Growth and development in children Flashcards
What is growth?
Timeline?
Growth represents the summation of all the processes (interaction of hormones and nutrients0 that convert the fetus through childhood into a sexually mature adult
Not a steady process
Rapid in utero, then slows from birth until about 2-3 years
Fairly constant growth rate until growth spurt at puberty
What is hyperplasia?
Enlargement of an organ or tissue caused by an increase in organic tissue from cell proliferation
Increase
An increase in the number of cells and rate of cell division
What is hypotrophy?
A degeneration in the functioning of an organ due to the reduction of the volume in cells
What is hypertrophy
Increase in cell size
What is the difference in puberty growth spurt between genders?
Girls enter puberty earlier than boy - have an earlier peak in height velocity
Puberty often lasts longer for boys - has a later and longer peak in height velocity
What influences growth?
Genetics
- Basic guideline for height and timing of growth spurt
- Inheritance of height from parents
- Environment does influence the expression of genes, epigenetics, study of changes caused by the environment, and modification of how the gene code is expressed
Endocrine
- Growth hormones
- Sex hormones
- Thyroid hormones
- Insulin-like growth factors
Emotional
- Emotional impairment can reduce growth
- Mediated by high amounts of stress hormones
- Reduction in growth from high levels of stress
Nutritional
- Enough nutrition?
- Malnourishment can shunt growth
Describe the different phases of growth in fetal life
1st trimester
- Differentiation of cells into tissues and organs
- Critical period, organeogensis
- Hyperplasia - cell division
2nd and 3rd trimester
- Slowing of cell division
- More hypertrophy
What controls foetal growth?
Insulin-like growth factors (IGFs)
- Structurally similar to insulin, slightly different to AA length chains
- Mitogens, trigger mitosis and stimulate cell division
Amount of IGF controls growth and the amount of binding proteins.
IGF II main growth factor for embryo
IGF I regulates growth in later gestation
What influences IGF levels
More glucose –> More insulin –> More IGF
Good nutrition supplies a steady stream of glucose to produce insulin then IGF I
What happens to growth around the time of birth?
Foetal growth is limited by substrates - the ability of the placenta to be able to supply the substrates
Cortisol and glucocorticoids increase to influence the maturation of organs to prepare to birth. Laying down of fat and maturation of organs.
Increases in growth hormone receptors. Earlier on in pregnancy GH are present by the receptors arent so they cant have as much effect, the increase in receptors allows more of an effect of GH
Increase in thyroid hormone, T3 increases
Rapid acceleration of growth until 2-3 years
What happens to growth during childhood?
More of an effect of GH
Requirement of normal thyroid functioning from 1st year
Localised growth, end of long bones in legs and arms, sensitive to GH
Puberty - interactions of GH and sex hormones in teens
Discuss the growth hormone
Released from the pituitary in response to Growth Hormone Releasing Hormone from the hypothalamus
Stimulated by high levels of insulin
Reduced by adrenal glucocorticoids - involved in the metabolism of carbohydrates, proteins, and fat, have an anti-inflammatory activity
Oestrogens increase sensitivity to the pituitary to GHRH which is why puberty occurs earlier in girls.
Negative feedback loop control
The function is to increase protein synthesis and mobilise fat stores to provide energy.
Why does puberty occur earlier in girls?
Oestrogen increases sensitivity of pituitary to growth hormone-releasing hormone, as girls have more oestrogen that boys they cause more of a sensitivity to GHRH
Describe the different pathways of indirect and direct effects of growth hormone
Direct:
GH –> Tissue e.g Fat (adipocytes) –> Mobilising energy from adipocyte
GH –> Chondrocytes (cartilage cells) –> promote long bone growth
GH –> Myoblasts –> Muscle growth
Indirect:
GH –> Liver –> IGF I –> Bones –> Increase bone length
The production of IGF I causes the effect to be indirect as its not GH acting itself
Describe the feedback loop system of GH
Somatostatin is produced by hypothalamus to reduce the release of GH so not too much is released
Growth hormone-releasing hormone is released by hypothalamus
How does GH have an effect?
GH binds to surface receptor on plasma membrane
Activates membrane bound tyrosine kinases which phosphorylate a group of proteins that activate gene transcription
Stimualtes lipolysis making fatty acids available for oxidation
Facilitates amino acid uptake for protein synthesis
Stimulation of chondrocytes to cause bone growth