Animals have to reach up to a certain age for reproduction. In human beings, the changes appear in the body after the age of around 11 years. This age is called adolescence or teenage (onset of puberty).
The changes that come are growth in height, body shape, a voice in boys get significantly deeper, increase in mental, intellectual and emotional maturity, increased activity of sex glands, maturity of ovaries and testes, development of breast in girls, beard and mustaches in boys.
All these changes are controlled by hormones. Hormones are the chemicals produced by the endocrine glands that are sent to the target site by the blood.
With puberty, girls start to menstruate every 28-30 days. This is the period when the egg cell matures, the uterine wall becomes thickened.
If fertilization takes place, the zygote is formed and starts developing into an embryo which gets implanted in the uterine wall. This is known as pregnancy.
Frequently Asked Question of Human Digestive System
- What is sexual reproductions?
Sexual reproduction needs two types of gametes, male gametes (sperm) produced in the male reproductive organs and female gametes (ova) produced in female reproductive organs.
Generally in animals, sperm from male and ovum from the female fuse to form a zygote, which grows into a new organism.
- What is menstruation?
Answer: The breakdown and removal of the inner, thick, and soft lining of the uterus along with its blood vessels in the form of vaginal bleeding are known as menstruation. Menstruation is also known as menstrual flow.
- What is a menstrual cycle?
Answer: The cycle of events taking place in the ovaries and uterus every 28 days or roughly 1 month and marked by the menstrual flow is called the menstrual cycle in the human female. The menstrual cycle is also known as the sexual cycle.
- What is sex determination?
Answer: Human cells have 23 chromosomes in each cell. Out of these chromosomes, one pair is the sex chromosome. In males the sex chromosomes are of two types known as X and Y. In females, both sex chromosomes are similar is X and X.
All eggs cells contain (22+X) that is 23 chromosomes. A sperm may either (22+X) or (22+Y). When the 22+X egg is fertilized by 22+X sperm, the zygote 44+XX will develop into a girl and if the 22+X egg is fertilized by 22+Y sperm, the zygote 44+XY will develop into a boy.
- What are oviparous and viviparous?
Answer: Animals that have internal fertilization like birds but they reproduce by laying eggs are known as oviparous whereas animals that give birth to young ones are known as viviparous.
- Definition of foetus.
Answer: An embryo in which all the body parts can be identified is called a foetus.
- What is the sex ratio?
Answer: Sex ratio is the ratio of the number of females to the number of males in a population. The female-male sex ratio must be maintained for a healthy society. The female child sex ratio is declining at an alarming rate in some sections of our society because of reckless female feticide.