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Bone function and_formation_2009


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Bone function and_formation_2009

  1. 1. Bone Function and Formation Chapter 7 (Part 1)
  2. 2. Parts of a Long Bone <ul><li>Long bones are defined as any bone that is longer than it is wide. </li></ul>
  3. 3. Parts of a Long Bone <ul><li>The expanded bulge at each end of a long bone is called the epiphysis </li></ul><ul><ul><li>The epiphysis articulates with other bones </li></ul></ul><ul><ul><li>Each long bone has a proximal epiphysis and a distal epiphysis </li></ul></ul><ul><ul><li>The epiphyseal surface that articulates with other bones is covered in articular cartilage </li></ul></ul>
  4. 4. Parts of a Long Bone
  5. 5. Parts of a Long Bone <ul><li>The long shaft of the bone is called the diaphysis </li></ul>
  6. 6. Parts of a Long Bone <ul><li>Bones are covered in a thin, tough layer called the periosteum . </li></ul><ul><ul><li>The periosteum covers the entire bone, except where there is articular cartilage </li></ul></ul><ul><ul><li>It is firmly attached to the bone and is continuous with ligaments and tendons connecting to the bone. </li></ul></ul>
  7. 7. Parts of a Long Bone Periostium
  8. 8. Parts of a Long Bone
  9. 9. Parts of a Long Bone <ul><li>The wall of the diaphysis is composed mostly of compact bone </li></ul><ul><ul><li>Very tightly packed bone cells </li></ul></ul><ul><ul><li>No spaces in the extracellular matrix. </li></ul></ul>
  10. 10. Parts of a Long Bone <ul><li>The wall of the diaphysis is composed mostly of compact bone </li></ul><ul><ul><li>Very tightly packed bone cells </li></ul></ul><ul><ul><li>No spaces in the extracellular matrix. </li></ul></ul>
  11. 11. Parts of a Long Bone <ul><li>In the center of the diaphysis, is a tube called the medullary cavity . </li></ul><ul><li>Special layer of cells called the endosteum produce marrow inside the cavity. </li></ul>
  12. 12. Marrow <ul><li>Bone marrow comes in two different types </li></ul><ul><ul><li>Red marrow produces red blood cells, white blood cells, and platelets </li></ul></ul><ul><ul><li>Yellow marrow stores fat inside the bone </li></ul></ul><ul><ul><li>As we age, red marrow is replaced with yellow marrow </li></ul></ul><ul><ul><li>The two can be converted from one to the other, as needed. </li></ul></ul>
  13. 13. Parts of a Long Bone <ul><li>The epiphysis is composed mostly of spongy bone . </li></ul><ul><ul><li>Lots of space between bone cells </li></ul></ul><ul><ul><li>Only a very thin layer of compact bone covers the epiphysis </li></ul></ul><ul><ul><li>Helps to reduce the bone’s weight </li></ul></ul>
  14. 14. Microscopic Anatomy <ul><li>Bone is composed of cells called osteocytes </li></ul><ul><ul><li>(os- = bone ) </li></ul></ul><ul><ul><li>Found in small chambers called lacunae </li></ul></ul><ul><ul><ul><li>Surround osteocytes </li></ul></ul></ul><ul><ul><ul><li>Made of hard extracellular material (bone matrix) </li></ul></ul></ul><ul><ul><ul><ul><li>Calcium carbonate </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Calcium phosphate </li></ul></ul></ul></ul>
  15. 15. Microscopic Anatomy <ul><li>Bone matrix is deposited in concentric circles called lamellae (singular: lamella) </li></ul>
  16. 16. Microscopic Anatomy <ul><li>The lamellae surround a central canal </li></ul><ul><li>Every central canal contains a blood vessel that supplies nutrients to the osteocytes in the surrounding lamellae </li></ul>
  17. 17. Microscopic Anatomy <ul><li>Osteocytes have cytoplasmic extensions called canaliculi </li></ul><ul><li>Used to help osteocytes obtain nutrients & communicate with surrounding osteocytes </li></ul>
  18. 18. Bone Formation <ul><li>During development, tissue that will become bone starts off as cartilage </li></ul><ul><li>There are two basic ways bone can form: </li></ul><ul><ul><li>Intramembranous Bone </li></ul></ul><ul><ul><li>Endochondral Bone </li></ul></ul>
  19. 19. Intramembranous Bone <ul><li>These bones develop into thin, sheet-like bones like those found in the cranium </li></ul><ul><li>Originates between two sheet-like layers of connective tissue </li></ul><ul><li>Bone forming cells called osteoblasts lay down spongy bone near the center between the membranes </li></ul><ul><li>Cells of the membrane form the periosteum </li></ul><ul><li>Cells of the periosteum produce osteoblasts that form compact bone to surround the spongy bone. </li></ul>
  20. 20. Intramembranous Bone
