Chapter 6 & 7
The Skeletal System
1
Skeleton
• Axial skeleton
–
–
–
–
Skull
Hyoid bone
Vertebral column
Thoracic (rib) cage
• Appendicular skeleton
– Limbs
– Girdles
2
• Long
Bone Shapes
– Upper and lower limbs
• Short
– Carpals tarsals
• Flat
– Ribs, sternum, skull,
scapulae
• Irregular
– Vertebrae, facial
3
Long Bone Structure
• Diaphysis
– Shaft
– Compact bone
• Epiphysis
– End of the bone
– Cancellous bone
– Covered by articular
cartilage
• Epiphyseal plate
– Growth plate
• Epiphyseal line
– Bone stops growing in
length
4
Long Bone Structure
• Medullary cavity
– Red marrow
– Yellow marrow
• Periosteum
– Outer bone surface
• Endosteum
– Lines bone cavities
5
Flat, Short, Irregular Bones
• Flat bones
– No diaphyses, epiphyses
– Sandwich of cancellous
between compact bone
• Short and Irregular
bone
– Compact bone that
surrounds cancellous bone
center
– No diaphyses and not
elongated
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Concept Check
1. What are the two divisions of the skeletal
system?
–
Appendicular & Axial Skeleton
–
Periosteum; Diaphysis
–
Articular Cartilage
–
Medullary cavity; bone marrow
2. What is the covering of a long bone
called? What does it cover?
3. What covers the epiphyses of a long
bone?
4. What is the hollow middle of a long bone
called? What is it filled with?
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Bone Matrix
8
Compact Bone
• Compact bone
– Haversian system—
osteons
– Contain living bone cells
– Delivery of nutrients &
removal of waste
•
•
•
•
•
Lamellae
Lacunae
Canaliculi
Haversian canal
Volkmann’s canals
9
Cancellous Bone
• Consists of trabeculae
(bony plates)
– Oriented along lines of
stress
10
• Bone matrix
Bone Histology
– Organic: collagen and proteoglycans
– Inorganic: Calcium & Phosphate
• Bone cells
•
•
•
•
•
•
– Osteoblasts- make new bone
– Osteocyte- mature bone cell
– Osteoclasts- break down old bone
Stem Cells or Osteochondral Progenitor Cells
Woven bone: collagen fibers randomly oriented
Lamellar bone: mature bone in sheets
Cancellous bone: trabeculae
Compact bone: dense
Remodeling
– Removing old bone and adding new
11
Bone Cells
• Osteoblasts
– Formation of bone
through ossification or
osteogenesis
• Osteocytes
– Mature bone cells
– Lacunae: Spaces
– Canaliculi: Canals
• Osteoclasts
– Responsible for bone
resorption
12
Bone Marrow
• Myeloid tissue—site
of blood cell
production
• Types of marrow
– Red marrow-blood
made
– Yellow marrow-fatty
13
Skeletal System Functions
•
•
•
•
Support- framework of body
Protection- “boxes” organs enclosed
Movement- muscles attached to bones
Components
– Bones, Cartilage, Ligaments, Tendons
• Storage- (minerals); major reservoir for Ca
&P
• Blood cell production- (hematopoiesis); in
bone marrow
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Concept Check
1. What are the parts that make up an
osteon?
-Lamellae, Lacunae, Canaliculi, Haversian Canal
(blood vessels), Volkman’s Canal,
2. What makes up spongy bone?
-Trabeculae
3. What are the functions of bone?
-Support, Protection, Movement, Storage, &
Blood Cell Production
15
Bone Development
• Skeleton made of cartilage before birth
• Changes into bone through osteogenesis
• Intramembranous ossification—bone formed
within a fibrous membrane; flat bones
– Groups of osteoblasts form centers of
ossification and lay down the matrix
– Collagen gets secreted and calcium salts are
deposited
16
Bone Development
• Endochondral ossification—forms most
bones; bones formed from cartilage
– Ring of bone forms around middle of cartilage
bone—primary ossification center
– Secondary ossification centers appear in the
epiphyses
– Until total growth, some of the bone remains
cartilage between the diaphysis and
epiphyses—EPIPHYSEAL PLATE
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Bone Growth & Resorption
• Osteogenesis—new bone growth
–
–
–
–
–
Osteoblasts create new bone
Osteoclasts eat away bone in medullary cavity
Bone growth occurs from small bone
Adulthood—osteogenesis balances
Age 35-40—process reverses from childhood
18
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
19
Concept Check??
1.
What are the three main types of cells found in
bone?
-Osteoblasts, Osteocytes, Osteoclasts
2. What is the difference b/n intramembranous
ossification & endochondral ossification?
Intramembranous -bone formed within a fibrous
membrane
Endochondral -forms most bones; bones
formed from cartilage
20
Skeletal Disorders
• Osteoporosis—most common bone disease
– reduces bone mass
– Makes bones porous, brittle, fragile
• Abnormal spinal curvatures:
– Lordosis—exaggerated curvature of lumbar
curve “sway back”
– Kyphosis—exaggerated curvature of thoracic
curve “hunchback”
– Scoliosis—abnormal side-to-side curvature of
vertebral column
– All due to poor posture or disease
21
Spinal Curvatures
www.informeddecision.com/ anatomy/abnormal.htm
22
Repair of Fractures
• Bone death to periosteal & haversian
system bld vessels occur—fx hematoma
• Osteoclasts remove dead bone & serves
as a framework for callus formation
• Callus “collars” broken ends & stabilizes
fx for healing
• Callus is replaced by bone
• About 4-6 weeks for entire process
23
Bone Fractures
• Compound fracturebone is broken and
projects through the
skin
• Simple fracturebone does not break
through skin
www.worldortho.com/
24
Bone Fractures
Complete fracture—bone is
broken entirely across
width
Incomplete fracture—part
of bone remains joined
Greenstick fracture—one
side of bone breaks while
other side bends
*more common in young
kids - lack of calcification
*most common in skulls
www.dynomed.com/
www.vh.org/
25
Bone Fractures
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Factors Affecting Bone Growth
• Nutrition
– Vitamin D
• Necessary for absorption of Ca from intestines
• Insufficient causes rickets and osteomalacia
– Vitamin C
• Necessary for collagen synthesis by osteoblasts
• Deficiency results in scurvy
• Hormones
– Growth hormone from anterior pituitary
– Thyroid hormone required for growth of all
tissues
– Sex hormones as estrogen and testosterone27
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
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