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23 Cards in this Set

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What are the 5 functions of bone?
1. protection
2. mineral storage
3. movement
4. support and shape
5. hematopoiesis
Of the composition of bone, what % of its mass is composed of cells?
5-8% of its mass are cells, th remaining 92-95% is extracellular matrix.
Of the extracellular matrix, what percent is made up of Organic matter?
35% is organic matter (osteoid)
90-95% of the organic matter is Type I collagen
Of the extracellular matrix, what percent is made up of Inorganic Matrix?
65% is inorganic matrix
70% of the inorganic matter is Hydroxyapatite
What are the four macroscopic components of a bone?
1. Cortical bone
2. trabecular bone
3. periosteum
4. endosteum
What are the characteristics of cortical bone?
- Lemellar collagen fibers
- dense and strong
- outer covering supports and protects bone
What are the characteristics of trabecular bone?
- lamellar and woven
- found in bone medullary cavity, skull, vertebral bodies
What are the characteristics/functions of periosteum?
- The outer fibrous and vascular layer of bone
- Inner cambium layer contains osteoblasts and osteoclasts
- functions in growth, repair and nutrition of bone
Where is the endosteum?
It lines the inner margin of the cortex and trabeculae.
- It also contains osteoblasts and osteoclasts
What are the four divisions of bone?
1. Epiphysis
2. Physis
3. Metaphysis
4. Diaphysis
What are the four types of cells in bone?
1. Osteoprogenitor cells (becomes fibroblasts, chondroblasts, or osteoblasts)
2. Osteoblasts
3. Osteocytes
4. Osteoclasts
What enzyme is contained in the cytoplasm of osteoblasts?
Alkaline Phosphatase
If a Dr. wanted to determine if there was a broken bone, what would be the purpose of doing a blood test?
The Dr. would be checking for alkaline phosphatase in the blood, as it is an indicator of osteoblastic activity and possible broken bone or tumor in the bone.
Which cell within bone mediates Wolff's Law?
Osteocytes
They regulate the cell environment
Within bone, where are osteocytes located?
Within the canniliculi. They transport fluid through the canniliculi.
Which cells within bone are multinucleated?
Osteoclasts
Where do osteoclasts reside within bone?
Howship's lacunae
Hyperemia in bone leads to what?
Increased osteoclastic activity, resulting in osteoporosis
Ischemia in bone leads to what?
Increased osteoblastic activity, resulting in bone sclerosis
When does ossification begin (what weeks?) in the fetus?
6th, 7th, and 8th weeks
Describe intramembranous bone formation
bones form directly from osteoblasts that are clustered within a fibrous membrane. There is no pre-existing cartilage model.
Where does intramembranous bone formation predominate during fetal growth development?
In the skull and facial bones, as flexibility is needed.
Describe endochondral bone formation
A pre-existing cartilage model calcifies and is replaced by bone.