male reproductive system, organs and functionns.pptx

Unique for its role in human reproduction, a gamete is a specialized sex cell carrying 23 chromosomes—one half the number in body cells. At fertilization, the chromosomes in one male gamete, called a sperm (or spermatozoon), combine with the chromosomes in one female gamete, called an oocyte. The function of the male reproductive system is to produce sperm and transfer them to the female reproductive tract. The paired testes are a crucial component in this process, as they produce both sperm and androgens, the hormones that support male reproductive physiology. In humans, the most important male androgen is testosterone. Several accessory organs and ducts aid the process of sperm maturation and transport the sperm and other seminal components to the penis, which delivers sperm to the female reproductive tract. Scrotum
The testes are located in a skin-covered, highly pigmented, muscular sack called the scrotum that extends from the body behind the penis. This location is important in sperm production, which occurs within the testes, and proceeds more efficiently when the testes are kept 2 to 4°C below core body temperature.
The dartos muscle makes up the subcutaneous muscle layer of the scrotum. It continues internally to make up the scrotal septum, a wall that divides the scrotum into two compartments, each housing one testis. Descending from the internal oblique muscle of the abdominal wall are the two cremaster muscles, which cover each testis like a muscular net. By contracting simultaneously, the dartos and cremaster muscles can elevate the testes in cold weather (or water), moving the testes closer to the body and decreasing the surface area of the scrotum to retain heat. Alternatively, as the environmental temperature increases, the scrotum relaxes, moving the testes farther from the body core and increasing scrotal surface area, which promotes heat loss. Externally, the scrotum has a raised medial thickening on the surface called the raphae.
Testes
The testes (singular = testis) are the male gonads—that is, the male reproductive organs. They produce both sperm and androgens, such as testosterone, and are active throughout the reproductive lifespan of the male.
Paired ovals, the testes are each approximately 4 to 5 cm in length and are housed within the scrotum. They are surrounded by two distinct layers of protective connective tissue. The outer tunica vaginalis is a serous membrane that has both a parietal and a thin visceral layer. Beneath the tunica vaginalis is the tunica albuginea, a tough, white, dense connective tissue layer covering the testis itself. Not only does the tunica albuginea cover the outside of the testis, it also invaginates to form septa that divide the testis into 300 to 400 structures called lobules. Within the lobules, sperm develop in structures called seminiferous tubules. During the seventh month of the developmental period of a male fetus, each testis moves through the abdominal musculature to descend into the

1. ANATOMY AND PHYSIOLOGY OF MALE REPRODUCTIVE SYSTEM This Photo by Unknown Author is licensed under CC BY-SA

2. INTERNAL STRUCTURES Epididymis This is a tightly coiled tube that is responsible for conducting the sperm from the tubule to the vas deferens. It has a length of approximately 20 feet long. Some sperm are stored in the epididymis, along with the semen. The sperm takes an estimated 12 to 20 days of travel along the epididymis, and a total of 64 days to reach maturity.

3. Vas Deferens carry the sperm from the epididymis into the abdominal cavity where it will end at the ejaculatory duct. It is a hollow tube that is protected by a thick fibrous coating and surrounded by arteries and veins.

4. Seminal Vesicles These are two convoluted pouches along the lower portion of the posterior surface of the  bladder . The seminal vesicles secrete a liquid that is viscous and alkaline and has high protein, sugar, and prostaglandin content, which makes the sperm increasingly motile.

5. Ejaculatory Ducts These ducts pass through the prostate gland to join the seminal vesicles and the urethra.

6. Prostate Gland chestnut-sized gland situated below the  bladder . It secretes a thin, alkaline fluid that adds protection to the sperm from being immobilized by the low pH level of the urethra. The urethra passes through its center like a doughnut.

7. Bulbourethral Glands Also called as Cowper’s gland located at either side of the prostate gland and seminal vesicles and empty through the short ducts towards the urethra. Semen is a product of 60% from the prostate gland, 30% from the seminal vesicles, 5% from the epididymis, and 5% from the bulbourethral glands.

8. Urethra It has a length of approximately 8 inches or 18 to 20 cm.

9. External Structures Scrotum support the testes and it regulates the temperature of the sperm (2-3°C lower than body temp). promote the production and viability of the sperm the scrotum contracts towards the body during a very cold weather and relaxes away from the body during a hot weather.

10. Testes 2 to 3 cm in width and are encapsulated in a protective, white fibrous capsule. Several lobules are contained in each testis, which also contains Leydig’s cells that produce  testosterone  and seminiferous tubules that produce spermatozoa. In most men, one testis is slightly lower than the other to prevent trauma and easily sit or do any muscular activity.

11. This sagittal view shows the seminiferous tubules, the site of sperm production. Formed sperm are transferred to the epididymis, where they mature. They leave the epididymis during an ejaculation via the ductus deferens.

12. Penis The penis has three parts: two are called the corpus cavernosa, and the other is the corpus spongiosum. These erectile tissues also contain the urethra, making the penis an outlet for both urinary and reproductive functions. The glans, a sensitive, bulging ridge of tissue, is located at the distal part of the penis. The prepuce, which is a retractable casing of skin, protects the glans at birth. It is also the part that is surgically removed during circumcision.

13. Spermatogenesis Production of sperm occurs in the seminiferous tubules that form the bulk of each testis. The process begins at puberty, after which time sperm are produced constantly throughout a man’s life. Sperm counts—slowly decline after age 35, and some studies suggest that smoking can lower sperm counts irrespective of age.

14. Structure of Formed Sperm Sperm are smaller than most cells in the body; the volume of a sperm cell is 85,000 times less than that of the female gamete. Approximately 100 to 300 million sperm are produced each day.

15. Figure . Sperm cells are divided into a head, containing DNA; a mid-piece, containing mitochondria; and a tail, providing motility. The acrosome is oval and somewhat flattened.

16. Duct System During ejaculation, sperm exit the tail of the epididymis and are pushed by smooth muscle contraction to the  ductus deferens  (also called the vas deferens). The ductus deferens is a thick, muscular tube that is bundled together inside the scrotum called the  spermatic cord .

17. From each epididymis, each ductus deferens extends superiorly into the abdominal cavity through the  inguinal canal  in the abdominal wall. Sperm make up only 5 percent of the final volume of  semen, that the male ejaculates. The bulk of semen is produced by three critical accessory glands of the male reproductive system: the seminal vesicles, the prostate, the bulbourethral glands.

18. Seminal Vesicles The paired seminal vesicles are glands that contribute approximately 60 percent of the semen volume. Seminal vesicle fluid contains large amounts of fructose, which is used by the sperm mitochondria to generate ATP to allow movement through the female reproductive tract.

19. Prostate Gland It excretes an alkaline, milky fluid to the passing seminal fluid—now called semen—that is critical to first coagulate and then decoagulate the semen following ejaculation.

20. Testosterone Testosterone, an androgen, is a steroid hormone produced by  Leydig cells . The continued presence of testosterone is necessary to keep the male reproductive system working properly, and Leydig cells produce approximately 6 to 7 mg of testosterone per day. low levels of testosterone can lead to infertility.

21. AGING AND THE MALE REPRODUCTIVE SYSTEM Declines in Leydig cell activity can occur in men beginning at 40 to 50 years of age. The resulting reduction in circulating testosterone concentrations can lead to symptoms of andropause, also known as male menopause. A reduction in spermatogenesis resulting in lowered fertility is also reported, and sexual dysfunction can also be associated with andropausal symptoms.

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