HUMAN ANATOMYFifth Edition
Chapter 1 Lecture
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Skeletal System
Frederic MartiniMichael Timmons
Robert Tallitsch
The Skeletal System:Osseous Tissue and Skeletal Structure
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
Figure 5.1 Structure of a Typical Bone
Cells of Mature Bone
Figure 5.2b,d The Internal Organization of Representative Bones
Compact and Spongy Bone - Histology
Compact Bone
Functional Differences between Compact and Spongy Bone
Figure 5.3a Anatomy of a Representative Bone
• Epiphyses, or ends• The diaphysis, or
shaft• The metaphysis:
– Connecting region between the epiphyses and diaphysis
Figure 5.4 The Periosteum and Endosteum
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
Sex Hormones: (estrogen, progesterone, testosterone)
Calcitriol:
Human Growth Hormone (hGH):
Thyroxine:
Calcitonin:
Parathyroid Hormone:
(Thyroid gland)
(Thyroid gland)
(Parathyroid gland)
(Skin and kidneys)
(Ovaries and Testes)
(Pituitary gland)
Stimulate Osteoblasts
Inhibits Osteoclasts
Stimulates Osteoclasts
Increases Ca2+ absorptionfrom intestine.
Bone disorders• Ricketts• Osteoporosis• Osteomyelitis• Osteomalacia• Pagets Disease• Osgood-Schlatter
[Insert fig 5.5]
Figure 5.5 Intramembranous Ossification
Intramembranous Ossification
ENDOCHONDRAL OSSIFICATION
Animation site
Endochondral Ossification• Bone development from hyaline cartilage• Bone growth in length• Shotgun Biology
Endochondral
Histology - epiphyseal plate
Figure 5.8 Epiphyseal Cartilages and Lines
Endochondral Ossification
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
LONGITUDINAL BONE GROWTH
Epiphysealplate
BONE GROWTH
Figure 5.11 Fracture Repair
Injury and Repair
Table 5.1 Common Bone Marking Terminology
Bone Markings
Figure 5.13 Shapes of Bones
Classification of Bones
Figure 5.14 Examples of Bone Markings
Bone Markings