Bone Flashcards
Osteoblasts
Bone forming cells
Osteoclasts
Bone removing cells
Osteocytes
The mature cells
Where are osteocytes located?
Lacunae
The organic matrix of bone provides what two things?
Tensile strength and flexibility
Mineral gives bone what?
Hardness
Endochondral ossification
when bone replaces the cartilage
-has physes and articular-epiphyseal complexes
What factors affect endochondral ossification?
GH, insulin-like growht factor, thyroxine, vitamin D
What is intramembranous ossification?
Bone forming within fibrous tissue (No cartilage model)
New bone (woven bone) turns into…
lamellar bone
Only mechanism of getting rid of bone
osteoclastic bone resorption
Osteoclastic bone resorption is stimulated by?
Parathyroid hormone, bone tension, interleukins
T/F? Bone is always being resorbed and formed.
True
What does Wolff’s law state?
bone remodels in order to accommodate the stress it encounters
Three layers of the joint capsule
- outer fibrous layer
- loose fibrovascular layer
- synoviocyte layer (single layer)
Nutritional source for the chondrocytes
Synovial fluid
Bone deformities/abnormalities of development can be due to what factors?
abnormal cartilage model, inadequate growth, genetic or acquired, defect EO at the physis or AE
Chondrodysplasia
Angular deformities, dwarfism
What is osteochondrosis?
focal defect in endochondral ossification, necrosis of articular cartilage
-lesion can’t withstand weight
What does necrosis of AC lead to often times?
osteoarthritis
Loss of bone =
resorption > remodeling
An example of diffuse loss of bone?
Osteoporosis or osteopenia
What are a few causes of diffuse loss of bone?
disease, poor nutrition, hyperparathyroidism
An example of focal bone loss?
bone lysis
What causes focal bone loss?
chronic inflammation, neoplasia
Inflammation in the middle of the bone marrow is?
osteomyelitis
-purulent exudate
What type of cells should you never see in bone?
epithelial cells
Increased amount of bone produced in a place it isn’t supposed to be
hyperostosis
Abnormally-dense bone form the failure of osteoclast activity
osteosclerosis
death of bone cells
osteonecrosis
What causes osteonecrosis?
ischemia
toxins
heat/cold
Necrotic bone stays in place until???
osteoclasts get rid of it
A piece of necrotic bone that is walled off and by itself
sequestrum
What happens if there is a fracture through the physis?
stunts growth, premature closure/abnormal growth
How do horses commonly get cranial hemorrhage?
hit their occipital bone and fracture the BASISPHENOID bone after flipping on their back
What is the first step in bone healing when there is a fracture?
Hematoma at fracture site, then necrosis at the edges of broken bone
What is a callus?
This soft callus is made of cartilage and fibrous tissue, and it replaces the blood clot that formed earlier.
-first soft, then hardens over time
A bone needs ________ to survive
blood supply
Osteomalacia
softened bone, osteoid
T/F? Osteomalacia happens in young animals?
No, adult animals only with closed physes
What can cause osteomalacia?
Calcium deficiency, vitamin D deficiency
T/F? Adult animals get rickets.
False. Young animals with OPEN physes only
What is rickets?
softened, bowed bones due to enlarged osteochondral junctions.
-Thickened physis
What is a cause of rickets?
Vitamin D, calcium defiencies, or too much phosphorous
What is fibrous osteodystrophy?
bone changes caused by too much parathyroid hormone stimulation
-osteoclasts getting too much signal from the PT to break down bone for Ca+
What are two mechanisms of fibrous osteodystrophy?
Nutritional and renal
