Bone Flashcards
What are the differences between Compact and Spongy/Trabecular/Cancellous Bone?
- Compact Bone
- Outer solid cortex surrounding spongy bone
- Lamellar bone
- Spongy/Trabecular/Cancellous
- Inner Layer
- Spaces for BM
- Lamellar or woven bone
Woven Bone
- Immature/Primary
- Replaced by Lamellar
- Loose arrangement of collagen fibers
- Forms during Fx repair or remodeling
- Mechanically weak, forms quickly
Lamellar Bone
- Mature/Secondary
- Regular parallel arrangement of collagen fibers
- Not visible on H&E stains
- Form of most adult bone
- Mechanically strong, forms slowly
Bone Matrix
What comprises Organic bone?
What comprises Inorganic bone?
- Organic Bone (33%)
- Type I collagen fibers
- Osteoid (Unmineralized bone)
- Inorganic Bone (65%)
- CaPO4, Hydroxyapatite
- Creates hardness/stiffness
Osteoprogenitor Cells
Origin and properties?
Location?
Give rise to what?
When are they reactivated?
Mesenchyme; Properties of SCs (Proliferation & Differentiation)
Inner layer of Periosteum and Endosteum
Osteoblasts
Reactivated during bone repair
Osteoblasts
Function?
- Function
- Deposit osteoid; Control mineralization of osteoid
- Give strong cytochemical reaction for AlkPhos
Osteocytes
What are they?
How do they communicate and receive nutrients necessary for survival?
What does the life of bone matrix depend on?
Osteoblasts trapped in Lacunae within Osteoid Matrix
Highly branched cells create complicated communicating network (Lacunae –> Canaliculi –> Connection of Osteocytes)
Survival status of the osteocytes
Osteoclasts
Derived from?
How do they perform bone resorption?
Important roles?
Where do they reside?
- Monocytes entering bone via blood stream
- Generate secluded acidic environment
- H+-ATPase: enzymatic degradation of organic bone matrix
- Bone remodeling and renewal
- Howship’s Lacuna
Periosteum and Endosteum
Functions
What does periosteum not cover?
- Nutrition of osseous tissue
- Continuous supply of new cells for growth and repair
- Articular surfaces of bone
Periosteum (outer layer of Compact Bone)
What is in the inner (osteogenic) layer?
What is in the outer layer?
Osteoprogenitor cells
Blood vessels and nerves; Fibroblasts and collagen fibers
Endosteum (compact bone inner layer)
What does is cover?
Where does it extend?
What cell differentiation occurs?
Covers spongy/trabecular bone walls
Extends into all cavities of bone
Osteoprogenitor cells –> become Osteoblasts
Interstitial Lamellae
Location?
What separates interstitial lamellae and osteon?
Between Osteons
Cement Line
Osteons (Haversian System)
Concentrically arranged Lamellae around longitudinal vascular channel
Outer Circumferential Lamellae
External surface of compact bone
Under Periosteum
Inner Circumferential Lamellae
Internal surface of compact bone
Subadjacent to Endosteum
Osteocytes
Where do they reside?
What are their extensions travel through?
Bone cells supporting matrix
Occupy a Lacuna
Radiating Canaliculi penetrate Lamellae
Intramembranous Ossification
What types of bones does this occur?
What are the steps?
- Flat bones
Endochondral Ossification
What type of bones?
What are the steps?
- Long bones
Endochondral Ossification at Epiphyseal Plate
Describe the Process
Chondrocytes (zone of reserved cartilage) Proliferate (zone of proliferation) and Hypertrophy (zone of hypertrophy) pushing Epiphysis away from Diaphysis
Chondrocytes become Calcified and die (zone of calcified cartilage)
Osteoclasts resorb/remove dead chondrocytes to lengthen medullary cavity (zone of resorption)
Bone Fracture Repair
What are the steps?
Formation of fracture hematoma
Fibrocartilaginous callus formation
Bony callus formation (Osteoblast)
Bone remodeling (Osteoclast)
