Growing skeleton Flashcards
describe foetal growth
fastest period of growth
accounts for 30% of adult height
main factors that determine growth are related to uterine environment (maternal diet, placental nutrient supply)
largely independent of paternal height
describe infantile growth
from birth to 18months
largely dependent on nutrition, good general health and normal thyroid
growth is at the highest rate it’ll ever be
contributes to 15% of adult height
describe childhood growth
slow but prolonged period of growth
contributes to 40% of adult height
genetics begin to have a significant impact on final height, mainly determined by parental height, provided there is adequate nutrition
what is required for childhood growth
growth hormone, which affects the physis
thyroid hormones, vitamin D and steroids which affect cartilage cell division
what are psychosocial causes of short stature
chronic unhappiness can decrease growth hormone secretion and therefore reduce activity at the physes
what is the period of pubertal growth
lasts until fusion of physes and cessation of growth in mid-late teens
contributes to 15% of the final height
growth is very raid but its a short time period
what is required for pubertal growth
sex hormones (mainly testosterone and oestradiol) cause the back to lengthen and boost growth hormone secretion
cause fusion of the epiphyseal growth plates and and cessation of growth at the end of puberty
why are final heights generally higher in males
peak height volume and physeal fusion occur later in males leading to an extra 2 years of childhood growth
if puberty begins early, which is not uncommon in females, the final height is reduced because of a shortened childhood stage and early fusion of the physes
what causes the onset of puberty
gonadotrophin-releasing hormone is released from the hypothalamus
LH and FSH are then released form the pituitary gland
testosterone, oestrogen and progesterone are then released from the gonads
describe the release of GnRH
begins at night in short pulses, these pulses eventually get longer and stronger until it is being released at all times of the day
GnRH is the trigger for the body to begin poverty in both biological sexes, and is a crucial part of the HPG axis
timing is very variable; 8-13 in girls, 9-14 in boys typically
effects of testosterone (pubertal)
bone density/growth - density greatly increases, disproportionate facial, shoulder width growth)
muscle mass - increases bulk and strength, doubled by end of puberty occurs later than PHV (around a year or two later)
main driver of physeal closure in men
what is the difference in testosterone levels in men vs women
females have around a quarter of that in males
effects of oestrogen (pubertal)
fat distribution - buttocks, hips, thighs, facia; subcutaneous fat. higher body fat % (2x average male)
bone density/growth - increased density, widened pelvis, anteverted hip (can cause difference in gait, hip sway)
main driver of physeal closure in females
what is testosterone metabolised to in females
oestradiol
what are the extra-skeletal effects of puberty
stereotypical clumsiness, changes are so rapid the brain can’t keep up (centre of mass, limb length)
large variance in when/how developments occur
body image and gender perceptions (self-perception, other’s perception, gender stereotypes)
