Topic 9 Flashcards
Functions of skeletal system
- support
- protection of vital organisms
- attached muscles and allows movement
- red marrow produces rbc and wbc
- stores Ca
Before week 8 skeleton embryo constructed of..
fibrous membranes and hyaline cartilage
Bone formation occurs
8 weeks to 20 years
2 types of ossification
- intramembranous
- endochondral
Intramembranous
flat bones (skull, mandible, clavicle), develop from fibrous CT membrane
Process of intramembranous ossification
- oesteoblasts produce spongy bone alone CT fibres
- periosteum forms and then osteoblasts under it lay down and compact bone
Fontanels
unossified membranes in the skill that remain at birth
Endochondral
hyaline cartilage used as a model for bone construction then ossifies to form spongy bone. periosteum forms and the osteoblasts beneath lay down compact bone.
articular cartilage and epiphyseal plates =
cartilage that has not been ossified
Bone growth in length and process
=endochondral growth at epiphyseal plates
process: cartilage grows to matrix near diaphysis becomes bone then growth stops when epiphyseal plate ossifies into epiphyseal line
Bone growth in diameter and process
= appositional growth
process: osteoblasts beneath periosteum secrete bone matrix. osteoclasts reabsorb bone on the endosteal surface so size of cavity keeps pace with growing bone
Mechanical stress is due to
muscle action
2 examples of of mechanical stress
- moderate exercise: increase osteoblast activity in areas of stress
- injury that restricts movement: decrease osteoblast activity and no change in osteoclast activity decrease bone mass
Weights or electric currents may speed..
healing by increase osteoblast activity
Ca and PO4 is required for
production of bone matrix
Vitamin C
required for collagen production
Vitamin D
increase absorption fof Ca from intestine (if lacking Vit D then rickets soft bone in tissue)
Growth hormone and thyroid hormone stimulate
bone growth
Estrogen and testosterone increase..
osteoblast activity
Estrogen in both sexes does what
ossification of epiphyseal plate
Calcitonin
inhibits osteoclast activity. increases Ca movement from blood to bone
Parathyoid hormone (PTH)
osteoclast activity increases and osteoblast activity decreases therefore blood Ca increases
Osteoporosis
decrease in bone mass
Risk factors of osteoporosis
- increasing age
- post menopause
- inadequate diet
- illness, excess PTH
- too little/excessive exercise
- drugs or smoking
Process of bone repair
- begins with formation of a blood clot
- clot replaced by a callus of fibrous network and fibrocartilage islets
- callus ossifies so intramembranous and endochondral ossification
- takes 4-6 weeks so cast required since movement can refractor new matrix
