Human Growth and Development

Postnatal Development

Secondary Sex Characteristic Changes in Males and Females

In addition to general body changes that occur in both males and females at puberty, physical changes in the genitalia, skin, hair growth, and voice are collectively termed the secondary sex characteristics.

Area of Body Males Females
General body changes Shoulders broaden, muscles thicken and height increases; body odor from armpits and genitals becomes apparent; skeletal growth ceases by about age 21 Pelvis widens; fat distribution increases in hips, buttocks, breasts; skeletal growth ceases by about age 18
External genital organs Penis increases in size; scrotum enlarges; penis and scrotum become more pigmented Breasts enlarge; vagina enlarges and vaginal walls thicken
Internal genital organs Testes enlarge; sperm production increases in testes; seminal vesicles, prostate gland, bulbourethral gland enlarge and begin to secrete Uterus enlarges; ovaries secrete estrogens; ova in ovaries begin to mature; menstruation begins
Skin Secretions of sebaceous gland thicken and increase, often causing acne; skin thickens Estrogen secretions keep sebaceous secretions fluid, inhibit development of acne and blackheads
Hair growth Hair appears on face, pubic area, armpits, chest, around anus; general body hair increases; hairline recedes in the lateral frontal regions Hair appears on pubic area, armpits; scalp hair increases with childhood hairline retained
Voice Voice becomes deeper as larynx enlarges and vocal cords become longer and thicker Voice remains relatively high pitched as larynx grows only slightly


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