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Male Reproductive System
The male reproductive system is the complementary of the female’s and are specially designed such that it will enable the transfer of the male gametes and the necessary nutrient it needs for it to get to the female. The male reproductive system consists of the gonads(testes), the ducts(seminiferous tubules, vasa efferentia, Vasa deferentia, ejaculatory duct and the urethra), the accessaory glands( prostate gland, seminal vesicles, cowper’s glands) and the external organ(penis).
The gonads are the testes which are paired, oval glands whose functions include the production of sperm and the production of male sex hormones. The testes consists of the semiferous tubules, tubuli recti, rete testis, testicular lobe, the vasa efferentia, tunica albuginea and the epididymis. The seminiferous tubules are where sperms are produced. Testerone is produced in the interstitial cells of leydig. The scortum, an external skin, protects and supports the testes and regulates the temperature, usually 3 degree Celsius lower than the body, to allow production and survival of sperms. The cremaster muscle elevates the testes when exposed to cold conditionds, moving them closer to the groin where they can absorb the body heat. During hot conditions, the process is reversed. The vasa efferntia acts as a collection and transportation for sperm out of the testes to the head of the epididymis. The epididymis then reabsorbs fluid secreted by the seminiferous tubules, thus concentrating the spem. Its also the site of the maturation of the sperms as well as help to convey the sperm to the vas deferens. The vasa deferentia is where sperms are stored and propels sperms during an ejaculation to the ejaculation duct.
The process whereby sperms are produces is known as spermatogenesis. It is formation and development of haploid spermatozoa within the testes. It occurs continuously starting at puberty and it takes about 70-75 days. Several hundred million of sperms are produced each day. First the diploid spermatogonia will grow into the primary spermatocyte. Under meiosis I, the secondary spermatocyte is produced. At meosis II, the early spermatoid forms and develops into the spermatoid in due time.
The spermatozoa, the minute and motile male gamete has 4 principle parts-head, neck, middle piece and the tail. The head is where the condensed and compact nucleus is and it also has the acrosome, a fluid filled sac shaped like a dome to help in the process of penetrating the egg when delivered successfully. The neck has the proximal centriole and the distal centriole whereby 2 centrioles are arranged at right angles to each other. The middle piece consists of the mitochondria that are arranged in a spiral to release energy for the sperms to swim up the oviduct. The tail helps to direct the sperms and provide the propelling force to move.
The hormonal control of the testicular function is controlled by following process. External stimuli teases the other brain areas which stimulates the hypothalamus to release a Gandotrophin releasing hormone(GnRH) which in turns stimulates the anterior pituitary. It then releases Gandotrophine Follicle stimulating hormone(FSH) to stimulate Sertoli cells to secrete oestrogens for spermiogenesis and Lutenising hormoneto(LH) stimulate interstitial cells of Leydig to secrete testosterone. The sertoli cells then also secretes inhibin to act on the anterior pituitary to prevent over secretion of FSH.
Testosterone is an androgen which aids in the development, growth and maintenance of the male sexual organs. It also helps in the development of secondary sexual characteristics like the increase growth of hair, particularly on the face, chest, axillary region and pubic region, enlargement of the larynx and thickening of the vocal folds, accompanied by deepening of the voice, thickening of the skin, increased muscular growth following which, shoulders become broader and the thickening and strengthening of bones. It also participates in spermatogenesis, spermiogenesis and stimulates protein anabolism.
Once the sperms have been activated to move during an ejaculation it undergoes the following pathway from the epididymis to the vas deferens, bypassing the seminal vesicles and later the prostate gland and then the cowper’s gland before it hits on the route along the urethra and out of the penis. The accessory glands provide the sperms with much nutrients it needs to survive.
The seminal vesicles secretes a viscous, alkaline fluid rich in fructose and prostaglandins. It maskes up 60% of the volume of semen. The alkalinity is to help the sperms neutralize its way in the female reproductive system while the fructose is the sperm’s respiratory substrate for motility and viability. The prostate gland secretes a thin, milky alkaline fluid that neutralizes the acidic ssecretions of the vagina and enhances the motility of sperms. Its secretions make up for about 20% of the volume of semen. The cowper’s gland secretes a mucus(antacid) for lubrication of the penis and an alkaline substance during intercourse.
Ultimately, the mixture of the various fluids is known as the semen, ejaculated from the urethra during inter course. The sperm number about 250 000 000 per ejaculation, but it only is 1% of the total volume of between 2-5 cm3 of semen. It also contains enzymes responsible for the final capitation of the sperm(activation). Furthermore, it has seminalplasmin(antibiotic), which destroys some vaginal bacteria and mucus to minimize friction between the penis and the vagina during intercourse.
The penis is the intermittent organ, used to deliver the the sperms to the next of the cervix, as close to the site of ovulation as possible. Usually, the penis in limp and flaccid but can be erected by dilation of blood vessels allowing huge amounts of blood to fill the sinuses in the corpora cavernosa and spongiosa. The glans penis has a high number of sensory cells and play an essential role in the initiation of the erection reflex. The foreskin/prepuce covers the gland and can be removed by a process known as circumcision.
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