Structure of Human Male Reproductive System


In this article, I give an account of the structure of the human male reproductive system. The various parts of the male reproductive system, their structure and about their functional aspects are discussed in this resource. The various accessory glands associated with the male reproductive system are also dealt in this resource.

Introduction

The chief organs of the human male reproductive system include a pair of testes (Plural) along with some accessory male organs. Testes are considered to be the chief organs of the male reproductive system because they are directly involved in the process of reproduction i.e. in the production of sperms or spermatozoa. The accessory reproductive organs associated with the male reproductive system are not directly involved in reproduction but aid or help in the process of reproduction indirectly. Scrotal sacs, Epididymis, Sperm ducts or Vas defer-ens, Inguinal canal, Spermatic cord, accessory glands- a pair of Seminal vesicles, Prostrate gland and a pair of Cowper's glands, urethra, and penis are considered to be the accessory reproductive organs. It is very important for a boy to know about his own reproductive organs, and a girl to know about her own reproductive organs as well as how Menstrual Cycle occurs in her in their adolescent age.

External view of Human Male Reproductive System
External View of Human Male Reproductive System (Courtesy:-https://en.wikipedia.org)

Morphology of Male reproductive System

The following is the morphology of the human male reproductive system.

Testes

A pair of the testes are lodged in a pair of scrotal sacs or scrotal pouches which hang externally below the abdomen. These testes are ovoid organs which are covered by a white fibrous connective layer called tunica albuginea. Each testis (Singular) measures around 3-5 cm. the length and around 3 cm. in width. Testes are the chief organs of the male reproductive system which are concerned with the production of male gametes-sperms or spermatozoa and thus directly involved in the process of reproduction. Testes not only are chief organs of reproductions but also they act as endocrine glands and thus produce the male hormone testosterone at puberty.

Scrotal sacs

Scrotum is a thin fold of skin which hangs behind the penis below abdomen region. A septum divides the scrotum into two pouch-like structures into which the testes, blood vessels, nerve supply, and spermatic cord enter. The scrotal wall includes muscle tissue and is elastic in nature. Scrotal sacs are part of male genitalia and will correspond to labia majora of female external genitalia.

Scrotal sacs play an important vital role in proper functioning of the sex organ testes. Actually, in male, the testes located inside the abdomen while the male baby growing inside mother's womb. But just before the time of birth the testes descend down into scrotal pouches through inguinal canals which connect from the abdomen to scrotal pouches. The reason for this is, testes are functional only when they get 2-3 degrees less temperature when compared to our body temperature and can produce motile sperms. If they remain inside the abdomen they get 37 degrees Celsius body temperature which makes them sterile. In some rare cases, the newly born male baby shows the testes enclosed inside the abdomen and not descend down into scrotal sacs. In such cases, doctors through surgery make them get lodged into scrotal sacs otherwise it leads to sterility.

Inguinal canals

Two oblique passages which extend from the anterior abdominal wall into the scrotum and through which the testes descend down into scrotal sacs just before the time of birth. Once the testes descend into scrotal pouches, the openings of the inguinal canals get sealed to prevent the retraction of testes into the abdomen. In some cases, after the descent of testes, the inguinal canals are not become closed which allows part of the intestine to get protruded into the inguinal canal which causes severe pain to the individual. In medical terminology, this defect is commonly known as a Simple Hernia. Doctors through surgery remove the intruded intestinal part and also close the partially closed inguinal canal to treat the defect.

Spermatic Cord

A cord-like structure which originates from the abdominal cavity and suspends the testis in the scrotum position is known as the Spermatic cord. The spermatic cord is made up of Vas deferens, blood vessels, muscle layer, and nerves.

Internal structure of Testis

Each testis (Singular) is internally divided into lobes and lobules by the fibrous connective layer, tunica albuginea which grows inwards into testis from the outer surface of the testis. In each lobe, some tightly packed long coiled tubules called Seminiferous tubules are present and such 1000 tubules can be found in a single testis. Each tubule measures 50 cm in length and 200 micrometers in diameter. Seminiferous tubules are the functional units of testis which produce the sperms. The wall of the seminiferous tubule is lined by germinative epithelium cells. These germinative epithelium cells through meiosis continuously produce sperm cells and secrete them into the lumen of seminiferous tubules. The process by which sperms are produced from sperm mother cells of seminiferous tubules through meiosis is known as spermatogenesis.

