Bones Review

Question 1

Give characteristics of the 3 types of bones

Answer 1

Long bones – compact bone mainly in the diaphysis, spongy bone in the epiphysis. Short bones – shell of compact bone with spongy bone and marrow in the center. Flat bones – two layers of compact bone with spongy bone in between. Irregular bones - vertebrae

Question 2

Where do new blood cells, blood supply and nerves come from?

Answer 2

periosteum endosteum

Question 3

Where is the source of osteoprogenitor/osteogenic cells?

Answer 3

periosteum endosteum

Question 4

What structure facilitates nutrition of new bone?

Answer 4

periosteum

Question 5

In Sharpey’s fibers in the ligaments and tendons, the collagen fibers of the ______ anchor into the bone.

Answer 5

Periosteum (from outside the bone)

Question 6

The bone matrix is initially laid down as unmineralized what?

Answer 6

osteoid

Question 7

Mineralization begins with the secretion of what.

Answer 7

Alkaline phosphatase

Question 8

What is the major component of bone?

Answer 8

Type I collagen (One for bOne)

Question 9

What is the major component of organic bone matrix?

Answer 9

Type I collagen (One for bOne)

Question 10

Describe the arrangement of college fibers.

Answer 10

“twisted”: in concentric rings called lamellae

Question 11

What substance in vinegar will remove mineralization? -> what is left after that process?

Answer 11

Acetic acid; collagen structure

Question 12

What is the function of canaliculi?

Answer 12

Allow osteocytes to talk to each other and receive nourishment; canaliculi are found in lamellar bone as well as in immature bone

Question 13

Where are osteoprogenitor cells derived from?

Answer 13

Mesenchymal stem cells in the marrow (they are not endodermal cells)

Question 14

How does osteocyte respond to PTH?

Answer 14

By releasing Ca2+ from bone

Question 15

Osteocytes are surrounded by?

Answer 15

Calcified extracellular matrix (it’s not found on the surface of bone)

Question 16

Where are osteoprogenitor cells found in? (2 places)

Answer 16

Periosteum and endosteum

Question 17

Where do osteoblasts reside in the periosteum?

Answer 17

The osteogenic layer of the periosteum

Question 18

What is the single main function of osteoblasts?

Answer 18

Synthesizes (secretes) osteoid (as several specific proteins)

Question 19

Where do you always find osteoblasts?

Answer 19

Always sits on top of a piece of bone: aligned on the surface of the bone

Question 20

What is osteoid?

Answer 20

Unmineralized organic matrix; uncalcified bone matrix; stuff before mineralization

Question 21

Osteoclasts sit in what?

Answer 21

Howship’s lacunae

Question 22

Where do you always find osteoclasts?

Answer 22

Also always sit on bone`

Question 23

What is the function of osteocyte?

Answer 23

Maintenance of the bone matrix!

Question 24

What two substances are in the osteoclasts that help them to carry out their function?

Answer 24

Hydrolytic enzymes (proteolytic enzymes) and hydrogen ions (organic acids)

Question 25

How does osteocyte touch each other? Through what?

Answer 25

Via gap junction

Question 26

Is osteoclast part of the osteon?

Answer 26

Never

Question 27

Where do osteoclasts derive from?

Answer 27

The fusion of mononuclear hematopoietic progenitor cells; mononuclear phagocyte system;
monocyte; macrophage (all four are equivalent terms)

Question 28

What happens in the clear zone of osteoclast?

Answer 28

Breaks down both collagen and mineralized part of bone (site of resorption and degradation)

Question 29

What is one distinguishing feature of osteoclasts in appearance?

Answer 29

Large, multinucleated

Question 30

What is the single main function of osteoclasts?

Answer 30

Resorption of bone matrix

Question 31

What two substances promote osteoclast apoptosis?

Answer 31

Bisphosphonates and estrogens

Question 32

Give the 4 steps of bone remodeling.

Answer 32

Resorption -> reversal -> formation -> resting

Question 33

Which structure initiates bone repair?

Answer 33

Periosteum

Question 34

What is collagenase

Answer 34

Enzymes that break the peptide bonds in collagen

Question 35

What is the structural and functional unit of bone?

Answer 35

Osteon aka Haversion systems

Question 36

Give 2 functions calcitonin.

Answer 36

Stimulates osteoblast and decreases osteoclast activity

Question 37

What is interstitial lamellae? How do they look like? (are they a complete circle?)

Answer 37

Remnants of older Haversion systems; partially destroyed so does not form a complete circle

Question 38

Intramembranous ossification occurs in which bone type?

Answer 38

Flat bones

Question 39

List the 4 zones of endochondral ossification in order.

Answer 39

Zone of proliferation -> hypertrophy -> calcification -> resorption

Question 40

What is carried in the Volkmann’s canal?

Answer 40

NERUVASCULAR SUPPLY (so nerves + blood vessels)

Question 41

Where is the primary ossification center? Secondary ossification site?

Answer 41

In the middle of diaphysis; in the epiphysis of developing long bones

Question 42

What is the function of the Volkmann’s canal?

Answer 42

Allows for communication b/w Haversion systems

Question 43

What hormones increase bone reabsorption?

Answer 43

PTH, glucocorticoids, thyroid hormone, vitamin D

Question 44

What hormones decrease bone reabsorption?

Answer 44

Calcitonin, gonadal steroids

Question 45

What hormones increase bone formation?

Answer 45

Growth hormone, vitamin D, gonadal steroids

Question 46

What hormones decrease bone formation?

Answer 46

glucocorticoids

Question 47

Give 3 functions of PTH.

Answer 47

Cause increased intestinal absorption of calcium, cause the kidneys to retain calcium, increase osteoclast activity

Question 48

Where is calcitonin produced in?

Answer 48

Thyroid gland