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71 Cards in this Set

  • Front
  • Back
Special structure harbored within bone:
Bone marrow
what percent of body weight is bone marrow?
What type of tissue is bone?
Specialized connective tissue - calcified ECM
Bone is a reservoir of:
What hormone induces bone resportion?
What acts in opposition to PTH?
3 Cells in bone:
What activates osteoclasts?
WWhat are the 2 types of stuff in bone matrix? How much of each?
-inorganic - 70%
-organic - 30%
What is the inorganic stuff?
Hydroxyapatite (Calcium + Phosphorus)
HHow much of the body's calcium is stored in bone?
What is the organic stuff in the bone matrix?
-Type 1 collagen
What has more proteoglycans; cartilage or bone?
What is the function of glycoproteins in bone?
Promote calcification
Why is bone so hard?
Because it has BOTH hydroxyapatite and Collagen type 1
What are osteoblasts?
Specialized fibroblasts
What are the 2 known osteoblast specific genes?
What is Cbfa-1 essential for?
Bone formation in the embryo
What proteins control the differentiation of fibroblasts into osteoblasts?
-Indian hedgehog
What do osteoblasts secrete?
The bone matrix
What is the old name for bone matrix?
What type of collagen is in osteoid?
Type I collagen
What type of collagen is in cartilage (hyaline)?
Type II
How is bone growth COMPLETED?
By glycoprotein-mediated calcium deposition.
What happens if you don't have any hydroxyapatite?
NO WEIGHT BEARING (remember the bone demonstration)
What injection allows the monitoring of appositional bone growth?
What is it called when calcification is impaired?
What is it called when osteoclasts destroy the bone matrix as it is made?
Osteitis fibrosa cystica
What are the mature cells that occupy lacunae in bone?
Where are lacunae located in bone?
In lamellae
How many osteocytes per lacuna?
How do osteocytes communicate?
By sticking cytoplasmic processes out of the lacunae into canaliculi.
What allows osteocyte processes to join?
Gap junctions
What do osteocytes do with their connections to each other and blood vessel endothelial cells?
Nourish each other and maintain the bone matrix.
What is the function of osteoclasts?
To destroy and remodel bone
What are osteoclasts made from?
Fusion of macrophages into a multinuclear cell.
What spaces do osteoclasts occupy within bone?
Howship's lacunae
What feature of osteoclasts allows them to attach to the ECM to chow down on bone?
What is the function of this ruffled border?
It forms a microenvironment that promotes bone resorption.
What cytokines activate osteoclasts?
What hormone inhibits osteoclasts?
How do activated osteoclasts resorb bone?
By releasing acid which dissolves the hydroxyapatite and activates cathepsin-K
What is Cathepsin-K?
Lysosomal enzyme secreted by osteoclasts.
What disease has a high rate of abnormal osteoclast remodeling?
What other non-inherited disease is due to osteoclast activity?
What are 2 different types of bone?
Is there any microscopic structural difference in compact and spongy bone?
What are the 2 important features of long bones?
-Diaphysis (shaft)
-Epiphysis (ends)
What type of bone is the diaphysis made of?
compact, but with spongy lining the marrow
What type of bone is the epiphysis made of?
Spongy bone with caps of compact.
What are Flat bones constructed out of?
2 compact bone plates surrounding a diploe - area of spongy bone.
What is the structural subunit of bone called?
an Osteon
What canals interconnect adjacent lamellae in osteons?
Volkmann's canals
Are Volkmann's canals connected to the Haversion canal?
What resides in Haversian and Volkmann's canals?
Blood vessels, nerves, and lymphatics.
What is the arrangement of collagen type I fibers in alternating lamellae in osteons?
Antihelical - it gives the bone more strength in spite of it being so light.
What type of bone is in adults?
What type of bone is in developing or regenerating bone?
Primary / Woven bone
How is secondary adult bone produced?
By resorption and remodeling of primary woven bone during development.
What are the 2 ways that bone develops?
1. Intramembranous
2. Endochondral
What happens in intramembranous bone growth?
Osteoblasts deposit osteoid onto mesoderm.
What happens in endochondral bone growth?
osteoblasts deposit osteoid onto CARTILAGE
By what type of process do LONG ONES form?
By what type of process do FLAT bones form?
Where does the bone form during intramembranous ossification of flat bones?
In ossification CENTERS
Onto what type of cartilage is osteoid deposited during long bone endochondral ossification?
onto HYALINE cartilage
What is the first step in endochondral ossification?
1. Formation of a BONE COLLAR around perichondrium of the future diaphysis
What happens after the bone collar forms?
Hypertrophy and apoptosis of the cartilage cells surrounded by the bone collar.
What are the 2 prominent processes that then occur in endochondral ossification?
-Bone production on the calcified cartilage matrix (by osteoblasts)
-Cavitation of the bone marrow
How is the process of endochondral ossification different at the epyphysis?
Some hyaline cartilage is retained as Articular Cartilage and Epiphyseal plate cartilage.
Why is it important that Epiphyseal plate cartilage be retained?
Because that's where the bone grows in length.