Bones and Skeletal Tissue

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Chapter 6,7 8

• Bones and Skeletal Tissue

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Bones and Cartilages of the Human Body
Figure 6.1
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How are bones classified?

• Axial skeleton bones of the skull, vertebral
  column, and rib cage
• Appendicular skeleton bones of the upper and
  lower limbs, shoulder, and hip

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Long bones

• Long bones longer than they are wide (e.g.,
  humerus)

Figure 6.2a
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Short bones

• Short bones
• Cube-shaped bones of the wrist and ankle
• Bones that form within tendons (e.g., patella)

Figure 6.2b
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Flat bones

• Flat bones thin, flattened, and a bit curved
  (e.g., sternum, and most skull bones)

Figure 6.2c
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Irregular bones

• Irregular bones bones with complicated shapes
  (e.g., vertebrae and hip bones)

Figure 6.2d
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What are the functions of bones?

• Support form the framework that supports the
  body and cradles soft organs
• Protection provide a protective case for the
  brain, spinal cord, and vital organs
• Movement provide levers for muscles
• Mineral storage reservoir for minerals,
  especially calcium and phosphorus
• Blood cell formation hematopoiesis occurs
  within the marrow cavities of bones

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What is the Gross Anatomy of Bones?

• Compact bone dense outer layer
• Spongy bone honeycomb of trabeculae (little
  beams) filled with red bone marrow

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What is the structure of a long bone?

• Diaphysis
• Tubular shaft that forms the axis of long bones
• Composed of compact bone that surrounds the
  medullary cavity
• Yellow bone marrow (fat) is contained in the
  medullary cavity

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Structure of Long Bone

• Epiphyses
• Expanded ends of long bones
• Exterior is compact bone, and the interior is
  spongy bone
• Joint surface is covered with articular (hyaline)
  cartilage
• Epiphyseal line separates the diaphysis from the
  epiphyses

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Structure of Long Bone
Figure 6.3a,b
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What are the bone membranes?

• Periosteum double-layered protective membrane
• Outer fibrous layer is dense regular CT
• Inner osteogenic layer is composed of osteoblasts
  and osteoclasts
• Richly supplied with nerve fibers, blood, and
  lymphatic vessels, which enter the bone via
  nutrient foramina
• Sharpeys fibers secures the underlying bone to
  the periosteum. They are tufts of collagen
  fibers.
• Endosteum delicate membrane covering internal
  surfaces of bone

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Structure of Long Bone
Figure 6.3a, c
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What is the structure of short, irregular, and
flat bones?

• Thin plates of periosteum-covered compact bone on
  the outside with endosteum-covered spongy bone on
  the inside
• Have no diaphysis or epiphyses
• Contain bone marrow between the trabeculae

Figure 6.4
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Where is the location of hematopoietic tissue
(Red Marrow)?

• In infants
• Found in the medullary cavity and all areas of
  spongy bone
• In adults
• Found in the middle of flat bones, and the head
  of the femur and humerus

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What is microscopic structure of bone compact
bone?

• Haversian system, or osteon the structural unit
  of compact bone
• Lamella weight-bearing, column-like matrix
  tubes composed mainly of collagen
• Haversian, or central canal central channel
  containing blood vessels and nerves
• Volkmanns canals channels lying at right
  angles to the central canal, connecting blood and
  nerve supply of the periosteum to that of the
  Haversian canal

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Microscopic Structure of Bone Compact Bone

• Osteocytes mature bone cells
• Lacunae small cavities in bone that contain
  osteocytes
• Canaliculi hairlike canals that connect lacunae
  to each other and the central canal

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Microscopic Structure of Bone Compact Bone
Figure 6.5a, b
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What is the chemical composition of bone?
(Organic)

• Osteoblasts bone-forming cells
• Osteocytes mature bone cells
• Osteoclasts large cells that reabsorb or break
  down bone matrix

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Chemical Composition of Bone Inorganic

• Hydroxyapatites, or mineral salts
• Sixty-five percent of bone by mass
• Mainly calcium phosphates
• Responsible for bone hardness and its resistance
  to compression

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What are the types of markings found on bones?

• Bulges, depressions, and holes that serve as
• Sites of attachment for muscles, ligaments, and
  tendons
• Joint surfaces
• Conduits for blood vessels and nerves

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Bone Markings Projections Sites of Muscle and
Ligament Attachment

• Tuberosity rounded projection
• Crest narrow, prominent ridge of bone
• Trochanter large, blunt, irregular surface
• Line narrow ridge of bone

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Bone Markings Projections Sites of Muscle and
Ligament Attachment

• Tubercle small rounded projection
• Epicondyle raised area above a condyle
• Spine sharp, slender projection
• Process any bony prominence

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Bone Markings Projections That Help to Form
Joints

• Head bony expansion carried on a narrow neck
• Facet smooth, nearly flat articular surface
• Condyle rounded articular projection
• Ramus armlike bar of bone

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Bone Markings Depressions and Openings

• Meatus canal-like passageway
• Sinus cavity within a bone
• Fossa shallow, basinlike depression
• Groove furrow
• Fissure narrow, slitlike opening
• Foramen round or oval opening through a bone

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How do bones develop?

• Osteogenesis and ossification the process of
  bone tissue formation, which leads to
• The formation of the bony skeleton in embryos
• Bone growth until early adulthood
• Bone thickness, remodeling, and repair

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Formation of the Bony Skeleton

• Begins at week 8 of embryo development
• Intramembranous ossification bone develops from
  a fibrous membrane
• Endochondral ossification bone forms by
  replacing hyaline cartilage

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Intramembranous ossification
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Functional Zones in Long Bone Growth

• Growth zone cartilage cells undergo mitosis,
  pushing the epiphysis away from the diaphysis
• Transformation zone older cells enlarge, the
  matrix becomes calcified, cartilage cells die,
  and the matrix begins to deteriorate
• Osteogenic zone new bone formation occurs

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Long Bone Growth and Remodeling

• Growth in length cartilage continually grows
  and is replaced by bone as shown
• Remodeling bone is reabsorbed and added by
  appositional growth as shown

Figure 6.10
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Fracture Repair
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