Histology of Bone - BM5 NLM1

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What is bone?
A solid, mineralised, vascular connective tissue
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In broad terms, bone tissue consists of four elements. Whatare they?
Periosteum, Endosteum, Bone matrix, Bone cells
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What is the Periosteum?
A layer of dense, vascular connective tissue that covers the outer surface of bone (apart from articulating surfaces)
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True or false: The Periosteum contains some bone stem cells and hence is important for bone growth and repair?
True
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True or false: The Periosteum forms the site of anchorage of tendons & ligaments?
True
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Whatis the Endosteum?
A layer of bone stem & forming cells that line the bone cavities and are important for bone growth, remodelling & repair
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What two substance make up the extra-cellular bone matrix, and in what approximate ratio?
Osteoid (30%), Inorganic Minerals (70%)
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What makes up Osteoid?
Mainly collagen type I embedded in a ground substance of proteoglycans, glycoproteins & water
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What makes up the majority of the inorganic minerals of the bone ECM (hint: aka Hydroxyapatite crystals)?
Calcium phosphate complexes
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What is the main function of the inorganic minerals in the bone ECM?
Binds to and mineralises the Osteoid
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Whatare osteoprogenitor cells?
Bone stem cells
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What are Osteoblasts?
Bone-forming cells that secrete and mineralise the Osteoid
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Where are Osteoblasts located?
Periosteum & Endosteum only
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Where are Osteoprogenitor cells located?
Periosteum & Endosteum only
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What are Osteocytes?
Mature Osteoblasts that are non-dividing, oval, flattened, and located individually in lacunae in the bone ECM
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What is the main role of Osteocytes?
To maintain the bone ECM
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What is the name of the long processes that eminate from Osteocytes?
Canaliculi
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What is the role of canaliculi?
To keep neighbouring Osteocytes in contact via gap junctions
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What are Osteoclasts?
Large, motile, multinucleated cells of bone marrow origin
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What is the function of Osteoclasts?
Bone resorption
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What do Osteoclasts secrete?
Organic acids & proteolytic enzymes
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Where are Osteoclasts located?
On the inner bone surfaces of eroded sites (Howship's lacunae)
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True or flase: Bone remodelling is the reorganisation of bone structure by a balanced process of resorption and deposition of ECM?
True
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True or false: bone remodelling is highly active in the young but negligible in adults?
True
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Cortical bone forms what layer(s)?
The outer layer of long bone & outer plate of flate bone
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True or false: the outer surface of cortical bone is covered by periosteum and the inner layer is lined by the endosteum?
True
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Cortical bone is primarily composed of what?
Lamellar/mature bone tissue
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The lamellar tissue that makes up cortical bone is arranged in Haversian Systems/Osteons. What are Osteons?
Parallel cylindrical units composed of central 'Haversion canals' surrounded by concentric osetocytes
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What do Haversion canals carry?
Blood vessels & nerves only
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What are Volkmann's canals?
The connecting systems between Haversion canals, bone cavities & the periosteum
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True or false: Cancellous/trabecular bone consists of lamellar bone & remodelled osteons arranged into bony plates that occupy the central cavity and bridge the cortical bone?
True
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True or false: in cancellous/trabecular bone, the density of the trabeculae varies in order to provide maximum strength?
True
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What covers the surfaces of trabeculae?
Endosteum
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What is contained in the bone cavities?
Bone marrow, vessels & nerves
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In adults, most bone marrow in bone cavities is what?
Yellow marrow
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Intramembranous ossifcation occurs in which fetal bone type?
Flat bones
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Endochondral ossification occurs in which type of fetal bone?
Long bones
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Other cards in this set

Card 2

Front

In broad terms, bone tissue consists of four elements. Whatare they?

Back

Periosteum, Endosteum, Bone matrix, Bone cells

Card 3

Front

What is the Periosteum?

Back

Preview of the front of card 3

Card 4

Front

True or false: The Periosteum contains some bone stem cells and hence is important for bone growth and repair?

Back

Preview of the front of card 4

Card 5

Front

True or false: The Periosteum forms the site of anchorage of tendons & ligaments?

Back

Preview of the front of card 5
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