Lecture 9- Bone

Question 1

What type of tissue is bone?

Answer 1

Connective

Question 2

What are the components of bone?

Answer 2

Cells and Extracellular Matrix (Bone Matrix)

Question 3

What cells make up bone?

Answer 3

1. Osteoblasts
2. Osteoclasts
3. Osteocytes
4. Bone lining Cells
5. Osteoprogenitor Cells

Question 4

What makes up Bone Matrix?

Answer 4

1. Fibers

2. Ground Substance

Question 5

What is general fibrous structure of bone and why is it like that?

Answer 5

Fibers are aligned parallel but are oriented in different directions.
Adds strength.

Question 6

What gives bone its strength?

Answer 6

A calcified bone matrix

Question 7

What cells help “maintain” the bone matrix?

Answer 7

Osteocytes

Question 8

How does the osteocyte gets its nutrients and get rid of waste?

Answer 8

Canaliculi

Question 9

What happens in the canaliculi?

Answer 9

Exchange of nutrients and waste products that travel down cell to cell of dendritic processes of osteocytes

Question 10

What structure aids w/ transfer of nutrients from one osteocyte to another?

Answer 10

Gap Junctions

Question 11

2 General Types of Bone Structure

Answer 11

1. Compact Bone

2. Cancellous Bone (AKA spongy or trabecular bone)

Question 12

Is compact bone and cancellous bone made of the same material?

Answer 12

Yes. Both Lamellar bone. Organized differently.

Question 13

Where do osteoblasts come from?

Answer 13

Bone lining cells or osteoprogenitor cells.

Question 14

Steps of the bone remodeling cycle (3).

Answer 14

1. Osteoclast (apoptosis)
2. Osteoblast Secretes bone matrix (osteoid - unmineralized bone)
3. Mineralization

Question 15

Where does bone remodeling occur?

Answer 15

1. On the surface of bone

2. In the middle of bone

Question 16

How does bone modeling occur in the middle of bone?

Answer 16

1. Clasts come through blood vessel, start working to make a connecting canal
2. Blasts stay on surface (bone lining cells) and fill in canal with bone (surround blood vessels)
3. Cytes sit in lacuna and maintain matrix and stim remodeling cycle from stress

Question 17

What is osteoporosis?

Answer 17

1. Decreased bone mass per unit volume of anatomical bone.

2. After 35, clast > blast

Question 18

Biphosphonates can help limit osteoporosis, but osteonecrosis may be a side effect, why?

Answer 18

Biphosphonates disrupt bone remodeling. When there is continual stress on the bones, they have a limited capacity for healing

Question 19

Different kinds of osteogenesis (2)

Answer 19

1. Intramembranous Ossification

2. Endochondral Ossification

Question 20

Most flat bones develop via _______ ossification.

Answer 20

Intramembranous

Question 21

Steps of intramembranous ossification (4)

Answer 21

1. Mesenchymal cells in CT membrane or sheet form clusters
2. Cluster differentiates into osteoblasts = ossification center
3. Osteoblasts secrete osteoid
4. Becomes mineralized

Question 22

What is condensed mesenchyme?

Answer 22

Mesenchyme that is more cellular

Question 23

What kind of bone is intramembranous bone?

Answer 23

Primary bone or Woven Bone = SPONGY

*NOT LAMELLAR BONE or secondary bone

Question 24

What are trabeculae made of and how is it oriented?

Answer 24

Collagen Fibers

Oriented Randomly

Question 25

What happens during the remodeling of woven bone? | Where can you find this kind of bone?

Answer 25

It become lamellar bone, with collagen fibers oriented in parallel. Flat bones like in the skull.

Question 26

What does endochondral ossification mean?

Answer 26

Cartilage that turns to bone.

Question 27

Steps of endochondral ossification.

Answer 27

1. Mesenchymal Cells Condense during fetal development 2. Develop into chondrocytes 3. Cartilage is developed into the shape of the bone that it will form (surrounded by perichondrium) 4. Cartilage deteriorates and becomes primary ossification center (woven bone), has blood vessel of periosteal bud 5. Secondary Ossification Centers develop at the ends of the bone

Question 28

Why is epiphyseal cartilage important?

Answer 28

It allows you to get taller

Question 29

Zones of epiphyseal growth plate (5)

Answer 29

Zone 1 - Hyaline Cartilage (resting zone) Zone 2 - Proliferation - making more chondrocytes Zone 3 - Hypertrophy Zone 4 - Calcification - osteoblasts come in and lay down bone Zone 5 - Ossification

Question 30

What happens to chondrocytes at the epiphyseal growth plate? (7)

Answer 30

1. Hypertrophy of chondrocytes 2. Compress surrounding cartilaganous matrix 3. Chondrocytes die (apoptosis) 4. Carilage matrix become more calcified (basophilic) 5. Blood vessels and osteoblasts invade the tissue 6. Lay down Osteoid 7. Mineralized to bone

Question 31

What type of bone will initially be formed at the growth plate?

Answer 31

Woven bone. Later remodeled into lamellar bone.

Question 32

When is full stature obtained?

Answer 32

When the epiphyses have fused (fully ossified, no more cartilage there)

Question 33

Which type of bone would you see in a new fracture and healed fracture?

Answer 33

1. Woven Bone 2. Lamellar Bone * Fractures heal quickly, woven bone is layed and remodeled

Question 34

What general things affect bone formation/turnover?

Answer 34

1. Major Systemic Regulators | 2. Stress on the bone

Question 35

What are the major systemic regulators of bone formation/turnover? (7)

Answer 35

1. Parathyroid Hormone (PTH) 2. Calcitrol (vit. D) 3. Calcitonin 4. Growth hormone/ IGF - 1 5. Glucocorticoids 6. Thyroid Hormones 7. Estrogen/androgens * First 3 are most important* * *Remember PCC**

Question 36

What is the main function of Vitamin D?

Answer 36

Increase Ca absorption from the gut

Question 37

Main function of PTH?

Answer 37

Released when serum Ca low | *Stimulates osteoclast activity to raise serum Ca

Question 38

What would a happen with deficiency of PTH?

Answer 38

Remodeling process would not be stimulated

Question 39

What does excess growth hormone in an adult result in and why?

Answer 39

Acromegaly | Periosteal growth happens b/c you do not have endochondral ossification as an adult

Question 40

What does excess growth hormone in a child result in and why?

Answer 40

Gigantism | Endochondral ossification at the epiphyseal plate

Question 41

What does insufficent growth hormone in a child result in?

Answer 41

Dwarfism

Question 42

What are the components of the joint capsule?

Answer 42

1. Fibrous Layer | 2. Synovial Membrane

Question 43

What is the orientation of collagen fibers in Articular Cartilage?

Answer 43

Curved fibers. Perpendicular to surface near the bone and parallel to surface neaer the surface.

Question 44

What is the advantage of curved fibers in articular cartilage?

Answer 44

Pressure is more evenly distributed, helps protect the chondrocytes from deformation.

Question 45

Where do chondrocytes in articular cartilage get their nutrients?

Answer 45

Synovial fluid. *When you stand and squish cartilage, the water is pushed out into synovial fluid, and when you sit back down, water goes back in and brings O2 and nutrients with it.