  21. 21. Intramembranous Bone
  22. 22. Endochondral Bone <ul><li>Most of the bones are endochondral </li></ul><ul><li>1. Blob of cartilage, shaped somewhat like the bone they will become, is what we start with </li></ul>
  23. 23. Endochondral Bone <ul><li>2. Near the middle of the long bone (diaphysis), the cartilage breaks down. </li></ul><ul><li>3. Osteoblasts invade the space left by cartilage breaking down, forming spongy bone </li></ul><ul><ul><li>This is called the primary ossification center </li></ul></ul><ul><li>4. Osteoblasts lay down a periosteum to surround the diaphysis </li></ul>
  24. 24. Endochondral Bone <ul><li>5. After a time of growth and ossification in the diaphysis, the cartilage in the epiphyses begins to break down </li></ul><ul><li>6. Osteoblasts invade the areas in the epiphyses </li></ul><ul><ul><li>Create a secondary ossificaiton center </li></ul></ul>
  25. 25. Endochondral Bone
  26. 26. Endochondral Bone <ul><li>As the primary and secondary ossification centers grow toward each other, they form an epiphyseal plate </li></ul><ul><li>AKA: Growth Plate </li></ul>
  27. 27. Endochondral Bone <ul><li>As toddlers and teenagers grow, bones lengthen by laying down new bone matrix from the epiphyseal plate </li></ul><ul><li>Damage = bad! </li></ul>
  28. 28. Homeostasis of Bones <ul><li>Throughout life, old bone tissue is broken down and “digested” by osteoclasts </li></ul><ul><li>New bone tissue is formed by osteoblasts . </li></ul>
  29. 29. Bone Function <ul><li>Support the body </li></ul><ul><li>Protect internal organs </li></ul><ul><li>Allow for attachment of muscles that help up move </li></ul><ul><li>Produce blood cells </li></ul><ul><li>Store inorganic salts </li></ul>
  30. 30. Protection <ul><li>The skull protects the brain, eyes, nasal & oral passages </li></ul><ul><li>The ribs protect the heart, lungs, windpipe, and esophagus </li></ul><ul><li>Pelvis (hips) protect internal reproductive organs (female) and the urinary bladder. </li></ul>
  31. 31. Movement <ul><li>Bones (and their associated muscles) act as levers in the body </li></ul><ul><li>Levers have three parts: </li></ul><ul><ul><li>A long, rigid rod or bar (the bone) </li></ul></ul><ul><ul><li>A pivot point (a joint) </li></ul></ul><ul><ul><li>Something that supplies a force to move the rod (muscle) </li></ul></ul>
  32. 32. Blood Cell Formation <ul><li>Blood cells form in the spleen and liver during prenatal development </li></ul><ul><li>Later, they form in the red marrow found in the medullary cavities of long bones. </li></ul><ul><li>Hematopoiesis </li></ul>
  33. 33. Storage of Inorganic Salts <ul><li>This is another homeostatic mechanism </li></ul><ul><ul><li>You know how much I love to test you on these </li></ul></ul><ul><li>The bones store a reserve of calcium salts, which are vital to metabolic processes and muscle contraction </li></ul><ul><li>The glands involved in this HM are the thyroid and parathyroid </li></ul>
  34. 34. Storage of Inorganic Salts <ul><li>If blood calcium levels get too low: </li></ul><ul><ul><li>Parathyroid (receptor) releases parathyroid hormone to stimulate osteoclast activity. </li></ul></ul><ul><ul><li>Osteoclasts (effectors) break down bone tissue, releasing calcium salts </li></ul></ul><ul><li>If blood calcium levels get too high: </li></ul><ul><ul><li>Thyroid gland releases calcitonin , which activates osteoblasts </li></ul></ul><ul><ul><li>Osteoblasts store calcium by forming new bone tissue. </li></ul></ul>Check page 132
  35. 35. Storage of Inorganic Salts
  36. 36. Osteoperosis <ul><li>Caused by increased osteoclast and decreased osteoblast activity. </li></ul><ul><li>Bone tissue is broken down and replaced with fatty tissue </li></ul><ul><li>Bones break easily </li></ul><ul><li>Most common in fair-skinned females after menopause </li></ul><ul><ul><li>Some research suggests it is due to a decline in Vitamin D </li></ul></ul>
  37. 37. Osteoperosis
  38. 38. Osteoperosis
  39. 39. Osteoperosis <ul><li>Preventing the disease: </li></ul><ul><li>Avoid smoking and excess alcohol </li></ul><ul><li>Exercise (especially early in life) </li></ul><ul><li>Bone mass usually begins to dwindle in the mid-30s. As you near this age, begin to take in extra calcium (milk or supplements) </li></ul><ul><li>Be sure to get plenty of Vitamin D </li></ul><ul><ul><li>Take supplements </li></ul></ul><ul><ul><li>Spend 10-15 minutes in direct sunlight everyday. Your skin makes Vitamin D using UV light. </li></ul></ul>