Flashcards in Bone Deck (59)
Is bone a type of connective tissue?
Yes, bone consists of cells, fibers and ground substance like other connective tissues
What is the osteoid?
The unmineralized organic matrix made of fibers and ground substance
What causes bone to become rigid?
The mineralization of the organic matrix by deposition of hydroxyapatite crystals
What are osteoblasts?
Osteoblasts are basophilic and cuboidal (if active, flattened if inactive) and produce the organic extracellular matrix
Where are osteoblasts found?
Surface of bone tissue
What are osteocytes?
Cells that are within bone lacunae to maintain bone matrix
Are osteocytes connected?
Yes. Osteocytes are connected by gap junctions on cell processes
What are osteoclasts?
Multinucleated macrophages that remove bone.
Osteoclasts are acidophilic with a ruffled border, located next to Howship's lacunae
Name an example of a syncytium
What % collagen fibers make up the osteoid?
90% collagen fibers, 10% ground substance
How much mineral does bone consist of?
65% mineral (hydroxyapatite)
Hydroxyapatite gradually deposits on and within the collagen lattice of osteoid
What is the endosteum
Loosely organized connective tissue that has 3 continuous regions and is located within the bone
Diaphyseal endosteum lines the walls of the marrow cavity
Trabecular endosteum covers the trabeculae of spongy bone
Osteonal endosteum goes in to blood vessel canals that are within the bone
What cells produce osteablasts?
Where do osteopregenitor cells originate?
Endosteum and inner layer of periosteum
What is the periosteum?
Thick outer connective tissue layer on bone that consists of a fibrous outer layer and an inner cellular layer
What are Sharpey's fibers?
Collagen fibers that anchor the periosteum to the bone
What is the Haversian system?
The osteon, the basic unit of mature compact bone
What are osteons composed of?
Concentric lamellae or layers of mineralized bone matrix around a central canal that holds blood vessels and connective tissue
How are osteons arranged?
Along the long axis of the bone
Where are osteocytes found in the osteon?
Positioned between the lamellae of the osteons
What are canaliculi?
Tiny channels that connect lacunae
What are Volkmann's (perforating) canals?
Channels in bone that transmit blood vessels from the periosteum or endosteum in to the bone.
This provides a functional connection between the endosteum and the periosteum so there is connective tissue covering all surfaces
How are perforating canals arranged?
Perpendicular to the Haversian canals (osteons)
Describe spongy bone
Spongy bone is found in the heads of long bones and fills most irregular bones
Describe compact bone
Compact bone forms the outer shell of all bone and shafts in long bones
What is intramembranous ossification?
Formation of bone within the mesenchymal tissue without a cartilage model
Most flat bones of the skull develop this way
How does intramembranous ossification work?
Mesenchymal cells differentiate to osteoblasts, osteablasts secrete the osteoid and become trapped.
Bone spicules form and fuse in to solid bone
What is bone formation from the periosteum called?
What is a bone spicule?
A small structure such as a calcium carbonate process that supports the soft tissue of certain invertebrates