- BONE
- EPIPHYSEAL
PLATE
- SYNOVIAL
JOINTS
- SKELETAL
MUSCLE
BONE
There are just 4 basic ways in which bone can react to
abnormal conditions:
1.
Local death
·
When an area of bone is completely deprived of
its blood suply, its reaction is local death (avascular necrosis of bone).
2.
Bone deposition greater than bone resorption
·
Generalized Reactions
1. Osteopetrosis (Marble bones)
Bone deposition is normal but bone resorption is defective.
2. Acromegaly
Bone deposition is increase by excessive intramembranous
ossification from the periosteum.
·
Localized Reactions:
1. Work Hypertrophy
The bone react to the extra stresses and strain of increased
function by increased bone deposition. Varus deformity of the foot à
the fifth metatarsal hypertrophies.
2. Degenerative Osteoarthritis
Subchondral sclerosis
3. Fractures
The periosteum and endosteum react to bony injury with localized
increased in bone deposition to form callus.
4. Infection
The periosteum reacts to infection by deposition of new bone.
5. Osteosclerotic Neoplasm
·
Osteoid osteoma (benign neoplasm)
·
Osteosarcoma (malignant neoplasm)
3. Bone deposition less than bone resorption
·
Generalized Reactions
1.
Osteoporosis
Bone deposition is decreased because of decreased formation of matrix and
resorption is increased. Examples: osteogenesis imperfecta, disuse osteoporosis,
steroid induced osteoporosis, postmenopausal osteoporosis.
2.
Rickets in Children and Osteomalacia in Adults
Although the osteoblastic formation of
matrix is normal, there is decreased calcification (hypocalcification)
of the matrix with a resultant decreased in the amount of calcified bone.
·
Localized Reactions
1.
Disuse Atrophy (disuse osteoporosis)
Decreased bone deposition whereas the bone resorption continues
unchanged.
2.
Rheumatoid Arthritis
The bone reacts to the periarticular soft tissue inflammation of RA by
decreased bone deposition and possibly increased bone resorption.
Decreased
in functionàdisuse
atrophy
4. Mechanical Failure of Bone (Fractures)
The periosteum and endosteum react to
bony injury with localized increased in bone deposition to form callus.