The epididymis is a mass of long narrow closely coiled tubule which lies along the inner side of each testis. Coiling forms three parts - 

Spermatogonia are diploid cells on the inside wall of seminiferous tubules that multiply by mitotic divisions. Some of the spermatogonia called primary spermatocyte undergo meiosis-I to give rise to secondary spermatocytes (haploid). Each secondary spermatocyte undergoes melosis-II to give rise to two haploid spermatids which are transferred to spermatozoa by spermiogenesis.

Vasa efferentia are fine ciliated ductules that arise from the seminiferous tubules of testis (where sperms are formed) and open into epididymis which is a mass of long narrow closely coiled tubule lying along the inner side of testis. Epididymis stores the sperms. Thus, if vasa efferentia get blocked, sperms will not be transposed from testes to epididymis.

Testes are the pair of oval organs, about the size of large olives that lie in the scrotum. The testes are responsible for making testosterone which is the primary male sex hormone, and for generating sperm. 

The primary reproductive organ of human male is testes, it produces male hormones  testosterone and sperm.

In mammals, sperm cells are produced in the seminiferous tubules of each testis. These sperm cells leave the testes and pass into a larger coiled tube known as the epididymis. The sperm cells attain maturity in the epididymis. The sperm cells are stored in this structure till they are ejaculated. During ejaculation, the sperms pass from the epididymis into the vas deferens and are ejaculated with the semen through the penis.

In males, testis are located in the scrotal sac and are extra abdominal in position. The temperature in the scrotum is 2$^o$ to 3$^o$ C less than the normal body temperature. This temperature is conducive for maturation of sperms. Thus the correct answer is option D.

In human males, the testes are situated outside the abdominal cavity within a pouch called scrotum. These type of testes is called extra-abdominal. Scrotum helps in maintaining the low temperature of the testes than the normal body temperature. It is necessary for sperm formation. But there are certain mammals in which the testes descend into scrotum only during breeding season. These mammals breed seasonally. Bat and otter are the examples of these mammals.

In human males, the testes are situated outside the abodominal cavity within a pouch called scrotum. These type of testes is called extra-abodominal. Scrotum helps in maintaining the low temperature of the testes than the normal body temperature. It is necessary for sperm formation. But there are certain mammals in which the testes remain permanently in the abdomen and does not cause any defect. Scrotum in absent in these mammals. Examples are elephant, aquatic mammals like whales, dolphins, seal and prototherians or egg-laying mammals like Ornithorhynchus.

Testes is the primary sex organ in human males. The testes are situated outside the abdominal cavity within a pouch called scortum. In adults, each testis is oval in shape, with a length of about 4 to 5 cm and width of about 2 to 3 cm. The testis is covered by a dense covering. They are enclosed in an outer tough capsule of collagenous connective tissue, the tunica albuginea. It is a protective layer.

Spermatogenesis is the process by which the formation of sperm which is the male gamete takes place and it is carried out in the tiny tubes like structure in seminiferous tubules of testes.

Testes are extra-abdominal in position. The testes are situated outside the abdominal cavity within a pouch called scrotum. The scrotum helps in maintaining the low temperature of the testes ($2 – 2.5^o$ C lower than the normal internal body temperature), which is necessary for spermatogenesis. The slightly cooler temperature of the scrotum is necessary for the development of normal sperm. So, the testes start their development in the abdominal cavity. But during the 7^th month of the foetal life, they descend into the scrotal sacs in presence of testosterone hormone.

To ensure the survival and growth of the sperms, testes have been placed outside the abdominal cavity within a pouch called scrotum so as to ensure the optimal temperature. The scrotum helps maintain the low temperature (by about 2-2.5 degrees than the normal body temperature) required for spermatogenesis. So, the correct option is '2.0−2.5o C lower than the normal body temperature'.

• In the case of premature delivery, $8^{th}$-month) of a male baby the testis are situated in because of testes descent into the scrotum outside the body just before birth.
• The testis is placed outside the body in scrotum because The scrotum helps in maintaining the low temperature of the testes (2–2.5°C lower than the normal internal body temperature) necessary for spermatogenesis. 
• So, the correct answer is "Abdominal birth'.

