be visual, tactile, auditory, olfactory or imagined). This enlargement and stiffening of the penis is caused by large amount of blood that fills the sinuse within the erectile tissues (corpora cavernosa and corpus spongiosum). The blood comes from the arterioles supplying the erectile tissues.
Erection is maintained by parasympathetic nerve fibres from the sacral portion of the spinal cord. Once sexual stimulation ends, the arterioles constrict and the blood drains out through the veins, returning the penis to its flaccid state.
Ejaculation
Ejaculation means, 'throw out'. It is the powerful release of semen through the urethra to the exterior. It is a sympathetic reflect coordinated by the lumbar portion of the spinal cord. As part of the reflex, the smooth muscle sphincter at the base of the urinary bladder closes, preventing urine from being expelled during ejaculation.
Each ejaculation contains about 50-200 million sperm per milliter. Only one sperm is needed to fertilize an ovum.
Low sperm count is a condition where the quantity of sperm drops below 15 million per milliter of semen. It is a major cause of infertility in men.
Premature Ejaculation
An ejaculation is premature if it occurs too early, for example, during foreplay or on or shortly after penetration. It is usually caused by anxiety, other psychological causes, or an unusually sensitive foreskin or glans penis. For most males, premature ejaculation can be overcome by various techniques (such as squeezing the penis between the glans penis and shaft as ejaculation approaches), behavioral therapy, or medication.
Male Circumcision
Circumcision(to cut around) is a surgical procedure in which part of or the entire prepuce is removed. It is usually performed several days after birth, and is done for social, cultural, religious, and (more rarely) medical reasons. Although most health-care professionals find no medical justification for circumcision, some feel that it has benefits, such as a lower risk of urinary tract infections, protection against penile cancer, and possibly a lower risk for sexually transmitted diseases. Indeed, studies in several African villages have found lower rates of HIV infection among circumcised men.
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Introduction
Sexual reproduction is the process by which organisms produce offspring by making germ cells called gametes. The male gamete (sperm cell or spermatozoon) then unites with the female gamete (egg cell or ovum or secondary oocyte) through a process called fertilization to form a single cell called zygote that begins to grow through cleavage (cell division).Unlike other systems, the reproductive system is different in males and females both structurally and functionally.
Study of the male reproductive system and the diseases that affect it is termed Urology.
Organs of the Male Reproductive System
The organs are grouped into:
1. Testis (main sex gland)
2. Ducts (epididymis, vas deferens, ejaculatory duct and urethra)
3. Accessory sex glands (seminal vesicle, prostate, and bulbourethral gland)
5. Supporting structures (scrotum, penis, and spermatic cord).
The organs can also be grouped into external and internal genitalia. The scrotum, penis and urethral opening are the external genitals. The rest are internal genitals.
Functions of the Male Reproductive System
1. The testis (plural testes) produce sperm and the male sex hormone testosterone.
2. The ducts transport, store and assist in maturation of sperm.
3. The accessory sex glands secrete fluid that aid sperm motility, viability and survival.
4. The penis is a copulatory organ. It contains the urethra, a passageway for ejaculation of semen and excretion of urine.
5. The scrotum surrounds the testes and provides a suitable temperature for sperm production.
Scrotum
The scrotum is a supporting structure for the testes. It consist of loose skin and underlying subcutaneous layer that hangs from the root of the penis.
Externally, the scrotum looks like a pouch of skin. It is separated into two lateral portions by a median ridge called raphe.
Internally, it is divided into two sacs by the scrotal septum. Each sac, contains a single testis. The scrotal septum is composed of a smooth muscle called dartos muscle. The scrotal tissue surrounding each testis also has a skeletal muscle called cremaster muscle. Contraction and relaxation of both cremaster and dartos muscles regulates the temperature of the testes. Note that normal sperm production requires a temperature that is 2-3°C below body temperature. Hence, in response to cold temperature, the cremaster and dartos muscles contract. Contraction of the cremaster muscle moves the testes closer to the body, where they can absorb heat. Contraction of the dartos muscle causes the scrotum to become tight (wrinkled in appearance) thereby reducing heat loss. Exposure to warmth reverses these actions.
