Pathophysiology: Objective 4

Front 1

What are the three types of bone cells?

Back 1

1. Osteoblast
2. Osteoclast
3. Osteocytes

Front 2

What is an osteoblast?

Back 2

1. Multifunctional monocuclear cells derived from osteogenic mesenchymal stromal cells.
2. Responsive to PTH and produce osteocalcin when stimulated by 1,25 dihydroxyvitamin D.
3. Active on the outer surfaces of bone, where they form a single layer of cells.

Front 3

What is the function of an osteoblast?

Back 3

1. They are bone-forming cells.
2. Synthesize collagen and proteoglycans, mineralize osteoid matrix.
3. Produce RANKL, which in turn stimulate osteoprotegerin (OPG), which inhibits osteoclast formation by binding to RANKL.

Front 4

What is an osteoid?

Back 4

(Osteoblast) They are non-mineralized bone matrix that synthesizes osteoblasts into initiating new bone formation.

Front 5

What is an osteoclast?

Back 5

1. They are large multi-nucleated cells that develp from the hematopoietic monocyte-macrophage lineage.
2. They are major resorptive cells of the bone.

Front 6

What is the function of an osteoclast?

Back 6

They resorb bone; a major role in bone homeostasis.

Front 7

What is a ruffled border?

Back 7

(Osteoclast) They are infoldings produced by the osteoclasts.

Front 8

What are integrins?

Back 8

(Osteoclast) The are attachments found on the bone surface that bind osteoclasts.

Front 9

What is an osteoprotegrin?

Back 9

(Osteoclast) It inhibits bone remodeling/resorption and it is key to the interaction between osteoblasts and osteoclasts.

Front 10

What is an osteocyte?

Back 10

1. They are transformed osteoblasts that are trapped or surrounded in the osteoid as it hardens as a result of minerals that enter during calcification.
2. It is the space in the hardened bone matrix called lacuna.
3. They have high nucleus/cytoplasm ratio with a thin layer of nonmineralized osteoid around it.

Front 11

What are the functions of an osteocyte?

Back 11

1. Transform osteoblast trapped in osteoid.
2. Signal both osteoblasts and osteoclasts.
3. Maintain bone matrix.
Mechanosensory receptors to reduce or augment bone mass.
4. Produce scleostin (SOST), which inhibits bone growth.

Front 12

What is a lacuna?

Back 12

(Osteocytes) It is a hardened bone matrix where a osteocyte is located.

Front 13

What are the non-mineralized bone structures?

Back 13

1. Bone Matrix
2. Collagen fibers
3. Proteoglycans
4. Glycoproteins

Front 14

What is the bone matrix made of?

Back 14

It is made of the extracellular elements of bone tissue.

Front 15

For non-mineralized bone, what is albumin's function?

Back 15

Transports essential elements to matrix; it maintains osmotic pressure of bone fluid

Front 16

For non-mineralized bone, what is glycoproteins' function?

Back 16

To promote calcification.

Front 17

For non-mineralized bone, what is osteocalcin's function?

Back 17

1. Promotes bone resorption
2. Inhibits calcium phosphate precipitation (attracts calcium ion to incorporate in hydroxyapatite crystals).
3. Serum osteoclacin is a sensitive marker of bone formation.
4. Vitamin K-dependent protein present in bone.

Front 18

For non-mineralized bone, what is sialoprotein's function?

Back 18

Promotes calcification.

Front 19

For non-mineralized bone, what are collagen fibers?

Back 19

They make up the bulk of the bone matrix.

Front 20

For non-mineralized bone, what are fibrils?

Back 20

They are collagen molecules assembled into three thing chains.

Front 21

For non-mineralized bone, what are proteoglycans?

Back 21

1. They are large complexes of numerous polysaccharides attached to a common protein core.
2. They strengthen bone by forming compression-resistant networks between collagen fibers.

Front 22

What are the types of bone tissue?

Back 22

1. Compact bone
2. Spongy bone

Front 23

What is the difference between compact and spongy bones?

Back 23

The type of organizations.

Front 24

What features are found in compact bone?

Back 24

1. They are highly organized, solid, and extremely strong.
2. They are part of the haversian system.

Front 25

What is the basic structure of compact bone?

Back 25

Mostly located in the diaphysis of the bone (middle area).

Front 26

What is the haversian system?

Back 26

1. Is the basic structural unit in compact bone.

Front 27

What does the haversian system consists of?

Back 27

1. A central canal called haversian canal.
2. Concentric layers of bone matrix called lamellae.
3. Tiny spaces (lacunae) between the lamellae.
4. Bone cells (osteocytes) within the lacunae
5. Small channels or canals called canaliculi.

Front 28

What is a cancellous (spongy) bone?

Back 28

Compared to compact bone, it is less complex and lacks haversian system.

Front 29

What are the features of the cancellous (spongy) bones?

Back 29

1. They have trabeculae,or lamellae arranged in plates or bars, that unite with one another to form an irregular meshwork.
2. Contain red bone marrow