Epiphyseal growth plate osteoblasts the bone forming

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epiphyseal growth plate . Osteoblasts , the bone-forming cells at the shaft edge of the epiphyseal growth plate, convert cartilaginous tissue at this edge to bone while cells called chondrocytes simultaneously lay down new cartilage in the interior of the plate. So the growth plate widens and is slowly pushed away from the center of the bony shaft as the shaft lengthens. This bone lengthening process is stimulated by GH, thyroid hormone & sex steroids. Epiphyseal closure occurs when growth plates are converted to bone as a result of hormonal influences at late puberty; stimulated by sex steroid. 2. Describe the actions of growth hormone. Are all of these the result of direct actions of growth hormone on target tissues? Explain. (Sect11E.1, Tab11.5)
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Biol 2173 Learning Objectives Spring 2013 Growth hormone, secreted by ant. pituitary gland, has no effect on fetal growth but is most important hormone for postnatal growth. It stimulates cell division in many target tissues. Thus, GH promotes bone lengthening by stimulating maturation & cell division of the chondrocytes in epiphyseal plates, thereby continuously widening plates and providing more cartilage for bone formation. GH exerts most of its cell division stimulating effect indirectly on target tissues through mediation of mitogenic hormone IGF-1, whose synthesis and release are induced by growth hormone. GH also stimulates protein synthesis mainly in muscle, which makes body grow (increases amino acid uptake and both synthesis and activity of ribosomes). Growth hormone has anti-insulin
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