Intro to Skeletal System

Question 1

What percentage of bone is inorganic/calcified?

Answer 1

70%

Question 2

What percentage of bone is organic/collagen?

Answer 2

30%

Question 3

Bone is anisotropic. What does this mean?

Answer 3

That bone is stronger in some orientations than others – it responds better to compression than shear stress.

Question 4

What is an osteocyte?

Answer 4

A mature bone cell that maintains the protein & mineral contents within the matrix.

Question 5

What does an osteoblast do?

Answer 5

It secretes osteoid, which creates cartilagenic bone.

Question 6

What does an osteoclast do?

Answer 6

It secretes acid to dissolve & remove bony matrix.

Question 7

What is the role of osteoprogenitor cells?

Answer 7

They produce osteoblasts, which is important for fracture repair.

Question 8

What is inside of the open space in spongy bone?

Answer 8

Marrow

Question 9

Where is compact bone most concentrated?

Answer 9

At the periphery/on the outside edges of the bone.

Question 10

Where are red and yellow marrow contained?

Answer 10

Within the medullary cavity

Question 11

Where is the periosteum and endosteum?

Answer 11

Peri = outside, end = inside

Question 12

When you get a shin splint, which part of the bone is being pulled?

Answer 12

The periosteum

Question 13

What is another name for an osteon and what shape is it?

Answer 13

A Haversian system, it’s concentric/circular

Question 14

What is at the centre of an osteon?

Answer 14

Blood vessel canal

Question 15

How does intramembranous (dermal) ossification occur? (4 steps)

Answer 15

1. Mesenchymal/stem cells -> osteoblasts -> ossification center
2. Osteoblasts -> osteocytes -> calcify bone
3. Blood vessel feeds developing bone
4. Adult bone develops into spongy and compact layers.

Question 16

How does endochrondal ossification occur? (4 steps)

Answer 16

1. Primary ossification center develops in the diaphysis
2. Medullary cavity forms as space for the marrow
3. Secondary ossification centers develop on the proximal and distal ends (epiphyses)
4. Growth plates (metaphyses) form and then calcify around age 25

Question 17

Why do some doctors mistakenly diagnose fractures in children?

Answer 17

Because their bones have not fully calcified, and cartilage cannot be seen on an x-ray.

Question 18

During growth, bone is resorbed on the inside by __________ & deposited on the outside by __________

Answer 18

Resorbed by osteoclasts, deposited by osteoblasts

Question 19

From strongest to weakest, rank the three types of stress on bones.

Answer 19

1. Compressive
2. Tensive
3. Shear

Question 20

What are the 4 steps of bone fracture repair?

Answer 20

1. Extensive bleeding, forming a large blood clot.
2. Internal callus unites the inner edges and external callus stabilizes the outer edges
3. Cartilage is replaced by bone, fragments are dissolved and the broken ends are united by spongy bone.
4. Swelling marks the location, but is remodeled over time.

Question 21

What is osteoporosis?

Answer 21

Bone death, where spongy bone becomes porous & does not react as well to stress. Starts to bend and snaps more easily than healthy bone.

Question 22

What are the 5 bone shapes?

Answer 22

Long (ie. limbs)
flat (ie. skull)
short (ie. wrist)
pneumatized (ie. nose cavity)
irregular (ie. vertebra)

Question 23

What are the three joint types?

Answer 23

Fibrous, Cartilaginous and Synovial

Question 24

What is the most stable joint type and what is an example of it?

Answer 24

Fibrous (ie. skull sutures)

Question 25

What is the difference between primary and secondary cartilaginous joints?

Answer 25

Primary joints disappear with age (ie. growth plates) and converted into bone.
Secondary joints persist throughout the lifetime.

Question 26

What is a synchondrosis?

Answer 26

Cartilage that is converted into bone with age.

Question 27

What is a symphysis?

Answer 27

Permanent cartilaginous union between bones.

Question 28

What is the name of the mobile joint between two long bones?

Answer 28

Synovial, the most common type.

Question 29

What is the great thing about synovial fluid?

Answer 29

It prevents friction extremely well, better than motor oil.

Question 30

What is the difference between a hinge joint and a ball-and-socket joint?

Answer 30

Hinge joints only move in one direction (flexion and extension), whereas ball-and-socket joints are much more mobile.