growth physiology Flashcards
(22 cards)
what is hyperplasia?
increase in cell numbers
what is hypertrophy?
increase in cell size
what cells can regenerate?
liver, skin, blood cells
what is growth affected by?
genes heredity environment -nutrition -disease -growth factors eg hormones
what hormones influence growth?
thyroid growth hormone sex hormones insulin cortisol vit. D PTH
why are thyroid hormones important?
essential for protein synthesis in brain of fetus and infant
rn for normal development of neurons
necessary for childhood growth
indirect effects
facilitates actions of GH and sympathetic NS
what are the symptoms of fetal/neonate hypothyroidism?
sparse hair
large tongue
permanent mental impairments
what is hypothyroidism?
deficiency of thyroid hormones in childhood impedes both brain development and skeletal growth
delayed tooth eruption
rectified by thyroxine supplements
not complete recovery
what are the effects of growth hormone?
metabolic and growth-promoting actions
main growth-promoting in postnatal, infancy and adolescence
what are the metabolic effects of GH?
mainly indirect
raise blood glucose
lower glucose uptake by cells
raise lipolysis, making fatty acids available for E prod.
facilitates uptake of aa for protein synthesis
what are the growth-promoting effects of growth hormone?
mainly indirect
exerted by IGF-1 produces in liver:
-cartilage, bone, soft tissues, viscera
-IGF-1 -> cartilage proliferation in long bones, until epiphyses close
how do sex hormones affect growth?
pubertal growth suprt
effects mediated by increased secretion of GH & IGF-1
stimulate bone growth & closure of epiphyseal growth plates
testosterone is anabolic steroid- anabolic effect on protein synthesis, increasing muscle bulk
what is the effect of insulin on growth?
no direct effect contributes to growth by: -promoting foetal growth -promoting post-natal growth by stimulating secretion of IGF-1 -facilitating protein synthesis
what is the effect of cortisol on growth?
when high, inhibits
stimulates protein catabolism
suppresses bone growth and promotes bone resorptions
raised in stress & illness-retarding effects of childhood illness
how does vit. d affect growth?
ensure adequate amounts of ca and po are available for bone formation
responsible for Ca2+ absorption from gut
how does PTH affect growth?
raises plasma Ca2+ levels for adequate bone formation
what happens when theres excess growth hormone?
in childhood: accelerates normal growth -> gigantism in adults: longitudinal growth not possible- appositional occurs in extremities hands feet and jaw increase in bulk acromegaly
what is achondroplasia?
defective cartilage growth
affects long bones and cartilage growth centres
eg spheno-occipital synchondrosis in cranial base
what is ageing?
gradual deterioration of all parts of body
complicated by disease
max life span hasn’t increased-more people living to it
what does a lifespan depend on?
genetics environment -nutrition -lifestyle -absence of disease
what is the biology of ageing?
decline in ability of cells to divide over time accumulation of damage: -errors in DNA -abnormal proteins -damage to organelles free radicals; shortening of telomeres
what is apoptosis?
programmed cell death occurs: in development eg tooth germ to replace worn out cells destroy tumour cells
