Chapter 6 Skeletal System:
Bones and Bone Tissue
Functions of the
Skeletal System
 Support
 Protection
 Movement
 Storage
 Hemopoiesis
Cartilage

Types
Hyaline cartilage
 Fibrocartilage
 Elastic cartilage


Fiber types
Collagen
 Proteoglycans
 Elastic Fibers

Hyaline Cartilage


Consists of
specialized cells
that produce
matrix
Cells


Chondroblasts
Chondrocytes

Perichondrium

Growth


Appositional
Interstitial
Bone Shapes

Long


Short


Carpals and tarsals
Flat


Upper and lower
limbs
Ribs, sternum,
skull, scapulae
Irregular

Vertebrae, facial
Long Bone Structure

Diaphysis



Epiphysis



End of the bone
Cancellous bone
Epiphyseal plate


Shaft
Compact bone
Growth plate
Epiphyseal line

Bone stops
growing in length
Long Bone Structure

Medullary cavity



Periosteum


Outer bone
surface
Sharpey’s fibers


Red marrow
Yellow marrow
Attachment
Endosteum

Lines bone cavities
Flat, Short, Irregular
Bones

Flat Bones


No diaphyses,
epiphyses
Diploe bone
• Sandwich of cancellous
between compact bone

Short and Irregular
Bone


Compact bone that
surrounds cancellous
bone center
No diaphyses and not
elongated
Bone Histology

Bone Matrix



Organic - Collagen and proteoglycans
Inorganic - Hydroxyapatite(Calcium and
Phosphate)
Bone Cells




Osteoprogenitors (stem cells) – produce osteoblasts
Osteoblasts – produce mineralized bone matrix
Osteocytes – mature bone cells
Osteoclasts – enzymatically break down bone
Bone Matrix
Bone Cells

Osteoblasts


Osteocytes




Formation of bone
through
ossification or
osteogenesis
Mature bone cells
Lacunae: Spaces
Canaliculi: Canals
Osteoclasts

Responsible for
bone resorption
Bone Types

Woven Bone - Collagen fibers randomly
oriented


Formed during fetal development or during
fracture repair
Lamellar Bone – Mature bone in sheets

Cancellous Bone
• Trabeculae – interconnecting rods of bone
• Stress Lines

Compact Bone
• Osteon - concentric lamellae
• Haversion canal, Volkman’s Canal, Lacunae and
Canaliculi
Cancellous Bone

Consists of trabeculae

Oriented along lines of stress
Compact Bone




Central or haversian
canals: Parallel to long axis
Lamellae: Concentric,
circumferential, interstitial
Osteon or haversian
system: Central canal,
contents, associated
concentric lamellae and
osteocytes
Perforating or Volkmann’s
canal: Perpendicular to
long axis
Bone Development

Intramembranous ossification


Develops in a membrane of connective tissue.
Centers of ossification
• Mesenchyme forms osteoprogenitors
• Internal vs external ossification
• Fontanels

Endochondral ossification

Develops in cartilage
• Primary and secondary ossification centers

Both methods of ossification


Produce woven bone that is then remodeled
After remodeling, formation cannot be
distinguished as one or other
Intramembranous
Ossification
Endochondral Ossification

Production of a cartilage model





Embryonic mesenchyme becomes chondroblasts.
Chrondroblasts produce cartilage template with
perichondrium.
Chondrocytes hypertrophy.
Cartilage is calcified and Chondrocytes die.
Ossification of cartilage model




Osteoprogenitor become osteoblasts.
Blood vessels and osteoblasts invade cartilage
template.
Osteoblasts produce bone matrix at ossification
centers
Endochondral bone is remodeled.
Endochondral Ossification
Endochondral Ossification
Endochondral Ossification
Growth in Bone Length

Appositional growth


New bone on old
bone or cartilage
surface
Epiphyseal plate
zones




Resting cartilage
Proliferation
Hypertrophy
Calcification
6.14
Growth in Bone Length
Zones of Bone Growth

Epiphyseal plate




Articular Cartilage



Increases size of epiphysis
Growth in bones that don’t have an epiphyseal
plate
Periosteum


Interstitial growth of cartilage
Appositional growth of bone.
Results in an increase in length of diaphysis
Increases the diameter of bone.
Endosteum

Increases the circumference of trabeculae.
Bone Remodeling


Coverts woven bone into lamellar bone
Bone constantly removed by osteoclasts
and new bone formed by osteoblasts
Growth in Bone Width
Factors that Affect Bone Growth


Genetic Factors
Nutrition

Vitamin D
• Necessary for absorption of calcium from intestines
• Insufficient causes rickets and osteomalacia

Vitamin C
• Necessary for collagen synthesis by osteoblasts
• Deficiency results in scurvy

Hormones

Growth hormone
• Giantism, Acromegaly
• Dwarfism (pituitary vs achondroplastic)


Thyroid hormone
Steroids (estrogen and testosterone)
Bone Repair
Hematoma formation
 Internal Callus formation



Consists of fibrocartilage
External Callus formation

Bone-cartilage collar that stabilizes the
fracture
Cartilage Ossification
 Remodeling of the bone

Bone Repair
Osteogenesis
Imperfecta
Calcium Homeostasis

Bone is the major storage site for
calcium in the body



Calcium moves into bone as
osteoblasts build new bone
Calcium moves out of bone as
osteoclasts break down bone
When osteoclast and osteoblast
activity is balanced, the movement
of calcium in and out is equal
Decreasing blood
Calcium

Parathyroids
Parathyroid
hormone
.
Kidneys
Active
Vitamin D
Small Intestine
Increased Calcium
absorption in
Reabsorption
of Calcium
Bone
Dissolution of
CaPO4 crystals
Increased blood
Calcium
Calcium Homeostasis
Effects of Aging on
Skeletal System
Bone Matrix decreases
 Bone Mass decreases
 Increased bone fractures
 Bone loss causes deformity, loss of
height, pain, stiffness

Stooped posture
 Loss of teeth