• Seminiferous tubules are present within the male testes. At seminiferous tubules, germination, maturation, and transportation of the sperm cells takes place. 
• They are made up of columnar Sertoli cells. The scrotum is a sac of skin that encases the testes and suspends them below the abdominal cavity. It provides a slightly cooler temperature than the body temperature.
•  Epididymis connects testicles to vas deference. It transports and stores sperm cells produced by testes. 
• The prostate gland is present between the bladder and the penis. It secretes alkaline secretion to semen which protects and nourishes the sperm.

• The sperms develop at a lower temperature than the internal body temperature which is 37 degree Celsius.
  
• To maintain a lower temperature during spermatogenesis the testis descends in the scrotal sac outside of the abdominal cavity.
• So, the correct option is 'Maintaining the scrotal temperature lower than the internal body temperature'.

The male testes are divided into compartments by the septa. Each testicular lobule contains s 1-3 highly coiled seminiferous tubules, blood vessels, and connective tissues. Each seminiferous tubules is line by germinal epithelium, the seminiferous tubule is the site of spermatogenesis. Sertoli or nurse cells are present that help in the nursing of the spermatozoa and their maturation. The sperms are then known as the male gametes.

The intratesticular genital duct includes the parts like Tubuli recti, Rete testes and Ductili efferentes. 

The testes are a pair of ovoid glandular organs that are central to the function of the male reproductive system. The testes are responsible for the production of sperm cells and the male sex hormone, testosterone. The main male sex organs are the penis and the testicles, which produce semen and sperm.
Therefore, the correct answer is option D.

• Testes are the glandular glands that secrete hormone as well as produces male gametes. 
• It is located in the scrotal sac, outside the body, because the process of spermatogenesis (sperm or male gamete production) requires a lower temperature i.e., 2-3${^0}$C lower than the normal body temperature. 

The testes are a pair of ovoid glandular organs that are primary to the function of the male reproductive system. Its function is to produce sperm cells and the male sex hormone, testosterone.
So, the correct answer is option A.

In mammals, the process of spermatogenesis or the formation of sperm requires a lower temperature than the normal body temperature to produce viable sperms. Hence, the sperms are stored outside the body in a sac-like structure called scrotum.
So, if the testes do not move from abdominal cavity to the scrotal sac, the sperms will not be formed.
Thus, the correct answer is option D.

The semen, secreted by male contains 100-200 millions of sperms. The healthy sperms in the semen then go to the cervix, then pass through the uterus and then ultimately arrive at the ampulla part of the fallopian tube where they come to meet the ovum. Although so many sperms encircle the ovum, only one sperm is allowed to penetrate the ovum.
Thus, the correct answer is option A.

The testes are the male gonads in animals. The primary function of the testes is to produce sperms and to produce the testosterone hormone.
So, the correct answer is option A.

The process of spermatogenesis or the formation of sperms require a lower temperature (1-6 degree C lower) than the normal body temperature to produce viable sperms. Hence, the sperms are stored outside in a sac-like structure called scrotum.
So, the correct answer is option D.

• The testes are the male gonad in the animals, produces sperm and the testosterone hormone and so is the primary male reproductive organ. 
• Ovum is produced by the female reproductive organ, ovary, which is also responsible for the production of estrogen.

• The reproductive organs in each gender include a primary sex organ and several secondary sex organs. 
• The primary sex organ is the one that produces the gametes of that sex i.e. the sperm or the ova. 
• So, in the male, the primary sex organ is testis. In the female, the primary sex organ is the ovary.

• The testis is the male gonad in animals. The primary function of the testes is to produce sperm (spermatogenesis) and to produce androgens, primarily testosterone.

• Each lobule of testes contains one to three seminiferous tubules in which the sperms are produced. 
• Each seminiferous tubule is lined on its inside by two types of cells called male germ cells (spermatogonia) and Sertoli cells. Sertoli cells are also known as nurse cells. 
• They provide nutrition to spermatozoa. Spermatozoa are developing sperms. It is formed during the last stage of spermatogenesis. This stage is known as spermiogenesis.
•  In this step, spermatids are transformed into spermatozoa (sperms) by the process of metamorphosis. Heads of spermatozoa are embedded in the Sertoli cells.

