Biological Transitions IWhat is puberty?Five physical characteristics of pubertyFive physical characteristics of puberty (cont.)Slide 5Slide 6Slide 7Slide 8Why does puberty happen?Individual Differences In PubertySlide 11Implications of pubertySlide 13Slide 14Slide 15Slide 16Slide 17Slide 18Biological Transitions IBiological Transitions IPuberty and Adolescent Puberty and Adolescent DevelopmentDevelopmentWhat is puberty?What is puberty?Pubertal development is the series of Pubertal development is the series of biological changes leading up to biological changes leading up to reproductive capability reproductive capabilityFive physical characteristics of Five physical characteristics of pubertypuberty1.1.Rapid acceleration in growthRapid acceleration in growthGreat increases in height and weightGreat increases in height and weightThe average person grows 10 inches during The average person grows 10 inches during puberty!puberty!During “peak height velocity,” boys grow During “peak height velocity,” boys grow about 4 inches per year, girls grow about 3.5 about 4 inches per year, girls grow about 3.5 inches per yearinches per yearAbout half of one’s adult body weight gets put About half of one’s adult body weight gets put on during pubertyon during pubertyFive physical characteristics of Five physical characteristics of puberty (cont.)puberty (cont.)2.2.Development of primary sex characteristicsDevelopment of primary sex characteristicsDevelopment of the sex glands (gonads) – testes in males and Development of the sex glands (gonads) – testes in males and ovaries in femalesovaries in femalesThese are the organs that play the These are the organs that play the primary primary part in reproduction part in reproduction They involve the production of eggs and spermThey involve the production of eggs and sperm–Females born with about 400,000 follicles (immature eggs) in each Females born with about 400,000 follicles (immature eggs) in each ovary; down to about 80,000 in each ovary by pubertyovary; down to about 80,000 in each ovary by puberty–Once a girl reaches Once a girl reaches menarchemenarche, one follicle develops into a mature egg , one follicle develops into a mature egg each cycle and is released (only about 400 are released in an average each cycle and is released (only about 400 are released in an average reproductive lifespan)reproductive lifespan)–Males not born with sperm, instead the first production of sperm occurs Males not born with sperm, instead the first production of sperm occurs at puberty (at puberty (spermarchespermarche))–Thereafter, the average male produces millions of sperm each dayThereafter, the average male produces millions of sperm each dayFive physical characteristics of Five physical characteristics of puberty (cont.)puberty (cont.)Average age of menarche: In US, approximately 12-Average age of menarche: In US, approximately 12-13 years of age13 years of ageAverage age of spermarche: Also around the age of Average age of spermarche: Also around the age of 1212BUT: The reproductively capable female looks much BUT: The reproductively capable female looks much more mature than her male counterpart of the same more mature than her male counterpart of the same age age –Males are fertile before they look like adults, but Males are fertile before they look like adults, but females often look like adults before they are fertilefemales often look like adults before they are fertileFive physical characteristics of Five physical characteristics of puberty (cont.)puberty (cont.)3. Development of secondary sex characteristics3. Development of secondary sex characteristicsBodily changes that occur as part of puberty, but are not Bodily changes that occur as part of puberty, but are not directly related to reproductiondirectly related to reproductionPubic hair (first appearance in boys 10-15; girls 7-14)Pubic hair (first appearance in boys 10-15; girls 7-14)Facial and underarm hair, and oil and sweat producing Facial and underarm hair, and oil and sweat producing glands (about two years after pubic hair)glands (about two years after pubic hair)Breasts (girls 7-13)Breasts (girls 7-13)Penis growth and voice changes (boys 11-14.5)Penis growth and voice changes (boys 11-14.5)Testes and scrotal sac growth (boys 10-13.5)Testes and scrotal sac growth (boys 10-13.5)Five physical characteristics of Five physical characteristics of puberty (cont.)puberty (cont.)4. 4. Changes in body compositionChanges in body compositionIncreases in muscle and fatIncreases in muscle and fatBoys increase in % muscle more than girls, girls Boys increase in % muscle more than girls, girls increase in % fat more than boys increase in % fat more than boys –Ratio muscle/fat boys: 3/1Ratio muscle/fat boys: 3/1–Ratio muscle/fat girls: 5/4Ratio muscle/fat girls: 5/4Related to changes in body image and athletic Related to changes in body image and athletic abilities, although social factors contribute too!abilities, although social factors contribute too!Five physical characteristics of Five physical characteristics of puberty (cont.)puberty (cont.)5. 5. Changes in circulatory and Changes in circulatory and respiratory systemsrespiratory systemsCapacity of the heart and lungs Capacity of the heart and lungs increases increases Magnitude of gains typically greater Magnitude of gains typically greater for males versus females (biologically for males versus females (biologically and environmentally influenced)and environmentally influenced)Why does puberty happen?Why does puberty happen?Hormones play an important roleHormones play an important role–Hormonal changes begin in the hypothalamus, when it starts to release Hormonal changes begin in the hypothalamus, when it starts to release gonadotropin-releasing hormone (GnRH), which stimulates and gonadotropin-releasing hormone (GnRH), which stimulates and regulates the production of hormones in other glandsregulates the production of hormones in other glandsSpecifically, it signals to the pituitary gland to release luteinizing hormone (LH) and Specifically, it signals to the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which in turn stimulate the gonads (the ovaries and follicle-stimulating hormone (FSH), which in turn stimulate the gonads (the ovaries and testes)testes)–What triggers the