bones Flashcards
functions
leverage for movement + muscle action
blood cell production
protection of organs
support against gravity
strorage- calcium, phosphorus and fat
long bones
eg humerus, femur
longer than they are wide
flat bones
eg ribs, cranium
formed of internal and external table separated by diploe
short bones
eg carpals
same width as length, transfer forces well
irregular bones
eg vertebrae
complex shapes
sutural bones
eg between skull bones
sesmoid bones
develop between tendons
eg patella
long bone structure
formed of diaphysis- shaft- compact bone which surround medulla cavity
epiphyses (ends)- spongy bone (trabecular)
articular cartilage
bone tissue
type of connective tissue
ground substance- makes up 2/3 mass of bone, minerals (hydroxyapatite, calcium and ions) which makes it hard but brittle
protein- reinforced with protein fibres incl collagen which is very dense and tough , 1/3 mass of bone
bone cells- 2% of bone mass
incl mesenchymal stem cells which form osteoblasts (form new bone) which form into osteocytes (mature bone cell) and osteoclasts which dissolve away old bone
osteoblasts
immature bone cells
secrete matrix protein
form new bone
located in periosteum
osteocytes
mature bone cells in lacunae
maintain bone matrix
connected via canniculi
osteoclasts
multinucleated cell
secrete acid and enzymes to dissolve bone matrix
structure of compact bone
osteon- basic functional unit, columnar and strong in long axis
central canal- tunnel for blood vessels, allowing blood flow
lamallae- concentric layers of matrix around central canal
lacunae-little lakes- osteocytes sit in, between lamallae
structure of spongy bone
no osteons
trabecullae- arches, rods and plates branching off
red marrow- between trabeculae, form red blood cells + provide nutrients to osteocytes
yellow marrow- stores fat, in medullary cavity
loading patterns
osteon structure provides strength in long axis
trabecular bone provides strength in a range of directions
trabeculae align according to habitual loading patterns
periosteum
membrane around outside of bone
outer layer= fibrous layer containing collagen fibres (continuous with bone), tendons and joint capsule
inner layer= cellular with metabolic function, lymph vessels and nerves
contains specialised cells
endosteum
membrane lining bone (inner surface)
line whole bone incl medullary cavity, central canal and trabeculae
bone formation
ossification- formation of/conversion into bone
intramembrane ossification- flat bone formation (inside bone)
endochondrial ossification- formation from cartilage
appositional bone growth- growth in width
intramembrane ossification
mesenchymal stem cells differentiate into osteoblasts (produce bone)
forms spicules of bone with cavities for blood vessels
trabecular bone formed
as forces are applied to surfaces, compact bone formed at top and bottom
endochondrial ossification
starts in cartilage model
chondrocytes in matrix enlarge then die
osteoblasts cover shaft (outer) in thin layer of bone
blood vessels and osteoblasts penetrate inside to form primary ossification centre
POC enlarges and marrow cavity is formed
secondary OC extends to epiphyses
growth in bone length
growth continues at epiphyseal cartilages during childhood
hormonal changes during childhood trigger fusion of epiphyseal cartilages
growth in length stops
appositional bone growth
increase in diameter of bone
outer layer- bone deposited by osteoblasts
inner layer- bone reabsorbed by osteoclasts
bone remodelling
continuous breakdown and reforming of bone tissue
reabsorption of by osteoclasts and formation by osteoblasts
bone remodelling
adaption to loading- ostoecytes detect forces and control growth, becoming stronger where there is more loading
calcium homestasis- 99% is calcium stored in bone
calcium needed for muscle contraction
hormones (PTH) control storage and release