The primary sex organ in the male is testis. Besides producing sperms they also produce hormones. Penis and prostate are examples of secondary sex organs. The scrotum is not a sex organ.

The tubular structures present inside the testis are known as seminiferous tubules. These tubules are responsible for producing the sperm cells through a process called spermatogenesis. 

Human male germ cell is sperm. Each sperm is a single cell. During the last step of spermatogenesis, spermatids are transformed into spermatozoa by the process of metamorphosis. These spermatozoa are known as sperms. Mature sperm consists of a head, a neck, a middle piece and a tail. A plasma membrane envelops the whole body of sperm. The sperm head contains a very little cytoplasm, an elongated haploid nucleus, the anterior portion of which is covered by a cap-like structure, acrosome. Sperm fertilizes with ovum and leads to the formation of zygote.

The sperms are produced in the testes in which the process of spermatogenesis takes place. The sperms move to the epididymis where they mature and are stored. The sperms pass through the vas deferens and then through the urethra. The sperms are ejaculated through the penis which is the copulatory organ. 

The testes are situated outside the abdominal cavity within a pouch called scrotum. The temperature in scrotum necessary for sperm formation should be 2$^o$C below body temperature. The slightly cooler temperature of the scrotum is necessary for the development of normal sperm. The testes of human males are extra-abodominal because it descends into the scrotal sacs.

Seminiferous tubule is the functional unit of testis of man. Each testis has about 250 compartments called testicular lobules, these compartments contain highly coiled tubules called seminiferous tubules. In seminiferous tubules, sperms are produced. Each seminiferous tubule is lined on its inside by two types of cells called male germ cell (spermatogonia) and Sertoli cells. These cells are also called nurse cells as they provide nutrition to the developing sperms. Head of developing sperms are embedded in the sertoli cells. The male germ cells undergo meiotic divisions finally leading to sperm formation.

In mammals, the testes occur in scrotal sacs outside the viscera because of the requirement of low temperature for spermatogenesis. The testes are situated outside the abdominal cavity within a pouch called scrotum. The scrotum helps in maintaining the low temperature of the testes (2–2.5$^o$ C lower than the normal internal body temperature), which is necessary for spermatogenesis. The slightly cooler temperature of the scrotum is necessary for the development of normal sperm. So, the testes start their development in the abdominal cavity and descend into the scrotal sacs during the 7$^{th}$ month of the fetal life, in presence of testosterone hormone.

The region outside the seminiferous tubules in testes is called interstitial spaces. It contain small blood vessels and interstitial cell. These interstitial cells are called Leydig cells. Leydig cells constitute the endocrine tissue of testes. It synthesise and secrete testicular hormones called androgens. Androgens are group of male sex hormones, mainly testosterone.

Sertoli cells occur in human testes. Each lobule of testes contains one to three seminiferous tubules in which the sperms are produced. Each seminiferous tubule is lined on its inside by two types of cells called male germ cells (spermatogonia) and sertoli cells. Sertoli cells are also known as nurse cells. They provide nutrition to spermatozoa. Spermatozoa are developing sperms. Heads of spermatozoa are embedded in the sertoli cells.

The region outside the seminiferous tubules in testes is called interstitial spaces. It contain small blood vessels and interstitial cell. These interstitial cells are called Leydig cells. These cells constitute the endocrine tissue of testes. It synthesise and secrete testicular hormones called androgens. Androgens are group of male sex hormones, mainly testosterone.

The testis is the male reproductive gland in humans and animals. They descend into a scrotal sac which is present beneath the penis. But in whales, elephants, dolphins, rhinoceros testis present internally.

At the age of 4-5 months testis descends into scrotal sacs in rabbits.

Head of the epididymis of the sperm which receives spermatozoa via the efferent ducts of the mediastinum of the testis which is also called as Caput epididymis.

