Advanced Biology

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Advanced Biology

• Bone Structure

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Long Bone

• Shaft Surrounds Marrow Cavity. Contains Yellow
  Marrow

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Long Bone

• Bone Ends Covered by Articular Cartilage
  (hyaline)
• B/W diaphysis and epiphysis is an epiphyseal line

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Membranes

• Periosteum Double layered, around whole thing.
  Outer layer, fibrous, is dense irregular CT.
  Inner layer, osteogenic, is osteocytes and
  osteoclasts

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Membranes

• Periosteum rich in nerve fibers, lymphatic
  vessels, BV. Enter shaft of bone via the
  Nutrient Foramen. Secured by Sharpeys Fibers.

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Membranes

• Endosteum Covering internal bone. Covers
  trabeculae (little beams) of spongy bone and
  lines the canal that passes through compact bone

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Short, Irr, Flat Bones

• Consist of thin plates of compact bone on
  outside, spongy bone within.
• Flat bones spongy bone is called Diploe.

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Microscopic StructureCompact Bone

• Osteon elongated cylinder. Tiny weight bearing
  pillars.
• A group of hollow tubes of bone matrix, one
  outside the other.
• Lamella Matrix tube (see fig 6.6)

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Compact Bone

• Collagen fibers of adjacent lamella run opposite,
  resist tension

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Compact Bone

• Haversian Canals Run length of bone. Contains
  BV and NF
• Volkmanns Canals Run Perpendicular to HC,
  transport BV through bone

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Spongy Bone

• Trabeculae align along lines of stress, help
  resist stress
• Only a few layers thick, containing lamellae and
  osteocytes connected by canaliculi (see fig 6.5)

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Bone Development

• An Ossification center appears in the fibrous CT
  membrane (Fig 6.7, 1)

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Bone Development

• Bone Matrix is secreted in the membrane (6.7, 2)

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Bone Development

• Woven bone and periosteum form (6.7, 3)

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Bone Development

• Bone Collar of Compact Bone forms (6.7, 4)
• Flat bones

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Bone Development

• Formation of bone collar around hyaline cartilage
  (Fig 6.8, 1)

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Bone Development

• Deterioration cartilage matrix (6.8, 2)

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Bone Development

• Invasion of internal cavities by the periosteal
  bud and spongy bone formation (6.8, 3)
• 1-3 happen during fetal development)

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Bone Development

• Formation of the medullary cavity as ossification
  continues appearance of secondary ossification
  centers in epiphyses (6.8, 4)
• Just before or after birth

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Bone Development

• Ossification of epiphyses when completed,
  hyaline cartilage remains only in the epiphyseal
  plates
• Growth during childhood and adolescence

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Growth in Long Bones

• See fig 6.10

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Bone Fractures

• Simple
• Bone breaks cleanly, but does not penetrate skin
• Sometimes called a Closed fracture

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Bone Fractures

• Compound
• Broken ends of the bone protrude through soft
  tissues and the skin
• May result in bone infection

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Bone Fractures

• Comminuted
• Bone fragments into many pieces
• Common in the aged

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Bone Fractures

• Compression
• Bone is crushed
• Common in porous bones

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Bone Fractures

• Depressed
• Broken bone portion is pressed inward
• Typical of skull fracture

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Bone Fractures

• Impacted
• Broken bone ends are forced into each other
• Occurs when one tries to catch themselves during
  a fall

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Bone Fractures

• Spiral
• Ragged break occurs when excessive twisting
  forces are applied to a bone
• Common sports fracture

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Bone Fractures

• Greenstick
• Bone breaks incompletely, much in the way a green
  twig breaks
• Common in children whose bones are more flexible