SKELETAL SYSTEM

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SKELETAL SYSTEM

• A. FUNCTION - 206 bones important for
• 1) Shape and support
• 2) Protection
• 3) Blood cell production
• 4) Calcium storage
• 5) Movement

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• B. STRUCTURE
• 1) Macroscopic
• a) compact bone, found in diaphysis.
• b) spongy bone (cancellous), found in
  epiphysis.

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• 2) Microscopic
• a) Haversian system (osteon) with
• 1) Haversian canal for blood vessels
• 2) lamellae - rings
• 3) osteocytes in lacunae
• 4) canaliculi - tiny canals for nutrients
• b) periosteum - collagen around the
  outsideof the bone.

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• 3) BONE CELLS
• a) osteocytes - the mature bone cells
• b) osteoblasts - immature bone cells.
  These cells make new bone.
• c) osteoclasts - bone eaters. These
  cells eat old bone.

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• 4) STRUCTURE OF LONG BONES
• a) long bones have a hollow
  diaphysis of compact bone filled with yellow
  marrow.
• b) They have epiphyses of spongy
  bone for joint articulation.
• c) There is an epiphyseal disk of
  hyaline cartilage for growth up to age 25. It
  becomes the epiphyseal line.

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• 5) STRUCTURE OF OTHER BONES
• a) Short bones - carpals and
  tarsals. Compact outside, spongy inside.
• b) Flat bones for protection - cranial
  bones, pelvis, ribs, sternum,
  scapula. Sandwich structure.
• c) Irregular bones - sphenoid,
  ethmoid, mandible, vertebrae. Compact
  outside, spongy inside.

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• d) Sesamoid bones - the patella and the
  small bones on the ball of the foot.

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• C. FORMATION AND GROWTH
• 1) INTRODUCTION
• a) Embryo is composed of soft tissues
  that eventually form a model of the
  bones.
• 1) Skull has a fibrous connective tissue
  model.
• 2) Other bones have a hyaline cartilage
  model.
• b) Prebone structures become bone.

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• 2) INTRAMEMBRANOUS FORMATION
• a) Occurs in skull
• b) Fibrous connective tissue has cells
  which develop into osteoblasts.
• c) They lay done bone connective
  tissue which take up calcium salts.
• d) Prebone structures become bone.

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• e) Fibrous connective tissue on the
  outside becomes the periosteum.
• f) Fibrous connective tissue in some areas
  remains as fontanels.
• 1) Allows for birth and brain
  growth.

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• 3) INTRACARTILAGINOUS FORMATION
  (endochondral)
• a) Occurs in rest of skeleton
• b) Hyaline cartilage takes up calcium and
  hardens.
• c) Blood vessels grow to inside
  bringing osteoblasts and osteoclasts.

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• d) Osteoclasts eat the hardened
  cartilage.
• e) Osteoblasts work on the outside
  and inside.
• f) Some cartilage does not become
  bone - remains as articular cartilage
  and epihyseal disks.

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• 4) GROWTH
• a) Occurs at the epiphyseal disk.
• b) Osteoblasts produce bone at the
  diaphysis side of the bone.
• c) New cartilage is produced at the
  epiphysis side of the disk.
• d) Osteoclasts reshape the bone.

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• 5) HORMONES
• a) Thyrocalcitonin - thyroid
  produces to stimulate osteoblasts. Decreases
  blood Ca.
• b) Parathyroid hormone
  (parathormone) - stimulates osteoclasts.
  Raises blood Ca
• c) Testosterone and estrogens
  stimulate osteoblasts.

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• D. DISORDERS OF BONE
• 1) RICKETS
• a) Soft bones due to lack of vitamin D -
  needed for Ca absorption.
• b) Vitamin D and UV exposure to
  treat.
• c) Called osteomalacia in the elderly.

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• 2) OSTEOPOROSIS
• a) Common disease of the elderly,
  especially women. Osteoclast activity gt
  osteoblast activity. Bones are holely
  and weak.

Osteoporosis
Normal
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• b) Causes
• 1) Lack of bone use.
• 2) Lack of estrogens
• 3) Lack of Ca
• 4) Lack of vitamin C
• 5) Old age
• c) Prevention and treatment

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• 3) OSTEOMYELITIS
• a) Inflammation of the bone marrow due to
  trauma which allows bacteria to enter.
• b) Treated with antibiotics

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• 4) FRACTURES
• a) Can be classified as
• 1) simple doesnt break
  through the skin.
• 2) compound - bone breaks through the
  skin.
• 3) comminuted bone splinters at site
  of impact
• 4) greenstick partial fracture

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• b) Fibrocartilage callous forms to
  stabilize. Osteoblast activity is
  increased. Osteoclasts help to reshape.
  Electrical potentials are involved in repair.
  

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NORMAL OSTEOPOROSIS
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