Skeletal System

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Chapter 10

• Skeletal System

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Outline

• Functions of the Skeletal System
• Attachment for muscles
• Support and protection
• Blood cell formation
• Storage of minerals, salts, and fat
• Tissues of the Skeletal System
• Bone Growth and Repair
• Bone Development
• Bone Repair
• Bones of the Skeleton
• Bone Classification
• Axial and Appendicular Skeleton
• Articulation
• Movements Permitted by Joints

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Tissues of the Skeletal System

• Bone.
• Composition bone,
• cartilage,
• and fibrous
• connective tissue
• Compact bone is highly organized and composed of
  tubular osteons.
• Osteocytes lie in lacunae, tiny chambers arranged
  in concentric circles around a central canal.
• Spongy bone contains numerous plates (trabeculae)
  separated by unequal spaces.
• Spaces are often filled with red bone marrow.

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Tissues of the Skeletal System

• Cartilage
• Cartilage flexible, gel-like matrix containing
  collagenous and elastic fibers.
• Function cushion from pressure, stresses of
  movement
• Chondrocytes are housed in lacunae
• Three types differ according to type and
  arrangement of fibers.
• Hyaline - Firm and flexible.
• Ends on long bones, nose, ribs, larynx, trachea
• Fibrocartilage - Strong.
• Vertebral disks, knee joint
• Elastic - Flexible.
• External ear and epiglottis

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Tissues of the Skeletal System

• Fibrous Connective Tissue
• Made of rows of fibroblasts separated by bundles
  of collagenous fibers.
• Makes up ligaments (connect bone to bone) and
  tendons (connect muscles to bones at joints).

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Bone Growth and Repair

• Several different types of cells are involved in
  bone growth and repair.
• Osteoprogenitor cells.
• Unspecialized cells found in inner periosteum,
  endosteum, central canal of compact bone
• Osteoblasts.
• Bone-forming cells, secrete bone matrix
• Osteocytes.
• Mature bone cells, osteoblasts surrounded by
  matrix
• Osteoclasts.
• White blood cell in red bone marrow, perform bone
  resorption (bone break down and calcium and
  phosphate deposition)

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Bone Development and Growth

• Ossification bone formation.
• Intramembranous ossification - Bones develop
  between sheets of fibrous tissue, ex. skull
• Endochondral ossification - Cartilage breaks down
  in the center of the diaphysis, ex. most bones,
  femur
• After birth, the ends of developing bones
  continue to grow, but secondary ossification
  centers soon appear.
• Growth plate remains between primary and
  secondary ossification centers.

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Endochondral Ossification
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Remodeling of Bones

• Remodeling
• Continual process of breakdown and rebuilding
• Osteoclasts derived from monocytes in red bone
  marrow break down bone, remove worn cells, and
  assist in depositing calcium in the blood.
• Osteoclasts disappear after breakdown
• Rebuilding/remodeling begins with osteoblasts
• Osteoblasts take calcium from blood and form new
  bone.
• Trapped osteoblasts are converted to osteocytes

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Bone Repair

• Fracture repair takes place over a span of
  several months in a series of four steps.
• Hematoma- escape of blood at the fracture site
• Fibrocartilaginous callus- beginning of tissue
  repair as fibrocartilage fills the space between
  the broken bone, lasts for approximately 3 weeks
• Bony callus- osteoblasts produce trabeculae of
  spongy bone replacing firbocartilage and joining
  ends of bone (3-4 months)
• Remodeling- creation of a new medullary cavity by
  osteoblasts building compact bone and osteoclasts
  absorbing spongy bone
• Naming of a fracture indicates what kind of break
  occurred.
• Complete, incomplete, simple, compound, spiral

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Bone Fracture and Repair
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Bones of the Skeleton

• Skeletal Functions.
• Support body.
• Protect soft body parts.
• Produce blood cells.
• Store minerals and fat.
• Permit flexible body movement.

