Chapter 5

Report
Skeletal 1
System
Chapter
Lecture
The
Skeletal
System:
Osseous
Tissue and
Skeletal
Structure
HUMAN ANATOMY
Fifth Edition
Frederic Martini
Michael Timmons
Robert Tallitsch
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Introduction - components
• The Bones - about 206
– Bone tissue, or osseous tissue, is the major
component of the skeletal system.
• Bones are dynamic organs made up of several
tissues types.
Introduction - Functions
• The skeletal system has a variety of
functions:
– Support: bones are the body’s infrastructure
– Storage of minerals: calcium salts; 98% of the
body’s calcium is in the bones and adipose
– Hematopoiesis: the bone marrow produces
new blood cells
– Protection: many delicate organs are
surrounded by bone
– Leverage: muscles pull on bone to produce
movement
Structure of Bone
• Bones:
– Support connective tissues:
• Cells
• Solid matrix containing calcium salts
– hydroxyapaptite
– Outer covering called periosteum:
• Continuous with the deep fascia
– Inner cellular lining is called the endosteum.
The Histological Organization
of Mature Bone
• The matrix:
– 2/3 of bone weight is calcium phosphate:
• Hydroxyapatite crystals:
– Very resistant to compression
• Collagen fibers:
– 1/3 of the bone matrix:
• Very resistant to stretch
• Collagen and hydroxyapatite make bone
tissue extremely strong.
• Cells account for about 2–3% of bone tissue.
Cells of Mature Bone
• Osteocytes = mature cells:
– Maintain bone tissue
• Osteoblasts immature, active cells:
– Found on inner and outer surfaces of a bone.
– Osteoblasts produce osteoid.
– The process of making new bone is called
osteogenesis.
• Osteoprogenitor cells:
– Found on inner and outer surfaces of a bone.
– Divide and differentiate to form new osteoblasts.
• Osteoclasts are giant multinucleated cells:
– Perform osteolysis
Specialized Bone Cells
Cells of Mature Bone
Figure 5.1 Structure of a Typical Bone
Compact and Spongy Bone - Histology
Figure 5.2b,d The Internal Organization of Representative Bones
Compact Bone
Functional Differences between Compact and
Spongy Bone
• Epiphyses, or ends
• The diaphysis, or
shaft
• The metaphysis:
– Connecting region
between the
epiphyses and
diaphysis
Figure 5.3a Anatomy of a Representative Bone
The Periosteum and Endosteum
Figure 5.4 The Periosteum and Endosteum
Bone Development and Growth
• Before six weeks of development the
skeleton is cartilage.
• Osteogenesis is bone formation.
– Ossification is bone replacing existing tissue.
• Calcification is the process of depositing
calcium salts into tissues.
Factors Regulating Bone Growth
• Ions:
– Calcium, phosphate, magnesium, citrate,
carbonate, sodium
• Vitamins:
– Vitamins A and C
– Vitamin D derivatives
Factors Regulating Bone Growth
• Parathyroid hormone (PTH) acts to
increase overall availability of calcium ions
in the blood.
– Increased osteoclast activity is the direct
result of PTH levels.
• Calcitonin is the antagonist of PTH.
• Growth hormone and thyroxine increase
osteoblast activity leading to bone growth.
• Sex hormones increase bone growth
dramatically during puberty.
Hormonal Control of Bone Tissue
Human Growth Hormone (hGH): (Pituitary gland)
Thyroxine: (Thyroid gland)
Sex Hormones: (Ovaries and Testes)
(estrogen, progesterone, testosterone)
Stimulate
Osteoblasts
Calcitonin: (Thyroid gland)
Inhibits Osteoclasts
Parathyroid Hormone: (Parathyroid gland)
Stimulates Osteoclasts
Calcitriol: (Skin and kidneys)
Increases Ca2+ absorption
from intestine.
Bone disorders
•
•
•
•
•
•
Ricketts
Osteoporosis
Osteomyelitis
Osteomalacia
Pagets Disease
Osgood-Schlatter
Intramembranous Ossification
[Insert fig 5.5]
Figure 5.5 Intramembranous Ossification
ENDOCHONDRAL OSSIFICATION
Animation site
Endochondral Ossification
• Bone development from hyaline cartilage
• Bone growth in length
• Shotgun Biology
Endochondral
Histology - epiphyseal plate
Endochondral Ossification
Figure 5.8 Epiphyseal Cartilages and Lines
STEPS OF ENDOCHONDRAL OSSIFICATION
•1. The perichondrium
covering the hyaline
cartilage “bone” is
infiltrated with blood
•vessels.
•2. Osteoblasts secrete
osteoid against the hyaline
cartilage diaphysis,
encasing it in a bony
collar.
STEPS OF ENDOCHONDRAL OSSIFICATION
•3. Chondrocytes
within the diaphysis
hypertrophy and the
surrounding cartilage
matrix starts to be
calcified.
•4. The chondrocytes,
however, die and the
matrix begins to
deteriorate.
STEPS OF ENDOCHONDRAL OSSIFICATION
•5. In month 3, the
forming cavities are
invaded by a collection
of elements called the
periosteal bud.
•6. The entering
osteoclasts partially
erode the calcified
cartilage matrix.
STEPS OF ENDOCHONDRAL OSSIFICATION
STEPS OF ENDOCHONDRAL OSSIFICATION
• 7. Osteoblasts
secrete osteoid
around the
remaining
fragments of
hyaline cartilage
forming
trabeculae of
spongy bone.
STEPS OF ENDOCHONDRAL OSSIFICATION
• 8. As the primary
ossification center
enlarges, osteoclasts
break down the newly
formed spongy bone
and open up a
medullary cavity in
the center of the
diaphysis.
STEPS OF ENDOCHONDRAL OSSIFICATION
•9. The epiphyses remain
formed of cartilage until
shortly before or after
birth.
•10. Secondary
ossification centers form
in the epiphyses. The
events of ossification are
like the events of the
diaphysis, except, that
spongy bone mains in the
internal and no medullary
cavity forms.
STEPS OF ENDOCHONDRAL OSSIFICATION
STEPS OF ENDOCHONDRAL OSSIFICATION
Epiphyseal
plate
LONGITUDINAL BONE GROWTH
BONE GROWTH
Injury and Repair
Figure 5.11 Fracture Repair
Bone Markings
Table 5.1 Common Bone Marking Terminology
Classification of Bones
Figure 5.13 Shapes of Bones
Bone Markings
Figure 5.14 Examples of Bone Markings

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