principles of growth Flashcards
what 4 periods can growth be divided into
intrauterine, infancy, childhood, adolescence.
nonpathological factors affecting growth
genetics, age, sex, nutrition, socioeconomic status, environmental influences.
what is meant by intrauterine environment
placental function (the nutrient supply!), maternal size and length of gestation.
what determines size at birth
Genetics and the intrauterine environment
after the first year of life what is the major determinant of of growth
life environment and nutrition
later on in childhood what is the major determinant of of growth
thyroid and growth hormone will largely determine growth and problems here if there are any will be picked up
At puberty and into adulthood what is the major determinant of of growth
the sex steroids will shape secondary sexual characteristics and further growth.
actions of Growth Hormone
ncreasing lipolysis, protein synthesis and gluconeogenesis it stimulates release of IGF-1 from the liver
effect of IGF-1
its effects on chondrocytes and growth plate of bones.
endocrine drivers at fetal/infant
Insulin and IGF2
endocrine drivers at child
Growth hormone and IGF1
endocrine drivers at adolescent
Growth hormone and sex steroids
gestational week 10-12 what happens
- tooth buds appear, these will form the baby teeth
- limbs are long and thin
- foetus can make a fist with its fingers
- genitals appear well differentiated by this point
- Erythrocytes start to be produced in the liver and heartbeat can be detected by ultrasound
gestational week 13-16 what happens
At week 15, the main development of external genitalia is complete
gestational week 22 what happens
- The foetus reaches a length of 28cm and weighs about 500g
- The eyebrows and eyelashes are well formed and all of the eye components are developed
- The foetus now has the startle reflex
- Footprints and fingerprints continue to form
- Alveoli forming in the lungs
gestational week 24 what happens
- nervous system develops enough to control some body functions
- Eyelids open and close
- cochlea are developed, though the myelin sheaths develop until 18 months after birth
- respiratory system while immature, has developed to the point where gas exchange is possible
gestational week 30 what happens
- amount of body fat rapidly increases.
- rhythmic breathing movements occur but the lungs are still not fully mature
- thalamic brain connections that mediate sensory input from the periphery form
- The bones of the foetus are fully developed but are still soft and pliable (flexible)
gestational week 34 what happens
- The lanugo (fine, soft hair) begins to disappear
- Body fat increases
gestational week 35-39 what happens
- It will have no lanugo except on the upper arms and shoulders
- Small breast buds are present on both sexes
some growth factors in fetal life
- Insulin like growth factors (IGF1 and IGF2
- fetal insulin
- fetal glucocorticoid
- thyroid hormone
role of Insulin like growth factors (IGF1 and IGF2) in fetal life
IGF1 in foetal plasma is positively correlated with foetal weight
role of fetal insulin
important in growth as involved in creating energy stores (foetal hyperinsulinaemia leads to macrosomia).
modulates the expression of foetal IGF
role of fetal glucocorticoid
role in foetal lung maturation by stimulating production of surfactant.
involved in prenatal development of the liver in controlling blood glucose (glycaemia).
role of thyroid hormone in fetal life
Foetus can get thyroid hormone maternally or synthesise its own. It is essential for normal foetal brain development
what is canalisation
idea that infants and children should stay within one or two growth centiles, any crossing of height centiles warrants further investigation
what is catch up growth
child’s height velocity is above the limits of normal, has been like this for at least 1yr AND this abnormally high velocity has occurred after a period of transient growth inhibition. catch up occurs after illness or undernutrition
what is catch down growth
seen when children are at high growth percentile in early infancy. Then between 6-18 months of age these children show a fall on their percentile growth chart.
what is puberty
the process of transition from childhood to the achievement of adult stature via the development of secondary sexual characteristics.
how do gonadotrophin levels change in first year of life
At birth, HPG axis is active .’.high levels of FSH/LH.
month 3-6 till adolescence HPG axis is quiescent .’. low gonadotropin levels.
characteristics of HPG reactivation
- inc in amplitude of GnRH pulses
- FSH/LH production is activated & feedback to the hypothalamus that amplifies GnRH release
what influences skeletal growth
both environmental and genetic factors
processes that happen in bone growth
subperiosteal apposition, endosteal resorption and remodelling
what is subperiosteal apposition
the process by which long bones add width on the outside by adding layers onto existing layers.
(bones make themselves thicker.)
what is endosteal resorption
the process by which bone is removed in central portion of the bone referred to as spongy bone.
-remodelling of bone (occurs in spongy bone)
how do growth hormone levels affect skeletal growth
increases the rate of mitosis of chondrocytes and osteoblasts and also increases the rate of protein synthesis (proteins such as collagen, cartilage matrix and enzymes required for cartilage and bone formation).
how does parathyroid hormone affect skeletal growth
increases the resorption of bone and thereby increases plasma levels of calcium. It also increases absorption of calcium by the small intestine and kidneys.
how does calcitonin affect skeletal growth
decreases resorption of bone and therefore will decrease plasma calcium.
how does oestrogen/testosterone affect skeletal growth
promote closure of the epiphysis of long bones, thereby stopping growth.
help retain calcium in bones and thus maintain a strong bone matrix.
what is skeletal dysplasia
Dwarfism (short stature)
abnormalities of cartilage and bone growth resulting in abnormal shape and sized skeleton.
Also disproportion of the long bones, spine and head
