Growth and Ageing Flashcards
what is hyperplasia?
increase in cell numbers
what is hypertrophy?
increase in cell size
what cells can regenerate?
liver, skin and blood cells
what is growth affected by?
genes, heredity, environment
what environmental factors contribute to growth?
nutrition, disease, growth factors such as hormones
what part of the body grows the fastes?
brain
what part of the body takes the longest to grow?
reproductive organs
what hormones influence growth?
thyroid hormones, growth hormones, sex hormones, insulin, cortisol, vitamin D and PTH
what is the thyroid hormone essential for in terms of growth?
normal development and growth, protein synthesis in brain of foetus and infant, normal development of neurons, childhood growth
what is the indirect action of the thyroid hormone on growth?
it facilitates actions of growth hormones and sympathetic nervous system
what are the physical signs or foetal/neonate hypothyroidism?
sparse hair, large tongue, permanent mental impairments
how does a deficiency of thyroid hormones effect the brain and skeleton?
it impedes the development of them
what oral effect does a thyroid hormone deficiency have?
delayed tooth eruption
how are the growth defects of hypothyroidism rectified?
by thyroxine supplements
what actions does the growth hormone have?
metabolic and growth promoting actions
when does the growth hormone have the most action in promoting growth?
postnatal period, infancy and adolescence
what are the metabolic actions of the growth hormone?
increased blood glucose levels, decreaed glucose uptake by cells, increased lipolysis making fatty acids available for energy produced, facilitates uptake of amino acids for protein synthesis
what is IGF-1 and what does it do
insulin growth factor which causes cartilage proliferation in long bones until epiphyses close
what are the 2 types of dwarfism
hypothyroid (infant proportions) and hypopituitary (normal proportions)
what are the sex hormones?
testosterone and oestrogen
what are sex hormones responsible for in terms of growth?
pubertal growth spurt, also stimulate bone growth but accelerate closure of epiphyseal growth plates
what are the effects of the sex hormones mediated by?
increased secretion of GH and IGF-1
what is the effect of testosterone on protein synthesis
it has an anabolic effect on protein synthesis increasing muscle bulk
how does insulin contribute to growth?
promotes foetal growth, promotes post-natal growth by stimulating secretion of IGF-1, facilitates protein synthesis (by making glucose available for energy production)
