Hormones and Reproductive Function : NCERT / CBSE Revision Notes
Hormones are the chemical substances secreted by endocrine glands to regulate many physicochemical functions in the human body.
Glands in our body are of two types –
Endocrine glands and Exocrine glands.
Endocrine glands or ductless glands secrete hormones directly into the blood stream.
Exocrine glands are the glands which possess ducts to release their secretions to the target sites.
Gonads are the sex glands which secrete sex hormones. These sex hormones control the onset of puberty and initiate the reproductive function.
Testosterone is the male sex hormone which brings about many changes in the body of males.
Testosterone initiates body changes such as the growth of facial hair and cracking of voice.
Estrogen is the female sex hormone which brings about changes in the body of females. Estrogen brings about body changes such as breast development, growth of pubic hair etc. Estrogen controls the growth and release of mature eggs.
At puberty, the level of sex hormones is sufficient to bring about the maturation of gametes, sperm and ovum. The reproductive phase of life lasts longer in males than in females. The reproductive phase of females is marked by the menstrual cycle.
The shedding of the uterine thickening along with its blood vessels at the end of menstrual cycle is called as menstruation. The menstrual cycle takes place every 28-30 days. Menarche is the first occurrence of menstruation. Menopause is the stoppage of menstruation.
It is the fusion of a sperm and an ovum to form a single cell, the zygote.
Sex chromosomes in sperms determine the baby’s gender. Humans have 23 pairs of chromosomes in each cell. A pair of chromosome forms the sex chromosomes. Males carry XY and females carry XX chromosomes. Reproductive cells give rise to gametes by the division of meiosis. A gamete is a mature reproductive cell - a sperm or an ovum. If a sperm carrying X fertilises the ovum with X chromosome, then the resulting baby is a girl. If a sperm carrying Y chromosome fertilises the ovum with X chromosome, then the resulting baby is a boy. Hence, males are responsible for the gender of the newly formed babies.
Gender determination of an unborn baby is considered illegal in India.
Other endocrine glands
Some glands other than gonads also play an important role in maintaining reproductive phase of the individual.
Thyroid gland present in the throat region produces thyroxine and calcitonin. Goitre is caused by the enlargement of the thyroid gland. Thyroxine is responsible for metamorphosis of the larva or tadpoles into adult frogs.
Endocrine part of pancreas is made up of alpha cells, beta cells and delta cells. Both insulin and glucagon secreted by beta cells and alpha cells respectively regulate glucose level in the blood. They also exhibit an effect on reproductive life of an individual.
The pituitary gland or the master gland controls the secretion of hormones from the other endocrine glands, including the thyroid, adrenal, testes and ovaries, and also secretes the growth hormone.
These glands are present above the kidneys. They mainly secrete a hormone called as adrenaline. Adrenaline maintains salt balance in the blood. It also helps the body to cope up with stress conditions such as hunger, fright, fight and flight.