Chapter 6: Osseous Tissue and Bone Structure

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Chapter 6 Osseous Tissue and Bone Structure
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The Skeletal System

• Skeletal system includes
• bones of the skeleton
• cartilages, ligaments, and connective tissues

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Functions of the Skeletal System

• Support
• Storage of minerals (calcium)
• Storage of lipids (yellow marrow)
• Blood cell production (red marrow)
• Protection
• Leverage (force of motion)

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Bone Shapes

• Long bones
• Flat bones
• Sutural bones
• Irregular bones
• Short bones
• Sesamoid bones

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Long Bones

• Are long and thin
• Are found in arms, legs, hands, feet, fingers,
  and toes

Figure 61a
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Flat Bones

• Are thin with parallel surfaces
• Are found in the skull, sternum, ribs, and scapula

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Sutural Bones

• Are small, irregular bones
• Are found between the flat bones of the skull

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Irregular Bones

• Have complex shapes
• Examples
• spinal vertebrae
• pelvic bones

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Short Bones

• Are small and thick
• Examples
• ankle
• wrist bones

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Sesamoid Bones

• Are small and flat
• Develop inside tendons near joints of knees,
  hands, and feet

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Bone Markings

• Depressions or grooves
• along bone surface
• Projections
• where tendons and ligaments attach
• at articulations with other bones
• Tunnels
• where blood and nerves enter bone

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Bone Markings
Table 61 (1 of 2)
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Bone Markings
Table 61 (2 of 2)
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Characteristics of Bone Tissue

• Periosteum
• covers outer surfaces of bones
• consist of outer fibrous and inner cellular
  layers
• Dense matrix, containing
• deposits of calcium salts
• bone cells within lacunae organized around blood
  vessels
• Canaliculi
• form pathways for blood vessels
• exchange nutrients and wastes

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Long Bones

• Diaphysis
• the shaft
• Epiphysis
• wide part at each end
• articulation with other bones
• Metaphysis
• where diaphysis and epiphysis meet

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Flat Bones

• Resembles a sandwich of spongy bone
• Between 2 layers of compact bone

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Compact Bone
The osteon is The basic unit of mature compact
bone Osteocytes are arranged in concentric
lamellae Around a central canal (Haversian canal)
containing blood vessels
Figure 65
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Spongy Bone

• Does not have osteons
• The matrix forms an open network of trabeculae
• Trabeculae have no blood vessels

Figure 66
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Red Marrow

• The space between trabeculae is filled with red
  bone marrow
• which has blood vessels
• forms red blood cells
• and supplies nutrients to osteocytes

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Yellow Marrow

• In some bones, spongy bone holds yellow bone
  marrow
• is yellow because it stores fat

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Bone Cells

• Make up only 2 of bone mass
• osteocytes
• osteoblasts
• osteoprogenitor cells
• osteoclasts

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Osteoblasts

• Immature bone cells that secrete matrix compounds
  (Make new bone)

Figure 63 (2 of 4)
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Osteocytes

• Mature bone cells that maintain the bone matrix
• Are between layers (lamellae) of matrix
• Connect by canaliculi in lamellae
• Do not divide

Figure 63 (1 of 4)
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Osteocyte Functions

• To maintain protein and mineral content of matrix
• To help repair damaged bone by turning into
  osteoblasts.

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Osteoprogenitor Cells

• Stem cells that divide to produce osteoblasts
• Are located in inner, cellular layer of
  periosteum (endosteum)

Figure 63 (3 of 4)
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Osteoclasts

• Secrete acids and protein-digesting enzymes to
  dissolve old bone matrix in a process called
  osteolysis

Figure 63 (4 of 4)
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Homeostasis

• Bone building (by osteoblasts) and bone recycling
  (by osteoclasts) must balance
• more breakdown than building, bones become weak
• exercise causes osteoblasts to build more bone
• Lack of exercise causes bone loss