The Skeletal System

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The Skeletal System
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Functions

• Supports the body (Like the frame of a house)
• Protects internal organs (skull protects brain,
  ribs protect the lungs)
• Provides for movement (uses a lever system)
• Stores mineral reserves (calcium)
• Provides a site for blood cell formation

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• How many bones does a human have?

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• How many bones does a human have?
• 206

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4 types of bones

• Long found in arms and legs

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• Short wrists and ankles

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• 3. Flat shoulder blades, cranium

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• 4. Irregular vertebrae

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Skeleton is divided into two parts

• Axial skeleton supports the central axis of the
  body. Consists of the skull, the vertebral
  column, and the rib cage.
• Appendicular skeleton- bones of the arms and
  legs, pelvis and shoulder area

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Are bones living tissue?

• Yes!! Bones are a solid network of living cells
  and protein fibers that are surrounded by
  deposits of calcium salts.

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Structure of bones

• Periosteum tough layer of connective tissue
  that surrounds the bone
• Contains blood vessels that carry oxygen and
  nutrients to the bone
• Growth, repair and development is started in this
  membrane.

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Two types of bone (osseous) tissue
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• Compact bone layer beneath the periosteum.
  Dense layer, but not solid.
• Running through compact bone are the Haversian
  canals which are a series of tubes that contain
  blood vessels and nerves.

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• Spongy bone found inside the outer layer of
  compact bone. Less dense tissue.
• Found in the ends of long bones and in the middle
  of short, flat bones.
• Not really soft and spongy, but quite strong
• Organized into a latticework structure near the
  ends of bones to help add strength.

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Other parts of the bone
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• Bone marrow soft tissue found in cavities
  within bones.
• Two types
• Yellow made up mostly of fat cells
• Red produces red blood cells, some kinds of
  white blood cells and platelets

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• Diaphysis central shaft of a long bone
• Epiphysis ends of long bones.
• Articular surface hyaline cartilage that covers
  the end of bones and the place of contact between
  bones

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• Bone processes projections, depressions, or
  holes on the surface of bone helps to provide
  for the attachment of muscle
• Medullary canal cavity within the diaphysis
  contains marrow and blood vessels.

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Development of Bones

• The skeleton of a newborn baby is composed almost
  entirely of a type of connective tissue called
  cartilage. (Also found in parts of the body where
  flexibility is needed ears, nose, ribs)
• That skeleton begins to form during the first 3
  months of pregnancy.

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• Cartilage is replaced by bone during the process
  of bone formation called ossification.
• The maturation processes of bone are complete at
  about age 21.
• The cells that are involved in this process have
  names that begin with osteo which means bone.

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• Osteoblasts create bone
• Osteocytes maintain the cellular activities of
  bone.
• Osteoclasts break down bone and reabsorb it
  into the blood so the calcium salts can be used
  in other parts of the body.
• These three types of cells play an important
  role in maintaining the homeostatic balance in
  the body.

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• Osteoblasts secrete mineral deposits that replace
  the cartilage in developing bones.
• When the osteoblasts become surrounded by bone
  tissue, they mature into osteocytes.
• Long bones have growth plates at either end where
  the growth of cartilage allows the bones to
  lengthen.

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• The new cartilage is replaced by bone tissue
  making the bones longer and stronger.
• During late adolescence or early adulthood, the
  cartilage in the growth plates is replaced by
  bone, the bones become completely ossified and
  the person stops growing.

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What if you break a bone?

• Osteoclasts remove the damaged bone tissue.
• Osteoblasts produce new bone tissue.
• This process can take months because it is slow
  and gradual.

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Compound Fracture
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Joints

• The place where one bone attaches to another
  bone.
• Joints permit bones to move without damaging each
  other.

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Classification of Joints

• Immovable (fixed) joints allow no movement.
  The bones are held together by connective tissue,
  or they are fused.
• Example the bones in the skull

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• Slightly movable joints permit a small amount
  of restricted movement. The bones are separated
  from each other.
• Example joints between adjacent vertebrae

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• Freely movable joints permit movement in one or
  more directions. Grouped according to the shapes
  of the surfaces of the adjacent bones.

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Types of Freely movable joints

• Ball and socket permit circular movement which
  is the widest range of movement.
• Example shoulder

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• Hinge joint permit back and forth movement like
  the opening and closing of a door.
• Example knee

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• Pivot joints allow one bone to rotate around
  another
• Example joint just below the elbow

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• Saddle joints permit one bone to slide in two
  directions.
• Example joints in the hand

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Structure of joints

• In freely movable joints, the ends of the bones
  are covered with a smooth surface layer of
  cartilage that protects the bones as they move
  against each other.
• The joints are also surrounded by a fibrous joint
  capsule that helps hold the bones together while
  still allowing them to move.

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• Joint capsule consists of two layers
• Ligaments layer of strips of tough connective
  tissue. They are attached to the membranes that
  surround bones and hold the bones together.

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• Synovial fluid lubricating film that enables
  the ends of the bones to slip past each other
  smoothly.
• - in some freely movable joints like the knee,
  the synovial fluid is in small sacs called
  bursae. A bursa reduces friction and acts like a
  tiny shock absorber.

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Disorders of the skeletal system

• Bursitis inflammation of the bursa. Symptoms
  are redness, swelling, heat and pain. Caused by
  too much fluid entering the bursa.

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• Arthritis inflammation of one or more joints.
  There are over 100 different types of arthritis
  affecting about 10 percent of the worlds
  population.