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MSK I > Histology of the Bone > Flashcards

Histology of the Bone Flashcards

1
Q

general features of bone

A

Cells, fibers, ground substance

contains extracellular matrix consisting of hydroxyapatite

dynamic: undergoes constant remodeling in response to chronic stress

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2
Q

general features of bone

A

mechanical support, locomotion, support, storage of calcium and phosphate ions

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3
Q

bone architecture: compact bone versus spongy bone

A

compact bone is called lamellar; encloses inner spongy layer

spongy bone is called trabecular or cancellous bone
lamellar or woven with spaces for bone marrow
have trabeculae

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4
Q

Long bones are ___ and include these two bones:

A

tubular, humerus, femur

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5
Q

Short bones are ____ and include these bones

A

cuboidal, ankle and wrist

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6
Q

Flat bones are ____ and include

A

protective, cranium

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7
Q

Irregular bones are ____ and include

A

various shapes, include the pelvis

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8
Q

sesamoid develop in ____ and an example is the

A

develop in tendons

patella

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9
Q

Diaphysis

A

the “shaft” compact bone surrounding marrow cavity

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10
Q

Epiphysis

A

ends of the bones

spongy bone surrounded by compact bone

contains growth plate or epiphyseal plate

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11
Q

Metaphysis

A

spongy bone between the end of the diaphysis and the epiphysis

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12
Q

periosteum

A

connective tissue covering the bone

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13
Q

endosteum

A

connective tissue lining the marrow cavity of the bone

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14
Q

which area contains the epiphyseal plates?

A

epiphysis

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15
Q

which bone area connects tissue lining of the marrow cavity?

A

endosteum

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16
Q

Connective tissue of the periosteum and endosteum

cell types, protein

fiber types

innervation/vascularization

limitations of periosteum

A

fibroblasts and collagen in the outer layer
Sharpey’s fibers = periosteal fibers that penetrate the bone matrix

osteoprogenitors cells line the inner layer
osteoprogenitor cells are also contained in the endosteum

note: osteoprogenitor cells become osteoblasts)

periosteum = highly vascularized + nerve supply

periosteum does not cover articular surfaces

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17
Q

what is a common injury associated with periosteal inflammation?

A

shin splints

“medial tibial stress syndrome”

it is an overuse injury

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18
Q

Lamellar bone

A

contains a regular, circumferential arrangement of collagen fibers

Haversian systems (osteons) structural unit

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19
Q

Haversian systems

A

Osteons

unit of structure in lamellar bone

circumferential arrangement of collagen fibers

lacunae are the spaces for cells (osteocytes) within the lamellae

Lacunae are the spaces for cells (osteocytes) within the lamellae

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20
Q

osteocytes are located in

what are osteocytes

A

lacunae within osteons

mature or differentiated osteoblasts

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21
Q

Canaliculli =

A

small canals that radiate from the lacuna and “house” cell processes

blood vessels occupy the central canal of a Haversian system

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22
Q

Osteons =

A

concentrically arranged lamella around a central haversian canal

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23
Q

what are in the haversian canal?

A

blood vessels

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24
Q

How do blood vessels get into the lamella?

A

Blood vessels from periosteum enter the lamella through Volkmann’s canal, perpendicular to the diaphysis, and branch to enter into Haversian canals

