U2 Lecture 2

Question 1

Bones are made of what type of tissue?

Answer 1

Connective tissue

Question 2

What makes up connective tissue?

Answer 2

extracellular matrix and cells

Question 3

What makes up extracellular matrix?

Answer 3

Ground substance and fibers

Question 4

What makes up ground substances?

Answer 4

Organic ( ex: non-collagenous proteins) and inorganic components

Question 5

Where are the organic components of bone extracellular matrix from?

Answer 5

osteoblasts

Question 6

What is the ground substance of organic components in ECM

Answer 6

• Glycosaminoglycans (GAGs)
• Glycoproteins = polysaccharide + protein (chondroitin sulfate, hyaluronic acid)
• negatively charged (they trap water)

Question 7

What type of collagen fibers are found in the organic components of ECM

Answer 7

Type 1 Collagen

Question 8

Define type 1 collagen

Answer 8

• fibrous protein arranged in helical form
• very resistant to pulling forces
• provides flexibility and a framework for deposition of calcium crystals

Question 9

Hierarchial organization of collagen in bone

Answer 9

osteoblasts -> tropocollagen -> microfibril -> fibril -> fiber -> lamella -> osteon -> compact bone -> bone

Question 10

What are the types of inorganic components in ECM

Answer 10

Water and hydroxyapatite crystals

Question 11

What is hydroxyapatite?

Answer 11

Calcium phosphate and calcium hydroxide, other minerals (calcium carbonate) and some ions (Mg2+, F-, and K+)

• salt

Question 12

Describe the formation of hydroxyapatite crystals in bone ECM

Answer 12

• salts (hydroxyapatite) are deposited within collagen fibers
• As the hydroxyapatite condenses, other inorganic salts and ions precipitate in the matrix to fill in the spaces between fibers

Question 13

Organizations of minerals in bone ECM

Answer 13

• small mineral plates bound by helical noncollagenous proteins (collagen cross links) form mineralized fibrils
• many mineralized fibrils bound by collagen cross links form osseous tissue fiber (collagen fiber)

Question 14

Functions of collagen for bone ECM

Answer 14

Provides flexibility and resistance to tension

Question 15

Functions of minerals for bone ECM

Answer 15

Provides firmness (resistance to compression)

Question 16

What happens when you soak bones in weak acid (vinegar)?

Answer 16

Removes minerals from bone -> bone becomes rubbery

Question 17

What happens when you apply denature protein to bone?

Answer 17

removes collagen from bone -> bone becomes brittle/crumbly

Question 18

Skeletal disorders

Answer 18

• rickets: inorganic component deficient (calcium deficient due to lack of vit. D leads to flexible bones)
• Scurvy: organic component deficient (problem with collagen synthesis due to vit. C deficiency leads to brittle bones)

Question 19

Spongy bone vs. Compact bone

Answer 19

• same chemical composition

- different 3D organization

Question 20

Organization of spongy bone

Answer 20

• irregular lattice of thin plates called trabeculae

- trabeculae made of osteocytes, lacuna, lamellae, canaliculi, osteoblasts, and osteoclasts (housed in lacunae)

Question 21

Locations of spongy bone

Answer 21

• epiphyses of long bone (on each end of the bone which is the part that grows)
• surrounding marrow cavities
• flat, short, irregular bones

Question 22

Functions of spongy bone

Answer 22

• withstands forces from many directions: trabeculae arranged along lines of stress
• lightens the skeleton (not as strong as compact bone)
• contains red marrow for hemopoiesis

Question 23

Compression and Tension

Answer 23

compression is opposite of tension

Question 24

Organization of compact bone

Answer 24

• solid network of bone organized in rings called osteons

- compact bone made of lacuna, central canal, interstitial lamellae, canaliculus, osteocytes, and blood vessels

Question 25

What is lacuna?

Answer 25

The space in compact bone which the osteocytes are found

Question 26

What is compact bone’s primary weakness?

Answer 26

Twisting forces