Bone Flashcards
Define bone
A rigid & specialized connective tissue with a mineralized ground substance
Functions of bone
- Support soft tissue
- Protective encasement of soft tissue
- Reservoir for minerals (Ca2+)
- Levers for muscles
- House bone marrow (hematopoesis)
What are the organic components of the bone matrix?
- Collagen type 1
- Glycoproteins (osteopontin, sialoprotein, osteocalcin)
- Aggrecans

Osteopontin
Binding sites for mineral components and integrins of bone cells
Sialoprotein
Assist in binding bone cells to Matrix
osteocalcin
Binds Ca2+
Aggrecans
Smaller with fewer glycosaminoglycans side chains
Basophilic staining (Matrix appears to stain acidophilic due to the abundance of collagen)

Hydration shell
Forms around hydroxyapatite crystals, allowing ion exchange between the crystals and extracellular fluid
What would occur if bone were decalcified (hydroxyapatite crystals removed)?
It becomes extremely flexible (the hardness is due to hydroxyappetite’s association with collagen)



How does bone mineralization begin?
The secretory vesicles in the osteoblast

Name the two classifications of bone tissue.
- Compact AKA dense bone
- Spongy AKA cancellous bone

What are the spaces of spongy bone filled with?
Blood vessels and Marrow
(note the location of spongy versus compact bone)

What is this classification of bone?
Compact AKA dense bone

The outer layer of periosteum contains _____. The inner layer contains _____.
- dense irregular collagenous connective tissue
- osteoprogenitor cells

Endosteum
- Lines bone cavities
- Then connective tissue with a single layer of osteoprogenitor cells and osteoblasts
Cells of bone
- osteoblast
- osteoclast
- osteocyte
- osteoprogenitor cells

Histology of osteoblasts

Cube or column shaped when active; flat when inactive
Under processes connect osteoblasts with neighboring osteoblast (gap junctions in between)

Lacuna
Space in The Matrix which is occupied by an osteocyte cell

Canaliculi
- Small tunnels radiating from each Lacuna (space in matrix which is occupied by osteocytes cell)
- Occupied by slender extensions from a pair of neighboring osteocytes
(denoted as C in micrograph)

Function of canaliculi
Important for passage of ions, nutrients, hormones, and other molecules to cell deep within the matrix


Green: Canaliculi
Red: Haversian Canal
Blue arrow: lacunae (space containing osteocyte
L: Lamellae (concentric rings
Osteoprogenitor cells are derived from _____.
mesenchyme stem cells
(differentiate into osteoblast or chondroblasts; active during growth & remodelin after fracture)

Location of osteoprogenitor cells
- Inner layer of periosteum
- Endosteum
- Lining of haversian canals
(pale nuclei & little cytoplasm. they are primarily identified by location)































































