MALE REPRODUCTIBE SYSTEM IN ENGLISH

                                                

                        MALE REPRODUCTIBE SYSTEM IN ENGLISH

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          MALE REPRODUCTIVE SYSTEM

Ø  Reproduction-  reproduction is the process of producing offspring. Human reproduction is a sexual reproduction . Reproduction system includes-  

Ø  Male reproductive system 

Ø  Female reproductive system 

Ø   

MALE REPRODUCTIVE SYSTEM-

Ø  The organs of the male reproductive system include

Ø  The testes,

Ø  A system of ducts

Ø  Accessory sex glands and

Ø  Several supporting structures, including the scrotum and the penis

 

SCROTUM

Ø  Scrotum- Scrotum is pouch like structure made up of skin, subcutaneous connective tissue and muscles which holds the testis. the scrotum looks like a single pouch of skin separated into lateral portions by a median ridge called the raphe

Ø   Internally, the scrotal septum divides the scrotum into two sacs, each containing a single testis  The septum is made up of a subcutaneous layer and muscle tissue called the dartos muscle

Ø  The dartos muscle (smooth muscle) is also found in the subcutaneous layer of the scrotum. 

Ø   The cremaster muscle is a series of small bands of skeletal muscle that descend as an extension of the internal oblique muscle through the spermatic cord to surround the testes.

Ø  The location of the scrotum (outside the pelvic cavity)  and the contraction of its muscle fibers regulate the temperature of the testes. Normal sperm production requires a temperature about 2–3C below  body temperature.  In response to cold temperatures, the cremaster and dartos muscles contract. Contraction of the cremaster muscles moves the testes closer to the body, where they can absorb body heat.

Ø  Contraction of the dartos muscle causes the scrotum to become tight (wrinkled in appearance), which reduces heat loss.

Ø  Exposure to warmth reverses these actions. Relaxation of the dartos muscle causes the scrotum to become loose and it moves away from the body and wrinkles disappears to allow heat loss.

 

TESTES-

Ø  The testes  or testicles, are paired oval glands in the scrotum measuring about 5 cm (2 in.) long and 2.5 cm (1 in.) in diameter. Each testis  has a mass of 10–15 grams.

Ø  The testes develop near the kidneys, in the posterior portion of the abdomen, and they usually begin their descent into the scrotum through the inguinal canals  during the latter half of the seventh month of fetal development.

Ø  A serous membrane called the tunica vaginalis  partially covers the testes. Internal to the tunica vaginalis there is a white fibrous capsule composed of dense irregular connective tissue known as the tunica albuginea.  It extends inward, forming septa that divide the testis into a series of internal compartments called lobules.

Ø  Each of the 200–300 lobules contains one to three tightly coiled tubules, the seminiferous tubules where sperm are produced. The process by which the seminiferous tubules of the testes produce sperm is called spermatogenesis

Ø  The seminiferous tubules contain two types of cells: spermatogenic cells (spermatogonia) , the sperm-forming cells, and Sertoli cells, which have several functions for  supporting spermatogenesis. spermatogonia, which remain dormant during childhood and actively begin producing sperm at puberty.

SPERMATOGENESIS-

Ø  In humans, spermatogenesis takes 65–75 days. It begins with the spermatogonia, which contain the diploid (46) number of chromosomes.

Ø  The spermatogonia divide continually through mitotic division to produce more cells. Some spermatogonia stay close to the basement membrane of the seminiferous tubule, acting as a pool of cells  to take part in future sperm production.

Ø  The rest of the spermatogonia lose contact with the basement membrane, squeeze through the tight junctions of the blood–testis barrier, undergo developmental changes, and differentiate into primary spermatocytes which are still diploid means they have 46 chromosomes.

Ø  At this stage primary spermatocyte undergo   meiosis I ( cell division) and produce two  secondary spermatocytes. Each secondary spermatocyte has 23 chromosomes (haploid number)  

Ø   Each secondary spermatocyte undergo   meiosis II ( cell division) and produce two  spermatids. Each spermatid has 23 chromosomes (haploid number)            

Ø  The final stage of spermatogenesis is  spermiogenesis in which  the development of haploid spermatids develops into sperm. Sperm then enter the lumen of the seminiferous tubule. Fluid secreted by Sertoli cells pushes sperm along their way, toward the ducts of the testes.

SPERM-

Ø  Each day about 300 million sperm complete the process of spermatogenesis.

Ø  A sperm is about 60 µm long and contains several structures such as head, neck,   mid piece and tail.

Ø  The flattened, pointed head of the sperm is about 4–5 micron long. It contains a nucleus with 23   chromosomes. In front of nucleus there is a caplike vesicle filled with enzymes that help a sperm to penetrate secondary oocyte known as acrosome. The neck is the constricted region just behind the head that contains centrioles.