Structure of Testis
Parts:- 1. Testicular septa
2. Convoluted seminiferous tubules
3. Testicular lobules
4. Straight seminiferous tubules
5. Vasa efferentia
6. Rete testis
Schematic representation of internal structure of Testis (Courtesy:-www.wikipedia.com)

The coils of long seminiferous tubules which are compactly packed in the lobes of the testis are held together by a connective tissue which includes Leydig cells or Interstitial cells which are endocrine in nature. At puberty time of male, these endocrine cells dissolve themselves to secrete a steroid male hormone called Testosterone. Puberty is the attainment of youth at which time the testes or ovaries reach maturity and are ready to form sperms in male or ova or eggs in males. Usually a male or female attains puberty in between 10-13 years. Testosterone hormone secreted by testes in the male will bring about some secondary sexual characters by which we can identify a male. These features include the development of beard and mustache, enlargement of testes, voice becomes deep, the growth of facial hair, hair grows in armpits and pubic region, chest becomes enlarged, and muscles in the shoulder becomes strong.

In between the germinative epithelial cells of seminiferous tubules, some special cells present are known as nurse cells or Sertoli cells. During the formation of sperms from germinative epithelial cells, the Sertoli cells dissolve themselves and provide nourishment for the newly formed sperm cells.

From each lobe of the testis arise ducts (12-14 ducts) which move upwards of the upper pole of testis together form a fitting cap like structure called epididymis. The ducts which arise from the lobes of the testis are known as vasa efferentia. The sperms which are formed in the seminiferous tubules are immature in nature and are transferred to epididymis through vasa efferentia. The epididymis is the region where the immature sperms stay for sometime till they mature.

From the epididymis, there arise a single distinct tube, which is about 6 meters long moves down along the lateral side of the testis and again rises up in the form of sperm duct or vas deferens. The sperm duct from each testis passes through an inguinal canal into the abdomen. Then these two sperm ducts loop over the ureter from their side and from behind the urinary bladder join the urethra. Sperm ducts carry the sperms from testis to urethra.

Accessory Glands

There are three accessory glands associated with the male reproductive system and they are as follows:-

  1. Seminal vesciles

    These are a pair of lobulated glands situated behind the urinary bladder and are joined to each of the sperm ducts just before they join urethra. These seminal vesicles pour an alkaline secretion into sperm duct as they carry sperms towards urethra. This alkaline secretion is made up of fructose, citrate, ascorbic acid, prostaglandins and various enzymes. This alkaline secretion nourishes the sperms, makes them more active, more motile, alive, and makes them mature completely. Fructose is a source of energy for the sperms. Seventy percent of semen include this alkaline secretion and it acts as a transport medium for sperms.

  2. Prostrate Gland

    There is a single large bilobed gland present which surrounds urethra close to its origin from the urinary bladder is known as a Prostrate gland. This gland also pours an alkaline secretion into urethra and aids in the formation of semen. This alkaline secretion includes proteolytic enzymes and citric acid. It helps in the motility and viability of sperms. Twenty percent of semen include this alkaline secretion which actually increases the content of semen. This alkaline secretion also helps in neutralizing the acidic condition of the vagina when the semen get deposited there during copulation by male otherwise the sperms will be killed. In some elderly persons, the Prostrate gland may become enlarged and may obstruct the bladder during urination.

  3. Cowper's glands or Bulbourethral Gland

    These are a pair of very small lobulated glands present just below prostrate gland on the urethra. They also secrete an alkaline secretion which lubricates and neutralizes the urethral tube as the semen passes out of the penis. As urine passes through the urethral tube which may make it acidic and thus to neutralize it Cowper's glands alkaline secretion helps in it.

