Bone 2 Flashcards
Epiphyseal GP zones
Reserve/resting zone Proliferation zone Maturation zone Hypertrophy zone Degenerative zone Osteogenic zone
Reserve zone
Layer of normal hyaline containin Chondrocytes
Proliferation zone
Layer of actively dividing Chondrocytes undergoing successive militia divisions and forming columns of cells surrounded by basophilic matrix of proteoglycans
Maturation zone
Chondrocytes have ceased dividing
Hypertrophy zone
Chondrocytes swell and become vacuolated
The matrix becomes calcified
Degen zone
Chondrocytes start to die and leave spaces around spicules of calcified cart for osteoprogenitor cells to invade
Osteogenic zone (metaphysis)
Osteoprogenitor cells diff into osteoblasts which congregate in surface of calcified cart spicules and bone formation commences
Calcified cart spicules strong basophilic woven bone eosinophilic
Cause of short or deformed bones
Premature GP closure due to trauma
Drugstore some antibiotics
Disease
Periosteum growth
To accomodate incr bone length width incr is req
Done via deposition of bone beneath periosteum by osteoprogenitor cells present in deepest periosteum layer diff into osteoblasts
Maintain cortical bone thickness by osteoclast activation in endosteum causing cortical bone remodelling
Growth of bone types
Length epiphyseal growth
Width growth originate at periosteum
Fracture repair stages
Inflammatory
Repair
Remodelling
Inflammatory stage duration
First few days
Repair stage duration
Weeks to months after
Remodelling stage duration
Months to years after
Inflammatory stage key events
Haematoma formed
Acute inflam response brings in phagocytic cells
Osteoclasts begin to clear clot and necrotic tissue
Neovascularisation establish new tissue blood supply
Granulation tissue formed at fracture site
Repair stage key events
Migration of mesenchymal cells to fracture site and periosteal and endosteum reaction brings in Chondrocytes and osteoblasts
Provisional callus formed bridging gap composed of varying amounts of hyaline cart and woven bone
Endochondral ossification occurs to produce a bony callus at which point a bony Union is achieved
Remodelling stage key events
Remodelling of callus commences in response to normal use
Replacement of woven bone with lamellae bone
Periosteal reaction remains for a log time after fracture repair
Specialised varieties of bones
Sesamoid
Splanchnic
Pneumatic
Splanchnic bones
Bones that develop in soft organs remote from the rest of the skeleton eg os penis ossa cordis os clitordis
Sesamoid bones
Bony structures found with in tendons eg patella navicular bone
If extirpated only reform if movement of the area is allowed
Sesamoid bone fx
Prevent tendon wear and injury as it passes over a joint and displaced tendon away from joint axis causing incr leverage of muscle acting via tendon
Reduce friction and change direction of pull of tendon. Form synovial joints with the major bones with which they are in contact
Pneumatic bones
In mammals confined to the skull and contain the paranasal sinuses which comms with the nasal cavity. Dev principally after birth when basal mucosa outgrowths invade certain flat bones and replace the diploe. Post natal remodelling of the skull can result in extensive changes in some species skull shape eg pigs cattle
Pneumatic bones in birds
Skeleton dev an extensive system of air filled cavities in comms with the respiratory organs. This is an important adaptation to lighten the skeleton for flight and is found to be more extensive in the best fliers
Compressive strain concentrated where
Conc on outer parts of any structure, so no need for a solid interior
Tubes v rods
Tubes are stiffer and harder to break by bending
Lighter so leg, etc is lighter
Bone stress natures
Compressive on caudal sides and tensile on cranial sides
Limb bones optimised for
Impact strength
So side under tensile stress gives first
Muscle pull affect on bone growth
- infraspinatous m red Infraspinous fossa, - trapezius m red scapula spine, - lower incisors shorten mandible
Most of mandible and cranium sig red if fed in soft food as mastication m not used much. Weightlessness &a lack of use cause bone loss, once gravitation cause heavier bones
Age and physiological affects on bone
Pregnancy lactation can have bone loss
Affect of neck m dev and rootin behaviour on shape of pig skull
What occurs post foetal dev bone formation and fracture repair
Woven bone replaced with lamellar bone in response to stress applied. B active in growth but occurs throughout life at slow rate and re activate when incr use, change in physiological state or in fracture repair. In adv age it decr sig
Result of bone remodelling
Several gen of haversion systems
Increased strength in areas of stress application
Osteoclast role in bone remodelling
They cut through bone producing a cutting come through the bone. Followed immediately by neovascularisation into resorptive cavity which is lined with osteoprogenitor cells which diff into osteoblasts which lay down osteoid producing a closing cone
What occurs as new lamellae are produced in bone remodelling
Osteoblasts become embedded and mature into osteocytes within lacunae of new haversion system
