The Skeletal System

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Chapter 6 7

• The Skeletal System

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Skeleton

• Axial skeleton
• Skull
• Hyoid bone
• Vertebral column
• Thoracic (rib) cage
• Appendicular skeleton
• Limbs
• Girdles

3
Bone Shapes

• Long
• Upper and lower limbs
• Short
• Carpals tarsals
• Flat
• Ribs, sternum, skull, scapulae
• Irregular
• Vertebrae, facial

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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

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Long Bone Structure

• Medullary cavity
• Red marrow
• Yellow marrow
• Periosteum
• Outer bone surface
• Endosteum
• Lines bone cavities

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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

• What are the two divisions of the skeletal
  system?
• Appendicular Axial Skeleton
• What is the covering of a long bone called? What
  does it cover?
• Periosteum Diaphysis
• What covers the epiphyses of a long bone?
• Articular Cartilage
• What is the hollow middle of a long bone called?
  What is it filled with?
• Medullary cavity bone marrow

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Bone Matrix
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Compact Bone

• Compact bone
• Haversian systemosteons
• Contain living bone cells
• Delivery of nutrients removal of waste
• Lamellae
• Lacunae
• Canaliculi
• Haversian canal
• Volkmanns canals

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Cancellous Bone

• Consists of trabeculae (bony plates)
• Oriented along lines of stress

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Bone Histology

• Bone matrix
• 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

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Bone Cells

• Osteoblasts
• Formation of bone through ossification or
  osteogenesis
• Osteocytes
• Mature bone cells
• Lacunae Spaces
• Canaliculi Canals
• Osteoclasts
• Responsible for bone resorption

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Bone Marrow

• Myeloid tissuesite of blood cell production
• Types of marrow
• Red marrow-blood made
• Yellow marrow-fatty

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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

• What are the parts that make up an osteon?
• -Lamellae, Lacunae, Canaliculi, Haversian Canal
• (blood vessels), Volkmans Canal,
• What makes up spongy bone?
• -Trabeculae
• What are the functions of bone?
• -Support, Protection, Movement, Storage,
• Blood Cell Production

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Bone Development

• Skeleton made of cartilage before birth
• Changes into bone through osteogenesis
• Intramembranous ossificationbone 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

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Bone Development

• Endochondral ossificationforms most bones bones
  formed from cartilage
• Ring of bone forms around middle of cartilage
  boneprimary ossification center
• Secondary ossification centers appear in the
  epiphyses
• Until total growth, some of the bone remains
  cartilage between the diaphysis and
  epiphysesEPIPHYSEAL PLATE

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Bone Growth Resorption

• Osteogenesisnew bone growth
• Osteoblasts create new bone
• Osteoclasts eat away bone in medullary cavity
• Bone growth occurs from small bone
• Adulthoodosteogenesis balances
• Age 35-40process reverses from childhood

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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

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Concept Check??

• What are the three main types of cells found in
  bone?
• -Osteoblasts, Osteocytes, Osteoclasts
• 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

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Skeletal Disorders

• Osteoporosismost common bone disease
• reduces bone mass
• Makes bones porous, brittle, fragile
• Abnormal spinal curvatures
• Lordosisexaggerated curvature of lumbar curve
  sway back
• Kyphosisexaggerated curvature of thoracic curve
  hunchback
• Scoliosisabnormal side-to-side curvature of
  vertebral column
• All due to poor posture or disease

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Spinal Curvatures
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Repair of Fractures

• Bone death to periosteal haversian system bld
  vessels occurfx 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

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Bone Fractures

• Compound fracture- bone is broken and projects
  through the skin
• Simple fracture- bone does not break through skin

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Bone Fractures

• Complete fracturebone is broken entirely across
  width
• Incomplete fracturepart of bone remains joined
• Greenstick fractureone side of bone breaks while
  other side bends
• more common in young kids - lack of
  calcification
• most common in skulls

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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 testosterone

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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