Skeletal System

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Skeletal System

• Axial Skeleton

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Introduction

• Skull, vertebral column, thoracic cage (ribs
  sternum)

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• Function
• 1. framework that supports organs
• 2. surface area for muscle attachment

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Skull

• Protects the brain and guards the entrance to the
  digestive and respiratory tract
• Cranial Bones occipital, parietal (2), frontal,
  temporal (2), sphenoid ethmoid bones
• Cranial bones protect the brain

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Skull

• Facial bones
• Function protect and support entrances to
  digestive respiratory tracts
• Superficial bones maxillary, nasal, zygomatic,
  Mandible. Allow for attachment of muscles that
  control facial expressions and help in
  manipulation of food

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• Deeper facial bones palatine vomer (separates
  oral and nasal cavities)
• Several bones of skull have sinuses
• Air filled chambers
• Function
• 1. helps to make bones lighter
• 2. has a mucus membrane that helps moisten and
  clean air

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• Sutures immoveable joints that are connections
  b/n skull bones
• 4 major sutures
• 1. lamboidal suture across posterior surface
  of skull. Separates occipital bone from the 2
  parietal bones.
• 2. coronal suture attaches frontal bone to
  parietal bones on either side
• 3. saggital suture from lamboidal suture to
  coronal suture b/n the 2 parietals
• 4. squamosal suture on each side of the skull
  boundary b/n temporal and parietal bones
• Cranial and Facial Bones see handout

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• Orbital and nasal complexes
• 1. Orbital complex formed form cranial and
  facial bones which surround each eye
• 2. Nasal complex surrounds nasal cavity

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• Skulls of Infants and Children
• Right before birth, brain enlarges and bones
  cannot keep up. So at birth some bones are
  connected by fibrous connective tissue. Flexible
  so brain is not damaged.
• Fontanels fibrous areas b/n cranial bones
• 4 types
• 1. frontal fontanel largest intersection of
  saggital, coronal sutures
• 2. occipital fontanel b/n lamboidal and
  saggital sutures

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• Skulls of Infants and Children
• 3. sphenoidal fontanel junctions b/n
  squamousal and coronal sutures
• 4. mastoid fontanel b/n squamousal and
  lamboidal sutures
• Occipital, sphenoid, and mastoid disappear
  within 1-2 months after birth
• Frontal until 2 years of age

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Vertebral Column

• Adult vertebral column 26 bones 24 vertebrae,
  sacrum coccyx
• Function
• 1. support
• 2. bears weight of head, neck and trunk
• 3. transfers weight to appendicular skeleton
• 4. protects spinal cord
• 5. maintains upright position

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• Divided into
• 7 cervical
• 12 thoracic (articulates with ribs)
• 5 lumbar
• 1 sacrum
• 1 coccyx
• With development, sacrum is made up of 5
  vertebrae until 25 than 1

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• Spinal curvature 4 curves
• Cervical
• Thoracic
• Lumbar
• Sacral
• Primary curves (accomodation curves) thoracic
  and sacral b/c appear late in fetal development
• Secondary curves (compensation curves) lumbar
  and cervical appear several months after birth
• Cervical infant learns to balance head
• Lumbar infants learns to stand

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• Cervical vertebrae
• 7 of them
• C1 atlas nod head yes
• C2 axis rotation to say no
• C7 vertebral prominens

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• Throracic
• 12 of them
• Contain facets for rib articulation
• Lumbar
• 5 largest
• Bear most weight
• Sacrum
• Fused components of 5 sacral vertebrae
• Coccyx
• tailbone

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Thoracic Cage

• Ribs
• 12 pairs
• First 7 true. Connected to sternum
• Ribs 8-12 false b/c do not attach directly to
  sternum
• Ribs 11 12 floating. Attach to vertebrae
• Sternum (breast bone) flat
• Manubrium articulates with clavicles first
  pair of ribs
• Body ribs 2-7
• Xiphoid process smallest part

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