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25
in the adult, what cells and where are these cells located when bone repair is required?
osteoprogenitor cells in the endosteum which differentiate into osteoblasts
26
from outside in
periosteium outer later (collagen, blood vessels, Volksmann canals) --> periosteum inner layer (osteoprogenitor cells) --> endosteum (osteoprogenitor cells and Volksmann canals) --> lamella with Volksmann canals and Haversian systems
27
Osteocytes
maintain bone matrix solitary cells, usually flattened or spindle shaped surrounded by mineralized matrix visually, think spidery looking cells surrounded by extracellular matrix
28
Osteocyte processes (where are they, how are they connected, and what purpose)
in canaliculi and are connected by GAP JUNCTIONS allows communication and transport of nutrients
29
interstitial lamella is the result of
bone remodeling
30
Bone matrix =
organic component = Type I collagen, proteoglycans, chondroitin sulfate, karatan sulfate inorganic component = calcium phosphate and hydroxyapatite
31
woven bone
usually temporary, weaker than lamellar difference between them is that collagen is not aligned also found in developing bone
32
osteoprogenitor cells
resemble fibroblasts, flattened, usually alone differentiation regulated by BMP & core binding factor alpha
33
CFBA1
core factor binding alpha 1: one of the two differentiation factors required by osteoprogenitor cells for production the other is BMP
34
osteoblasts
differentiated, bone forming cells ACTIVE cells: basophilic and cuboidal (Squamous cells in inactive bone) found in association with newly secreted matrix differentiation controlled by CBFA-1 and RunX2 and osteocalcin Sox9 directs the differentiation of osteoprogenitor cells into osteoblasts
35
factors that stimulate differentiation of osteoprogenitor cells versus factors that stimulate differentiate osteoprogenitor cell differentiation into osteoblasts
BMP, CBFA-1 = osteoprogenitor cells | CBFA-1+RunX2+osteocalcin = transcription factors for osteoprogenitor cell into osteoblasts; Sox9 directs differentiation
36
Osteoblast differentiation: gene required, 1st indicator, and deficiency outcome of 1st indicator
OB-specific genes direct differentiation CBFA-1/Runx2 ---> first indicator (tissue marker) of osteogensis mice deficient of CBFA-1/RunX2 have cartilage skeletons instead of bone
37
what do osteoblasts do
they deposit osteoid
38
osteoid
osteoblast deposition consisting of: non-mineralized collagen 1, osteocalcin, osteopontin, sialoprotein osteoblasts control bone mineralization
39
osteoblasts deposit a lot of matrix and become disconnected from the outer surface of developing bone. what happens to them
they become flattened and a lacunae develops around them
40
how do basophils appear under the microscope?
basophilic
41
Osteoclasts
bone MOs, derived from monocyte-mac progenitor cells mononuclear phagocyte system located in Howship's lacunae subosteoclastic compartments
42
Howship's lacunae
location of MOs
43
"osteoclasia" translates
bone resorption
44
what do osteoclasts "have" intracellularly
lots of mitochondria and acidified vesicles
45
which part of the osteoclast has a ruffled boarder
the side closest to the bone
46
what does the osteoclast do
breaks down mineralized bone with acid
47
osteocytes are actively regulated by what two hormones?
calcitonin and PTH
48
Bone formation 1: intramembranous osteogensis occurs in the following sequence (5 steps)
Mesenchymal cells aggregate mesenchymal cells form osteoblasts: bone blastema is formed bine matrix deposited by cells of blastema, forming primary bone. ossification centers fuse to form trabeculae (spongy bone)
49
three things to keep in mind about intramembranous ossification that distinguishes it from the other form of bone formation
1) develops from a well vascularized primitive connective tissue 2) bone formation is not preceded by cartilage 3) an aggregate of mesenchymal cells differentiates directly into osteoid producing osteoblasts
50
bones formed by intramembranous bone formation include
clavicle, frontal and parietal bones, parts of occipital, temporal, mandible, and maxilla bones
51
Endochondral osteogenesis
this is when bone replaces a cartiaginous template chondrocytes in the cartilaginous template become isolated by the extracellular matrix (mostly type II collagen)
52
endochondral osteogenesis beginning with chondrocytes secreting _____ collagen
Chondrocytes secrete type X collagen, promoting angiogenesis increased blood supply promotes calcification of matrix and chondrocytes undergo apoptosis primary centers of ossification form in the diaphysis and secondary form in the epiphysis
53
How does endochondral ossification begin?
Chondrocytes in the cartilaginous template become isolated by the ECM (mostly type II collagen) chondrocytes then hypertrophy and secrete Type X collagen which in turn promotes angiogensis blood vessels deliver calcium and promotes general calcification of ECM. then chondrocytes undergo apoptosis. primary ossification forms in the diaphysis and secondary centers of ossification form in epiphysis
54
Primary ossification centers
occur where proliferation of chondrocytes have hypertrophied and secrete angiotactic factors
55
Secondary ossification centers
occur in the epiphyseal sites: vascularization of the epiphysis delivers bone forming chondrocytes in the epiphyseal plate secretes IHH which promotes chondrocyte proliferation but inhibits hypertrophy these cells add to the bone in both diaphysis and epiphysis. eventually epiphyseal plate becomes epiphyseal lines and cease growing
56
Reserve Zone
hyaline cartilage right under the epiphyseal cartilage
57
Proliferative Zone
chondrocytes prolif: VERTICAL LINES or stacks, share a common territorial matrix
58
Hypertrophic Zone
Chondrocytes enlarge, secrete Type X collagen and vascular endothelial growth factor Matrix calcifies transverse septa are thinner angiogenesis is stimulated
59
Vascular invasion zone
blood vessels invade osteoprogenitor cells move in blood vessels transverse septa osteoblasts beneath the sites of vascular invasion begin to deposit osteoid on the cartilaginous cores forming trabecular bone
60
"osteoclasts chase"
the ossification front begins in the vascular invasion zone: chondrocytes are destroyed
61
in which direction do chondrocytes proliferate in the proliferative zone?
away from the ossification front, which increases the length of the cartilage
62
proliferating chondrocytes express _____ in the prolifierative zone
CFBA-a/RunX2
63
in which direction does the osteoclast chasing/osteocyte running occur?
in the direction of the epiphyseal cartilages
64
Unlike intramembranous ossification, endochondral ossification occurs because of
chondrocytes at primary ossification centers have secreted type II collagen (hyaline cartilage) which is the template that is eventually replaced by bone
65
where do the osteoprogenitor cells come from in intramembraneous ossification versus endochondral ossification
intramembranous ossification center, mesenchymal cells become osteoblasts and directly deposit osteoid endochondral ossification requires osteoprogenitors imported via vascular supply from the perichondria arrive and are responsible for secreting bone matrix
66
bone remodeling: compact bone remodeling occurs within the
osteon
67
a _______ indicates the edge of a remodeled osteon
cement line
68
in ________ more bone is resorbed than replaced
osteoporsis
69
Activation/Resorption/Reversal/Formation
Osteoblasts are recruited in the Haversian canals, differentiate into osteoclasts, which begin resorption of the inner lamella moving outward, leaving "interstitial lamella" when osteoclasts stop, osteoblasts are recruited and begin depositing osteon (osteoclast/osteoblast reversal) cement line indicates the boundary of newly organized lamella
70
when a bone breaks...
the vascular supply is disrupted: blood clot forms. haversian system fails to receive blood, it dies. MOs scavenge/clean area of debris intense proliferation of osteoprogenitor cells from periosteum and endosteum osteoblasts form cellular collar around fracture site immature bone is formed (woven bone) trabeculae unite to form bony callus that temporarily unite the bone fragments woven bone is remodeled into lamellar bone
71
endosteum (for real this time) line
haversian canals and marrow cavities
72
Shin splits
Medial Tibial stress syndrome periosteum

MSK I (14 decks)

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