Histology Exam 2: Bone

Front 1

Bone is what type of tissue?

Back 1

specialized connective tissue

Front 2

What makes up bone (basic)?

Back 2

cells and extracellular matrix

Front 3

What is specialized about the extracellular matrix in bone?

Back 3

It's calcified (hydroxyapatite crystals of calcium phosphate) extracellar matrix with osteocytes embedded in matrix

Front 4

What is the main component of the adult skeleton?

Back 4

Bone

Front 5

What are main functions of bone (basic)?

Back 5

1. protects vital organs
2. supports fleshy structures
3. storage of Ca (reserve, 99%) and phosphate
4. harbors bone marrow where blood cells originate

Front 6

Why is bone called a dynamic tissue?

Back 6

It is constantly
1) changing shape, and
2) absorbing and reabsorbing in response to biomechanical forces

Front 7

What are the basic building blocks of bone (specific)?

Back 7

collagen fibrils (type I collagen mainly, 90%) and hydroxyapatite crystals

Front 8

What is the major structural component of bond matrix?

Back 8

Type I collagen

Front 9

What percentage of total weight of bone matrix proteins is due to collagen? What makes up the remaining percentage?

Back 9

90%, Other 10% is noncollagenous matrix proteins (make up ground substance)

Front 10

What two components mineralize to form bone tissue?

Back 10

1. Collagen
2. ground substance

Front 11

What are the four cell types of bone?

Back 11

1. Osteoprogenitor cell (from mesenchyme, give rise to osteoblasts)
2. Osteoblasts (from osteoprogenitor, give rise to ECM and become osteocytes)
3. Bone-lining cells (from osteoblasts, remain on surface-no active growth)
4. Osteoclasts (from blood, "macrophages" of blood)

Front 12

What is the importance of canaliculi?

Back 12

Metabolites cannot diffuse through bone so exchanges between cells and blood capillaries depend on these spaces which perforate the matrix

Front 13

The process of new bone formation

Back 13

osteogenesis

Front 14

Compare the functions of the four different bone cell types.

Back 14

1. Osteoprogenitor-BONE FORMATION
2. Osteoblasts-differientate, more active secretory than osteoprogenitor cells; SYNTHESIZE and secrete type I COLLAGEN and bone matrix proteins
3. Bone-lining cells-maintenance and nutritional support of osteocytes in the underlying bone matrix; regulate movement of Ca/P in and out of bone
4. Osteoclasts-BONE RESORPTION

Front 15

Osteoprogenitor cells are stimulate to differentiate into the more active secretory cells called what?

Back 15

Osteoblasts

Front 16

Where are osteoblasts located?

Back 16

Located at the surface of the bone, resembling epithelium (side by side)

Front 17

What is the function of osteoblasts?

Back 17

Synthesize and secrete Type I collagen and bone matrix proteins

Front 18

What is the initial unmineralized bone?

Back 18

osteoid

Front 19

What is morphologically different between osteoblasts and osteocytes?

Back 19

1. Osteoblasts-cuboidal basophilic
2. Osteocytes-flattend, basophilia declines

Front 20

What do osteoblasts become?

Back 20

Osteocytes; when a lacuna forms

Front 21

Osteoblasts that have become surrounded by osteoid or unmineralized bone matrix

Back 21

osteocyte

Front 22

What is the main function of osteocytes?

Back 22

to maintain the bone matrix

Front 23

What is the osteocyte function of responding to mechanical forces applied to bone called?

Back 23

Mechanotranscduction; allows osteocytes to synthesize new matrix or degrade matrix to maintain calcium homeostasis

Front 24

What bone cell lies in lacunae?

Back 24

osteocytes

Front 25

How do osteocytes contact processes of neighboring osteocytes and bone-lining cells?

Back 25

1. canaliculi
2. gap junctions

Front 26

List characteristics of osteocytes.

Back 26

1. flat, almond-shaped cells
2. Less rER than osteoblasts
3. Actively involved in bone maintenance

Front 27

What does death of osteocytes result in?

Back 27

1. Resorption of bone matrix by osteoclast activity,
2. followed by repair of bone tissue by osteoblast activity

Front 28

Within bone matrix there are spaces, what are these called? What bone cells do these spaces contain?

Back 28

lacunae; osteocyte

Front 29

small tunnels that extend from osteocyte; what is their function?

Back 29

canaliculi; connect adjacent lacunae and allow contact between cells of neighboring osteocytes

Front 30

How do osteocytes communicate?

Back 30

gap junctions

Front 31

How does bone maintain viability?

Back 31

depends on osteocytes

Front 32

Where are bone-lining cells located?

Back 32

in sites of bone that are not remodeling

Front 33

What is the difference between periosteal and endosteal cells?

Back 33

1. Periosteal: bone-lining cells on EXTERNAL bone surfaces
2. Endosteal: bone-lining cells on INTERNAL bone surfaces

Front 34

Where are bone-lining cells derived from?

