Bone

Question 1

Organic and inorganic components to bone

Answer 1

• Inorganic: hydroxyapatite (Ca and P)

- Organic: type I collagen and ground substance

Question 2

Compact vs Cancellous bone

Answer 2

• Compact: dense bone, main type in diaphysis

- Cancellous: lower density trabecular bone, found in epiphysis, short bones, and irregular bone

Question 3

Both compact and cancellous bone show two type of organization

Answer 3

• Mature Lamellar Bone (discrete sheets of matrix)

- Woven bone: newly formed with randomly arranged components

Question 4

Woven Bone

Answer 4

• Abundance of collagen, poorly mineralized
• Osteocytes are plentiful and random
• Important in bone development, fracture repair and bone remodeling

Question 5

Mature lamellar bone

Answer 5

• Collagen fibers laid down in concentric lamellae
• Osteocytes are contained within lacunae in regular pattern
• Main type of bone found in adults

Question 6

Osteon

Answer 6

• Haversian system

- Complex of concentric lamellae, central canal with artery, v and nerve, endosteum

Question 7

Between successive lamellae are

Answer 7

Lacunae with osteocytes

Question 8

Lacunae are interconnected by

Answer 8

Canaliculi

Question 9

Dendritic processes of adjacent cells are in contact via

Answer 9

Gap Junctions

Question 10

Osteon cells receive nutrients via

Answer 10

Vessels in the Central Canal

Question 11

Spaces between the lattice of Trabeculae are sites of

Answer 11

Marrow formation

Question 12

Periosteum

Answer 12

Outer Covering of bone

• Consists of inner cellular and outer fibrous layer
• Collagen fibers of the outer layer are continuous with adjacent bone, joints, tendons, and ligaments

Question 13

Osteogenic cells

Answer 13

-Progenitors, develop into osteoblasts

Question 14

Osteoblasts

Answer 14

-Secrete matrix, synthesize collagen, GAGs, glycoproteins

Question 15

Osteoid

Answer 15

• Osteoblasts form it
• Zone of unmineralized fivers
• Osteoblasts act on this material to mineralized it, transforming it into bone
• When osteoblasts are trapped within this matrix, they become osteocytes

Question 16

Osteocytes

Answer 16

• Cytoplasmic projections travel within canaliculi to communicate across gap junctions
• Maintain matrix and ion balance (namely Ca and P)

Question 17

Internal remodeling

Answer 17

• Osteoclasts cut path, osteoblasts secrete matrix and fibers to form new lamellae
• Older osteons fill in central canal

Question 18

Osteoclast formation and function

Answer 18

• Multinucleated osteoclast cells are formed from the fusion of monocytes
• Forms a ruffled border on the bone side, seals the resorption reaction edge

Question 19

How osteoclast degrade bone

Answer 19

-Collagenase and other enzymes digest collagen and dissolve Ca

Question 20

Two forms of both grown

Answer 20

Intramembranous and endochondral

Question 21

Intramembranous ossification overview

Answer 21

• Bone ossified directly from mesenchyme
• Mostly flat bones, mandible, medial clavicle
• Contributes growth of short bones and the thickening of long bones

Question 22

Endochondral ossification overview

Answer 22

• Bone ossified from cartilaginous precursor
• Derived from mesenchyme
• Endochondral growth is the norm for most of the weight bearing bones

Question 23

Intramembranous Ossification steps

-bone grows within condensation of mesenchyme tissue

Answer 23

1. ) ossification center develops (osteoblasts divide and secrete osteoid)- site of new bone formation
2. ) Calcification begins (osteoblasts differentiate into osteocytes trapped in matrix) osteoblasts on the outer edge remain active
3. ) development of trabeculae (spongy) by action of osteoclasts on calcified bone (bone marrow cavity formed)
4. ) development of periosteum on surface of osteoblasts layer

Question 24

Bone grows within what in endochondral ossification

Answer 24

• Cartilaginous mold

- Mold formed in mesenchyme during fetal development

Question 25

Endochondral Ossification steps

Answer 25

1. ) Hyaline cart mold secreted by chondroblasts 2. ) bony collar forms through intramembranous ossification and helps maintain shape 3. ) model lengthens and widens 4. ) blood vessels invade, stimulating growth at the primary ossification center. Vessels fuse to create foramina 5. ) Primary ossification center replaces the zone of calcified cartilage. Calcification kills chondrocytes and accelerates cartilage degen 6. ) osteoclasts create and open medullary cavity as osteoblasts continue to secrete bone 7. ) Secondary ossification center forms around epiphyseal vessels around the time of birth 8. ) Epiphyseal line is where the primary and secondary ossification centers joint; Articular cartilage represents remnant of hyaline cartilage model

Question 26

Bone growth after early development occurs at

Answer 26

Epiphyseal plate

Question 27

Synchondrosis vs Symphysis

Answer 27

Synchondrosis is temporary hyaline cartilage connection between blocks of bone during development Symphysis is permanent cartilaginous connection between bones; hyaline and fibrocartilage

Question 28

Synovial joints

Answer 28

Complex cartilaginous joint with capsule, Articular cavity, and Articular cartilage

Question 29

Articular cavity

Answer 29

Filled w synovial fluid derived from plasma - Lubes and cushions joint movement - Provides nutrients to Articular cartilage

Question 30

Articular Cartilage

Answer 30

—Hyaline - Reduces friction - Absorbs shock

Question 31

Osteoporosis

Answer 31

- Bone resorption exceeds bone formation - Leading to decreased bone mineral density - At risk: immobilized pt and post menopausal women - Routinely tested for bone density using DEXA scans

Question 32

Osteopetrosis

Answer 32

-Genetic disease characterized by dense, heavy bones “marble bones”

Question 33

Causes of Osteopetrosis

Answer 33

- Defective proton pumps/chloride channels - Osteoclasts lack ruffled border - Obliteration of bone marrow cavities causes reduced blood cell formation, anemia, and WBC loss

Question 34

Osteosarcoma

Answer 34

- Arise from osteoprogenitor cells | - Cancer originating directly from bone (primary bone tumor) is uncommon

Question 35

The skeleton is often the site of

Answer 35

-Secondary, metastatic tumors Arising when cancer cells move into bones from malignancies in other organs

Question 36

Common origination of secondary metastatic tumors

Answer 36

Breast, lung, prostate, kidney, thyroid

Question 37

Bone Fractures

Answer 37

Initial repair by fibrocartilage formation, then osteogenic activity

Question 38

Endosteum contains

Answer 38

-Osteoblasts and osteoclast

Question 39

How do osteoblasts become osteocytes

Answer 39

-Trapped in osteoid

Question 40

Bone Fracture steps

Answer 40

1. ) hematoma forms 2. ) Fibrocartilage Callus forms 3. ) Hardy callus forms of WOVEN BONE by ossification 4. ) Woven bone replaced by lamellar