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LMB > Lecture 7-Bone > Flashcards

Lecture 7-Bone Flashcards

1
Q

In evolution, skeletons began to appear after the evolution of what? Why?

A
  • carbonic anyhydrase

- allows deposition of Ca

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1
Q

What are the similarities between bone and cartilage? (3)

A
  • both hard tissues
  • have living cells in lacunae (matrix)
  • arise from mesenchymal cells
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2
Q

What are the differences between bone and cartilage? (2)

A
  • bone is heavily vascularized

- bone has access to blood vessels via canaliculi while cartilage is less calcified so uses long range diffusion

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3
Q

What external factor dictates whether cartilage or bone will form from mesenchymal cells?

A
  • presence/absence of O2: if O2 is present then bone forms, if absent, then cartilage forms
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4
Q

Bone is a dynamic tissue in that it _____

A

is constantly remodeling/turning over

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5
Q

What is the effect of mechanical stress on bone?

A
  • allows for proper bone remodeling since it has plasticity which is exploited by orthodontists
  • without the mechanical stress there can be loss of bone during flight or immobilization
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6
Q

What is the piezoelectric potential? What does a (+) and (-) potential mean?

A
  • electric potential generated in bone by pressure on the hydroxyapatite crystals and cell membranes
  • Pressure on the crystals causes a (+) potential: bone reabosrption
  • (-): bone deposition
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7
Q

How much of bone is fibrous (inorganic) vs. organic?

A
  • 75% is inorganic/fibrous

- 25% is organic

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8
Q

Describe the composition of the organic component of bones

A
  • Fibers: 90% type I collagen

- Ground substance: Glycosaminoglycans (chondroitin and keratan sulfates); glycoproteins

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9
Q

Does the bone MATRIX have cells?

A

no

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10
Q

Osteonectin and osteopontin fall under what classification? What are they?

A
  • glycoproteins of the organic component of bone

- anchor minerals to collagen and in initiate mineralization/crystal formation

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11
Q

Osteocalcin and bone sialoprotein

A
  • types of glycoproteins in the organic component of bone

- Ca binding proteins

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12
Q

What are the glycoproteins of the organic component of bone?

A
  • osteonectin and osteopontin

- osteocalcin and bone sialoprotein

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13
Q

What is osteoid?

A
  • part of the organic component of bone

- newly secreted organic matrix that’s not yet fully calcified

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14
Q

Describe the inorganic composition of bone. (6)

A
  • comprises 50-70% of bone
  • mostly CaPO3 salts in amorphous or crystalline form
  • also hydroxyapatite (Ca10(PO4)6(OH)2)
  • Ca citrate
  • bicarb
  • Fl
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15
Q

Water makes up __% of bone mass

A

15

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16
Q

What is the hydration shell?

A
  • in the inorganic component of bone
  • surrounds hydroxyapatite crystals and facilitates with Ca exchange with fluids
  • major source of blood Ca
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17
Q

Mineralized bone matrix is deposited where? Describe the 2 different types of these.

A
  • in layers called lamellae
  • Spongy/cancellous: spicules or trabeculae with large marrow spaces in between
  • Compact/cortical bone: more elaborate architecture with circumferential lamellae and cylindrical columns called osteons/Haversian systems. These also contain interstitial lamellae
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18
Q

What are 2 ways to prepare bone sections for microscopy?

A
  • decalcification leaving only organic material but flexible and with the same shape
  • grinding into translucent sections; can see the arrangement of bone
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19
Q

Mesenchymal cells differentiate into ____

A

osteoblast –> osteocyte –> cartilage or bone

20
Q

Osteoblasts (3)

A
  • secrete organic material like type I collagen and amorphorous substance to make osteoid
  • non-dividing
  • highly secretory (and therefore lots of RER and golgi)
21
Q

osteoid

A
  • incompletely ossified material
22
Q

osteocytes (3)

A
  • mature osteoblasts trapped in their own material (osteoid-eosinophilic) called lacunae
  • terminally differentiated therefore reduced RER and golgi
  • extend filopodia in canaliculi
23
Q

osteoclasts (5)

