Bones Lecture Test 2

Front 1

osteogenic cells

Back 1

•stemcells–Multiply continuously to makeosteoblasts

Front 2

osteoblasts

Back 2

•bone-formingcells–Make soft organic matter of matrixwhich thenhardens by mineral deposition

Front 3

osteoclasts

Back 3

•bone-dissolvingcells found on the bone surface–Unusually large cells formed fromthe fusion of several stem cells

Front 4

osteocytes

Back 4

•formerosteoblasts that have become trapped in the matrix they have deposited–Whenstressed, produce biochemical signals that regulate bone remodeling

Front 5

What constitutes the matrix of bone?

Back 5

•–Organic matter (1/3 of matrix)—madeby osteoblasts•Collagen, carbohydrate–proteincomplexes•Flexibility

•–Inorganic matter (2/3 of matrix) •85% hydroxyapatite (crystallizedcalcium phosphate salt)•10% calcium carbonate•Other minerals (fluoride, sodium,potassium, magnesium)•Strength

Front 6

Organic matter in the matrix of the bone is made by....

Back 6

Osteoblasts

Front 7

What are the bone types?

Back 7

•Compact (cortical)—looks compact,more dense•Spongy (trabecular/cancellous)—looks “spongy”

Front 8

What is compact bone made of?

Back 8

•Osteon = basic structural unit of compactbone•–Concentric lamellae (layers ofmatrix and cells)–Cylinderof tissue around a central canal•BVsand nerves

Front 9

Spongy bone consists of...

Back 9

–Thinplates of bone called trabeculae –Spacesfilled with redbone marrow

Front 10

Advantage of spongy bone over compact bone

Back 10

Lighter but still strong

Front 11

How is spongy bone related to mechanical stress?

Back 11

Lamallae line/form at the line of stress for strengthening purposes

Front 12

Where is bone marrow found?

Back 12

•Marrow cavity and spaces betweentrabeculae

Front 13

Types of Bone Marrow

Back 13

•Red (myeloid tissue)–Hemopoietic—producesblood cells–Morein children–Adults—skull,vertebrae,ribs,sternum,part of pelvicgirdle,and proximalheads of humerusand femur•Yellow–Fatty–Nolonger produces blood

Front 14

Two Types of Bone Development

Back 14

Intramembraneous ossification; endochondral ossification

Front 15

Where does intramembranous ossification take place?

Back 15

Skull and clavicle

Front 16

Key points to intramembranous ossification

Back 16

–Startw/ soft CT, end up with bone–Osteoblastsreplace CT w/ spongy bone–Outersection of bone calcifies further to become compact bone–Resistscracking–Middleof bone remains spongy

Front 17

Steps in intramembranous ossification

Back 17

1) Condensationof CT into soft sheetpermeatedwith blood capillaries; -CTcells enlarge and turn into osteogenic cells

2) Depositionof osteoid tissue by osteoblastsonsurface; entrapment of firstosteocytes;formation of periosteum

3) Honeycombof bony trabeculae formed bycontinuedmineral deposition; creation ofspongybone

4)Surfacebone filled in by bone deposition,convertingspongy bone to compact bone.Persistenceof spongy bone in the middle layer

Front 18

End result of intramembranous ossification? What happens with skull fractures?

Back 18

Spongy bone sandwich; Skull fracture may leave innerlayer of compact bone unharmed

Front 19

Key points to endochondral ossification

Back 19

–Intracartilaginousossification—bone forming to replace a cartilage “model”–Mostbones in human body–Hyalincartilage into calcified cartilage–Calcifiedcartilage into spongy bone–Spongybone remodeled into either compact or spongy

Front 20

Steps to endochondral ossification

Back 20

1) Early cartilage model (perichondrium on outside; hyalin on inside)

2) Formationofprimaryossificationcenter,bonycollar, andperiosteum

3)Vascularinvasion,formationof primarymarrowcavity, andappearanceof secondaryossificationcenter

4)Boneat birth, withenlargedprimary marrowcavity and appearanceofsecondarymarrow cavityin one epiphysis

5)Boneof child, withepiphysealplate atdistalend

6)Adultbone with asinglemarrowcavityand closedepiphysealplate

Front 21

How does cartilage change with endochondral ossification throughout childhood?

Back 21

•During infancy and childhood, theepiphyses fill with spongy bone••Cartilage limited to the articular cartilage covering each joint surface, and tothe epiphyseal plate–Epiphysealplate persists through childhood and adolescence–Servesas a growth zone for bone elongation

Front 22

Bone grows in which directions?

Back 22

–Length– interstitial growth–Width –appositional growth

Front 23

Where does bone elongation take place?

Back 23

•Epiphyseal plate—region of transition fromcartilage to bone–growthzone–hyalinecartilage in middle–transitionzone on each side where cartilage is replaced by bone

Front 24

Steps in bone elongation

Back 24

1) Chondrocytes divide and produce collagen (cartilage) –add length to bone

2)Chondrocytesdie –leave space

3) Osteoblasts lay down bone matrix on top of cartilage base

Bone elongations –a result of cartilage growth withinthe epiphyseal plate

Front 25

How does epiphyseal line form?

Back 25

Epiphysealplate closes when cartilage is gone: •A line of slightly denser spongybone between epiphysis and diaphysis •Lengthwise growth is finished•Occurs at different ages (lateteens to early twenties)

Front 26

Types of dwarfism

Back 26

•Achondroplastic dwarfism–Long bones stop growing inchildhood•Normal torso, short limbs–Failure of cartilage growth inepiphyseal plate–Spontaneous mutation producesmutant dominant allele–

•Pituitarydwarfism–Lack of growth hormone–Normal proportions with shortstature

Front 27

What is appositional growth?

Back 27

•bonesincrease in width throughout life–Deposition of new bone at thesurface–Osteoblasts on deep side ofperiosteum deposit osteoid tissue–Osteoclasts of endosteum enlargemarrow cavity

Front 28

What is bone remodeling?

Back 28

•Throughoutlife—10% per year–Repairs microfractures,releases minerals into blood, reshapes bones in response to use and disuse–osteoblasts and osteoclasts workingtogether–Bone grows in response tomechanical stress•Racket arm of tennis players•Bones of athletes•Greater trochanter of children

Front 29

Steps in healing of fractures

Back 29

1) HematomaformationThehematoma is convertedtogranulation tissue by invasionofcells and blood capillaries.

2)Softcallus formationDepositionof collagen andfibrocartilageconverts granulationtissueto a soft callus.

3) Hardcallus formationOsteoblastsdeposit a temporarybonycollar around the fracture tounitethe broken pieces whileossificationoccurs.

4) BoneremodelingSmallbone fragments areremovedby osteoclasts, whileosteoblastsdeposit spongyboneand then convert it tocompactbone.

Front 30

When does ossification occur?

Back 30

•Ossification for a lifetime with growth andremodeling of bones