Download Bone tissue

Introduction
• Human skeleton initially cartilages and fibrous membranes
• Hyaline cartilage is the most abundant cartilage
• By age 25 the skeleton is completely hardened
• 206 bones make up the adult skeleton (20% of body
mass)
• 80 bones of the axial skeleton
• 126 bones of the appendicular skeleton
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Bone Classification
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• Bone Classification:
• Long Bones
(b)
• Short Bones
• Sesamoid Bones
• Flat Bones
• Irregular Bones
• Wormian Bones
(sutural)
(c)
(d)
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(a)
(e)
Classification of Bones
 Long bones
 Typically longer than wide
 Have a shaft with heads at both ends
 Contain mostly compact bone
• Examples: Femur, humerus
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 5.4a
Classification of Bones
 Short bones
 Generally cube-shape
 Contain mostly spongy bone
 Examples: Carpals, tarsals
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 5.4b
Classification of Bones on the
Basis of Shape
Figure 5.1
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Slide 5.4c
Classification of Bones
 Flat bones
 Thin and flattened
 Usually curved
 Thin layers of compact bone around a layer
of spongy bone
 Examples: Skull, ribs, sternum
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 5.5a
Classification of Bones
 Irregular bones
 Irregular shape
 Do not fit into other bone classification
categories
 Example: Vertebrae and hip
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 5.5b
Classification of Bones on the
Basis of Shape
Figure 5.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 5.5c
Parts of a Long Bone
• Epiphysis
• Distal
• Proximal
• Diaphysis
• Metaphysis
• Compact bone
• Spongy bone
• Articular cartilage
• Periosteum
• Endosteum
• Medullary cavity
• Trabeculae
• Bone marrow
• Red marrow and yellow marrow
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Epiphyseal plates
Articular cartilage
Proximal
epiphysis
Spongy bone
Space containing
red marrow
Endosteum
Compact bone
Medullary cavity
Yellow marrow
Diaphysis
Periosteum
Distal
epiphysis
Femur
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Microscopic Structure
• Bone cells are called osteocytes
• in a lacuna
• Osteocytes transport nutrients and wastes by
cellular processes in canaliculi
• The extracellular matrix of bone is largely collagen
and inorganic salts
• Collagen gives bone resilience & strength
• Inorganic salts make bone hard
10
Compact Bone
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• Osteon
aka Haversian System
• Central canal
• Perforating canal aka
Volkmann’s canal
• Osteocytes
• Lamellae
• Lacunae
• Bone matrix
• Canaliculi
Osteon
Central canal
containing blood
vessels and nerves
Endosteum
Periosteum
Nerve
Blood
vessels
Pores
Central
canal
Perforating
canal
Compact
bone
Nerve
Blood
vessels
Nerve
Trabeculae
Bone matrix
Canaliculus
Osteocyte
Lacuna
(space)
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Microscopic Anatomy of Bone
Figure 5.3
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide
Microscopic Anatomy of Bone
 Lacunae
 Cavities containing
bone cells
(osteocytes)
 Arranged in
concentric rings
 Lamellae
 Rings around the
central canal
 Sites of lacunae
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 5.3
Slide
Microscopic Anatomy of Bone
 Canaliculi
 Tiny canals
 Radiate from the
central canal to
lacunae
 Form a transport
system
Figure 5.3
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide
Spongy Bone
• Spongy bone is aka cancellous bone
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Spongy
bone
Compact
bone
(a)
Remnant of
epiphyseal plate
Spongy bone
Compact bone
(b)
(c)
Spongy
bone
Compact
bone
a: © Ed Reschke; b,c: Courtesy of John W. Hole, Jr.
