Class 5,6 - Puberty Flashcards
Puberty has three chief physical manifestations
- Rapid acceleration in growth, resulting in dramatic increases in height and weight
- Development of primary (present at birth) sexual characteristics, including gonads (sex glands) which result in hormonal changes
- Development of secondary (emerge within pubeirty) sexual characteristics, (changes in genitals, breasts, pubic, facial & body hair)
Four Points on growth chart
(1) Menarche is the last sign of puberty
(2) Boys lag behind girls
Wide variations in onset
(3) – Early as age 5 (girls) and age 6 (boys)
– Late at age 13 (girls) and age 13.5 (boys)
(4) Wide variation in duration
– Girls: 1. 5 to 6 years
– Boys: 2 to 5 years
thelarche
Breast buds - 10.5
pubarche
Pubic hair
girls - 11
boys - 12.5
Peak Height Velocity
girls - 11.5
boys- 13.5
Menarche
12.5
Spermarche
12-14
Testicular growth
Penis growth
11.5
12
Growth during childhood is
relatively stable
girls grow slightly faster than boys untill __
Then both genders average about __
~4 years
average about 5-6 cms/year and 2.5 kgs/year until puberty (i.e., about 2 inches and 5 lbs)
General rule of thumb about child growth
A child grows 10 inches in first year of life
About 5 inches in the second year (or ½ of first year)
Then about 2.5 inches/year until puberty
as puberty approaches—before sudden acceleration - growth takes a __
preadolescent dip
peak height velocity girls vs boys
Girls average a PHV of 9 cm/yr (3”) at age 12 and a total gain in height of 25 cms (or ~10”)
Boys attain a PHV of 10.3 cms/yr (4”) at age 14 and gain 28 cms (11”) in height during pubertal growth period
Pubertal growth accounts for ___of adult height
20%
Boys tend to be taller than girls before age __
Then girls taller between ___
than boys at__
11
Then girls are taller between 11-13
Boys overtake them by age 14
Height gain results more from increase in ___ length vs.___ length
torso vs leg
Sequence of puberty growth
Sequence is fairly regular
Extremities (head, hands feet) first to show growth
Then arms and legs
Then torso and shoulders
Pubertal growth accounts for___of adult weight
50%
peak weight velocity
In boys, PWV occurs at about same time as PHV (age 14) and averages 9 kg/year (i.e, ~20lbs/year); more bone/muscle than fat
In girls, peak weight gain lags behind PHV by about 6 months and reaches 8.3 kg/year (~18lbs) at about 12.4 more fat than bone/muscle
Sex Differences in Body Composition before puberty
Few sex differences in muscle development and only slight differences in body fat
Sex Differences in Body Composition during puberty
Muscular tissue grows faster in boys vs. girls
Body fat increases more in girls vs boys
Boys: muscle to fat ratio: 3:1
Girls: muscle to fat ratio: 5:4
Sex differences in strength & athletic ability appears in
about half of sex differences in athletic performance is simply result from
early adolescence
differences in body fat
Who is most susceptible to be overly concerned about weight—even if in the normal range (prompted by rapid increases in body fat prompts girls)
Girls who mature early & begin dating early
Girls who spend a lot of time talking about looks with their friends
Who are teased about their weight (by boys)
Who are pressured to be thin
Is mass media’s excessively positive portrayal of of thinness to blame? for girls being overly concerned about weight—even if in the normal range
yes but also friend talk is also to blame
also weight concous (also talk with girls who do the same) Co-Rumination and Selection & Socialization
Co-Rumination
It is comparing themselves with friends & not just media exposure that leads to unhappiness about body image
Selection & Socialization
Girls who are especially weight-conscious often hang around with peers who share the same concerns
North & South America, Europe and Asia
There is strong pressure for girls to be thin in many cultures,
less vonurable to feelings of body disfatsfaction
black teenagers, Less likely to diet, Ethnic differences in conceptions of ideal body type
two main biological processes of puberty
gonadarche - Pubertal maturation linked to increased activity of gonads (testes, ovaries)
adrenarche - Pubertal maturation linked to increased activity of adrenal glands
Gonadarche
“True central puberty”
Driven by Growth & maturation of gonads
(Ovaries in girls & testes in boys)
Increased production of sex steroids, e.g., estradiol & testosterone
stimulated by Pituitary gland releases gonadotropin hormones
gonadotropin hormones
Luteinizing hormone LH
Folic stimulating hormone FSH
Gonads respond by growing & releasing sex steroids T & E
But what triggers the pituitary gland to release gonadotropin hormones
Hypothalamus- stimulating Gonadotropin Releasing Hormones
GnRH (facilitated by Kisspeptin (Metastin))
Hypothalamus
Monitors hormone levels via regulation of pituitary
Triggers production of kisspeptin which causes a cascade of pituitary activity resulting in LH and FSH
production of kisspeptin afftected by
leptin and melatonin
leptin
Stimulates kisspeptin
Protein produced by fat cells
Regulates hunger & appetite
Signals brain that we are “full enough” and “fat enough”
melatonin
Suppresses kisspeptin
Regulates sleep cycle