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What is the skeletal systems supporting connective tissue?
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What is the skeletal systems dense connective tissue proper?
Ligaments
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What is the function of the bones?
- Support the body
- Storage for minerals and lipids (98% calcium, marrow)
- Blood cell production
- Protection (ribs, skull, pelvis?
- Leverage (change magnitude & direction of muscle)
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What is bone tissue made of?
- Supporitng connective tissue
- Specialized cells
- Matrix
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What does the bone matrix consist of?
- Calcuim salts on 2/3 collagen fibers
- Strong solid matrix (withstand compression)
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Name the cells of bone tissue?
- Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclast cells
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What are osteoprogenitor cells? What is their function?
- Mesenchymal cells
- Mitosis & differentation (daughter cells) repair
- & regrowth
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What do daughter cells become?
Osteoblasts
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What is the function of osteoblasts?
- Produce new bone (secrete bone matrix)
- Becomes mineralized, may respond to
- Mechanical or hormonal stress to
- Initate osteogensesis
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What are osteocytes? What is their function?
- Mature bone cells
- Maintain the matrix (dynamic)
- Controls release of calcium to the blood
- & depositing of Ca++ salts in the matrix
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What is a chamber, or cave within an osteocyte?
Lacunae
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What are the layers in an osteocyte called?
Lamellae
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Within the osteocyte, what are the channels called?
Canaliculi
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What is the purpose of the canaliculi?
- Connects to blood supply inside or outside
- Their are gap junctions between them
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What is the function of the osteoclast cells?
- Dissolve bone matrix
- & release Ca++ to blood
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At a young age which is more active osteoblasts or osteoclast cells?
Osteoclast cells
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What are the two types of bone matrix?
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How does the spongy bone look? What is the function?
- Open framework (struts)
- Forms marrow
- Lighter
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What will trabeculae do in the spongy bone if stressed?
Align themselves to support the bone
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What is the quaility of the compact bone? What is the function?
- Dense & solid
- Forms walls of bones
- Osteon
- Thicker at high stress areas
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What is a osteon?
Functional unit of mature compact bone
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In an osteon, where are the osteocytes & matrix found?
In concentric circles around central canal
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In an osteon where do the canaliculi interconnect?
The lacunae
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Name and define the three parts of the long bone?
- Epiphysis-end
- Metaphysis-transition
- Diaphysis-shaft
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What does physis mean?
Growth
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Name the layers of the bone?
- Periosteum membrane
- Compact bone
- Spongy bone
- Endosteum
- Marrow
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What is the periosteum membrane? What is it's function?
- Outside surrounds the bone
- Necessary for bone growth and repair
- Attachement
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Where is the marrow located?
Inside the endosteum
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What is the endosteum? It's function?
- Thin layer of connective tissue
- Lines the surfaces of bony tissue
- That forms the medullary cavity
- Active in growth and repair
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Which cells are present in the endosteum?
- Osteoprogenitor cells
- Osteoblasts
- Osteoclast cells
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Define ossification?
Replacing other tissue with bone tissue
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What is the process of ossification in a human embryo 'skeleton'?
- Fibrous connective tissue (mesenchymal cells)
- & hyaline cartilage loosely shaped like bones
- Undergo ossification to become bones
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When does ossification begin?
6-7 week embryo (1/2 inch long)
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Name the two ways ossification can occur?
- Intramembranous (within a membrane)
- Endochondral (within a cartilage)
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What bones are the outcome of intramembranous ossification?
- Skull
- Jawbone
- Collar bone
- Patella
- (flatbones)
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What is the process from beginning to end of intramembranous ossification?
- Ossification centers begin in
- Fibrous connective tissue
- (meschymal cells differentiate into osteoblasts)
- These center secrete matrix which undergoes
- Calcification and center gets larger
- The bone becomes spongy bone and then produces
- The outer compact bone
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What are fontanels?
- Soft spots
- Membrane left that is not ossified
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Describe the endochondral ossification process?
- Cavities form in the cartilage model by
- Bursting chondrocytes
- A bone collar is formed around the shaft of the model by
- Osteoblasts. Blood vessels penetrate the collar
- & cartilage and enter the central cavity and bring osteoblasts
- That produce spongy bone. The bone shaft becomes thicker
- Capillaries enter epiphysis bringing osteoblasts
- That create secondary ossification centers
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How are most bones formed?
Through endochondral ossification
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What is a chondrocyte?
The only cells found in cartilage
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How are osteocytes important to bone maintenance?
- They are continually removing &
- Replacing calcuim salts
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How much of the adult skeleton is demolished and rebuilt, or replaced each year?
1/5th
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What two bone cells remain active throughout our lives?
- Osteoblast
- Osteoclast cells
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When does bone growth occur?
- When osteoblasts are creating more
- Matrix then osteoclast cells are removing
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What is true for the bone cells of older individuals?
- Osteoclast cell activity is
- Higher than osteoblasts
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What is osteoporosis?
The result of too little mineralization of bones
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What is linked to osteoporosis?
- Deficiency of mineral in youth
- Loss of estrogen at menopause
- Imbalance of activity of osteoblasts and osteoclasts
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