Testes
A serous membrane called tunica vaginalis partially covers and protects the testes. Internal to the tunica vaginalis is a white fibrous capsule composed of dense irregular connective tissue called tunica albuginea.
The tunica albuginea forms extensions (septa) that project inward to divide the testis into compartments called lobules.
There are about 200-300 lobules in each testis. Each lobule contains 1-4 tightly coiled tubules called seminiferous tubules where sperm production takes place through a process called spermatogenesis.
The seminiferous tubules contain two types of cells:
i. Spermatogenic cells (sperm forming cells).
ii. Sertoli or sustentacular cells (sperm supporting cells).
The spaces between the seminiferous tubules are called interstitial spaces. Within these spaces are cells called Interstitial cells of Leydig or simply Leydig cells. These cells are responsible for the secretion of testosterone, the male sex hormone or androgen. Testosterone promotes the development of masculine characteristics. It also promotes a man's libido (sexual drive).
Ducts of the testis.
Each testis has a series of ducts that convey the produced sperm cells towards the epididymis.
From the lumen of the seminiferous tubules, pressure generated by fluid secreted by sertoli cells, pushes sperm into short ducts called straight tubules. Various straight tubules join to form a network called rete testis. From the rete testis, sperm moves into coiled tubes called efferent ductules where they finally discharge into the epididymis.
Epididymis
The epididymis is a comma-shaped organ. It is an extremely long structure but highly coiled making it just 4cm long. It will measure about 6 metres long if it were uncoiled.
Each epididymis has a head, body and tail. The head is the largest superior portion that connects with the efferent ducts of the testes, the body is the narrow midpoint while the tail is the smaller inferior portion that connects with the ductus (vas) deferens.
The epididymis is lined with pseudostratified columnar epithelium that contains sterocilia (a kind of microvilli). The sterocilia aids in the reabsorption of degenerated sperm.
Functionally, the epididymis is the site for sperm maturation, the process b which sperm acquire motility and ability to fertilize an ovum. It takes about 14days for a sperm to be fully mature. The epididymis also propel sperm into the ductus (vas) derens during sexual arousal. Any unused sperm is eventually reabsorbed.
Ductus (vas) deferens (2)
The ductus or vas deferens begins where the tail of the epididymis becomes less convoluted. It is about 45cm long and passes into the pelvic cavity through the spermatic cord. The Vas deferens is also lined by pseudostratified columnar epithelium.
Functionally, the ductus deferens conveys sperm during sexual arousal from the epididymis towards the urethra. It also stores sperm for several months reabsorbs unused sperm.
Ejaculatory duct (2)
The ejaculatory duct is 2cm long and is formed by the union of the duct from the seminal vesicle and the end of the ductus deferens (please view pics while reading).
It passes through the prostate gland and connects with the prostatic urethra.
Functionally, the ejaculatory duct ejects sperm and seminal vesicle secretions into the urethra.
Urethra
The male urethra is urogenital (shared by both reproductive and urinary systems). It serves as a common passageway for both semen and urine. It is about 20cm and passes through three structures; prostate, deep muscles of the perineum and the penis. Due to this, it is divided into 3 parts:
i. Prostatic urethra (2-3cm) which is the part that passes through the prostate.
ii. Membranous urethra (1cm) passes through the deep perineal muscles.
iii. Penile (spongy) urethra which is about 15-18cm and passes through the penis.
The reproductive function of the urethra is to convey sperm to the exterior (probably the vagina).
Accessory Sex Glands
The accessory sex glands secrete most of the liquid portion of semen. Note that semen consist of sperm cells and secretions from the accessory glands. The accessory sex glands include the seminal vesicles, prostate and bulbourethral (cowper's ) glands.
Seminal vesicle (2)
The seminal vesicle is a pouch-like structure about 5cm long. It secretes an alkaline fluid that contains fructose, prostaglandins and clotting proteins.
The alkalinity helps to neutralize the acidic environment of the male uretha and the female reproductive tract that otherwise, would inactivate and kill sperm.
The fructose is used for energy (ATP) production by sperm.
Prostaglandins contribute to sperm motility and viability.
Note that seminal vesicle secretion makes up 60% of semen.
