Define Gonads, Structure, Testes, Ovaries, and Function

Define Gonads

Define Gonads The male and female gonads are endocrine glands that produce sex hormones essential for the development of the reproductive organs and the proper functioning of the reproductive process.

  • The gonads secrete the same set of hormones secreted by the adrenal cortex in the form of androgens. The release of hormones from the gonads is regulated by the release of gonadotropin-stimulating hormone from the pituitary gland.
  • The male gonads are called testes, while the female gonads are called ovaries. The sex hormones secreted by the male and female gonads are different but perform more or less similar functions.
  • There are a pair of testicles in men that secrete the hormone testosterone as the main sex hormone. The hormone is responsible for the development of male sexual organs, as well as the development of secondary sexual characteristics in men.
  • The gonads are in the form of ovaries in women. There are two ovaries in women that secrete two hormones, estrogen and progesterone, which are responsible for different processes such as ovulation, the menstrual cycle, and the development of secondary sexual characteristics in women.
  • The synthesis and release of sex hormones by the gonads are regulated by two hormones secreted by the pituitary; luteinizing hormone and follicle-stimulating hormone.
  • These hormones also function as sex hormones by assisting in the formation of male and female gametes.

 Testes Structure

  • Human testes are made up of 900 seminiferous tubules that contain cells that later differentiate and mature into male gametes.
  • There are two testes in humans, each of which is the size of a plum and is about 4 cm long.
  • The seminiferous tubules of the testes are surrounded by interstitial endocrine cells, also known as Leydig cells. These cells produce testosterone, the most important sex hormone in humans.
  • Interstitial Leydig cells represent approximately 20% of the total mass in adult testes. Cells are almost non-existent in boys, but they increase in number after puberty.
  • The cells of the testes undergo sporulation to form sperm-forming cells that, in the presence of hormones such as luteinizing hormone and follicle-stimulating hormone, turn into sperm.

Ovaries structures 

  • The ovaries in humans occur in pairs and are present in the ovarian fossa of the lateral wall of the pelvis.
  • Each ovary is enclosed within a capsule and consists of two parts; cortex and medulla. The cortex is the outer part of the ovary that consists of fibrous tissue surrounded by germinal epithelium.
  • The medulla is located in the middle of the ovary and is made up of blood vessels, nerves, and connective tissue.
  • The cortex carries the epithelial cells that surround the ovary and then develop into female gametes after maturation and differentiation.
  • The cells of the ovaries secrete the hormone estrogen and a small amount of testosterone. The hormone progesterone, in turn, is secreted by the corpus luteum during the menstrual cycle.

Ovaries and Testes

The following are the hormones produced by the testes or the male gonad;


  • Testosterone is the main sex hormone in men that is secreted by the interstitial cell of the Leydig cells of the testes.
  • Testosterone is the most abundant male hormone secreted by the testes, much of which is converted to the active hormone dihydrotestosterone once it reaches target cells.
  • Testosterone is responsible for the sexual characteristics in men, which defines the male body.
  • Some testosterone is even produced during the fetal stage once the testes are stimulated by chorionic gonadotropin from the placenta.
  • Although testosterone is a sex hormone, it also aids in general bodily functions by increasing protein formation, muscle build-up, red blood cells, and basal metabolic rate in the body.
  • The synthesis and release of testosterone in the body is regulated by a gonadotropin-releasing hormone from the hypothalamus, which influences luteinizing hormone and pituitary gland follicle-stimulating hormone.

The following are the hormones secreted by the ovaries or the female gonad;

The Estrogen

  • Estrogens are secreted in large amounts by the ovaries, although the adrenal cortices also secrete some estrogen.
  • Estrogens are essential for the proliferation and growth of cells in the ovary that determine secondary sexual characteristics in the female.
  • Three estrogens are secreted in significant amounts in the body; β-estradiol, estrone, and estriol.
  • Beta-estradiol is the most synthesized estrogen in the ovary, but some oestrone is also secreted.

The Progesterone

  • Progesterone is the most important progestin produced by the ovaries. Progesterone works primarily to prepare the uterus during pregnancy and the mammary glands for lactation.
  • In non-pregnant women, progesterone is secreted in significant amounts only during the second half of the ovarian cycle. At this time, progesterone is secreted by the corpus luteum.
  • The placenta also secretes a certain amount of progesterone during pregnancy, around the fourth month of pregnancy.

 The Gonads (Ovaries and Testes) Function 

The following are some of the functions of the gonads;

  • The most important function of the gonads is to stimulate the reproductive organs to generate male and female gametes that form the basis of sexual reproduction.
  • Gonads are also responsible for the development of secondary sexual characteristics in males and females.
  • The hormones secreted by the gonads are responsible for different essential processes in life such as the menstrual cycle.
  • The progesterone produced by the ovaries prepares the uterus and other reproductive organs for pregnancy and childbirth.
  • The hormones produced by the gonads aid in the general development of the body by assisting in protein accumulation and muscle growth.

Diseases of testes

The Testicular tumors

  • The testicular tumor is common in boys and young men and can be malignant and spread to other organs as well.
  • The testicular tumor is one of the most common tumors that occurs in men and it can be due to several different reasons.
  • One of the common reasons behind tumors is cryptorchidism, where the testicles do not descend from the scrotal sac during birth.
  • Some of the common symptoms associated with testicular tumors are the development of lumps on tests followed by the feeling of heaviness in the scrotum.

The Hydrocele

  • Hydrocele is a condition in which the medulla of the testicles fills with fluid, causing the organ to swell.
  • It is a common reason for scrotal inflammation that can range from acute to chronic in some cases.
  • Although hydrocele generally occurs secondarily as a result of other infections, it can also arise within the testicles.

Diseases of the ovaries

The Ovarian cancer

  • Ovarian cancer is one of the most common forms of cancer that occurs in women in their 20s and 30s.
  • The condition is usually benign, but some of the cases can be malignant, especially in the case of middle-aged women.
  • The epithelial cell tumor arises from the epithelial cells of the ovary, which can cause discomfort in the abdominal cavity.
  • The formation of tumors in the ovary can cause alterations in the menstrual cycle and increased risk during pregnancy.
  • Hormone-secreting cell tumor is another form of benign tumor of the ovaries, which results from the formation of tumors in the stromal cells of the sex cord.

Polycystic ovary syndrome (PCOS)

  • Polycystic ovary syndrome is a hormonal imbalance resulting from increased androgen levels in women.
  • The most common characteristic of the condition is alterations in the menstrual cycle, where cycles occur frequently or remain prolonged.
  • The condition has been associated with heart problems and weight gain in some women.


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