Secondary Sex Characteristics
The fourth major physical change at puberty is the development of the secondary sex characteristics. These are the physical features which distinguish males from females and which make members of one sex appealing to members of the other sex. They are unrelated to reproduction though indirectly they are related by making males appealing to females and vice versa. That is why they are called “secondary” as compared with sex organs proper which are called “primary” sex characteristics because they are directly related to reproduction. As long as the body remains childlike in appearance, there is no “sex appeal.” This, however, changes when the secondary sex characteristics appear.
As puberty progresses, boys and girls become increasingly dissimilar in appearance. This change is caused by the gradual development of the secondary sex characteristics which, like other developments at puberty, follows a predictable pattern.
The pattern of development of several of the important secondary sex characteristics, in relation to growth in height, and several primary sex characteristics which diagrams the sequence of events at puberty for boys and girls, and indicates the range of ages at which these developments take place. The secondary sex characteristics of boys and girls are summarized below:
Important Secondary Sex Characteristics
Pubic hair appears about one year after the testes and penis have started to increase in size. Axillary and facial hair appear when the pubic hair has almost completed its growth, as does body hair. At first, all hair is scanty, lightly pigmented , and fine in texture. Later it becomes darker, coarser, more luxuriant, and slightly kinky.
The hips become wider and rounder as a result of the enlargement of the pelvic bone and the development of subcutaneous fat.
The skin becomes coarser, less transparent, and sallow in color, and the pores enlarge.
Shortly after the hips start to enlarge, the breasts begin to develop. The nipples enlarge and protrude and, as the mammary glands develop, the breasts become larger and rounder.
The sebaceous, or oil-producing, glands in the skin enlarge and become more active, which may cause acne. The apocrine glands in the armpits start to function, and perspiration increases as puberty progresses.
Pubic hair appears after hip and breast development is well under way. Axillary hair begins to appear the menarche, as does facial hair. Body hair appears on the limbs late in puberty. All hair except facial hair is straight and lightly pigmented at first and then becomes more luxuriant, coarser, darker, and slightly kinky.
The muscles increase markedly in size and strength, thus giving shape to the arms, legs, and shoulders.
The skin becomes coarser, thicker, and slightly sallow, and the pores enlarge.
Voice changes begin after some pubic hair has appeared. The voice first becomes husky and later drops in pitch, increases in volume, and acquires a pleasanter tone. Voice breaks are common when maturing is rapid.
The sebaceous and apocrine glands become more active as puberty progresses. Clogging of the sebaceous glands can cause acne, while the apocrine glands in the armpits produce perspiration, which is especially heavy and pungent just before and during the menstrual period.
Slight knobs around the male mammary glands appear between the ages of twelve and fourteen. These last for several weeks and then decrease in number and size.
The muscles increase in size and strength, especially in the middle of puberty and toward the end, thus giving shape to the shoulders, arms, and legs.
The voice becomes fuller and more melodious. Huskiness and breaks in the voice are rare among girls.