The Skeletal SystemPt 1

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The Skeletal SystemPt 1

• Anatomy 2005

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The Skeletal System

• Sitting, standing , walking, picking up a pencil,
  and taking a breath all involve the skeletal
  system. Without the skeletal system, we would
  have no rigid framework to support the soft
  tissues of the body and no system of joints and
  levers so critical for movement.

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The Skeletal System

• The term skeleton is derived from a Greek word
  meaning dried. Despite this concept of the
  skeleton as dry, and nonliving, the skeletal
  system actually consists of dynamic, living
  tissues that are capable of growth, detect pain
  stimuli, adapt to stress, and undergo repair
  after injury.

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The Skeletal System

• The skeletal system consists of bones (206 in
  adults) and joints, along with the cartilage and
  ligaments that occur at the joints.
• The skeletal system serves at least five major
  functions
• The skeleton
• 1. supports the body.
• 2. protects soft body parts.
• 3. produces blood cells
• 4. stores minerals and fat (calcium phosphate)
• 5. permits flexible body movement (w/muscles)

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Anatomy of the bone

• Bones are classified according to shape and size
  long bones, short bones, flat bones, irregular
  bones, and round bones.

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Short Bones

• Short bones are cubes shaped. Their length and
  width are approximately the same.

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Flat Bones

• Flat Bones are platelike and have broad surfaces.

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Irregular Bones

• Irregular Bones have varied shapes with many
  places for connections with other bones.

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Round Bones

• Round Bones are circular.

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Long Bones

• Long bones are longer than they are wide.
• Long bones are normally used for scientific
  investigations.

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Long Bones
A long bone has a shaft (diaphysis) and two ends
(epiphysis), which are covered by articular
cartilage. The diaphysis contains a medullary
cavity with yellow marrow and is bounded by
compact bone.
The epiphyses contain spongy bone with red bone
marrow that produces red blood cells.
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Anatomy of a Bone

• Compact Bone
• Dense bone that contain many cylinder shaped
  units called osteon.
• Here collagenous protein fibers and mineral
  deposits of calcium phosphate salts are found.
• Within each osteon, is a central canal that
  nerves and blood vessels use for passage.

• Spongy Bone
• Sometimes called cancellous bone.
• Red bone marrow produces blood cells.
• In adults, red bone formation (hematopoiesis)
  occurs in the spongy bone of the skull, ribs,
  sternum, vertebrae, and in the ends of the long
  bones.

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Bone Growth and Repair

• Bones are composed of living tissues. It
  develops, grows, remodels, and repairs, itself.
  In all these processes, osteoclasts break down
  bone, and osteoblasts build bone.

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Bone Formation

• Ossification refers to the formation of bone.
• The bones of the skeleton form during embryonic
  development in two distinct ways intramembranous
  and endochondral.
• Intramembranous ossification occurs when bone is
  developed between sheets of fibrous connective
  tissue.
• Endochondral ossification occurs when hyaline
  cartilage is replaced with bone. Most bone of
  humanskeletons form this way.

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Bone Remodeling

• In adults, bone is continually being broken down
  and built up again.
• Osteoslasts derived from monocytes in red bone
  marrow break down bone, remove worn cells, and
  assist in depositing calcium in the blood.
• After about three weeks, the osteoclasts
  disappear, and the bone is repaired by the work
  of osteoblasts.
• As they form new bone, osteoblasts take calcium
  from the blood.
• If adults do not get enough calcium in their diet
  (1000-1500mg daily), then osteoporosis may
  result.

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Bone is a major storage site for calcium in the
body, and movement of calcium into and out of the
bone helps to determine blood calcium levels,
which is critical for normal muscle and nervous
system function.
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Bone Repair

• Fractures are of various types, but repair
  requires four steps 1) hematoma (6-8 hrs), 2)
  fibrocarilaginous callus (3 wks), 3) bony callus
  (3-4 months), and 4)remodeling

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The Skeleton

• The skeleton is divided into the axial skeleton
  and the appendicular skeleton. The tissues of the
  axial and appendicular skeletons are bone (both
  compact and spongy), cartilage (hyaline,
  fibocartilage, and elastic cartilage), and dense
  connective tissue, a type of fibrous connective
  tissue.

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The Skeleton

• The bones of the axial skeleton are colored
  orange, and the bones of he appendicular skeleton
  are colored yellow.

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Axial Skeleton

• The axial skeleton lies on the midline of he body
  and consists of the skull, the hyoid bone, the
  vertebral column, and the thoracic cage.
• The skull is formed by the cranium and the facial
  bones. The cranium includes the frontal bone, two
  parietal bones, one occipital bone, two temporal
  bones, one sphenoid bone, and one ethmoid bone.
  The facial bones include two maxillae, two
  palantine bones, two zygomatic bones, two
  lacrimal bones, two nasal bones, eh vomer bone,
  two inferior nasal conchae, and the mandible.

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The Skull
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The Skullside view
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Axial Skeleton

• The U-shaped hyoid bone is located in the neck.
  It anchors at the tongue and does not articulate
  with any other bone. It suspends from the styloid
  process of the temporal bones by the stylohyoid
  muscles and ligaments.
• The typical verteba has a body , a vertebral arch
  surrounding the vertebral foramen, and a spinous
  process. The first two vertebrae are the atlas
  and axis. The vertebral column has four
  curvatures and contains the cervical, thoracic,
  lumbar, sacral, and coccygeal vertebrae, which
  are separated by intervertebral disks.

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Supports head
Pivots when head moves form side to side
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Axial Skeleton

• The rib cage contains the thoraic vertebrae, ribs
  and associated cartilages, and the sternum.

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Part II will be posted after Xmas!!!