The male sex hormone testosterone is secreted by testes which are under the control of hypothalamus and pituitary gland.

sertoli cells or nurse cells which helps nourishing sperms and spermatogenesis.

Sertoli cells or nurse cells which are a part of seminiferous tubules helps in process of spermatogenesis or production of sperms, nutrition, and morphogenesis of sperms.

Gonads have a dual function, production of hormones and gametes. In the male, testes produce sperms and testosterone. 

Testes are the primary reproductive organs which produce sperms and hormone known as testosterone. This hormone is important for sexual development and puberty i.e., development of secondary sexual characteristics like facial hair, sexual behaviour etc.
The ovary is the female reproductive organ which produces the mature ovum which further fuses with sperm to form a zygote. 
Pancreas is a heterocrine gland which secretes insulin, glucagon and somatostatin as endocrine and pancreatic juice an exocrine gland.
Adrenal are endocrine glands, which secretes various cortisol.
Thus, the correct answer is option D.

The testes are a pair of primary male reproductive organ. The testes are responsible for the production of sperm cells and the male sex hormone, testosterone.
Thus, the correct answer is option A.

As and when the body ages, both male and female experience changes in their body gradually. These changes are not only in ageing but also in their reproductive systems. Females, start producing eggs (female gamete) once they start menstruating at the age of 12-15 and seizes to produce at the age of around 40. This phase is called menopause in females. In contrast, there is no such thing as andropause in males reported by WHO. Production of sperms may reduce or halt in a man due to the reduced secretion of testosterone or decrease in Leydig cells. But a healthy man will continue in sperm production throughout his lifetime. So, the correct answer is option D.

Important male reproductive hormones are FSH, LH, and testosterone.

Sertoli cells are supportive, nutritive cells that secrete a polypeptide hormone which is known as inhibin.

• The temperature of the scrotum is maintained at 2 degree celsius less than the normal body temperature.
• Spermatogenesis requires this lower temperature.
  
• This temperature of the scrotum is important for the production of viable sperm. 
• If the temperature increases it will lead to the decrease in viable sperms causing sterility.

The male reproductive is located in the pelvic region. It includes a pair of testes along with a pair of accessory ducts, glands and external genitalia. Each testis has  250 compartment called testicular lobules. Each lobule contains one to three highly coiled seminiferous tubules in which sperms are produced. The regions outside the seminiferous tubules called interstitial spaces contain small blood vessels called and Leydig cells. Leydig cells secrete a testicular hormone called androgens. The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens.

In mammals in the embryonic stage, the testis is posteriorly connected to the scrotal sac by an elastic cord called as gubernaculum. It helps in the descent of testis during the 7th month of pregnancy. So the correct answer is C.

1. In frog,The mature spermatozoon is dependent upon external sources of nutrition so that it joins from 25 to 40 other spermatozoa, all of whose heads may be seen converging into the cytoplasm of a relatively large, columnar-type basal cell known as the Sertoli cell. This is functionally a nurse cell.

2. Spermatozoa are carried passively down the ureter to the slight dilation near the cloaca, known as the seminal vesicle. Within the vesicle the spermatozoa are stored briefly in clusters until amplexus and oviposition occur.

3. The spermatozoa are produced in subdivisions of the testes known as seminiferous tubules. These are closely packed, oval-shaped sacs, which are separated from each other by thin partitions (septula) of supporting (connective) tissue known as interstitial tissue.

So, the correct answer is 'None of the above'.

The scrotum is a pouch, suspended from the groin, that contains the testes and some of the male sex accessory ducts. One function of the scrotum is to help maintain the temperature necessary for spermatogenesis by locating the testes outside of the body cavity. The temperature in the human scrotum is 3.1 °C (5.6 °F) lower than the normal temperature within the body (37 °C, or 98.6 °F). If the temperature is maintained to the level of abdominal temperature, The germinal epithelium will degenerate resulting in sterility.

Gonads- A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes (sex cells) and sex hormones of an organism. In the female of the species the reproductive cells are the egg cells, and in the male, the reproductive cells are the sperm.