Every human being is genetically unique, even the identical twins! Isn’t that amazing? What do you think is the reason behind such genetic diversity in humans?
One of the major reasons is that humans reproduce sexually which involves a male and a female parent. As the genetic factors of the parents mingle during the fusion of their gametes, the offspring produced inherit genetic variations and become unique.
Do human males and females look identical? No, right? There are many distinguishing characteristics, both external and internal, which separate a human male from a female. One of the main being the difference in their external genitalia and their reproductive systems. Intrigued? Come, let’s learn more about the male reproductive system here.
You may also want to read about the female reproductive system structure.
Male reproductive system consists of male external genitalia, primary sex organs (testes) and secondary sex organs. Let’s learn more about these in detail.
This includes two parts:
Penis is an organ which conducts urine and semen in males. It consists of erectile tissue which facilitates erection to help in the transfer of semen into the vaginal tract of females. It has an opening called urethral meatus and an enlarged end known as glans penis. Glans penis is covered by foreskin which is a sheath.
A sac-like structure which holds the testes in males is known as scrotum. It is present outside the abdominal cavity. Internally, scrotum is divided into two sacs by scrotal septum, each containing a testis. Externally, the septum is marked by a scar-like raphe. Scrotum helps in maintaining temperature which is 2-2.5oC lower than normal body temperature so as to provide ideal temperature for sperm production and viability.
Primary sex organ is an organ which is directly involved in production of gametes. It is the source of sex hormones. In males, the primary sex organs are the pair of testes.
Each testis is oval in shape, 4-5 cm long and 2-3 cm wide. The testes lie outside the body cavity, in the scrotal sacs because sperm production and maturity requires temperature less than that of normal body temperature.
In most mammals, the testes develop in the abdominal cavity but descend into the scrotum, through the inguinal canal, a little before birth. In some mammals like whales, dolphins etc. testes are located in the main body cavity. Main functions of testes include production of sperms and androgen.
Once testes descend into scrotum, the inguinal canal is sealed by connective tissue which prevents testes from descending back into the abdominal cavity. When the inguinal canal is closed improperly, a loop of intestine can ascend into the inguinal area and cause inguinal hernia.
The outer protective covering of testes is known as tunicae. Tunicae is further divided into three layers:
Testes are further divided into approximately 250 compartments known as testicular lobules. Each lobule consists of one to three highly coiled seminiferous tubules.
Seminiferous tubules are the highly coiled structure which are 70 cm long. It is the site for sperm production.
Each tubule is lined internally by two types of cells:
The region surrounding the seminiferous tubules is called interstitial space which consist of blood vessels, immunogenic cells and Leydig cells or interstitial cells. Leydig cells produce and secrete androgens or testicular hormones.
Organs involved in transportation, maturation and storage of gametes are known as secondary sex organs. Secondary sex organs also provide assistance in reproduction. These include the male accessory glands and ducts.
Rete testis, vasa efferentia, epididymis, vas deferens and ejaculatory duct collectively are called male accessory ducts which are involved in transport of sperms.
Seminal vesicles, prostate gland and Cowper’s gland are the male accessory glands and their secretions collectively form seminal plasma which is rich in calcium, fructose and certain enzymes.
The open end of the seminiferous tubules form a network known as rete testis from which 15-20 fine ciliated ductules, named vasa efferentia, arise.
It is a highly coiled structure attached to testes where the sperms are stored till they become mature and motile.
It is a thick walled tube that helps in transfer of sperms from epididymis. It ascends into the abdominal cavity and loops over the urinary bladder and comes down to join the duct from the seminal vesicle.
Male reproductive system constitutes a pair of seminal vesicles which secrete alkaline secretion that helps in neutralising male and female tract. It contributes to 60% secretion of the semen. Secretions of seminal vesicles constitute calcium, fructose, prostaglandins and clotting factors.
Vas deferens and duct from seminal vesicles combine together to form a duct known as ejaculatory duct which helps in mixing the sperm and secretions from the seminal vesicles. The ejaculatory duct further opens into the urethra and also receives secretions from the ducts arising from the prostate and bulbourethral glands.
It is an individual gland surrounding urethra that contributes in producing 20-25% part of semen. Its main function is to nourish and activate the sperm with the help of its alkaline secretions.
Solution: Testes are present outside the abdominal cavity in scrotum which maintains a temperature 2-2.5oC less than that of body temperature which is a mandatory requirement for sperm production and viability.
Hence, the correct option is c.
Solution: The sperms are produced in the seminiferous tubules of the testes from which they follow the following path -
Rete testis ⟶ Vasa efferentia ⟶ Epididymis ⟶ Vas deferens ⟶ Ejaculatory duct ⟶ Urethra ⟶ Urethral meatus (opening of urethra outside the body).
Thus, the correct option is a.
Solution: Sertoli cells are present in the seminiferous tubules and are responsible for nourishment of male germ cells or spermatogonia.
The spermatogonia divide meiotically to produce sperms and the interstitial cells produce male sex hormones or androgens. The epididymis stores the sperms till they become mature and motile.
Hence, the correct option is a.
If the vas deferens is cut and a part is removed then the pathway of sperms is obstructed and they would not reach the female body and would fail to fertilise the egg.
Hence, the correct option is c.
Question 1.- Why are the testes situated outside the abdominal cavity?
Answer. Testes are present outside the abdominal cavity in the scrotum. This maintains a temperature 2-2.5oC less than that of body temperature which is essential for sperm production and viability.
Question 2.- What are the functions of testes?
Answer. The testes are the primary sex organs which are involved with the production of the male gametes, that is sperms. The testes are also responsible for producing the androgens or the male sex hormones.
Question 3.- What does the human male reproductive system consist of?
The human male reproductive system consists of -
Question 4.- What are testicular lobules?
Answer. Testes are further divided into approximately 250 compartments known as testicular lobules. Each lobule consists of one to three highly coiled seminiferous tubules.