Lecture 4 (FIRST MIDTERM)

Question 1

Spongy bone is able to resist stress because of the…

Answer 1

trabeculae

think of the analogy of the rolled up magazine

Question 2

Stress lines are thickest in what regions?

Answer 2

where stress is the highest

Question 3

What is the periosteum?

Answer 3

the outside covering of bone; fibrous outside, cellular inside; functions in growth and repair

Question 4

What is the endosteum?

Answer 4

the inside covering (the marrow cavity); functions in growth and repair

Question 5

How many layers of periosteum?

Answer 5

Two

Question 6

What are the layers of periosteum?

Answer 6

Fibrous outside (dense irregular connective tissue) and cellular inside

Question 7

Compared to the periosteum, what does the endosteum lack?

Answer 7

the fibrous outside covering

Question 8

The cellular layer of the periosteum and the endosteum contain what kind of cells?

Answer 8

osteoprogenitor cells

Question 9

Two modes of bone formation:

Answer 9

Endochondral ossification and intremembranous ossification

Question 10

How does the cellular layer of periosteum connect so strongly to the bone?

Answer 10

Perforating fibers go deeply into the bone from the periosteum; when osteoprogenitor cells turn into osteoblasts, they secrete osteoid around the fibers and they become bone. The fibers are actually embedded in bone.

Question 11

Intramembranous ossification is also called what?

Answer 11

Dermal ossification

because bone develops directly inside the dermis

Question 12

Endochondral ossification:

Answer 12

• bone that forms inside cartilage

- cartilage is converted to bone (by bonding minerals to cartilage)

Question 13

Endochondral ossification has a ___________ ______________.

Answer 13

cartilaginous precursor

Question 14

Endochondral ossification is typical of the formation of what bones?

Answer 14

irregular

Question 15

2 ways bones grow with the method of endochondral ossification:

Answer 15

Interstitial growth and appositional growth

Question 16

Epiphyseal growth is another way to refer to…

Answer 16

interstitial growth

Question 17

The way bones grow with intermembranous ossification:

Answer 17

with bony spicules that spread out.

-common in flat bones (many in the skull)

Question 18

In the cartilage during endochondral ossification, what starts growing larger and larger and creates big spaces, which eventually “kills” itself but cutting off nutrition to itself?

Answer 18

chondrocytes

Question 19

The spaces left from the “dead” chondrocytes is invaded by what?

Answer 19

blood vessels

Question 20

What differentiates into the first osteoblasts?

Answer 20

fibroblasts

Question 21

What migrates in with the blood vessels?

Answer 21

fibroblasts

Question 22

The primary center of ossification is located where?

Answer 22

inside of the diaphysis

Question 23

During ossification, perichondrium now turns into…

Answer 23

periosteum

Question 24

Secondary centers of ossification are located where?

Answer 24

epiphyses

Question 25

Where does interstitial (epiphyseal) growth occur?

Answer 25

metaphysis

Question 26

How does appositional growth occur?

Answer 26

The cells of the inner layer of the periosteum differentiate into osteoblasts and deposit bone matrix to outside.
Osteoclasts from inside the bone are slowly removing bone matrix from the inner surface.
Bone eventually increases in diameter.

Question 27

How can they tell how much more you’re gonna grow?

Answer 27

Look at the amount of cartilage still there among the bones

Question 28

Where does appositional growth occur?

Answer 28

at the periosteum

Question 29

How does intramembranous ossification occur?

Answer 29

Mesenchymal cells aggregate and form clusters that become osteoblasts and start forming osteoid

Question 30

Where does intramembranous ossification occur?

Answer 30

inside the dermis

Question 31

Endochondral bone comes from cartilage, so it’s from mesoderm. HOWEVER, intramembranous (dermal) bone comes from…

Answer 31

neural crest cells

Question 32

Since intramembranous bone forms in the dermis, there is no cartilaginous precursor. Is there a perichondrium? Periosteum?

Answer 32

Neither, UNTIL the very end when there is already some bone (a plate) formed

Question 33

Mesenchymal cells that form in intramembranous ossification condense to form what?

Answer 33

an ossification center

Question 34

Bone as a dynamic tissue increases bone formation by…

Answer 34

• Exercise
• Estrogen/testosterone (more hormone, more bone. less hormone, less bone)
• Growth hormone

Question 35

As you get older, your ________ activity slows down while your __________ activity doesn’t really slow down.

Answer 35

osteoblast, osteoclast

Question 36

Difference between osteopenia and osteoporosis:

Answer 36

Osteopenia: lack of bone; normal with age
Osteoporosis: porous ; not normal