    Semen is a mixture of sperms and alkaline secretions of the accessory glands seminal vesicles, prostate gland and Cowper's glands. For each ejaculation during copulation 3-5 ml. of semen is released and which contain a normal count of 40 million to 60 million sperms. A sperm count of 10-20 million is considered to be a low count which makes the possibility of fertilization and pregnancy difficult.

    Structure of Penis

    The following is the structure of Penis:-
    Structure of Penis
    Internal Structure of Penis (Courtesy:-www.wikipedia.com)

    The penis is both an excretory as well as a copulatory organ in the male. It lies in front of scrotum below the abdomen. It is a cylindrical and also a highly vascular organ. The penis consists of three columns of tissues- spongy (Corpus spongiosum), vascular and erectile (Corpus cavernosum) tissue around the urethra. Penis on its outer surfaces is covered by a layer of skin. The distal end of the penis is somewhat enlarged and is known as glans penis. At the end of the penis, a retractable loosely arranged skin is present known as foreskin or prepuce. Small spaces and gaps present between the erectile tissue are known as sinuses. During sexual excitement, blood gushes into these vascular spaces and makes the erectile tissue to expand which makes the penis stiff and rigid. In this stiff and rigid condition, only a male introduce the penis into the vagina of a female and deposit semen at cervix region. The inability of a male to introduce penis into the vagina and deposit semen is known as impotency.

    Here is a video to know about the structure of Human Male Reproductive System:

    Courtesy:-Youtube


Comments

Author: Natarajan26 Dec 2017 Member Level: Diamond   Points : 8

A detailed article that explains the male reproductive system. Children often mistake testes for kidneys; you may laugh, but it is a common misconception. We have to educate children in year 4 or year 5 when they learn about organ systems and the function that kidneys are in the abdomen and in the back and not in the scrotum.

Glad that the author has brought out about undescended testis. Here a simple advice is for the mother, father or grandparents to observe the male infant as he grows, the testis should be in the scrotum, sometimes when a child is crying, it can move upwards. It is better to see a qualified pediatric surgeon if the scrotum is very small or the testis is not felt. This is important because it is difficult for many general doctors to differentiate between retractile testis (little higher than normal, does not need surgery) and undescended testis (often needs surgery sooner to preserve testicular function).

Many adults have one testis that is undescended and people ignore it if this is the case then at least see a surgeon because an undescended testis can also develop diseases that are difficult to diagnose as it is hidden from view.

The epidydimis is the place where sperms are stored and they are carried by the vas or the sperm tube. This is important to understand because, after family planning operation in men, the doctors often ask for 3 or more semen analysis before declaring the operation as successful because sperms formed prior to the operation can be stored in the tube and can still be viable and healthy for a few months.

The prostate gland is something that is not felt easily or seen as it is located on a deeper plane. Many men forget about the prostate gland, it get's enlarged as men grow older and can cause an obstruction for the outflow of urine. A decrease in the speed at which the urine comes out, increasing pressure needed to pass urine, increased number of times a male individual needs visit the washroom to empty his bladder are all indications that the prostate has enlarged and should seek medical counsel. At an early stage medicines would help, at a later stage or in very big prostates surgery would be needed.

A lot of people confuse between Impotency and Sterility, especially in Men, it becomes a taboo subject to discuss and hence leads to many misconception and broken marriages. Impotency is a failure to achieve and maintain an erection that is needed for normal intercourse, hence leading on to pregnancy in the normal fashion. A person who is impotent does not mean that he is sterile. A Sterile male with respect to reproduction is one who does not have the minimum number of healthy, moving sperms in his semen, he can still have a normal erection. It is very important to know that both diseases need different types of treatment and can still father a child.

Author: Hakimuddin Kuwakhedawala26 Dec 2017 Member Level: Gold   Points : 1

My appreciation to the author for writing an informative article. It is really a good article for the biology students. Testes produce sperm and need 35 degree Celsius temperature. In the beginning, the testes are situated near the kidney but before the delivery, testes reaches testes sac. The body temperature is 37 degree Celsius but testes need 35 degree Celsius for proper functioning.

Testes also produce male hormone androgen which is responsible for the secondary sexual characteristics in a male. Leydig cells produce Androgen hormone. Leydig cells are found in between seminiferous tubules of testes.



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