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Anatomy > Bone > Flashcards

Bone Flashcards

1
Q

What is bone tissue

A

-specialized CT with mineralized matrix and cells ( osteoblasts, osteoclasts and osteocytes )

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2
Q

Functions of Osseous tissue

A
  • provide solid framework for the body
  • provide attachments for muscle and tendons
  • converts skeleto-muscular energy into movement
  • protects vital organs
  • calcium reservoir
  • blood formation occurs in bone marrow
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3
Q

Osteoblasts origin

A

-mesenchymal stem cells from the mesoderm

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4
Q

Osteoblasts function, type of secretion and where found

A
  • synthesize and secrete matrix vesicles
  • secrete calcium hydroxyapatite to calcify matrix
  • proteoglycans ( osteonectin - bind cells to ecm )
  • collagen 2

-found at surface of bone matrix

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5
Q

Shape of osteoblasts and how they connect to each other

A
  • cubodial

- adherent and gap junctions

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6
Q

What happens to osteoblasts as they mature

A
  • die by apoptosis ( major pathway )
  • differentiate into osteocytes
  • flatten and become bone lining cells
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7
Q

Lacunae and canaliculi

A
  • cavities in matrix in which osteocytes are trapped

- dendritic like extensions of osteocytes and which extend into matrix

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8
Q

How does bone mineralization occur

A
  • after Osteoid has been secreted
  • osteoblasts secrete vitamin k dependent osteocalcin which binds to Ca2+ ions and increase conc of mineral locally
  • also secrete matrix vesicles rich in alkaline phosphate and enzymes
  • the enzymes hydrolyze phosphate from macromolecules and increase conc locally
  • the matrix vesicles serve as foci for crystal formation which grow and more minerals are secreted and embedd collagen in it forming matrix
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9
Q

Osteocytes how they form and function

A

-by osteoblasts surround by matrix they secrete

  • maintain matrix
  • serve as detectors of stress and cracks in bone
  • trigger remedial functions in other cells
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10
Q

Function of canaliculi

A
  • exchange of metabolites from vessels hi each other and matrix
  • communication through gap junctions attaching canaliculi
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11
Q

Osteoclasts how they form and structure

A
  • osteoblasts and other bone marrow cells secrete RANK Ligand which binds to rank receptors on monocytes
  • this induces a signaling cascade stimulating the precursor to fuse together

-large motile and multi nucleated

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12
Q

Function of osteoclasts

A

Bone resorption during remodeling or to release Ca2+ into blood stream

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13
Q

Howship / resorption lacunae

A

-enzyme etched depressions occupied by osteoclasts during bone resorption

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14
Q

What is bone remodeling and function

A

-replaced of bone through resorption with new bone

  • remove brittle old bone
  • repairs micro cracks
  • repairs fractures
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15
Q

What is resorption

A

-when inorganic matter of bone is dimineralized and organic part is degraded

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16
Q

What is a characteristics of osteoclasts

A

-the enzyme TRAP tartrate resistant acid phosphatase

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17
Q

Origin of osteoclasts and they precursor

A

Hematopoietic in origin

-precursor is monocyte

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18
Q

What hormones control osteoclasts formation

A
  • vitamin D3
  • parathyroid
  • cytokines ( IL-1 , IL-6 )
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19
Q

How do osteoclasts prepare for resorption

A
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20
Q

Describe bone respiratory

A
  • osteoclasts at ruffled border attach to membrane using proteins forming resorption compartment
  • pumps protons from H2CO3 into inorganic matrix to demineralize it forming howship lacunae and exposes organic part
  • organic part degraded by enzymes and vesicles phagocytosis then endocytized
21
Q

