1. Path 1 Flashcards

1
Q

What is the periostium of a bone?

A

Membrane of the bone that covers the outer surface of bone: contains blood vessels and nerves.

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2
Q

What is the cortical bone?

A

“Compact bone” that makes up the hard exterior of the bone

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3
Q

What is the trabecular bone?

A

Spongy bone with ALOT of surface area that is soft and flexible, found at the ends of long bones

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4
Q

What is the medullary cavity of bones?

A

Contain marrow: makes RBC.

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5
Q

Osteoblasts

A

Located on surface of matrix.

  1. Make bone matrix, by laying down osteiod
  2. Regulates mineralization
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6
Q

Osteoclasts

A

Specialized MO, derived from circulating monocytes, that secrete acid (H+) and proteases => resorb bone matrix

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7
Q

Osteocytes

A
  • Inactive osteoblasts burried in bone matrix that become osteocytes:
    • 1. Control Ca2+ and phosphate levels.
      1. Mechanotransduction: detect mechanical forces and translate them into biological activity
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8
Q

What is the bone matrix?

How is it made and what makes it up?

A
  • Extracellular component of bone made by osteoblasts.
      1. Osteoblasts lay down: Osteoid, organic, non-mineralized protein made up of type 1 collagen and smaller amounts of GAG, like osteopontin (osteocalcin)​, which helps w bone formation, mineralization and Ca2+ homeostasis
    • Later, it is mineralized with Ca2+ and phosphate.
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9
Q

What makes up osteoid??

A
  • Osteoid is made up of mainly type 1 collagen and a smaller amount of glycoaminolgycans, like osteopontin (aka osteocalcin).
    • Osteopontin helps with: bone formation, mineralization and Ca2+ homeostasis.
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10
Q

What makes the bone hard?

A

Hydroxyapatite, which holds 99% of body calcium; 85% phosphorus.

Located in bone matrix.

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11
Q

Woven vs Lamellar Bone

A

Woven bone (primary or immature) is the FIRST type of bone formed.

    • Made rapidly in fetal development
    • Disorganized collagen fibers and weaker.
    • ABNL to see in adults: but can be seen in adults after injury

Woven bone is LATER remodeled into lamellar bone.

    • Made slowly with parallel collagen
    • Stronger
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12
Q

What regulates levels of Ca2+ and phosphate in blood and bone?

A
  1. Vitamin D => adds Ca2+ and phosphate to bone
  2. PTH ==> removes Ca2+ and phosphate to bone
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13
Q

When is PTH secreted?

A

↓ blood Ca2+:

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14
Q

When to ↓ blood Ca2+, what happens?

A

↓ blood Ca2 => PTH is secreted => (+) osteoclasts indirectly, by ↑ RANKL on osteoblasts => RANKL on osteoblasts binds to RANK-R on osteoclasts => (+) osteoclasts => bone resorption => ↑ blood Ca2+ and phosphate. Also:

  • ↑ 1-a-hydroxylase activity =>
    • ↑ active vitamin D
    • ↑ absorption of Ca2+ from gut
    • ↑ Ca2+ resorption from kidneys

↓ Phosphate reabsorption from kidneys => ↑ excretion

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15
Q

Levels of what = inadequate mineralization?

A
  1. ↓ VitD
  2. ↓ Ca2+
  3. ↓ Phosphate
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