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32 Cards in this Set
- Front
- Back
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Functions of bone:
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1. Protection of vital organs
2. Harbors bone marrow 3. Attachment site for muscles 4. Ca++ and PO3 reservoir |
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What are osteoblasts and where do they come from?
What is their function? |
Osteoblasts are primitive cells that give rise to mature bone cells.
They are derived from mesenchyme Their function is to deposit bony matrix and become an osteocyte (mature cell) |
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What is the function of an osteoclast?
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Function: Break down bone
They are macrophages |
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Mature Bone vs Immature Bone
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Immature Bone:
Seen during development or during fracture repair. Collagen fiber deposition there Has an abundant number of osteocytes working on them Has a lower mineral content than mature bone Mature Bone: Lower proportion of osteocytes See a layered arrangement that you don't see in immature bone |
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Parts of a bone:
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Epiphysis: contains spongy, tribecular bone and marrow cavities
Diaphysis: covered in the bony collar (compact bone) Endostium: on the end surfaces of inner cavities |
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What is an osteon?
How do they communicate? What is their blood supply? |
Composed of multiple concentric lamellae of mature bone
Communicate via gap junction Blood supply through each osteon comes through the central canal (arteries, nerves, veins, lymphatics all come through the canal) NOTE: Lacunae are the spaces between the matrix that is used to contain the osteocyte |
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What are channels left by the processes within the bone matrix in an osteon called?
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Cannaliculae
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How does the periostium stick to the bone?
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It secretes type 1 collagen, which enables it to penetrate the bone and hold on tightly
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What is Volkmann's Canal?
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A canal that communicates adjacent central canals
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What are the 3 types of lamellar arrangement?
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1. Outer Circumferencial Lamella
2. Osteons - Concentric Lamella 3. Inner Circumferencial Lamella |
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Characteristics of Osteoblasts:
Origin, Shape, Location, Synthesize what?, Deposit what? |
Origin: Mesenchyme
Shape: Stellate shaped Synthesize?: Type 1 collagen, Ground substance, osteonectin (anchors mineral components to collagen) Deposit: Osteoid (unmineralized, uncalcified matrix) |
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How many osteocytes can talk to each other via canelliculae?
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About 10
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Osteoclasts:
Ruffled Boarder: |
Macrophages in the bone that break down bone matrix. The enzymes secreted create a space called the HouseShip's Lacuna
Ruffled boarder has an actin core and resembles microvilli (it increases the surface area for breakdown) |
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What is the role of parathyroid hormone in osteoclast and osteoblast activity?
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Inhibits osteoblasts and stimulates osteoclasts.
Break down matrix when calcium is low and acts on kidney tubule systems to promote Ca++ retention. Works on intestines to promote absorption of Ca++ from foods. |
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What is the role of calcitonin in osteoclast activity?
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Downregulates the activity of osteoclasts. More Ca++ is secreted into the bone matrix so that our blood Ca++ levels don't go any higher.
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What are the 2 main processes in Osteogenesis?
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1. Intermembranous Ossification: Mesenchyme --> Osteoblast --> osteoid (flat bone formation from within)
2. Endochondral Ossification (hyaline cartilage mold replaced by bone matrix - long bone formation) |
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Name and describe the layers involved in recovery from bone injury.
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Zone of reserve cartilage
• Inactive, but serves as the source of cartilage for the developing bone Zone of proliferation • Lines of dividing chondrocytes Zone of hypertrophy • Chondrocytes get bigger Zone of calcified cartilage • The cartilage in this zone is calcified and becomes new bone Zone of reabsorption • Have new matrix being laid down where the old cartilage cells once were |
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What is the function of cartilage and what is it made of?
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Function: To resist mechanical stress without deformation.
Contents: GAGs, Proteoglycans, Macromolecules (collagen, hyaluronic acid, glycoproteins) |
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What are the 3 main types of cartilage?
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1. Hyaline - Type II
2. Elastic - Type II and elastic fibers 3. Fibrocartilage - dense network of Type I |
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Is cartilage vascular?
Where does it get nutrients? |
NO
Gets nutrients from adjacent CT or from synovial fluid |
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What is a chondroblast?
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Immature precursor cell of the catrilage
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What is a chondrocyte?
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A chondroblast trapped in its own matrix
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What is a lacuna?
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A cavity of matrix where the chondrocyte is located
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What is perichondrium?
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Sheath of dense CT surrounding cartilage that carries blood, nerves, and lymphatics
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Discuss the mitotic activity of chondrocytes.
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Chondroblasts become chondrocytes when they get trapped in their matrix.
Chondrocytes divide mitotically and then as the individuals in the cluster synthesize cartilage, they grow apart |
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How are water and nutrients delivered to chondrocytes?
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Stress and contracture
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Function of chondrocytes is hormonally dependent. Explain.
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Synthesis of sulfated GAGs is stimulated by Growth Hormone, Thyroxin, and Testosterone
Inhibition of synthesis of GAGs is done by Cortisone, Hydrocortisone, and Estradiol Growth of the cartilage is stimulated by Somatotropin |
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What is the most common type of cartilage?
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Hyaline Cartilage
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What are the contents of the ECM in hyaline cartilage?
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1. Condroitin Sulfate
2. Keratin Sulfate 3.Hyaluronic Acid 4. Chondronectin ( promotes adherence of the chondrocyte to the ECM) |
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What stains are needed to view elastic cartilage?
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1. Verhoeff Weigert resorcin fuscin
2. Silver Stain |
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What are the 3 types of cartilage?
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1. Hyaline
2. Elastic 3. Fibrocartilage (makes annulis fibrosis) |
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What are the 2 growth patterns of Chondrogenesis?
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1. Interstitial Growth: Mitotic Division of pre-existing chondrocytes
2. Appositional Growth: Differentiation of perichondrial cells |