Prostate (1)
The prostate gland is a doughnut-shaped gland about the size of a golf ball. It slowly increases in size from birth to puberty. It then expands rapidly untill about age 30 where it maintains a stable size untill about age 45, where further enlargement may occur. If not managed properly, the enlargement poses serious health threat in men.
Functionally, the prostate secretes a milky slightly acidic fluid. This fluid gives semen its milky appearance.
The secretion contains citric acid used for ATP generation.
The secretion also contain substances that helps in coagulation of semen and subsequent breaking of the clot.
Bulbourethral gland (2)
Also call Cowpers's gland, it is about the size of a pea.
During sexual arousal, this gland secrete an alkaline fluid into the urethra that protects the passing sperm by neutralizing acids from urine in the urethra. They also secrete mucus that lubricates the end of the penis and lining of the urethra, decreasing the number of sperm damage during ejaculation. Some males usually release a drop or two of this mucus following sexual arousal and erection. This droplet do not contain sperm cells.
Penis
The penis helps in copulation. It contains the urethra making it a passageway for the ejaculation of sperm and excretion of urine.
Structurally, the penis is cylindrical and consist of body, glans penis and a root.
Body: The body of the penis is composed of three masses of erectile tissues. These include:
Two copora cavernosa
One corpus spongiosum
These tissues contain blood sinuses (spaces) that are filled with blood following sexual arousal leading to erection (enlargement of penis).
Glans penis: This is formed by the enlarged distal end of the corpus spongiosum. It forms a round margin called corona. The external urethral orifice emerges from the glans penis. In an uncircumcised male, the glan penis is covered by the prepuce or foreskin.
Root: The root of the penis is the attached proximal portion of the penis. The weight of the penis is supported by two ; The fundiform ligament and the suspensory ligament.
Spermatic cord
The spermatic cord is a supporting structure that ascends out of the scrotum. It contains the vas deferens and the vessels that supply and drain the testes. Such vessels like testicular artery, testicular vein, autonomic nerves, and lymphatic vessels.
Note that testosterone produced by the testes is carried into general circulation by the testicular veins.
The spermatic cord passes through the inguinal canal which is an oblique passageway in the anterior abdominal wall.
The term varicocele refers to a swelling in the scrotum due to dilation of the veins that drains the testes. It usually resolves on its own.
Erection
Erection is the enlargement of the penis following sexual stimulation (which can be visual, tactile, auditory, olfactory or imagined). This enlargement and stiffening of the penis is caused by large amount of blood that fills the sinuse within the erectile tissues (corpora cavernosa and corpus spongiosum). The blood comes from the arterioles supplying the erectile tissues.
Erection is maintained by parasympathetic nerve fibres from the sacral portion of the spinal cord. Once sexual stimulation ends, the arterioles constrict and the blood drains out through the veins, returning the penis to its flaccid state.
Ejaculation
Ejaculation means, 'throw out'. It is the powerful release of semen through the urethra to the exterior. It is a sympathetic reflect coordinated by the lumbar portion of the spinal cord. As part of the reflex, the smooth muscle sphincter at the base of the urinary bladder closes, preventing urine from being expelled during ejaculation.
Each ejaculation contains about 50-200 million sperm per milliter. Only one sperm is needed to fertilize an ovum.
Low sperm count is a condition where the quantity of sperm drops below 15 million per milliter of semen. It is a major cause of infertility in men.
Premature Ejaculation
An ejaculation is premature if it occurs too early, for example, during foreplay or on or shortly after penetration. It is usually caused by anxiety, other psychological causes, or an unusually sensitive foreskin or glans penis. For most males, premature ejaculation can be overcome by various techniques (such as squeezing the penis between the glans penis and shaft as ejaculation approaches), behavioral therapy, or medication.
Male Circumcision
Circumcision(to cut around) is a surgical procedure in which part of or the entire prepuce is removed. It is usually performed several days after birth, and is done for social, cultural, religious, and (more rarely) medical reasons. Although most health-care professionals find no medical justification for circumcision, some feel that it has benefits, such as a lower risk of urinary tract infections, protection against penile cancer, and possibly a lower risk for sexually transmitted diseases. Indeed, studies in several African villages have found lower rates of HIV infection among circumcised men.
END
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