Chapter_7-Bone_Tissue.txt

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Chapter_7-Bone_Tissue.txt
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  1. osteology
    the study of bone
  2. skeletal system
    composed of bones, cartilages, and ligaments joined tightly to form a strong, flexible framework for the body
  3. cartilage
    covers many joint surfaces in the mature skeleton
  4. ligaments
    hold bones together at the joints
  5. tendons
    are structurally similar to ligaments but attach muscle to bone
  6. the skeleton plays at least 6 roles:
    • 1. support
    • 2. protection
    • 3. movement
    • 4. electrolyte balance
    • 5. acid-base balance
    • 6. blood formation
  7. osseous tissue
    or bone, is a connective tissue in which the matrix is hardened by the deposition of calcium phosphate and other minerals
  8. mineralization/calcification
    the hardening process of bones
  9. what is the hardest substance in the body?
    tooth enamel, not bone
  10. bones are classified into 4 groups according to their shapes and corresponding functions:
    • 1. long bones
    • 2. short bones
    • 3. flat bones
    • 4. irregular bones
  11. compact (dense) bone
    much of a typical long bone is composed of an outer shell of this dense white osseous tissue
  12. the cylinder encloses a space called the medullary cavity, or marrow cavity, which contains bone marrow.
    at the ends of the bone, the central space is occupied by a more loosely organized form of osseous tissue called spongy (cancellous) bone.
  13. the principle features of a long bone are its shaft called the diaphysis, and en expanded head at each end called the epiphysis.
    • diaphysis - provides leverage
    • epiphysis - is enlarged to strengthen the joint and provide added surface area for the attachment of tendons and ligaments
  14. The skeleton is about ____ compact bone and ______ spongy bone by weight.
    • 3/4 compact bone
    • 1/4 spongy bone
  15. the joint surface where one bone meets another is covered with a layer of hyaline cartilage called the articular cartilage.
    together with a lubricating fluid secreted between the bones, this cartilage enables a joint to move far more easily than it would if one bone rubbed directly against the other.
  16. nutrient foramina
    blood vessels pentrate into the bone through minute holes called nutrient foramina.
  17. externally, a bone is covered with a sheath called the periosteum.
    -this has a tough, outer fibrous layer of collagen and an inner osteogenic layer of bone-forming cells.
  18. some collagen fibers of the outer layer are continuous with the tendons that bind muscle to bone, and some penetrate into the bone matrix as perforating (Sharpey) fibers.
    some collagen fibers of the outer layer are continuous with the tendons that bind muscle to bone, and some penetrate into the bone matrix as perforating (Sharpey) fibers.
  19. periosteum
    provides strong attachment and continuity from muscle to tendon to bone.
  20. osteogenic layer
    is important to the growth of bone and healing of fractures
  21. the internal surface of a bone is lined with endosteum.
    - a thin layer of reticular connective tissue with cells that dissolve osseous tissue and others that deposit it
  22. in children and adolescents, an epiphyseal plate of hyaline cartilage seperates the marrow spaces of the epiphysis and diaphysis. on x-rays, it appears as a transparent line at the end of a long bone.
    - a zone where the bones grow in length. in adults, the epiphysial plate is depleted and the bones can grow no longer, but an epiphysial line marks where the plate used to be.
  23. diploe
    spongy layer in the cranium
  24. types of bone cells:
    • 1. osteogenic (osteoprogenitor) cells
    • 2. osteoblasts
    • 3. osteocytes
    • 4. osteoclasts
  25. osteogenic (osteoprogenitor) cells
    stem cells that develop from embryonic mesenchymal cells and then give rise to most other bone cell types
  26. osteoblasts
    bone forming cells
  27. osteocytes
    • former osteoblasts that have become trapped in the matrix they deposited;
    • also known as mature bone cells
  28. osteoclasts
    bone-dissolving cells found on the bone surface
  29. osteocytes reside in tiny cavities called lacunae, which are interconnected by slender channels called canaliculi.
    osteocytes reside in tiny cavities called lacunae, which are interconnected by slender channels called canaliculi.
  30. osteocytes have multiple functions:
    • -some resorb bone matrix;
    • -others deposit it - they contribute to the homeostatic maintenance of both bone density and blood concentrations of calcium and phosphate ions.
  31. the matrix of osseous tissue is, by dry weight, about one-third organic and two-thirds inorganic matter.
    • - the organic matter, synthesized by the osteoblasts, includes collagen and various protein-carbohydrate complexes such as glycosaminoglycans, proteoglycans, and glycoproteins.
    • - the inorganic matter is about 85% hydroxyapatite, a crystallized calcium phosphate salt, 10% calcium carbonate, and lesser amounts of magnesium, sodium, potassium, fluoride, sulfate, carbonate, and hydroxide ions.