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Bone Classification

• Bones are classified according to their shape,
  and whether they occur in the axial skeleton or
  the appendicular skeleton.
• Bone shape
• Long bones
• Short bones
• Flat bones
• Round bones
• Irregular bones
• Axial - Midline.
• Appendicular - Limbs and their girdles.

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The Axial Skeleton

• The axial skeleton lies in the midline of the
  body and consists of
• Skull.
• Hyoid bone.
• Vertebral column.
• Rib cage.

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The Skull

• The skull is formed by the cranium and the facial
  bones.
• Fontanels
• Newborn feature
• Intramembraneous ossification
• Sinuses
• The cranium contain eight bones.
• Frontal bone
• Two parietal bones.
• Occipital bone.
• Two temporal bones.
• Sphenoid bone.
• Ethmoid bone.

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The Facial Bones

• The most prominent facial bones are the mandible,
  maxillae, zygomatic bones, and nasal bones.
• Mandible is the movable, lower jaw.
• Maxillae form upper jaw.
• Zygomatic bones form cheek prominence.
• Nasal bones form the bridge of the nose.

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Hyoid Bone

• The hyoid bone is not part of the skull, but is
  part of the axial skeleton.
• Only bone that does not articulate with another
  bone.
• Anchors the tongue and is the attachment site for
  swallowing muscles.
• Important for human speech.

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The Vertebral Column

• Column made of thirty-three vertebrae.
• Spinal cord passes through the vertebral canal
  and gives off spinal nerves.
• Vertebrae named according to location.
• Cervical.
• Thoracic.
• Lumbar.
• Sacrum.
• Coccyx.

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The Vertebral Column

• Intervertebral disks composed of fibrocartilage
  are found between the vertebrae and provide
  padding to absorb shock caused by movements and
  also provide flexibility of the column.

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The Rib Cage

• The rib cage is composed of the thoracic
  vertebrae, ribs and associated cartilage, and the
  sternum.
• Twelve pairs of ribs.
• All connect to thoracic vertebrae in back.
• Upper seven pairs (true ribs) connect to sternum
  by costal cartilage.
• Next three pairs (false ribs) attach to sternum
  by common cartilage.
• Last two pairs (floating ribs)do not attach to
  sternum.

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Thoracic Vertebrae and Rib Cage
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The Appendicular Skeleton

• The appendicular skeleton consists of bones
  within the pectoral and pelvic girdles and their
  attached limbs.
• The pectoral girdle and upper limb (arm) are
  specialized for flexibility.

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The Appendicular Skeleton

• The Pelvic Girdle and Lower Limb.
• The pelvis is a basin composed of the pelvic
  girdle, sacrum, and coccyx.
• Pelvis bears the weight of the body, protects
  organs within the pelvic cavity, and serves as
  attachment point for the legs.
• Femur is the longest and strongest bone in the
  body.

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Articulations

• Bones are joined at joints.
• Fibrous joints are sutures between bone
  immoveable, found between
• cranial bones
• Cartilaginous joints are connected by hyaline
  cartilage ex. costal cartilage of ribs
• Synovial joints separate the bones by a cavity.
• Hinge.
• Ball-and-socket.

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Movements Permitted by Synovial Joints

• Angular Movements.
• Flexion - Decreases joint angle.
• Extension - Increases joint angle.
• Adduction - Movement towards midline.
• Abduction - Movement away from midline.
• Circular Movements.
• Rotation - Movement around axis.
• Supination - Rotation with palm upward.
• Circumduction - Movement in wide circle.
• Special Movements.
• Inversion (sole inward) and eversion (sole
  outward).
• Elevation (lifting up) and depression (moving
  down).

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Joint Movements
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Homeostasis

• Rib cage enables oxygen to enter bloodstream.
• Red bone marrow produces red and white blood
  cells.
• Jaw and teeth chew food, aiding digestion.
• Bones protect internal organs.
• Calcium storage.
• Efficient locomotion.