Download Chapter 6: Osseous Tissue and Bone Structure

Chapter 6: Osseous Tissue and
Bone Structure
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Cells of Bone

Osteoprogenitor -precursor to osteoblast

Osteoblasts -produce bone matrix

Osteocytes -trapped osteoblast

Osteoclasts -dissolve bone matrix
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Compact Verses Spongy Bone
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Long Bone Structure
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Flat Bone Structure
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Ossification
•
Endochondrial
•
Intramembranous
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Intermembranous
•
Typical of flat bones
•
Ossification of mesenchymal cells
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Endochondral Ossification
• Long bones
• Hyaline cartilage breaks down
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Postnatal Bone Growth
• Interstitial growth:
• Increase bone length (adolescence)
• Appositional growth:
• Increase thickness and remodeling of all bones
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Epiphysial Plate
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Bone Growth
• Growth hormone stimulates cell division
• Thyroid hormone modulates growth hormone
• Testosterone and estrogens (at puberty)
– Promote adolescent growth spurts
– End growth by inducing epiphyseal plate closure
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Bone Resorption
• Osteoclasts secrete
– Lysosomal enzymes (digest organic matrix)
– Acids (convert calcium salts into soluble forms)
• Dissolved matrix is transcytosed across
osteoclast, enters interstitial fluid and then
blood
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Control of Remodeling
• What controls continual remodeling of bone?
– Hormonal mechanisms that maintain calcium
homeostasis in the blood
– Mechanical and gravitational forces
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Bone Remodeling
•
Balance between resorption and formation
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Bone growth
Cartilage
grows here.
Bone remodeling
Articular cartilage
Epiphyseal plate
Cartilage
is replaced
by bone here.
Cartilage
grows here.
Cartilage
is replaced
by bone here.
Copyright © 2010 Pearson Education, Inc.
Bone is
resorbed here.
Bone is added
by appositional
growth here.
Bone is
resorbed here.
Figure 6.11
Hormonal Control of Blood Ca2+
• Calcium is necessary for
– Transmission of nerve impulses
– Muscle contraction
– Blood coagulation
– Secretion by glands and nerve cells
– Cell division
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Hormonal Control of Blood Ca2+
• Primarily controlled by parathyroid hormone (PTH)
• Calcitonin has minor role
• Leptin influences bone remodeling
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Exercise and Bones
•
Builds stronger bone
•
Inactivity leads to weak bones
–
Astronauts shrink as much as 4 inches
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Bone Repair
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Homeostatic Imbalances
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Heterotrophic Bones -abnormal bone formation
–
Tendons, joints, kidneys, testes, sclera of the eye
–
Fibrodysplasia Ossificans Progressiva
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Dwarfism -pituitary failure
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Acromegaly -bone/cartilage thickening along facial contours
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Gigantism -growth hormone overproduction
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Marfan Syndrome -excessive cartilage at epiphyseal plates
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Rickets -vitamin D deficiency
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Paget's disease
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Osteoporosis
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Osteoporosis
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