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15 Cards in this Set

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Bone
- mineralized ECM
- support, protection, and storage (of calcium)
- Matrix
- Osteocytes
Bone Matrix
- collagen I and V (mostly type I)
- GAGs (glycoaminoglycans- provide support for bones- compression)
- other proteins like PDGF and BMP
Cells present in bone
Osteocytes:
- lacunae and canaliculi (canals)
- osteoprogenitor cells --> osteoblasts (start secreting ECM) --> osteocytes (surrounded by matrix)
- bone lining cells (on bone sufaces)
- osteoclasts (bone reabsorption)

- Hydroxyapatite- gives bone its rigidity
Classification of Bone:
- Types of tissue
- Types of bones
* Two types of tissue:
1. Compact (dense)- on outside
2. Spongy (cancellous- on inner area; bone marrow here)

* Types of Bones:
- long bone (ex: femur)
- short bone (ex: wrist bones)
- flat bone (ex: skull)
- irregular bone (ex: vertebral column)
Long Bone
* Regions:
- Epiphysis- end
- Metaphysis- flaring out region
- Diaphysis- long shaft part (mostly compact bone)
Structural components of bone
- periosteum- outer layer on outside of bone.
Layers:
1. Outer layer- high collagen concentration
2. Inner layer- progenitor cells (make bone)

- endosteum- similar lining on inner side and also lines the canals

- marrow- in the cavities of spongy bone (developing RBC found here)
Marrow
Red = marrow involved in making RBC (only in certain regions in adults)

Yellow = inactive in making RBCs, so has higher portions of fats
Osteocytes
- cells imbedded in bone and produce ECM
- live singularly inside lacunae
- cells communicate by diffusion thru canaliculi
Mature Bone has...
- osteons (spiraling circles)
- concentric lamellae
- osteonal canal (Haversian system- where blood vessels go through)
- interstitial lamellae
- circumferential canals
- perforating canals
- caniculi

- Volkmann (or perforating) canals- connect one osteonal canal to another
Bone Cell Types
From Mesenchyme cells:
1. Osteoprogenitors- on outside of bone
2. Osteoblasts- (osteoprogenitors differentiate to form these) located on growing bone
3. Bone Lining Cells- cells that remain on the surface
4. Osteocytes- surrounded by ECM (embedded)

separate:
5. Osteoclasts- involved in bone reabsorption
Bone Cells
* Osteogenitor cells- periosteal and endosteal

* Osteoblasts- produce ECM
Osteocyte Stages
- Quiescent: mature bone

- Formative: actively producing matrix (more machinery is present)

- Resorptive: bone being reabsorbed (lysosomes more abundant)
Bone-Lining Cells
- supportive surface cell that helps osteocytes
- derived from osteoblasts
- periosteal or endosteal cells
Osteoclasts
- large, multinucleate cells that are involved in bone reabsorption/remodeling
- resorption bay- ability to reabsorb bone
- ruffled border and clear zone
Bone Formation methods
2 methods:

1. Intramembranous Ossification- mesenchyme cells to osteoblasts; seen in flat bones and peripheral long/short bones

2. Endochondral Ossification- produce cartilagenous skeleton first and then replace to bone (hyaline cartilage model replaced with bone)