Growth Physiology Flashcards
what can growth involve
- increase in cell numbers
- increase in cell size
- some cells can grow or regenerate but others cannot
what is hyperplasia
increased cell numbers
what is hypertrophy
increased cell size
what are some cells that can regenerate
liver
skin
blood cells
what are some cells that cannot regenerate
neurons
which factors can affect growth
- genes, hereditary
- environment
what are environmental factors that impact growth
- nutrition
- disease
- growth factors, such as hormones
what are some hormones influencing growth
- thyroid hormones
- growth hormone
- sex hormones
- insulin
- cortisol
- vitamine D, parathyroid hormone
are the impacts of thyroid hormone on growth direct or indirect
indirect
when does the brain and face stop growing
12
when does growth of the head reach a plateau
12
why is most orthodontic treatment not carried out until after 12
growth is not stable until after this
what is the first growth spurt associated with
growth hormone, plateau happens
what is the second growth spurt associated with
presence of reproductive organs and associated homrones
what is the second growth spurt associated with
reproductive organs
why do vitamin D and parathyroid hormone have an effect on growth
their role in mobilisation of calcium and bone formation
what are the functions of thyroid hormone
- normal development and growth
- protein synthesis in the brain of the fetus and infant
- normal development of neurons
- childhood growth
- facilitates the action of growth hormone and the sympathetic nervous system
symptoms of fetal hypothyroidism
sparse hair
large tongue
permanent mental impairments
explain hypothyroidism
- deficiency of thyroid hormones in childhood can impede both brain development and skeletal growth
- delayed tooth eruption
- growth defects can be rectified by thryoxine supplements
- some improvement in mental functions, recovery incomplete
- extent of recovery varies with onset and duration of the hypothyroid state
describe the action of growth hormone
metabolic and growth promoting actions
main growth promoting effects in postnatal period, infancy and adolescence
describe the metabolic actions of growth hormone
- increase blood glucose levels
- decrease glucose uptake by cells
- increase lipolysis, make fatty acids available for energy production
- facilitate the uptake of amino acids for protein synthesis, especially in the liver and muscle
what are some growth hormone effects exerted by
insulin growth factor 1
where is IGF1 produced
liver
what are the effects exerted by IGF1
- cartilage, bone, soft tissues, viscera
- cartilage proliferation in long bones until the epihphyses close
what are the growth centres of the bone called
epiphyses
describe the role of sex hormones in growth
- responsible for the pubertal growth spurt
- effects mediated by increased secretion of growth hormone and IGF1
- stimulate bone growth, accelerate the closure of epiphyses
- testosterone has anabolic effects on protein synthesis
- testosterone is the anabolic steroid
how does insulin contribute to growth
- promotes foetal growth
- promotes post natal growth by stimulating the secretion of IGF1
- facilitates protein synthesis by making glucose available for energy production
describe the effects of cortisol on growth
- inhibits growth when levels are too high
- stimulate protein catabolism
- suppresses bone growth and promotes bone resorption
- raised levels of cortisol in stress and illness account for the growth retarding effects of childhood illnesses
how do vitamin d and parathyroid hormone contribute to growth
by ensuring adequate amounts of calcium and phosphate are available for bone formation
what is vitamin D responsible for
calcium absorption from the gut
how does parathyroid hormone have an impact on plasma calcium levels
increases them
what does excess growth hormone in childhood lead to
gigantism
what does excess growth hormone in adulthood lead to
longitudinal growth is not possible and the appositional growth occurs in extremities
hands feet and jaw will increase in bulk and lead to acromegaly
describe acromegaly
this is when there is excess growth hormone being produced after the epiphyses are closed so a person is just bulky
what is diastema
gaps between the teeth
how does the skull change in acromegaly
increased mandible growth and enlarged sella turcica
what is achondroplasia
defective cartilage growth that affects long bones and cartilage growth centres like the spheno occipital synchondrosis in the cranial base
what does ageing involve
gradual deterioration of all parts of the body
complicated by disease
what does an individuals lifespan depend on
genetics
environment
no evolutionary advantage to it
what environmental factors increase longevity
good nutrition
lifestyle
absence of disease
describe the biology of ageing
decline in the ability of cells to divide
accumulation of damage, errors in dna sequence, abnormal proteins and damage to organelles like mitochondria
shortening of telomeres due to free radicals
when does apoptosis occur
in development from a tooth germ
replaces worn out cells
destroys tumour cells
what is ageing accompanied by
reduced performance of body systems and organs
