Growth and Development
A human being’s body is at continuous growth state from the moment of the formation of the zygote until they are an adult. Growth is a permanent increase in size and dry mass caused by an increase in cell number or cell size or both. When a zygote starts forming organs of the fetus like the brain for example, the organism is said to be developing. Development is an increase in complexity of an organism as it grows to adulthood.
Growth keeps on going after birth till adolescence. Adolescence is the time at which a child’s growth rate increases as the child becomes a teenager. A sudden rise in growth rate of an organism is called a growth spurt. A human being experiences two growth spurts at his lifetime, the first is at his early years from age 1-3, and then the child’s growth rate then decreases and stabilizes. The second growth spurt is the adolescent one, which for girls, occurs at the age of about 9-10 years old. And for boys, adolescent growth spurt occurs at an age of about 12-13 years old. The adolescent growth spurt ends at an age of around 17 years old.
During the adolescent growth spurt, some changes occur on the body. One of these changes is their sex organs starting to become mature, this is called puberty. Puberty takes place between ages of 11-17 but generally it is earlier in girls than boys. During puberty large amounts of sex hormones are released by the body causing changes.
Puberty in Boys:
The main sex hormone of males is called testosterone. At puberty, the testicles secrete large amounts of testosterone into the blood. The testicles now start to become fully mature and start producing sperms. The chest and shoulders of the boy become broader and muscles increase in size. Hairs start to grow around his sex organ and under his armpits; facial hair may grow as well. Sweat glands become more active and voice of the boy deepens.
Puberty in girls:
During puberty for girls, the ovaries become mature and they start secreting estrogen hormone. The changes that take place in the girls body is enlargement of breasts and hip. The girl’s voice tone becomes sharper. The ovaries become mature and start releasing eggs. Periods or the menstrual cycle also starts.