pathophysiology Flashcards
What are the stages of intramembranous ossification?
- ossification center appears in the fibrous CT membrane. Mesenchymal cells from the mesoderm cluster and differentiate into osteoblasts forming ossification center.
Bone matrix(osteoid) is secreted within the fibrous membrane, trapped osteoblasts become osteocytes.
Woven bone and periosteum form; bone matrix is laid down between blood vessels creating trabeculae. It condenses and becomes the periosteum.
Bone collar(thickened periosteum) of compact bone forms and red marrow appears.
Stages of endochondral ossification
- formation of bone collar around hyaline cartilage model
- cavitation of the hyaline cartilage within the cartilage model
- invasion of internal cavities by the periosteal bud ad spongey bone formation
- formation of the medullary cavity as ossification continues, appearance of 2ndry ossification centers in the epiphyses
- ossification of the epiphyses when completed hyaline cartilage remains only in the epiphyseal plates and articular cartilages
Postnatal bone growth:
-what are the three functional zones in long bone growth?
Growth zone: cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
Transformation zone: older cells enlarge, matrix becomes calcified, cartilage cells die, and the matrix begins to deteriorate.
Osteogenic zone: ne b one formation occurs.
Describe appositional growth of bone
Appositional Growth:
-osteoblasts beneath periosteum secrete bone matrix forming ridges that follow the course of periosteal blood vessels.
- as the bony ridges enlarge and meet, the groove containing the blood vessel becomes a tunnel.
- periosteum lining the tunnel is transfored into an endosteum and the osteoblasts just deep to the tunnel endosteum secrete bone matrix, narrowing the canal.
- Osteoblasts beneath endosteum form new lamellae, a osteon is created. This process is repeated continuing to enlarge bone diameter.
During infancy and childhood, epiphyseal plate activity is stimulated by what hormone?
How does remodeling of bone occur?
What two control loops regulate bone remodeling?
Epiphyseal plate activity is stimulated by growth hormone, in puberty testosterone, and estrogen.
Remodelling: osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces.
Control loops regulating bone remodeling:
-hormonal mechanisms (Calcitonin;deposition in bone and PTH; osteocytes degrade bone and release Ca) maintaining calcium homeostasis in blood
-mechanical and gravitational forces acting on the skeleton.
What is Wolffs law? Supportive observations?
Wolffs Law: a bone grows or remodels in response to the forces or demands placed upon it.
Observations:
- long bones are thickest midway along the shaft (where bending stress is greatest)
- curved bones are thickest where they are most likely to buckles.
Describe each Bone fx:
- nondisplaced
- displaced
- complete
- incomplete
- linear
nondisplaced: bone ends retain their normal position
displaced: bone ends are out of normal alignment
complete: bone is broken all the way through
Incomplete: bone is not broken all the way through
Linear: fx is parallel to the long axis of the bone
Describe each bone fx:
- Transverse
- compound (open)
- Simple (closed)
Transverse: the fx is perpendicular to the long axis of the bone
compound (open): both ends penetrate the skin
simple (closed): bone ends do not penetrate the skin
Describe each bone fx:
- comminuted
- spiral
- depressed
- compression
comminuted: bone fragements into three or more pieces (elderly)
spiral: ragged break when bone is excessively twisted (sports injury)
depressed: broken bone portion pressed inward. (skull fx)
Compression: bone is crushed (common in porous bones)
describe each type of bone fx:
- epiphyseal
- greenstick
epiphyseal: epiphysis separates from diaphysis along epiphyseal line
greenstic: incomplete fx where one side of the bone breaks and the other side bends. (breaking a fresh twig in half)
Stages of bone fx healing
hematoma formation: site becomes swollen, warm, and red.
fibrocartilaginous callus formation: (new capillaries grow into the tissue and phagocytic cells begin cleaning)
Bony callus formation: begins 3-4 weeks after injury ad continues until firm union is formed 2-3 months later
Bone Remodeling: excess material is removed and compact bone is laid down to reconstruct shaft walls
Osteomalacia
- what is this
- cause
- main sx
- what is this called in children?
What
-bones are inadequately mineralized causing softened, weakened bones
Cause
-insufficient Ca or Vit D deficiency
Main Sx
-pain when weight is put on the affected bone
In children its called Rickets
Rickets
-signs and sx
Signs and Sx
- soft spot is slow to close
- bony necklace
- curved bones
- big, lumpy joints
- bowed legs
Osteoporosis
- What is this
- What type of bone is most vulnerable?
- MC in who
- inciting events
- Tx
What
-group of diseases in which bone reabsorption outpaces bone deposit
Type
-spongy bone of the spine is most vulnerable
MC in post-menopausal women
Events
-sneezing or stepping off a curb can cause fractures
Tx
- Ca and Vit D supplements
- weight bearing exercise
- MHT
- statins increase bone density
- progesterone cream prompts new bone growth
Paget’s Disease
- characterized by what
- sx
- Localized where
- cause
- tx
Characterized by
- excessive bone formation and breakdown
- -reduced mineralization causes spotty weakening of the bone (osteoblasts keep working but clasts fade out)
Sx
- may develop arthritis and deafness
- may be painful
Usually localized in the spine, pelvis, femur, and skull
Cause
-unknown!
Tx
- Didronate
- Fosamax
- calcitonin (build up bone)
- bisphosphonates (prevent the loss of bone mass)