Back 34

Osteoblasts

Front 35

What are the two main functions of bone-lining cells?

Back 35

1. Feeds osteocytes in underlying bone matrix (maintenance and nutritional support)
2. Regulate movement of Ca and P in and out of bone

Front 36

What is the main function of osteoclasts?

Back 36

Bone resorption

Front 37

a shallow bay called a resorption bay directly under the osteoclast

Back 37

Howship's lacunae

Front 38

Where osteoclast adheres to matrix

Back 38

clear zone

Front 39

Characteristics of osteoclasts

Back 39

1. large
2. multinucleated (5-50)
3. Found at sites where bone is being removed
4. cells have RUFFLED BORDER surrounded by CLEAR ZONE
5. close to bone matrix

Front 40

Are osteoblasts related to osteoclasts?

Back 40

No!

Front 41

Where are osteoclasts derived from? What does it give rise to?

Back 41

Blood (fusion of mononuclear hemopoietic progenitor cells); neutrophilic granulocyte and monocyte

Front 42

Osteoclasts are occasionally found where? Where are they readily found?

Back 42

Howship's lacunae; ossifcation zone of growth plate

Front 43

Giant multinucleated, break down bone

Back 43

osteoclast

Front 44

Acidification facilitates the dissolution of calcium phosphate and is optimal for lysosome activity

Back 44

bone resorption

Front 45

T/F Bones are organs of the skeletal system.

Back 45

True

Front 46

What are the structural components of bone?

Back 46

1. Bone tissue
2. Connective tissue (i.e., hemopoietic tissue, fat tissue, blood vessels, nerves)

Front 47

If bone forms a joint then what must be present?

Back 47

hyaline cartilage

Front 48

What are the four types of bone, description and examples of each?

Back 48

1. Long bones-longer in one dimension, shaft and 2 ends; ex: tibia or metacarpals
2. Short bones-equal length and diameter; ex: carpals of hand
3. Flat bones-thin and plate-like, has two layers of thick compact bone and intervening layer of spongy bone; ex: skull cap, sternum
4. Irregular bone-does not fit in other 3 categories; ex: vertebra

Front 49

What are hydroxyapatite crystals?

Back 49

A mineral in bone

Front 50

What is a hydration shell?

Back 50

surface of crystals that is hydrated

Front 51

What do minerals and collagen fibers contribute to bone resistance?

Back 51

1. Minerals-hardness
2. Collagen-Holds it together

Front 52

Bone matrix is made of what two types of matter? Give examples of each.

Back 52

1. 50% is inorganic (i.e., calcium, phosphorous, carbonate)
2. Organic (i.e., collagen type I, glycoproteins, proteoglycans)

Front 53

Collagen fibers which bind periosteum to bone

Back 53

Sharpey's fibers

Front 54

Compare and Contrast Periosteum and endosteum.

Back 54

1. Endosteum is thinner than periosteum.
2. Endosteum lines internal body cavities and periostium covers external bone surface.
3. Endosteum is single layer of flattened osteoprogenitor cells and CT; periosteum is outer layer of collagen and fibroblasts.

Front 55

What are the principle functions of peri/endosteum?

Back 55

1. Nutrition of osseous tissue
2. Provide new osteoblasts for bone growth and repair

Front 56

mature bone is composed of structural units (Havarian systems)

Back 56

osteons

Front 57

Consist of concentric lamellae of bone matrix, surrounding a central canal (the osteonal (Haversian) canal)

Back 57

osteon

Front 58

The lamallae of the osteon contains what?

Back 58

vascular and nerve supply

Front 59

What can happen to excess Ca?

Back 59

It can be removed from blood and stored in bone

Front 60

Acts on bone to raise low blood calcium levels to normal; promotes osteoclastic bone resorption with release of calcium accompanying resorption

Back 60

PTH

Front 61

Acts to lower elevated blood calcium levels to normal

Back 61

calcitonin

Front 62

Acts by stimulating both osteocytes and osteoclasts to resorb bone

Back 62

PTH

Front 63

Inhibits resorption by inhibiting the effect of PTH on osteoclasts

Back 63

Calcitonin

Front 64

holds synovial fluid

Back 64

articular cavity

Front 65

bone capped here by CT that holds bones together

Back 65

joints

Front 66

What determines the type and degree of movement between bones?

Back 66

Joints

Front 67

Diarthroses v. Synarthroses

Back 67

1. Diathroses: free movement between bones
2. Synarthroses: limited to no movement

Front 68

Provide lubrication and nutrients and oxygen to the avascular tissue

Back 68

synovial fluid

Front 69

Why are bones set when they break?

Back 69

speeds healing process and results in superior structural and functional restoration

Front 70

How long does it take a healthy person to heal a broken bone?

Back 70

6-12 weeks

Front 71

disease that results in decrease of bone mass

Back 71

osteoporosis

Front 72

Rickets in children, or softening of bones as the osteoid is less mineralized than normal

Back 72

osteomalacia