Hormones control the changes which occur in adolescence. They are released from various glands in the human body. The pituitary, thyroid, and adrenal gland are examples of the endocrine gland which secrete hormones directly in the blood. Further in the chapter, we will understand how the gender of the baby is determined.

Hormones are chemical substances that are secreted from endocrine glands. In this virtual tour activity, we will study various glands. The first one is the pineal gland is a tiny endocrine gland found in the brain. We will also study in detail other glands which are the pituitary gland, thyroid, Adrenal, Pancreas found in both males and females while a pair of the testis is found in males and ovaries in the female.

Do you know, 23 pairs means 46 chromosomes are present inside the nucleus of other human cells apart from gametes? If the sperm containing an x chromosome fertilizes the ovum, the zygote develops into a female and if the sperm cell containing a Y chromosome fertilizes the ovum, the zygote develops into a male. Hence the sex of the child depends upon the chromosomes inherited from the father.

Females have two X chromosomes and males have one X and one Y chromosome. The gametes contain only one set of chromosomes that is either an X or a Y. The ovum cell has an X chromosome and the sperm cell has a Y chromosome. Both attract each other and make a zygote cell. Here, the newly made zygote cell has X and Y as sex chromosomes, X, and Y as sex chromosomes. This zygote will develop into a male.