4.5 Primary and Secondary sexual characteristics

The human males are born with the penis, scrotum and testicle.

The human females are born with ovaries, vagina and uterus.

These are primary sexual characteristics of human males and females cause they are born with this at first and that's why it is called primary.

Secondary sexual characteristics occur after the primary. Puberty begins in the early teen years - 11, 12, 13, 14, 15, … 19(end of puberty). There is word “teen” at the end of this ages and that's why it is called teen ages.

Puberty or Adolescence is a period when secondary sexual characteristics begin to happen and develop. Secondary sexual characteristics begin to develop so that sexual maturity is reached. Sexual maturity means the potential for sexual reproduction exists.

Secondary sexual characteristics in males include

Growth of sex organs
Increase in body hair
Increase in muscle mass
Increase in growth of long bones of arms, legs
Deepening of voice

Secondary sexual characteristics in females include

Increase in growth rates of long bones of arms
Develop more hair specially in pubic area
Hips start to be broaden, more fats deposited in breasts, buttocks and thighs that helps her to carry the coming baby
Menstrual cycle will begins

Secondary Sexual Characteristics	Males	Females
Growth of Sex Organs	Yes	No
Increase in Body Hair	Yes	Yes
Increase in Muscle Mass	Yes	No
Increase in Growth of Long Bones of Arms, Legs	Yes	Yes
Deepening of Voice	Yes	No
Develop More Hair in Pubic Area	No	Yes
Broaden Hips	No	Yes
Deposit More Fats in Breasts, Buttocks and Thighs	No	Yes
Begin Menstrual Cycle	No	Yes

The changes that occur during puberty are controlled by sex hormones. These sex hormones are secreted by endocrine system. The beginning of Puberty in males causes the hypothalamus to produce different kinds of hormones. Then these hormones interact with pituitary gland.

The hypothalamus is a small region of the brain located near the pituitary gland. It plays a crucial role in many important functions, including releasing hormones and regulating body temperature, hunger, moods, and sleep.

Puberty in females begins early teen years. LH causes eggs to be released into oviduct(Fallopian Tube) whereas FSH stimulates the development of follicles - are a group of epithelial cells in the ovary. FSH in males causes the production of males gametes that is sperm cells. LH in males causes the endocrine cells to produce male hormone - Testosterone.