Human Growth - Role of Endocrine System PDF

Human Growth Role of Endocrine System University ofGalway.i e  What do we mean by growth? “... the organized addition of new tissue as occurs normally in development from infancy to adulthood.” (Goodman,...

Human Growth Role of Endocrine System University ofGalway.i e  What do we mean by growth? “... the organized addition of new tissue as occurs normally in development from infancy to adulthood.” (Goodman, 2003.) The lengthening of the skeleton (particularly the long bones of the legs and the vertebral column), but also the increase in size of all soft tissues. Human growth is a complex process starting at conception and completing in adolescence at the time of growth plate fusion University ofGalway.i e Growth is an increase in size of a tissue/ organism due to Hypertrophy Increase cell size Hyperplasia Increase cell number Remember Increase extracellular matrix around cells University ofGalway.i e Control of Growth Human growth Not Linear Different growth patterns – Neonate, Infant, Puberty Major factors control growth differ throughout growth periods Growth depends on hormone but is influenced by other factors –Genetics –An adequate diet University –Chronic disease and stressful environmental conditions ofGalway.i e ALLOMETRIC GROWTH IN HUMANS Allometric Growth - differential growth of body parts Body proportions change between infancy and adulthood. University ofGalway.i e University ofGalway.i e Structure Of Long Bones University ofGalway.i e Chondrocyte Bone Elongation Proliferation: Rapid division in the zone of proliferation increases cartilage. Cartilage Expansion: New cartilage pushes older cartilage toward the diaphysis, lengthening the bone. Hypertrophy and Calcification: Chondrocytes enlarge and the matrix calcifies Ossification: Osteoblasts invade and replace calcified  Epiphyseal Lines When long bone stops growing, between the ages of 18 – 25 epiphyseal cartilage disappears epiphyseal plate closes visible on X-rays as an epiphyseal line At this point, bone has replaced all the cartilage and the bone can no longer grow in length This 7 year old boy presented to the ED complaining of wrist pain after being struck with a soccer ball.  Growth Hormone (GH) 191 amino acid protein hormone Species specific activity Half-life = 19 minutes Secreted in a pulsatile fashion Released from somatorophs in larger quantities than other pituitary hormone Greatest secretion in the newborn Decreases at 4 years Burst during puberty Decreases again Pulsatile Secretion GH Pathway of GH Control University ofGalway.i e  Ghrelin and GH Endorphin-derived peptides shown to stimulate GH release (1977) Development of molecules called growth hormone secretagogues GHS stimulate GH release through the IP3 pathway GHS receptor was cloned from human pituitary in 1996 Its natural ligand was only identified in 1999 and called ghrelin  University ofGalway.i e Actio ns of Ghreli n