Summary Bone physiology

BONE PHYSIOLOGY
FUNCTION
 Framework → for body, supports soft tissue & provides points of attachment for
skeletal muscles
 Protection → of internal organs (e.g. heart & lungs)
 Movement → muscles contract & pull on bones → producing movement
 Mineral storage → Calcium & phosphorus distributed to body on demand
(maintenance of mineral homeostasis)
 Storage of blood cell-producing cells → long bones contain red marrow which
produces blood cells (hemopoiesis)
 Rich source of growth factors & cytokines

MUSCULOSKELETAL SYSTEM FUNCTION:
 Protect & support soft tissues
 Anchor muscles, tendons and ligaments
 Rigid levers that operate muscles
 Locomotion

PHYSIOLOGICAL FUNCTION:
 Critical for red-blood cell production (marrow cavity)
 Fat storage
 Calcium reserve & release (metabolism)

PROPERTIES
 Living tissue, responds to external stress-deposits where needed absorbs where it is
not
 Strength (mineral)
o Tensile- high stretch
o Compression - High top to bottom pressure
o Torsion - Low twisting
 Elasticity (protein) - slightly higher than wood
 As you get older your bones have less Calcium - > become more porous and very
brittle
 Woman have lower Calcium -> baby's use calcium from mother to form their own
bones
 shaped & re-shaped by the cells that reside within it, conforms to mechanical needs
 Morphology (size and shape) altered in life
o Looking at bones you can see how a person lived

BONE COMPOSITION
 70& mineral (Ca2+ and PO4- as hydroxyapatite)
 22% protein (95% Type I collagen + 5% proteoglycans & other material)
 8% water

HISTOLOGY
 Bone is completely solid but contains spaces which make bones lighter & provide
channels for blood vessels(supplying nutrients to bone cells)
Two types of bone:
 Cortical(Compact)

, o Few spaces, dense & solid
o Concentric ring structure
o Provides protection & support
o Largely mechanical role
o Makes up bone shaft walls
 Trabecular (cancellous/spongy)
o Large spaces filled with red marrow (less dense than compact bone)
o Irregular latticework
o More metabolically active
o Found at ends of long bones, short bones & between flatbones




CLASSIFICATION OF BONE
 Flat : protection and muscular attachment (e.g. skull)
 Long(tubular) : marrow cavity (e.g. femur)
o Most common of red blood cell production and fat cells
o Have a shaft & heads on both ends
o Contains mostly compact bone
 Short (compact) : as tall as they are wide (e.g. wrist)
 Irregular bone: e.g. vertebrae
 Sesamoid bone: patella (e.g. knee cap)

STRUCTURE OF LONG BONE
 Diaphysis
o Shaft
o Heavy wall of compact bone (dense)
o Central space - Medullary (marrow) cavity
 Epiphysis
o Wide part at each end
o Articulation with other bones
o Mostly spongy (cancellous/ trabecular) bone
o Covered with compact bone (cortex)

, 1. Metaphysis
o Where diaphysis and epiphysis meet
o Growth plate




BONE (OSSEUS) TISSUE:
[dense supportive connective tissue]
 Bone matrix
o Strong calcified (calcium salt deposits = solid matrix)
o Resists shattering (flexible collagen fibres)
o MATRIX PROTEINS: 1/3 of bone matrix is protein fibres(collagen)
o

 To form crystals of hydroxyapatite
 Which incorporates other calcium salts and ions
o HARDENED matrix = bone
 Periosteum & Endosteum
o Covers bone surfaces
o Fibrous layer
o Cellular layer
 Bone cells -make up only 2% of bone mass
o Osteoblasts - produce new bone
o Osteocytes - new bone once it's calcified
 Form complex network that can sense changes and trigger response
(creating more bone -> when you are more active )
o Osteoprogenitor cells(stem cells) - create osteoblasts
- important in repair
 Osteoclasts (multinucleated) - dissolve bone for bone remodelling
o Secrete collagen digestive enzyme
 Exercise stimulates bone remodelling - strengthen bones
o Putting pressure on bones
o Body responds → osteocytes send signal
→ osteoclast break down bone
→ stimulate osteoblast - build more bone (making it
stronger)
→ promotes the number of osteoblast