15
Bone Development
and Growth
• Parts of the skeletal system begin to develop
during the first few weeks of prenatal development
• Bones replace existing connective tissue in one of
two ways:
• As intramembranous bones
• As endchondral bones
16
Intramembranous Bones
• Intramembranous Bones
• These bones originate within sheetlike layers of
connective tissues
• They are the broad, flat bones
• Skull bones (except mandible)
• Are known as intramembranous bones
17
Endochondral Bones
• Endochondral Bones
• Bones begin as hyaline cartilage
• Form models for future bones
• These are most bones of the skeleton
• Are known as endochondral bones
18
Endochondral Ossification
• Hyaline cartilage model
• Epiphyseal plate
• Primary ossification center
• Osteoblasts vs. osteoclasts
• Secondary ossification centers
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Cartilaginous
model
Developing
periosteum
Remnants of
epiphyseal
plates
Secondary
ossification
center
Compact bone
developing
Spongy
bone
Epiphyseal
plates
Blood
vessel
Calcified
cartilage
(a)
(b)
Medullary
cavity
(c)
Medullary
cavity
Compact
bone
Medullary
cavity
Remnant of
epiphyseal
plate
Epiphyseal
plate
Primary
ossification
center
Secondary
ossification
center
(d)
Articular
cartilage
Spongy
bone
Articular
cartilage
(e)
(f)
19
Growth at the Epiphyseal Plate
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• First layer of cells
Bone tissue
of epiphysis
• Closest to the end of
epiphysis
• Resting cells
• Anchors epiphyseal plate
to epiphysis
• Zone of resting cartilage
1 Zone of
resting
cartilage
2 Zone of
proliferating
cartilage
3 Zone of
hypertrophic
cartilage
• Second layer of cells
4 Zone of
calcified
cartilage
• Many rows of young
Ossified
bone of
diaphysis
cells
• Undergoing mitosis
• zone of proliferating
cartilage
(a)
(b)
b: © The McGraw-Hill Companies, Inc./Al Telser, photographer
20
Growth at the Epiphyseal Plate
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• Third layer of cells
Bone tissue
of epiphysis
• Older cells
• Left behind when new
cells appear
• Cells enlarging and
becoming calcified
• zone of hypertrophic
cartilage
1 Zone of
resting
cartilage
2 Zone of
proliferating
cartilage
3 Zone of
hypertrophic
cartilage
• Fourth layer of cells
4 Zone of
calcified
cartilage
• Thin
Ossified
bone of
diaphysis
• Dead cells
• Calcified extracellular
matrix
• zone of calcified
cartilage
(a)
(b)
b: © The McGraw-Hill Companies, Inc./Al Telser, photographer
21
Homeostasis of Bone Tissue
• Bone Resorption – action of osteoclasts and parathyroid
hormone aka parathormone aka PTH
• Bone Deposition – action of osteoblasts and calcitonin
• Occurs by direction of the thyroid and parathyroid glands
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Developing
medullary
cavity
Osteoclast
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© Biophoto Associates/Photo Researchers, Inc.
Factors Affecting Bone
Development, Growth and Repair
• Deficiency of Vitamin A – retards bone development
• Deficiency of Vitamin C – results in fragile bones
• Deficiency of Vitamin D – rickets, osteomalacia
• Insufficient Growth Hormone – dwarfism
• Excessive Growth Hormone – gigantism, acromegaly
• Insufficient Thyroid Hormone – delays bone growth
• Sex Hormones – promote bone formation; stimulate ossification
of epiphyseal plates
• Physical Stress – stimulates bone growth
23
Bone Function
• Bones shape, support, and protect body structures
24
Support, Protection,
and Movement
• Support, Movement & Protection
• Gives shape to head, etc.
• Supports body’s weight
• Protects lungs, etc.
• Bones and muscles interact
• When limbs or body parts move
25
Blood Cell Formation
• Blood Cell Formation
• Also known as hematopoiesis
• Occurs in the red bone marrow
26
Inorganic Salt Storage
• Inorganic Salt Storage
• Calcium
• Phosphate
• Magnesium
• Sodium
• Potassium
27