BONES

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BONES

• Chapter 5 Vertebrate Anatomy

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Major Functions of Bone

• Support
• Backbone, etc.
• Protection
• Skull, ribs
• Movement
• Levers against which muscles work
• Mineral storage
• Blood cell formation

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Two Major Types of Bone

• Compact Bone
• Spongy Bone

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Compact Bone

• Dense
• Smooth and solid in appearance

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Spongy Bone

• Honeycombed
• Contains marrow in spaces

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Bones are Classified by Shape

• Long Bones
• Short Bones
• Flat Bones
• Irregular Bones

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Long Bones

• Bones that are longer than they are wide.
• Shaft with two ends
• Primarily compact bone
• Spongy bone at interior
• All bones of the limbs are long bones

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Short Bones

• Roughly cubelike in shape
• Contain mostly spongy bone
• Bones of the wrist and ankle

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Flat Bones

• Thin, flattened and usually a bit curved
• Two roughly parallel compact bone surfaces with
  spongy bone within
• Skull bones scapulae (shoulder blades)

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Irregular Bones

• Bones that fit none of the other classes
• Vertebrae
• Hip bones (pelvic bones)
• These bones have complex shapes
• Consist mainly of spongy bone

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Bones are Organs

• Bones are supplied and associated with many other
  tissues, thus they are organs
• Supplied with nerves, blood vessels, lymph
  vessels
• Covered with membranes (epithelial tissues)

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Structure of a Typical Long Bone

• Diaphysis shaft of the long bone
• Thick collar of compact bone surrounds a central
  marrow cavity
• Epiphysis ends of a long bone
• Exterior of epiphyses are formed by compact bone
• interior contains spongy bone
• Joint surface of each epiphysis is covered with
  articular cartilage
• Epiphyseal line
• Remnant of a structure called the epiphyseal
  PLATE
• Epiphyseal plate is the disk-like plate which
  allows for growth of the long bone during
  childhood
• Cushions opposing bone ends during movement

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Epiphysis detail

• Click here for a detailed view of the epiphysis

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Structure of Long Bone, cont.

• Both internal and external surfaces are covered
  with membranes
• Outer membrane periosteum
• Covers shaft
• Richly supplied with blood vessels, nerves, etc.
• Vessels enter through holes in the bone called
  nutrient foramen
• Membrane also is anchoring point for tendons and
  ligaments
• Inner membrane - endosteum

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Structure of Short, Irregular and Flat bones

• Simple design
• Outside compact bone
• Inside spongy bone

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Blood forming tissue in bones

• Red marrow
• Typically found in cavities of spongy bone in
  long bones and flat bones
• In adults, most blood formation occurs in
• Head of femur/humerus
• Sternum
• Hip bones
• In adults, the marrow cavity containing yellow
  marrow (fat) extends well into the epiphyses of
  most long bones

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Chemical Composition of Bone

• Both inorganic and organic compounds make up bone
• Proper combination of organic and inorganic
  components allows bones to be durable without
  being brittle
• Organic components
• Composed of
• Cells
• Organic portion of matrix
• Provide flexibility and tensile strength
  (strength under tension)
• Inorganic components
• Mineral salts
• Calcium phosphate is the main mineral salt
• Provide hardness

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Bone Markings

• Bones have many bumps, bulges, depressions,
  holes, etc.
• Bumps are typically are points for muscle
  attachment
• Holes are typically points for blood vessels or
  nerves to pass through

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Terms for Bone Markings

• Condyle smooth rounded projection that allows
  for articulation
• Articulation usually a place where two bones
  meet and move against each other, but sometimes
  no movement occurs.
• The image shows the occipital condyles at the
  base of the skull. These articulate with the
  first vertebra.

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Terms for Bone Markings

• Crest
• A narrow ridge of bone
• The images show the sagittal crest of a badger

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Terms for Bone Markings

• Foramen
• A hole
• Usually for passage of blood vessels and/or nerves

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Terms for Bone Markings

• Process
• Any bony prominence or projection
• To the right is the mastoid process
• Also visible is the styloid process
• Both are sites of muscle attachment to the skull

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Terms for Bone Markings

• Spine
• A sharp slender process or projection
• This photo shows the neural spines on vertebrae
  of a dinosaur

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Terms for Bone Markings

• Suture
• A seam
• Irregular lines produced by interlocking bones
• An immovable joint
• The photo shows sutures of the skull

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Terms for Bone Markings

• Fossa
• A depression
• Often an articulating surface
• May meet with a condyle on another bone

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Types of Fractures

• Simple
• only bone damage little or no tissue damage
• Complete break

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Types of Fractures

• Compound bone breaks through the soft tissue to
  the outside
• High risk of infection

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Types of Fractures

• Compression
• This type of bone fracture generally occurs after
  a fall where the vertebral column is compressed
  and then under the extreme pressure cracks or
  breaks.
• Crushing of bone

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Types of Fractures

• Comminuted more than two fragments of bone
  broken off.

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Types of Fractures

• Impacted
• Ends of bone become wedged together

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Types of Fractures

• Spiral
• Fracture caused by twisting force that creates an
  oblique fracture around and through the bone

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Types of Fractures

• Greenstick
• incomplete fracture in which only one side of the
  bone has been broken.

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Types of Fractures

• Depression

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Homeostatic Imbalances of Bone

• Osteoporosis
• Diseases in which bone resorption outpaces bone
  replacement
• Bone marrow becomes porous and lighter
• Spine is most vulnerable also neck of femur
• Estrogen and testosterone are important in
  maintaining normal bone density
• After menopause, estrogen secretion in women
  diminishes and contributes to bone loss
• Other causes of bone loss
• Lack of exercise
• smoking

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Preventing Osteoporosis

• Take calcium beginning at age 35-40
• Drink flouridated water
• Do weight bearing exercise

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Other diseases of bone

• Osteomalacia
• Bones inadequately mineralized
• Rickets
• Bones bend/deform
• Children mostly affected
• Caused by low calcium vitamin D