Biological Transitions I Puberty and Adolescent Development 1 What is PUBERTY Pubertal development is the series of biological changes leading up to reproductive capability 2 Five physical characteristics of puberty 1 Rapid acceleration in growth 1 Great increases in height and weight 2 The average person grows 10 inches during puberty 3 During peak height velocity boys grow about 4 inches per year girls grow about 3 5 inches per year 4 About half of one s adult body weight gets put on during puberty 3 2 Development of primary sex characteristics Development of the sex glands gonads testes in males and ovaries in females These are the organs that play the primary part in reproduction They involve the production of eggs and sperm 2 Females born with about 400 000 follicles immature eggs in each ovary down to about 80 000 in each ovary by puberty 3 Once a girl reaches menarche one follicle develops into a mature egg each cycle and is released only about 400 are released in an average reproductive lifespan 4 Males not born with sperm instead the first production of sperm occurs at puberty spermarche 5 Thereafter the average male produces millions of sperm each day 4 Five physical characteristics of puberty cont Average age of menarche In US approximately 1213 years of age Average age of spermarche Also around the age of 12 BUT The reproductively capable female looks much more mature than her male counterpart of the same age Males are fertile before they look like adults but females often look like adults before they are fertile 5 Five physical characteristics of puberty cont 3 Development of secondary sex characteristics Bodily changes that occur as part of puberty but are not directly related to reproduction Pubic hair first appearance in boys 10 15 girls 7 14 Facial and underarm hair and oil and sweat producing glands about two years after pubic hair Breasts girls 7 13 Penis growth and voice changes boys 11 14 5 Testes and scrotal sac growth boys 10 13 5 6 Five physical characteristics of puberty cont 4 Changes in body composition Increases in muscle and fat Boys increase in muscle more than girls girls increase in fat more than boys Ratio muscle fat boys 3 1 Ratio muscle fat girls 5 4 Related to changes in body image and athletic abilities although social factors contribute too 7 Five physical characteristics of puberty cont 5 Changes in circulatory and respiratory systems Capacity of the heart and lungs increases Magnitude of gains typically greater for males versus females biologically and environmentally influenced 8 Why does puberty happen Hormones play an important role Hormonal changes begin in the hypothalamus when it starts to release gonadotropin releasing hormone GnRH which stimulates and regulates the production of hormones in other glands 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 testes What triggers the hypothalamus to start this process Some evidence suggesting that the process starts once a threshold level of body fat is reached Fat cells produce a protein leptin which provides a signal to the hypothalamus research more conclusive for females than males 9 Individual Differences In Puberty Timing and tempo No relation between timing and tempo Trends within the US Racial differences AA EA Why Answers not clear does not appear to be related to differences in income weight or area of residence speculation that it may be due to differences in exposure to hormones found in environment International differences Earlier puberty in regions of world with better health care and nutrition Secular Trend Decline in average age of puberty over time Most developed countries have maturation occurring 3 4 months earlier per decade but this may slow down 10 Individual Differences In Puberty Timing of puberty influenced by environmental factors Girls have earlier puberty when they grow up with a relatively high levels of stress b homes with highest level of conflict and or c stepfathers living in home Why Stress may trigger hormonal secretions alternatively perhaps chemicals secreted by stepfather trigger puberty Odd but consistent finding 11 Implications of puberty Reactions of self to changes Body image May be particularly challenging for girls 12 Jessica Simpson Shocks Fans With Noticeably Fuller Figure Tuesday January 27 2009 Felicity Huffman Eva Longoria Parker Not Pregnant Just Fat If stars gain 2 pounds or look bloated there are pregnancy rumors Implications of puberty Reactions of others to changes Treat adolescent differently New types of attention Increase in proportion of time spent with peers Distance in parent child relationships increases More negative interaction less positive interaction more conflict This is particularly the case with the mother in two parent households less change with pubertal development found in single parent households 18