Human Growth Flashcards
What are the four stages of growth?
- ) Intrauterine
- ) Postnatal
- ) Pubertal
- ) Adult growth/senescence
What occurs in hypothyroid dwarfs (cretins)?
They retain their infantile proportions
What occurs in hypopituitary dwarfs?
They have proportions similar to their chronological age until puberty; do not mature sexually so they have juvenile features as adults
What are the two periods of rapid growth?
Infant growth
Pubertal growth spurt
What is infant growth?
A continuation of the rapid fetal growth period
What is pubertal growth spurt due to?
GH
Androgens
Estrogens
What sex does puberty occur first?
Females
When does the pubertal growth spurt cease?
Closure of the epiphyseal plates in long bones by estrogen
What are the two types of growth involved in human growth?
Linear and mass growth
What percentage does genetics play into growth with good nutrition and poor nutrition respectively?
Good nutrition: 80% genetics
Poor nutrition: 60% genetics
What occurs in long bone growth?
Chondrocytes in the epiphyseal growth plates begin to proliferate and create more cartilage that then is calcified to bone
What does estrogen cause in chondrocytes?
Increase apoptosis of chondrocytes thus closing of epiphyseal plates
What do glucocorticoids cause?
Slows chondrocytes proliferation process inhibiting growth
What is the “catch up” affect?
High glucocorticoids such as chronic stress, illness, or therapy can cause slowing of growth but once the glucocorticoids are removed the chondrocytes proliferate rapidly to catch up to what their normal rate would be
What nuclei produce SST?
Ventromedial
Paraventricular
What nuclei produce GHRH?
Paraventricular
Arcuate
What does GHRH cause?
Acts on somatotrophs via G alpha s increasing GH synthesis and release
What does SST cause?
Acts on somatotrophs via G alpha i inhibiting GH release
What is the dominant form of GH released?
22 kDa
What is GH synthesized as?
Preprohormone
How is the secretion of GHRH and GH described?
Pulsatile
When is the largest pulse of GHRH and GH secreted?
During sleep
What does GH release from effector cells via a JAK STAT receptor?
IGF-1