  32. bone is a class of materials that engineers call a composite.
    - a combination of two basic structural materials, in this case a ceraamic and a polymer.
  33. in bone, the polymer is the collagen and the ceramic is the hydroxyapatite and other minerals.
    the ceramic component enables a bone to support the weight of the body without sagging.
  34. when bones are deficients in calcium salts, they are soft and bend easily.
    one way to demonstrate this is to soak a clean dried bone, such as a chicken bone in vinegar for a few days
  35. such mineral deficienciency and flexibility are the central problems in the childhood disease, rickets.
    - in which the soft bones of the lower limbs bend under the body's weight and become permanently deformed
  36. the protein component gives bone a degree of felxibilty.
    • without protein, a bone is excessively brittle.
    • without collagen, a jogger's bones would shatter under the impact of running.
  37. concentric lamelle
    layers of matrix concentrically arranged around a central (haversian or osteonic) canal and connected with each other by canaliculi
  38. a central canal and its lamelle constitute an osteon (heaversian system)
    - the basic structural unit of compact bone
  39. along their length, central canals are joined by tranverse or diagonal passages called:
    perforating (Volkmann) canals
  40. spongy bone consists of a lattice of delicate slivers of bone called spicules and trabeculae.
    • spicules - rods or spines
    • trabeculae - thin plates
    • - although calcified and hard, it is named for its spongelike appearance. it is permeated by spaces filled with bone marrow.
  41. bone marrow
    a general term for soft tissue that occupies the marrow cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger central canals
  42. in a child, the marrow cavity of nearly every bone is filled with red bone marrow (myeloid tissue).
    - often described as hemopoietic tissue - tissue that produces blood cells - but it is actually composed of multiple tissues in a delicate but intricate arrangement, and is properly considered an organ in itself (axial region)
  43. in adults, most of the red marrow turns to fatty yellow bone marrow, like the fat at the center of a ham bone.
    yellow bone marrow no longer produces blood, although in the event of chronic or severe anemia, it can transform back into red marrow.
  44. in adults, red blood marrow is limited to:
    the skull, veretebrae, ribs, sternum, part of the pelvic (hip) girdle, and the proximal heads of the humerus and femur (appendicular)
  45. ossification or osteogenesis
    the formation of bone
  46. in the human fetus and infant, bone develops by two methods called:
    intramembranous and endochondral ossification
  47. intramembranous ossification
    • -produces the flat bones of the skull and most of the clavicle (collarbone).
    • -such bones develop within a fibrous sheet similar to the dermis of the skin, so they are sometimes called dermal bones.
  48. endochondral ossification
    • - a process in which a bone develops from a preexisting model composed of hyaline cartilage.
    • -begins around the 6th week of fetal development and continues in a person's 20s.
    • -most bones of the body, including the vertebrae, ribs, sternum, scapula, pelvis, and bones of the limbs develop this way
  49. ossification does not end at birth, but continues throughout life with the growth and remodeling of bones.
    bones grow in two directions: length and width.
  50. from infancy through adolescence, an epiphyseal plate is present at one or both ends of a long bone, at the junction between the diaphysis and epiphysis.
    from infancy through adolescence, an epiphyseal plate is present at one or both ends of a long bone, at the junction between the diaphysis and epiphysis.
  51. the epiphyseal plate is a region of transition from cartilage to bone, and functions as a growth zone where the bones elongate.
    growth here is responsible for a person's increase in height.
  52. bone elongation:
    a result of cartilage growth
  53. interstitial growth (inside, out)
    - cartilage grwoth from within, by the multiplication of chondrocytes and deposition of new matrix in the interior
  54. the most common form of dwarfism results from:
    a failure of cartilage growth in the long bones
  55. bones also continually grow throughout life in:
    diameter and thickness
  56. appositional growth (outside, in)
    the deposition of new tissue at the surface
  57. in addition to their growth, bones are continually remodeled throughout life by the absorption of old bone and deposition of new.
    this process replaces about 10% of the skeletal tissue per year
  58. the orderly remodeling of bone depends on a precise balance between deposition and resorption, between osteoblasts and osteoclasts.
    if one process outpaces the other, or both processes occur too rapidly, various bone deformities, developmental abnormalities, and other disorders occur
  59. mineral deposition
    • -(mineralization) is a crystallization process in which calcium, phosphate, and other ions are taken from the blood plasma and deposited in bone tissue, mainly as crystals of hydroxyapatite.
    • -deposition begins in fetal ossification ad continues throughout life.
  60. mineral resorption
    • - the process of dissolving bone.
    • - it releases minerals into the blood and makes them available for other ones.
