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Histo > Bone Lecture 1 > Flashcards

Bone Lecture 1 Flashcards

1
Q

Fxns of bone

A

Structural support

Protection of vital organs

Hematopoiesis (red bone marrow)

Reservoir for Ca2+ (calcium) and PO4- (phosphate)

Mechanical levers for movement

Storage of adipocytes (yellow bone marrow)

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2
Q

What makes up Long Bones?

A 
Epiphysis
Metaphysis (growth plate)
Diaphysis
Periosteum
Endosteum
Compact/cortical bone
Spongy/Trabecular bone
Articular cartilage
Red & yellow marrow
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3
Q

Characteristics of flat/short/irregular bones

A 
Two outer plates
Cortical bone (dense)

Diploe (middle layer)
Spongy bone
Contains red marrow

Locations
Skull, ilia, ribs, sternum

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4
Q

Long Bone types

A

Bones of extremities

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5
Q

Short Bone types

A

Cube-shaped bones of wrist/ankle

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6
Q

Irregular Bone types

A

vertebrae, sacrum, mandible

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7
Q

Flat Bone types

A

cranium, sternum, ilium, scapula

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8
Q

Sesamoid Bone types

A

Bones within a tendon (patella)

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9
Q

Osteoblasts characterisitics

A

Located at surfaces of bone tissue

Cells are side by side, similar to an epithelial cell layer

Actively synthesize osteoid = organic matrix of bone

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10
Q

What do osteoids contain?

A

Type I collagen
GAGs, PG aggregates
Glycoproteins – osteonectin, osteocalcin

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11
Q

What do osteoblasts create?

A

hydroxyapatite crystals (calcium and phosphate) to “calcify” (harden) the matrix

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12
Q

Osteocytes

A

Osteocytes are osteoblasts that have become surrounded by calcified organic matrix

Calcification occurs “around” osteocyte, creating a lacuna

Osteocytes function to maintain matrix of bone

Osteocyte maintains small amount of non-calcified matrix at its immediate periphery within the lacuna

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13
Q

Osteocytes fxning

A

Osteocytes have cytoplasmic processes extending from the cell

Calcification of matrix “around” these processes creates canaliculi (small canals)

Osteocytes use canaliculi to form connections and gap junctions with adjacent cells

Allows easy nutrient exchange between cells

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14
Q

Osteoclasts

A

Multinucleated (5-50 nuclei)–highly active

Motile-never locked in a matrix

Derived from blood monocytes

Located in Howship’s lacunae when actively resorbing bone

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15
Q

Fxn of Osteoclasts

A

Function as bone macrophages to resorb matrix of bone during bone remodeling

Resorption (break down) of bone

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16
Q

Ruffled Border of osteoclasts importance?

A

necessary for proper bone resorption
Creates a microenvironment for demineralization and organic matrix removal

Site of adhesion of the osteoclast to the bone matrix

17
Q

Bone Resportion process

A

Osteoclast secretes collagenase to digest organic matrix of bone (especially collagen)

Osteoclast also pumps protons (acid) into lacunae to promote localized digestion of ECM proteins

Resorption is controlled by cytokines and hormones
Thyroid hormone, calcitonin – reduce activity

Osteoblasts have receptors for parathyroid hormone (PTH); PTH causes osteoblasts produce osteoclast stimulating factor –increase activity

18
Q

Bones ECM organic components

A

Osteoid
Type I Collagen

Ground substance (GAGs, PGs, glycoproteins)

19
Q

Bones ECM inorganic components

A

Minerals
Calcium and phosphorous salts
Hydroxyapatite crystals

20
Q

Osteoid: Un-calcified bone matrix

A

Type I collagen in large fiber bundle form

Ground Substance
GAGs - Chondroitin-4-sulfate

Glycoproteins = osteocalcin, osteonectin & bone sialoprotein
Each aids in process of calcification of bone

Removal or loss of osteoid of bone results in:
Brittle bone

21
Q

Bone inorganic components

A

Calcium and Phosphorous Salts
50% of dry weight
50% are replaced each year in bones

Hydroxyapatite crystals (combination of salts)
Ca10(PO4)6(OH)2
Give bone its rigidity

De-calcification of bone results in
Flimsy/rubbery bone

22
Q

Periosteum/Endosteum

A

External and internal surfaces of bone are covered by layers of bone-forming cells

Periosteal fibroblasts along with their associated dense connective tissue ECM

Functions:
Nutrition of osseous tissue

Continuous supply of new osteoblasts necessary for maintenance, repair and growth of bone

23
Q

Periosteum outer layer

A

Fibroblasts
Collagen fibers (mostly type I)
Sharpey’s fibers - Bind periosteum to bone

24
Q

Periosteum inner layer

A

Osteoprogenitor cells

Fibroblast-like cells with the potential to divide and differentiate into osteoblasts

25
Q

Endosteum fxn

A

Lines all internal cavities within the bone

Provides nutrient supply to bone cells

Single layer of flattened osteoprogenitor cells

Small amount of loose connective tissue

Some collagen fibers, minimal ground substance

Osteoprogenitor cells provides a reservoir for new osteoblasts for bone maintenance, growth and repair

26
Q

Primary Bone

A

Immature or woven bone
First to appear in fracture repair and in embryonic development of bone
Organic matrix fibers (collagen) are irregularly arranged

27
Q

Secondary Bone

A

Mature or lamellar bone

Collagen fibers and cells have a lamellar (layered) arrangement

28
Q

Primary bone purpose and characterisitics

A

Type of bone that is produced when bone is initially formed; occurs in adults only during fracture healing

Replaced by mature, lamellar bone as fracture repair progresses

Characteristics:
Irregular array of collagen fibers

Lower mineral content compared to lamellar bone

Higher proportion of osteocytes vs. lamellar bone

29
Q

Lamellar (mature) bone

A

Outer circumferential lamellae

Inner circumferential lamellae
Around marrow cavity

Interstitial lamellae
Between the 2 circumferential systems

30
Q

Haversian System Components: Haversian Canal

A

Parallel to long axis of bone

Form the central point of Haversian systems

31
Q

Haversian System Components: Volkmann’s Canal

A

Oriented perpendicular to long axis of bone

Connect blood supply between Haversian systems

32
Q

Haversian System – Fiber Orientation

A

In each lamella of the system, collagen fibers are oriented parallel to each other

Fibers orientation in adjacent lamellae may change up to 90º

Formation of collagen fibers within lamella imparts significant mechanical strength to bone for resisting tensile forces in many directions

Histo (12 decks)

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