Effect of bone resorption

A

Ca2+ released into blood steam

-old bone degraded

22
Q

Proteins which attach to membrane from osteoclasts

A

Osteopontin

-bone sialoprotein BSP

23
Q

What is sealing zone and use

A
  • area between osteoclasts and matrix

- produces conducive micro environment for resorption

24
Q

Enzymes which degrade organic part of bone

A

Acid phosphatase

-cathepsin K

25
Q

Hormones which affect bone resorption and where they come from

A
  • RANKL helps osteoclasts form and mature
  • osteoprotegerin from osteoblasts bind with RANKL and inhibit osteoclasts formation
  • parathyroid from parathyroid gland responses to low Ca in blood and directly stimulates osteoblasts to make RANKL
  • calcitonin from parafollicular cells inhibit bone resorption
26
Q

Wolffs Law

A

-bone that bear high mechanical weight resorp at a high rate

27
Q

Effect of vitamin D on resorption

A

-aids in intestinal digestion of calcium leading to high levels of calcitonin and low levels of parathyroid thus inhibited resorption.

28
Q

Components of bone matrix and their proportions

A
  • 50% dry weight is calcified bone
  • ions such as Ca and Mg
  • organic matter is 90% collagen
  • glycoproteins ( osteonectin )
  • proteoglycans
29
Q

Surface of hydroxyapatite is hydrate

So !?

A

-facilitates exchange between the mineral and bodily fluids

30
Q

Periosteum structure and function

A
  • outer fibrous dense layer of CT with collagen 1 and blood vessels
  • inner cellular later with mesenchymal CT and osteoblasts
  • supply blood vessels to bone
  • protective layer
31
Q

What are sharpey fibers

A

-bundles of periosteum collagen which penetrate matrix and bind peri to matrix

32
Q

Endosteal function and structure

A

-cover trabeculae In spongy bone

-has cells ( progenitor, osteoclasts , )
And sparse Delicate network of collagen

33
Q

Woven bone structure and where found

A

-irregular arrangement of cells and matrix that intertwines

  • found in fracture as hard callus
  • in developing bones
34
Q

Woven bone characteristics

A
  • low mineral content
  • low density and can’t bear much mechanical stress
  • high conc of osteocytes
35
Q

Other name for woven

A

Primary bone

Immature bone

36
Q

Which bone developed the quickest

A

Woven

37
Q

Lamellae bone structure , characteristics , where found and synonyms

A

-parallel layer of thin sheets of collagen and matrix

  • heavily calcified
  • regularly spaced cells
  • found in all adult bones
  • mature bone
  • secondary bone
38
Q

Types of lamellae, description, where found and function

A

1 interstitial bone - parallel groups of lamellae in between osteons. Made of leftover osteons from respiration

2 circumferential lamellae - external and internal found beneath periosteum and cancellous bone. Strengthens Cortical bone with osteons

3 concentric lamellae - parallel sheats of lamellae forming concentric circles and protecting Haversian canals

39
Q

What is an osteon

A

-cylindrical tube parallel to long axis of diaphysis with concentric lamellae each and a Haversian canal in the middle

40
Q

What is Haversian canal

A

-narrow tube between concentric lamellae with blood vessels and nerves

41
Q

What is in between lamellae

A

-lacunae

42
Q

Cement line

A

-outer boundary layer of a osteon

43
Q

How are osteons formed

A

-by laying of matrix around pre existing blood vessels

44
Q

Volkmanns canal structure and use

A

-transverse canals that connect Haversian canals together and to blood vessels of the periosteum

45
Q

What is replaced in cortical bone during remodeling

A

-osteon

46
Q

Describe bone remodeling

A
  • osteoclasts tunnel a core through bone resorbing existing bone
  • tunnel invaded by capillaries and progenitor which diff into osteoblasts secrete osteoid in a cyclic manner which then calcifies forming concentric lamellae
47
Q

What happens to trapped osteoblasts during resorption

A

-diff into osteocytes

48
Q

Cancellous bone description, structure and function

A
  • found in the middle of bone
  • has spicules known as trabeculae in which intertwine and are covered by endosteal
  • filled with bone marrow where blood is made
  • 20% of bone
  • less dense
  • spongy consistency
49
Q

Cortical bone description, structure and function

A
  • found at the peripheral of bones - underneath periosteum
  • 80% mass of bone
  • has osteons and parallel lamellae

Anatomy (15 decks)

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