The Skeleton

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The Skeleton

• Form follows function

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Five Major Functions

• Provides shape and support
• Enables movement
• Protects vital organs
• Produces blood cells
• Stores minerals

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Vertebrates

• Have backbones that protect spinal cord
• Each backbone is called a vertebra
• Humans have approx. 33 vertebrae

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Human Spinal Column

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Snake Spinal Column

• Snakes have hundreds of vertebrae

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Skulls Protect Brains

• Brain size shapes skull size and shape
• From large to small, form follows function

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Rib Cage

• Protects Heart Lungs
• Ribs connected to breast bone with cartilage to
  allow expansion when breathing

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Human Skeletons

• Humans have approximately 206 bones
• Femur is the longest bone approx. one fourth of
  your height
• Smallest bones in ear, approx. 1/10 inch
• Bones are living approx. 1/3 of bone is living,
  2/3 are minerals (calcium and phosphorus)

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Bone Structure

• Human long bone

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Bone Structure cont.

• Periosteum outer covering, tough protective,
  contains bone forming cells, nerves and blood
  vessels
• Compact bone outer layer of bone, very dense
  and strong
• Spongy bone inner layer at ends of long bones,
  contains air pockets to reduce weight, strong but
  light

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Bone Marrow

• Long bones have internal cavity filled with bone
  marrow
• Makes red and white blood cells
• Approx. 5 billion red cells per day
• Humans have about
• ½ pound bone marrow

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Bone Growth

• Skeleton starts as cartilage
• As you grow cartilage turns to bone
• While growing areas of cartilage remain at ends
  of bones to allow growth in length
• Growth stops when all the cartilage is ossified
  (turned to bone)
• Women stop growing 16- 18 (most growth complete
  by 15
• Men stop growing 18-21

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X-Rays

• X-rays show bones not soft tissue
• This infant skull shows soft spot, room for skull
  to enlarge and allow brain to develop

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Growth Plate

• The growth plate can be seen at the top of the
  shaft of the tibia

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Bone Cells

• Two types
• Osteoblasts make new bone
• Osteoclasts eat away bone
• Work together to make and shape bones
• Bone is continually being replaced and reshaped
  to match stresses

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Joints

• Where two bones meet
• Ends of bones in moveable joints covered in
  cartilage to reduce friction
• Bones held together by ligaments
• Joint surround by capsule, filled with fluid to
  reduce friction

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Joint Structure

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Joints

• Different types of joints allow different ranges
  of motion
• Ball and Socket most range of motion, hip and
  shoulder
• Hinge motion in one plane, knee and elbow
• Gliding small bones glide over one another,
  ankles and wrists

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Joints cont.

• Pivot one bone sits and rotates around another,
  head on your neck
• Immoveable suture joints in skull

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Injuries

• Three major types
• 1. fractures break or crack the bone
• 2. sprain stretches or tears ligaments,
• tendons and/or muscles around joint
• 3. dislocation bone not in its correct
• position in the joint

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Fractures

• Simple break or crack where bone does not break
  the skin
• Compound- break where bone is displaced and
  breaks through the skin

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Sprains

• Injury to soft tissue around the joint
• Very painful

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Dislocations

• Bone is forced out of normal position in the
  joint
• Shoulder
• dislocation

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Bones to Know