FOM 3.1.3 Flashcards

1
Q

What are is this, what is it stained with and what are the arrows pointing at?

A

This is hyaline cartilage stained with H and E. The arrows are pointing at chondrocytes in their lacunae.

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2
Q

How does hyaline cartilage accomplish its role as a shock absorber?

A

Hyaline cartilage functions like a shock absorber or biomechanical spring: solvation water is bound water which interacts with the negatively charged proteoglycans and is squeezed out of cartilage on compression and returns and binds during decompression.

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3
Q

What is the rigidity of the hyaline cartilage dependent on?

A

Rigidity is dependent on the electrostatic interactions between type II collagen fibrils and the GAGs comprising the proteoglycans resulting in a cross-linked matrix.

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4
Q

What is responsible for rigidity of cartilage?

A

Type II collagen binding to the proteoglycan aggregate

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5
Q

How is the protein portion of the GAG synthesized and processed?

A

It is synthesized in the ER and sugars are added to it in the golgi

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6
Q

What is a main differenct between cartilage and bone andhow does this affect the way nutrients are delivered to it?

A

Cartilage lacks blood vessels, it is AVASCULAR which requires that nutrients and waste seep through the matrix by diffusion.

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7
Q

Deposition of lime salts in the form of hydroxyapatite crystals does what for bone?

A

It prevents the diffusion of metabolites and prevents interstitial growth, both of these occur in the cartilage

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8
Q

What is are the two types of bone?

A

Compact bone: dense without cavities

Cancellous (trabecular) bone: 3-dimensional lattice of branching bony spicules, forming trabeculae around marrow spaces

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9
Q

What are the arrows in this picture pointing to?

A

The top arrows are pointing to cancellous bone and the bottom arrows are pointing to compact bone

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10
Q

What does each of the numbers correspond to?

A
  1. Compact bone
  2. Periosteum
  3. Marrow cavities
  4. Trabecular bone
  5. Epiphysis
  6. Metaphysis
  7. Diaphysis
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11
Q

What is the composition of the bone matrix?

A

Organic Matrix 35% - consisting of 85-90% type I collagen, proteins, glycoproteins

Inorganic Salts - Hydroxyapatite crystals

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12
Q

What is an osteoprogenitor cell and what is its role?

A

Pluripotent stem cell from mesenchyme. Capable of differentiating into osteogenic cells, osteoblasts. Found in the periosteum and endosteum as bone lining cells in non-growing regions and differentiate into osteoblast following a fracture

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13
Q

What are osteoblasts and what are their role?

A

These cells synthesize and secrete organic matrix of the bone: types I collagen, non-collagenous protein and alkaline phosphatase.

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14
Q

What are osteocytes?

A

Osteoblasts that have trapped themselves in calcified matrix

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15
Q

What is an osteoclast?

A

These are giant multinucleated cells that are derived from monocytes. Produce an acidic environment ideal for the dissolution of bone matrix. These are also said to have a ruffled border

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16
Q

What is the fate of mesenchyme cells in bone?

A

These become osteoprogenitor cells that develope into osteoblasts and the osteocytes. Also bone lining cells

17
Q

What is the fate of bone marrow monocyte precursors?

A

These form monocytes that will form osteoclasts

18
Q

What is RANK-L?

A

RANK-L is synthesized by osteoblasts and it is a receptor that stimulates osteoclastogenesis

19
Q

What is osteoprotegerin?

A

This is a decoy receptor for RANK-L

20
Q

What is osteoid and how is it used?

A

Osteoid is type I collagen and proteoglycans, this is all synthesized by osteoblasts.

21
Q

What are the main characteristics of an osteoclast?

A

The ruffled border

The bone matrix

The tight seal

Multiple nuclei

High amounts of lysosomes

22
Q

What is the periosteum?

A

Dense connective tissue with osteogenic potential that surrounds the bone. This means there is osteoprogenitor cells comprising the bone lining the outside

23
Q

What is the endosteum?

A

It is found lining the marrow cavity and has osteogenic potential. Means there are osteoprogenitor cells that line the inside

24
Q

What are each of the arrows pointing at?

A

Blacks lines - bone matrix

Blue arrows - osteocytes

Yellow - Skeletal muscle

Darker green line- periosteum the inner layer is the osteopregenitor cells

Lime green - osteoblasts on the surface of the bone

25
Q

What is the ARF cycle?

A
26
Q

What is the effect of PTH on bone?

A

Parathyroid hormone produced by the parathyroid gland and functions to increase serum Ca++ levels through several mechanisms shown in the figure. In bone, PTH increases the number of osteoclasts and the ruffled border activity of existing osteoclasts

27
Q

What is the action of PTH on osteoclasts and osteoblasts?

A

Osteoblast are exposed to PTH - first effect is to release MCSF leads to increase differentiation of osteocytes from monocyte precursor

Osteoblast then release RANK-L which binds to RANK on osteoclast- binding to osteoclast stimulates ruffled border activity.

28
Q

Where would you want a drug to target for a disease like osteoperosis where the osteoclasts are winning?

A

You would want it to target RANK-L

29
Q

What is osteoprotegerin?

A

increase removes RANK-L and counteracting the action of the osteoclasts

30
Q

What are the roles of bisphosphonates?

A

kill osteoclasts by inducing apoptosis in osteoclasts

Also have a role in inhibiting osteoclast aggregation

31
Q

What would be another ideal target for treatment of osteoperosis?

A

Increased expression of osteoprotegerin by osteoblasts

32
Q

What is M-CSF and what does increasing it do?

A

Increasing M-CSF increases the number of osteoclasts and increase the activity of osteoclasts

33
Q

What is the purspose of chondronectin?

A

Chondronectin promotes adherence of chondrocytes to the matrix

34
Q

What is the purpose of osteocalcin?

A

Required for mineralization

35
Q

The molecular basis for shock absorption within articular cartilage is what?

A

Hydration of glycosaminoglycans