Bone

Question 1

Bone is composed of

Answer 1

Osteoid (30%), Mineral (50%) and Water (20%)

Question 2

Composition and function of osteiod

Answer 2

Predominantly collagen I; adds flexibility to rigid bone tissue

Question 3

Composition and function of mineral

Answer 3

Hydroxyapatite (carbonated); stiffness, rigidity and strength

Question 4

As time goes on, what happens to crystal structure of the bone

Answer 4

Crystals become less perfect (insert interstitial atoms), collagen begins to cross link which increases the bone stiffness; This cross linking can be reducible and non reducible.

Question 5

The two types of bone tissue are

Answer 5

Cortical and Trabecular

Question 6

The location cortical bone is

Answer 6

The shafts of lone bones, external shell of trabecular bone areas

Question 7

Function of water

Answer 7

Provides nutrients and oxygen

Question 8

The location of trabecular bone is

Answer 8

At the ends of long bones; at the centers of flat bones

Question 9

Does trabecular or cortical bone degrade first?

Answer 9

Trabecular due to fragility

Question 10

The function of cortical bone is to

Answer 10

Resist high loading

Question 11

The function of trabecular bone is to

Answer 11

Distribute high stress

Question 12

Flat bones are formed by

Answer 12

Direct bone formation on the fibrous scaffold

Question 13

Long bones are formed by

Answer 13

Endochondral ossification; made on a cartilage precursor

Question 14

Fracture healing works by

Answer 14

Cartilage formation and then replacement by bone

Question 15

The bone cell types are

Answer 15

• Osteoclasts (OCs)
• Osteoblasts (OB’s)
• Osteocytes

Question 16

The function of osteoclasts is

Answer 16

Resorb bone

Question 17

The function of osteoblasts is

Answer 17

Lay down new bone (osteoid)

Question 18

The function of osteocytes is

Answer 18

These are just OB’s locked in their matrix; they sense force due to damage and send OB’s to make OCs; OCs will remodel the bone damage away, and OBs will refill it.

Question 19

Osteocytes and their processes reside in the

Answer 19

Lacunae and canaliculi

Question 20

Bone disease is a result of

Answer 20

An alteration of the bone regeneration process

Question 21

0th level bone element and size

Answer 21

Tissue; >3mm

Question 22

1st level bone element and size

Answer 22

Osteon, plexiform bone, intersticial bone; 100-300 micrometers

Question 23

2nd level bone element and size

Answer 23

Lamellae, canaliculi, lacunae, cement lines; 3-20 micrometers

Question 24

3rd level bone element and size

Answer 24

Collagen fibrils, mineral crystals; 60-600nm

Question 25

A lamellae is

Answer 25

The concentric layer(s) around a blood vessel in cortical bone

Question 26

Parameters affecting stiffness of cortical bone

Answer 26

- Density of collagen x links - Mineral content - Porosity - Tissue age - Crystal perfection

Question 27

To determine the mineral content of bone you

Answer 27

- micro CT or | - Ash weight (you burn the bone)

Question 28

Voight model of bone

Answer 28

Applies a compression load on bone; bone model is alternating strips of bone and air parallel to the load; strain is equal in every portion; gives us the maximum stiffness as we vary porosity

Question 29

What way do we determine the porosity affect on bone

Answer 29

Voight model (max affect) and Reuss Model (min affect)

Question 30

Reuss model of bone

Answer 30

Applies a compression load; bone model is alternating strips of bone and air normal to the load; stress is the same in each section; gives us the minimum stiffness as we vary porosity

Question 31

To calculate the effective contributions of individual constituents to the stiffness we need to use

Answer 31

The strain localization matrix, combined with the stiffness matrix of each component and the distribution of each component (volume fractions of mineral, collagen and carbonate)

Question 32

The unit of trabecular bone remodeling is

Answer 32

The trabecular packet

Question 33

When trabecular bone is remodeled it has what structure

Answer 33

A lamallar structure, laid down in layers (trabecular struts) that can be plate like or rod like

Question 34

Parameters that might affect tissue-level stiffness of trabecular bone

Answer 34

- # of trabecular packets per # of struts - Porosity (~50%), Cortical is ~10% - Anisotropy - material =/= mechanical anisotropy

Question 35

Degree of anisotropy is

Answer 35

1 - length of small axis/length of large axis; determined by the eigenvalues of the fabric tensor

Question 36

The strain localization matrix [m] is used to

Answer 36

Integrate material properties into the constitutive equation; these are the properties of the mechanical constituents (eg. mineral, collagen, etc.)

Question 37

The fabric tensor [A] tells us

Answer 37

The distribution of the material (aka structure)

Question 38

Plexiform bone is

Answer 38

A type of cortical bone; woven bone formed more rapidly than lamellar bone tissue; not found in humans