    • - carried out by osteoclasts
  61. the space between the osteoclast and the bone thus becomes filled with concentrated hydrochloric acid with a pH of about 4.
    the acid dissolves the bone minerals. the osteoclasts also secretes an enzyme called acid phosphate that digests the collagen of the bone matrix.
  62. The adult body contains about 1,100 g of calcium...
    with 99% of it is in bones.
  63. Bone has two calcium reserves:
    • 1. A stable pool of calcium which is incorporated into hydroxyapatite and is not easily exchanged with the blood
    • 2. Exchangeable calcium, which is 1% or less of the total but it is easily released to the tissue fluid
  64. The adult skeleton exchanges about ____ of it's calcium with the blood each year.
    18%
  65. The calcium concentration in the blood plasma is normally:
    9.2 to 10.4 mg/dL
  66. hypocalcemia
    • calcium deficiency
    • - excessive excitability of the nervous system, leads to muscle tremors, spasms, or tetany
  67. tetany
    • -the inability of the muscle to relax
    • -occurs when the calcium concentration falls to 6 mg/dL
  68. hypercalcemia
    • -blood calcium excess
    • -nervous and muscle cells are less excitable than normal
    • -at 12 mg/dL and higher, causes depression of the nervous system, emotional disturbances, muscle weakness, sluggish reflexes and sometimes cardiac arrest
  69. calcium homeostasis is regulated by three hormones:
    • calcitrol
    • calcitonin
    • parathyroid hormone
  70. calcitrol
    • -a form of vitamin D produced by the sequential action of the skin, liver, and kidneys
    • -intended to raise the blood calcium concentration
  71. calcitrol behaves as a hormone:
    a blood borne chemical messenger from one organ to another.
  72. although calcitrol promotes bone resorption, it is also necessary for bone deposition.
    without it, calcium and phosphate levels in the blood are far too low for normal deposition
  73. the result is a softness of the bones:
    • rickets in children, and
    • osteomalacia in adults
  74. calcitonin
    secreted by C cells (clear cells) of the thyroid gland when blood calcium concentration rises too high
  75. parathyroid hormone (PTH)
    secreted by the parathyroid glands, are released when blood calcium is low.
  76. stress fracture
    a break caused by abnormal trauma to a bone
  77. pathologic fracture
    a break in a bone weakened by some other disease, such as bone cancer or osteoporosis
  78. the healing process of a fracture:
    • 1. formation of hematoma and granulation tissue
    • 2. formation of a soft callus
    • 3. conversion to hard callus
    • 4. remodeling
  79. closed reduction
    a procedure in which the bone fragments are manipulated into their normal position without surgery
  80. open reduction
    involves the surgical exposure of the bone and the use of plates, screws, or pins to realign the fragments
  81. orthopedics
    the branch of medicine that deals with the prevention and correction of injuries and disorders of the bones, joints, and muscles
  82. osteoporosis
    the most common bone disease
  83. Paget disease
    • results in rapid, disorderly bone remodeling and weak, deformed bones
    • most common in males over 50
  84. osteomyelitis
    inflammation of osseous tissue and bone marrow as a result of bacterial infection
  85. brittle bone disease
    a defect in collagen deposition that renders bones exceptionally brittle; also causes tooth deformity
  86. osteogenic sarcoma
    most common and deadly form of bone cancer
  87. closed fracture
    skin is not broken; simple fracture
  88. open fracture
    skin is broken; bone protrudes through skin, or wound extends to fractured bone; compound fracture
  89. complete fracture
    bone is broken into two or more pieces
  90. incomplete fracture
    partial fracture that extends partway across bone; pieces remain joined
  91. nondisplaced fracture
    the portions of bone are still in correct anatomical alignment
  92. displaced fracture
    the portions of a fractured bone are out of anatomical alignment
  93. comminuted fracture
    bone is broken into three or more pieces
  94. greenstick fracture
    bone is bent on one side and has an incomplete fracture on the opposite side
  95. hairline fracture
    fine crack in which sections of the bone remain aligned; common in the skull
  96. impacted fracture
    one bone fragment is driven into the marrow cavity or spongy bone of the other
  97. depressed fracture
    broken portion of bone forms a concavity, as in skull fractures
  98. linear fracture
    fracture parallel to long axis of bone
  99. transverse fracture
    fracture perpendicular to long axis of bone
  100. oblique fracture
    diagonal fracture. between linear and transverse
  101. spiral (torsion) fracture
    fracture spirals around the axis of the long bone, like a spiral staircase, as the result of a twisting stress such as might occur in a skiing accident
  102. epiphyseal
    epiphysis is seperated from the diaphysis along the epiphyseal plate; seen in juveniles
  103. colles
    fracture of the distal end of the radius and ulna; common in osteoporosis
  104. pott
    fracture at the distal end of the tibia, fibula, or both; a common sports injury

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