bone growth Flashcards
functions of bone
protects organs, blood cell production, mineral storage pool, levers for muscle action, supports body shape
mechanical properties of bone
CABLE -LIKE FLEXIBILITY (some flexibility)- made out of mainly collagen, so resistant to TENSION PILLAR-LIKE STIFFNESS- collagen enforced by hydroxyapatite crystals, so resistant to COMPRESSION
DIAGRAM structure of bone
bone has two types of tissue- woven (immature bone), and lamellar (mature bone)- lamellar more organised, woven more irregular
woven bone in adults
not found in adults- only in repairing fractures
DIAGRAM features of the long bone (femur)
head (epiphysis) has spongy bone, shaft (diaphysis) has compact bone, and distal end also epiphysis most of shaft is hollow (medullary cavity) with marrow inside
arrangement of lammellar bone
outer compact layer (CORTICAL bone), with inner spongy/CANCELLOUS/trabecular bone (NOT woven, even though it looks irregular)
what is lamellar bone arranged like this
so that bone is not too heavy, and it allows space for lots of bone marrow
DIAGRAM cortical vs spongy bone and blood supply
they have structures of OSTEONS, which has a central canal of vessels- bone has a large blood supply
periosteum DIAGRAM
the outer surface of bone- needed for bone growth/repair also vascular, and well innervated (pain in bone due to this region)
bone cells
osteogenic cells form osteblasts (form bone matrix), which form osteocytes (maintain bone tissue) osteoclasts also present (has RUFFLED BORDER), which breaks down bone matrix
bone development landmarks
skeleton develops at 6 weeks of fetal life, and continues until 25 yrs of age
bone development- two types of ossification
intramembranous- in vascular connective tissue, where bone matrix (osteoid) built around collagen, and its mineralised to form woven bone, which becomes lamellar endochondral
use of intramembranous ossification
for flat bones like in skull, and mandible
endochondral ossification and growth in bone length
long bones have to cope with large forces whilst still needing to grow eg as a toddler- thus wouldn’t make sense to grow at its ends, so shaft ossified first, THEN epiphyses
DIAGRAM how endochondral ossification works when growing
a cartilage model of bone develops: this model then is calcified and dies: primary ossification centre forms at shaft and matrix calcified- secondary centre forms at epiphyses, and cartilage/epiphyseal plates form between the shaft and epiphyses, where growth occurs (first shaft, then epiphyses
DIAGRAM adult vs child hand
hand not broken, arrows pointing to epiphyseal plates wrist bones in child spaced out due to cartilage in between
adaptability of bone
grows whilst withstanding force can remodel- increases/decreases density depending on usage (eg less dense in space), or even external shape can also repair in fractures
keys of growth/remodelling
large blood supply osteocytes maintain matrix, but activate osteblasts as well osteoclasts important for remodelling
growth in bone DIAMETER (width)
known as apposition ie cells in periosteum activated to become osteoblasts, which form ridges- these ridges close off to form central canal, and bone grows around it
DIAGRAM healing of fractures
hematoma forms in fractures, which is infiltrated by connective tissue cells and blood cells, which forms woven, then mature bone thus BLEEDING IMPORTANT
role of calcium
if Ca2+ high, calcitonin by parafollicular cells releasts, INHIBITING osteoclasts, and Ca2+ uptake into bone promoted if low, PTH released, promoting osteoclast bone resorption+ reabsorption by kidneys