A
  • multinucleated cell formed by VitD promoted fusion of monocytes/macrophages that function in bone reabsorption
  • non-dividing
  • mobile
  • located on bone resorptive and free surfaces in cavitations called Howships lacunae (since they’re chewing away at the bone)
  • Ruffled borders to increase SA for bone reabsorption
24
Q

osteogenic cell

A

another name for mesenchymal osteoprogenitor, a committed mesenchymal cell

25
Q

Committment of osteogenic cells (mesenchymal cells) is controlled by what? (2)

A
  • BMP (bone morphoenic protein)

- osteogenin

26
Q

Self renewal of osteogenic cells is controlled by what factors? (3)

A
  • PDGF
  • TGF beta
  • IGF
27
Q

Differentiation of osteogenic cells (mesenchymal cells) is controlled by what factors? (2)

A
  • BMP

- VitD3

28
Q

How do BMP levels change with age?

A

decreases

29
Q

What stimulates osteoblast secretion of osteoid?

A
  • GH (somatotropin)

- sex steroids

30
Q

Bone apposition

A
  • deposition of osteoid between osteoblast layer and existing bone
31
Q

VitD of Ca deficiency results in what?

A

osteomalacia/poor mineralization

32
Q

Canaliculi

A

osteocytes extend their filapodia through these, they are canals connecting cells (i.e., gap junctions) and can exchange nutrients

33
Q

Osteocyte osteolysis

A
  • reduced Ca release in lacunae
34
Q

What increases osteocyte osteolysis and what decreases it?

A
  • PTH increases reabsorption and therefore this

- Cacitonin from thyroid decreases resorption and therefore this

35
Q

Osteocytes are only found where?

A
  • in compact bone
36
Q

What are the 2 mechanisms by which osteoclasts cause bone resorption. Explain the process.

A
  • focal decalcification: acidification of the immediate environment by citric acid, bicarb (formed by CO2 and H2O) and carbonic anhydrase (at ruffled border). Partial degradation of CaPO3 by H ions. These remnants are taken back up by osteoclasts and transported to bvs and therefore other parts of the body.
  • extracellular digestion: by hydrolytic enzymes collagenase (degrades type I collagen which is the major part of fibrous component), acid phosphatase and sulfatase
37
Q

Which 2 parts of the bone make up the bone proper?

A
  • periosteum (think of this as the bone equivalent to perichondrion)
  • endosteum
38
Q

What are the 2 parts of the periosteum? Describe both.

A
  • fibrous periosteum: outer fibrous layer, highly vascularized
  • osteogenic periosteum: inner cellular layer with osteogenic cells (mesenchymal) and osteoblasts
39
Q

How does the periosteum attach to bone?

A
  • collagen fibers called Sharpey’s fibers that originate from the Volkmann’s canals which contain blood vessels
40
Q

Describe the endosteum of the bone.

A
  • single cell layer of progenitor cells, osteoblasts and osteoclasts that lines the internal surfaces of the bone (trabeculae, Haversian canals)
  • important for bone nutrition and maintenance
41
Q

Can periosteum and endosteum give rise to cartilage as well as bone?

A
  • yes, they both have osteoblasts
42
Q

What is woven bone?

A
  • primary, immature bone
  • random disposition of collagen fibrils
  • usually seen in embryonic development and bone repair
43
Q

What is lamellar bone?

A
  • secondary, mature bone
  • organized collagen in lammellae
  • cancellous (spongy) or compact (cortical)
  • adult, from remodeling of woven bone
44
Q

Trabeculae

A

network of irregular lamellae in spongy (cancellous) bone

45
Q

What are the spaces of spongy/cancellous bone filled with?

A
  • hematopoietic tissue
46
Q

Most spongy bone will be converted to _____ except for ______ (3)

A
  • compact bone
  • teeth
  • short bones
  • epiphyses and diaphysis of long bones
47
Q

anastomosis occurs where in bone?

A
  • with trabeculae trapping blood and lymphatic vessels in canals
48
Q

Desscribe the early stage of bone formation in spongy bone.

A
  • trabeculae coalesce and trap blood vessels and mesenchymal cells

LMB (3 decks)

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