Bone

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Chapter 5
Bone
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? Bone ??? bone tissue ??
periosteum ?? bone marrow is a
specialized form of connective tissue.
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??????
??? Osteocytes ???? Osteoblasts
???? Osteoclasts ???? Osteoprogenitor
cell
Cells

??? Bone matrix
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Functions
? Support ? Protection ? Storage for
calcium?phosphate
Bone supports fleshy structures.
Bone protects vital organs, such as brain, heart,
lung.
Both calcium and phosphate can be mobilized
from the bone matrix and taken up by the blood as
needed to maintain appropriate levels throughout
the body.
? Harbor the bone marrow
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More Features of Bone
? The exchanges between osteocytes and blood
capillaries depend on communication through
the canaliculi. ? All bones are lined on both
internal and external surface by layers of
tissue containing osteogenic cells. Endosteum
on the internal surface and periosteum on
the external surface. ? Bone is difficult to
section. To observe cells and matrix, A
common technique based on the decalcification
standard fixatives is used.
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???? Bone Cells
There are four cell types in bone
????Osteoprogenitor cell ???Osteocytes
????Osteoblasts ????Osteoclasts
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osteoblasts????
-- They are located at the surfaces of bone. --
They are polarized cells. Quiescent
osteoblasts(not producing bone matrix) become
fattened. -- They are responsible for the
synthesis of the organic components of bone
matrix. Matrix are secreted at the surface,
producing a layer of new matrix, called
osteoid. -- Some osteoblasts are gradually
surrounded by newly formed matrix and become
osteocyte. Lacuna is formed.
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??? osteocyte
?? bone lamell ???
bone lacuna ??? bone
canaliculi.
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???? osteoclast
. Ruffle border??? Clear zone??
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??? Bone Matrix
??? Organic matter
???? Collagen 90 ?? Ground substance
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??? Inorganic matter
?? bone mineral ?????? Ca10

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(?)????Structure of long bones
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??? Periosteum ??? endosteum
External and internal surfaces of bone are
covered by layers of bone-forming cells and
connective tissue called periosteum and ednosteum.
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??? Periosteum
?? ?????????? ?? ???? osteoprogenitor cells
???? osteoprogenitor cell ??????
???Endosteum
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Epiphysis
Epiphysis is composed of spongy bone
covered by a thin layer of compact bone. But on
the articular surface, it is covered by articular
cartilage.
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Diaphysis
In long bones, the shaft ,called diaphysis,
is composed of compact bone, with small component
of spongy bone on its inner surface around the
bone marrow cavity.
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????? Tpyes of long bones
epiphysis
??? Compact bone ??? Spongy bone
diaphysis
epiphysis
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??? Compact bone
--has no cavities. --forms the outside of the
bone.
??? Spongy bone
--has numerous interconnecting cavities. --forms
the interior of the bone.
Compact bone and trabecula have the same
basic histological structure.
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primary bone It is the first bone tissue
to appear in embryonic development and in
fracture repair and other repair
processes. secondary bone is usually
found in adults. It characteristically shows
collagen fibers arranged in lamellae.
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???? Inner circumferential lamellae ????
Outer circumferential lamellae ????? Haversion
system ??? /Osteon ???Intermediate lamellae
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??? Osteon (Haversian System)
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????? osteogenesis
?????(????) Intramembranous ossification
??????(?????) Endochondral ossification

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????Intramembranous Osteogenesis
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?????Endochondral Osteogenesis
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?????Endochondral Osteogenesis
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?????
1.??????? 2.????? 3.????? (1)?????????
(2)?????????????? ????? ?????
????? ????? ???
(3)???????????????
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Epiphyseal cartilage is divided into five zones
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Medical application
Fracture Repair
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Summary
Matrix organic matter, inorganic matter and
a little water
Cells osteoprogenitor cell, osteoblast,
osteocyte and osteoclast
Structure of long bones
periosteum and endosteum, epiphysis, diaphysis
Osteon
Hisgogenesis
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Homework
1. Review the structure of bone. 2. Describe the
two processes of ossification.