Ø  The middle piece contains mitochondria which provide the energy  for locomotion of sperm to the site of fertilization and for sperm metabolism. The last and longest portion of the sperm is tail, hich help in movement of the sperm. Once ejaculated, most sperm do not survive more than 48 hours within the female reproductive tract.

EPIDIDYMIS-

Ø  The epididymis is a comma-shaped organ about 4 cm (1.5 in.) long that lies along the posterior border of each testis. The efferent ducts from the testis join the epididymis at the larger, superior portion of the epididymis called the head.

Ø  The body is the narrow mid-portion of the epididymis, and the tail is the smaller, inferior portion. The ductus epididymis would measure about 6 m (20 ft) in length if it were uncoiled. It is lined with pseudostratified columnar epithelium and encircled by layers of smooth muscle. Functionally, the epididymis is the site of sperm maturation, the process by which sperm acquire motility and the ability to fertilize an ovum.

VAS DEFERENS

Ø  The ductus deferens (vas deferens),  is about 45 cm (18 in.) long. It starts from tail of epididymis and ascends along the posterior border of the epididymis through the spermatic cord and then enters the pelvic cavity. he dilated terminal portion of the ductus deferens is called ampulla

Ø  The muscularis is composed of three layers of smooth muscle; the inner and outer layers are longitudinal, and the middle layer is circular. Functionally, the ductus deferens conveys sperm during sexual arousal from the epididymis toward the urethra by peristaltic contractions of its muscular coat.

SPERMATIC CORD-

Ø  The spermatic cord is a paired structure whose main function is to support and suspend the testis inside the scrotum. It consists of the ductus (vas) deferens, the testicular artery, veins , autonomic nerves, lymphatic vessels, and the cremaster muscle.

EJACULATORY DUCT-

Ø  Each ejaculatory duct is about 2 cm (1 in.) long and is formed by the union of the duct from the seminal vesicle and the ampulla of the ductus (vas) deferens. They terminate in the prostatic urethra, where they eject sperm and seminal vesicle secretions

SEMINAL VESICLE-

Ø  Seminal vesicles or seminal glands are pouchlike structures and about 5 cm (2 in.) in length. Through the seminal vesicle ducts they secrete an alkaline, viscous fluid that contains fructose  prostaglandins, and clotting proteins and become a constituent of semen.    

Ø  The alkaline nature of the seminal fluid helps to neutralize the acidic environment of the male urethra and female reproductive tract that otherwise would inactivate and kill sperm. Semen is a mixture of sperm and seminal fluid, a liquid that consists of the secretions of the seminiferous tubules, seminal vesicles, prostate, and bulbourethral glands.

PROSTATE GLAND-

Ø  The prostate is a single, doughnut-shaped gland. It measures about 4 cm from side to side, about 3 cm from top to bottom, and about 2 cm  from front to back. Prostatic secretions make up about 25% of the volume of semen and contribute to sperm motility and viability.

BULBOURETHRAL GLAND

Ø  The paired bulbourethral glands   or Cowper’s glands, are of about the size of peas. They are located inferior to the prostate on either side of the membranous urethra. bulbourethral glands secrete an alkaline fluid into the urethra that protects the  sperm by neutralizing acids from urine in the urethra.

PENIS-

Ø  The penis contains the urethra and is a passageway for the ejaculation of semen and the excretion of urine. It is cylindrical in shape and consists of a body, glans penis, and a root.

Ø  The body of the penis is composed of three cylindrical masses of tissue, each surrounded by fibrous tissue called the tunica albuginea.  The two dorsolateral masses are called the corpora cavernosa.

Ø  The smaller midventral mass, the corpus spongiosum penis, contains the spongy urethra and keeps it open during ejaculation. The distal end of the corpus spongiosum penis is a slightly enlarged, acorn-shaped region called the glans penis

Ø  Skin and a subcutaneous layer enclose all three masses. These three cylandrical masses are also known as erectile tissue. Erectile tissue is composed of numerous blood sinuses (vascular spaces) lined by endothelial cells and surrounded by smooth muscle and elastic connective tissue. Covering the glans in an uncircumcised penis is the loosely fitting prepuce  or foreskin.

Ø  The root of the penis  consists of the bulb of the penis which is the expanded portion of the base of the corpus spongiosum penis, and the crura of the penis  which are  the two separated and tapered portions of the corpora cavernosa .

Ø  The bulb of the penis is attached to the inferior surface of the deep muscles of the perineum and is enclosed by the bulbospongiosus muscle.

Ø  Crura of the penis bends laterally away from the bulb of the penis to attach to the ischial and inferior pubic rami and is surrounded by the ischiocavernosus muscle