Catos Skeletal Tissues - Bone

Front 1

The three functions of bone.

Back 1

Mechanical support/structure, Mineral homeostasis, hematopoesis after fetal month 5 until death.

Front 2

Two types of tissues in bone.

Back 2

1. Spongy (cancellous/trabecular)
2. Compact (cortical)

Front 3

Categorize and subcategorize the bony matrix.

Back 3

1. Organic: Osteoid: 95% Type I collagen with chondroitin sulfate and osteocalcin (to bind Ca)
2. Inorganic: primarily calcium and phosphate in crystalline hydroxyapatite.

Front 4

The two lineages of bone cells

Back 4

Osteoblast lineage and the osteoclast progenitor pathway.

Front 5

Stem cells that differentiate into osteoblasts.

Back 5

Osteogenic cells (or osteoprogenitors)

Front 6

What is the function of osteoblasts?

Back 6

To form bone by secretion of the bone matrix (surprise) and potentially calcify.

Front 7

What do osteoblasts mature into?

Back 7

Osteocytes.

Front 8

Characterize osteocytes and their primary function.

Back 8

Osteocytes inhabit bony lacunae where they project into the canaliculi and maintain Ca homeostasis.

Front 9

How do osteocytes talk to each other?

Back 9

Gap junctions. Ultimately the Ca they pass is given to osteoblasts.

Front 10

What hormone stimulates osteocytes to regulate Ca?

Back 10

Parathyroid hormone, or PTH.

Front 11

Characterize osteoclasts and their primary function

Back 11

Multinucleated cells living on bony surface in Howship's lacunae, also modify Ca levels via resorption.

Front 12

What is the enzyme that catalyzes bone resorption?

Back 12

Carbonic anhydrase in osteoclasts.

Front 13

Flow chart of bone resorption

Back 13

Carbonic anhydrase makes carbonic acid which dissociates into bicarbonate -> bicarbonate leaves with sodium while the protons get pumped into compartment ->acidic pH eats inorganic matrix -> Acid phosphatase and cathepsin K eat organic components.

Front 14

Name the two important lysosomal hydrolases.

Back 14

Acid phosphatase and cathepsin K.

Front 15

What are the two regulators of bone resorption?

Back 15

PTH and vitamin D.

Front 16

Precursor of osteoclasts?

Back 16

GM-CFU, along with monocytes.

Front 17

What happens when osteoblasts release M-CSF?

Back 17

The GM-CFU precursor will become a multinucleated osteoclast.

Front 18

How long is the bone remodeling cycle?

Back 18

100 days

Front 19

Does bone reshape due to changes in mechanical stress?

Back 19

Yep.

Front 20

What are the three lamellar arrangements of bone matrix (presume you know lamellar means in a row)?

Back 20

1. Haversian system (osteon)
2. Interstitial lamellae
3. Circumferential lamellae.

Front 21

What is the lamellar pattern of the Haversian system?

Back 21

Concentric rings.

Front 22

Define Haversian canal

Back 22

The passageway through the center of a Haversian system that contains vasculature.

Front 23

What connects Haversian canals?

Back 23

Volkmann's canals

Front 24

What's special about interstitial lamellae?

Back 24

They are the oldest lamellae from remodeled Haversian systems.

Front 25

Two types of circumferential lamellae

Back 25

1. Outer: made by osteogenic layer of periosteum.
2. Inner: made by endosteum

Front 26

Define Sharpey's fibers

Back 26

Anchor outer circumferential lamellae to bone.

Front 27

Where will you NOT find the periosteum?

Back 27

Synovial articular surfaces, tendon/muscle insertions, sesamoid bones.

Front 28

What is the one way bone can grow? Why?

Back 28

Appositionally. Osteocytes are trapped and cannot divide.

Front 29

What is the bony growth called after a fracture?

Back 29

Extraosseous callus.

Front 30

Contents of the endosteum and it's relationship to the periosteum

Back 30

Osteogenic cells, osteoblasts, reticular fibers. It is continuous to the periosteum.

Front 31

Stick a pin through the skull from the outside in and list the layers you'll strike in order.

Back 31

Pericranium (periosteum), outer table, diploe (spongy bone), inner table, dura mater.

Front 32

Blood supply of the outer bone and periosteum.

Back 32

Periosteal arteries that poke through Volkmann's canals

Front 33

Where does the nutrient artery enter the bone? What does it supply?

Back 33

Through the nutrient foramen, or multiple. The inner bone and marrow up to the epiphyseal plate.

Front 34

Name the two arterial supplies of the ends of bones and their origin.

Back 34

The metaphyseal and epiphyseal arteries, from the associated joint.

Front 35

What are the four bony surfaces and their locations?

Back 35

1. Periosteal: outermost
2. Haversian surfaces: duh
3. Cortical-endosteal surface: inner cortex

Front 36

Does a resting bone surface contain any cells?

Back 36

No.

Front 37

What does centripetal osteonal lamellar development really mean?

Back 37

The lamellae form in a Haversian system from the cement line IN to the canal.

Front 38

What are the two phases of bone formation, in order?

Back 38

Matrix formation followed by calcification.

Front 39

What three factors contribute to the necessary threshold for bone mineralization?

Back 39

1. Osteocalcin binds Ca
2. Alkaline phosphatase increases Ca and P concentrations
3. Matrix vesicles in osteoblasts bud off and hydroxypatite forms within. They rupture and crystals grow.

Front 40

How long does it take to mineralize osteoid?

Back 40

10 days.

Front 41

What are the two main mechanisms of bone formation and their main difference?

Back 41

Endochondral vs. Intramembraneous. Endochondral uses a cartilagenous precursor. BOTH ULTIMATELY GROW APPOSITIONALLY, so this distinction is somewhat moot after development.

Front 42

Flow chart of intramembraneous ossification.

Back 42

Mesenchyme become cancellous bone -> becomes compact bone -> Mesenchymal cells become osteoblasts, which produce osteoid -> the oldest osteoid calcifies -> trabecular growths come together around vasculature.

Front 43

What is the key step in forming bone from a cartilagenous precursor (we think)?

Back 43

The perichondrium of the hyaline cartilage becomes vascularized, stimulating local cells to differentiate into osteoblasts.

Front 44

How do the early osteoblasts in endochondral ossification kill the chondrocytes?

Back 44

By forming a periosteum and a bony sheath, the avascular cartilage cannot receive diffusive nutrients, dies, and calcifies.

Front 45

Who comes in with the periosteal bud?

Back 45

Hematopoetic stem cells for the marrow. Osteogenic cells for the bone.

Front 46

Where does the periosteal bud come from and where does it go?

Back 46

The periosteum forms the bud and it enters the diaphysis.

Front 47

Flow chart of endochondral ossification (post-bud)

Back 47

Osteogenic cells differentiate into osteoblasts -> new osteoid is formed -> oldest osteoid calcifies. Meanwhile, chondrocytes are proliferating and dying, extending the bone.

Front 48

What is the secondary center of ossification?

Back 48

The epiphyseal plates laid down at birth. Made of hyaline cartilage. Will continue to proliferate until 20 years of age when plate dies.

Front 49

What are the five zones of the epiphyseal plate, from epiphysis to diaphysis?

Back 49

1. Resting cartilage
2. Proliferating cartilage
3. Hypertrophying cartilage
4. Calcifying cartilage
5. Ossification -- osteoblasts attach to trabeculae.

Front 50

Characteristics of immature (woven) bone.

Back 50

No lamellae, random cellular arrangement, more ground substance, initially mineralized, rapid formation.