Testis and Ovary
விந்தகமும் அண்டகமும்
Relaxin and inhibin are not antagonists — they act on completely different targets. NEET's 'NOT antagonistic' question is built around exactly this pair.
The idea
A pair of testes is present in the scrotal sac (outside the abdomen) of the male individual. The testis performs dual functions as a primary sex organ as well as an endocrine gland. The testis is composed of seminiferous tubules and stromal or interstitial tissue. The Leydig cells or interstitial cells, present in the intertubular spaces, produce a group of hormones called androgens, mainly testosterone. Androgens regulate the development, maturation and functions of the male accessory sex organs like the epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc. These hormones stimulate muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice etc. Androgens play a major stimulatory role in the process of spermatogenesis, act on the central neural system and influence male sexual behaviour (libido), and produce anabolic (synthetic) effects on protein and carbohydrate metabolism. Females have a pair of ovaries located in the abdomen. The ovary is the primary female sex organ which produces one ovum during each menstrual cycle. In addition, the ovary produces two groups of steroid hormones called estrogen and progesterone. The ovary is composed of ovarian follicles and stromal tissues. Estrogens are synthesised and secreted mainly by the growing ovarian follicles. After ovulation, the ruptured follicle is converted to a structure called the corpus luteum, which secretes mainly progesterone. Estrogens produce wide-ranging actions such as stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g. high pitch of voice), mammary gland development, and also regulate female sexual behaviour. Progesterone supports pregnancy; it also acts on the mammary glands and stimulates the formation of alveoli (sac-like structures which store milk) and milk secretion.
Why it matters
Gonads make gametes and also the hormones that build the reproductive organs, secondary sex characters and the uterine conditions needed for pregnancy.
NEET lens
Know: Leydig cells → androgens (testosterone) — accessory sex organs, secondary sex characters, spermatogenesis, libido, anabolic effects. Ovary: estrogen from growing follicles; progesterone from corpus luteum (supports pregnancy, mammary alveoli and milk secretion). In 'NOT antagonistic' questions, relaxin–inhibin is the answer (aldosterone–ANF, PTH–calcitonin, insulin–glucagon are antagonistic pairs).
Clinical significance
Oral contraceptive pills contain synthetic progestogens with or without estrogen to prevent ovulation. Misuse of anabolic steroids (synthetic androgens) by athletes can cause infertility and liver damage.
Introduction
The testes and ovaries are primary sex organs and also endocrine glands, producing the sex steroids.
Core concept
Testis: in scrotum; seminiferous tubules + interstitial tissue; Leydig (interstitial) cells → androgens (mainly testosterone). Androgens: development, maturation and functions of epididymis, vas deferens, seminal vesicles, prostate, urethra; muscular growth, facial and axillary hair, aggressiveness, low-pitched voice; stimulate spermatogenesis; act on CNS (male sexual behaviour, libido); anabolic effects on protein and carbohydrate metabolism. Ovary: in abdomen; one ovum per menstrual cycle; ovarian follicles + stroma. Estrogens: mainly from growing follicles — growth and activity of female secondary sex organs, follicle development, female secondary sex characters (high-pitched voice), mammary development, female sexual behaviour. Progesterone: from corpus luteum (after ovulation) — supports pregnancy; mammary alveoli formation and milk secretion.
Go deeper
Placenta also secretes hormones (hCG, hPL, estrogens, progestogens) and relaxin is secreted by the ovary in later pregnancy; inhibin (from Sertoli cells in testis and granulosa cells in ovary) inhibits FSH — covered in Human Reproduction.
From Class 10
Class 10 linked testosterone and estrogen with puberty changes. NEET names the exact cells that secrete them and their actions.