🐣Dev and Ageing🐣 - Postnatal & Child Development Flashcards
Outline the effects of genetics on prenatal growth
Minor effect overall
Maternal size important in determining birth size
Paternal genetic factors have little effect on birth
Maternal factors tend to override foetal genetic factors in determining prenatal growth
Outline the effects of genetics on postnatal growth
Largely determines final adult height
Sex chromosomes have an effect:
XY boys are taller than XX girls
Outline the effects of endocrine factors on prenatal growth
Insulin and insulin-like growth factors (IGFs) are major prenatal hormones influencing growth:
IGF-2 most important for embryonic growth
IGF-1 most important for later fetal and infant growth
(Growth hormone has no effect on early growth)
Outline the effects of endocrine factors on postnatal growth
Human growth hormone (hGH) is the major hormone controlling growth after birth
Outline the effects of nutrition on prenatal growth
Placenta provides all nutrients to growing foetus, therefore essential for growth
Placental insufficiency most common cause of intrauterine growth restriction
Placenta also controls hormones necessary for foetal growth
Maternal diet influences nutritional availability
Outline the effects of nutrition on postnatal growth
Adequate nutrition is essential for growth Starvation due to lack of substrate availability as a can limit growth potential
Obesity occurs mostly as a result of excessive intake of food
Poor nutrition may delay the onset of puberty Malabsorption of nutrients may cause reduced growth
Outline the effects of environment on prenatal growth
Uterine capacity and placental sufficiency important in providing optimal environment for foetus
Placental function is more influential in foetal growth than uterine capacity
Outline the effects of environment on postnatal growth
The following factors are known to influence growth:
Socioeconomic status
Chronic disease
Emotional status
Altitude (mediated by lower oxygen saturation levels)
Outline postnatal growth
Head disproportionately large for the body (1/3rd vs 1/7th in adulthood) at birth
Grows rapidly for the first 2 years, before slowing
Cranial sutures open at birth, close by 18months
What are the 4 recognised phases of growth?
Foetal
Infantile
Childhood
Pubertal
Outline the foetal phase of growth
Fastest period of growth over life-course
Accounts for approximately 30% of eventual height
Foetus repeatedly doubles in size over gestation
Growth mainly driven by hyperplasia during foetal life:
~42 cycles of cell division before birth,
~only further five cycles of cell division occur from birth to adulthood
Outline the infantile phase of growth
Covers 0-18 months after birth,
Accounts for approximately 15% of eventual height.
Rapid, but decelerating growth (vs foetal phase)
Length increases by 50%, head circumference by 30% and weight triples vs birth
Growth largely nutrition dependent
Outline the childhood phase of growth
Covers 18 months to 12 years of age
Accounts for approximately 40% of eventual height.
Steady, slow prolonged growth
5-6 cm annual increase in height, and 3-3.5kg annual increase in weight
Good nutrition and health important, but endocrine growth regulation increasing
Outline the pubertal phase of growth
Also known as the pubertal growth spurt
Contributes 15% of eventual height.
Rising levels of sex hormones boost GH production
~25cm (XY boys) ~20cm (XX girls) increase in height over 3-4 years
Temporary growth spurt as sex hormones also cause fusion of growth plates
Describe how the levels of reproductive hormone change over childhood
Black line shows normal healthy levels
What is “mini-puberty”?
Gonadotrophin secretion commences towards the end of the first trimester, peaks mid-pregnancy, then declines
HPG axis is transiently activated after birth (mini-puberty), after release from restraint by placental hormones
Continues for around 6 months after birth before declining
What is the purpose of “mini-puberty”?
Elevated sex steroids in males during mini-puberty seems to be important for normal gonadal development (testicular tissue and penile development)
Role of mini-puberty less clear in female infants
Oestradiol levels fluctuate through first few months after birth
Follicular development occurs in the ovary
Important for patterning and development of mammary tissue
Elevated sex steroids in mini-puberty may also influence programming of body composition and linear growth - may explain higher growth velocity observed in boys vs girls
What triggers puberty?
Control of puberty onset remains unclear, but influenced by metabolic status
Release of neurokinin KNDy neurons may regulate release of Kisspeptin peptides, which act on GnRH neurons to promote pulsatile GnRH release
What implicates kisspeptin signalling’s role in puberty?
Mutations in KISS1R affect puberty timing, implicating Kisspeptin-KISS1R signalling in regulation of this process
Outline the developmental events of puberty
The developmental events of puberty typically follow a predictable pattern
Compliance with this sequence is known as consonance
Outline the developmental events of puberty in girls
Outline the developmental events of puberty in boys
What are the developmental domains?
Gross motor skills
Fine motor skills
Speech, language and hearing skills
Social behaviour and play skills
Outline the developmental milestones of gross motor skills
Outline the developmental milestones of fine motor skills
Outline the developmental milestones of language skills
Outline the developmental milestones of social/behavioural skills
