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Histology - Exam 2 > Exam 2 - Osteochondrogenesis and Joint Components > Flashcards

Exam 2 - Osteochondrogenesis and Joint Components Flashcards

1
Q

bone histogenesis

A

occurs by intramembranous and endochondral bone formation - both produce bone that appears histologically identical

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2
Q

bone remodeling

A

combo of bone formation and resorption that occurs throughout life: old osteons constantly replaced as osteoclasts form an erosion tunnel, apoptose after 2 weeks, then osteoblasts form new osteon

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3
Q

where does bone remodeling occur

A

inside compact bone and at bone surfaces

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4
Q

speed of bone remodeling: primary vs. secondary bone

A

slower process in secondary bone than primary bone

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5
Q

composition of old osteon

A

high mineral content, low water content

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6
Q

relationship b/w bone and calcium

A

bone is buffer for calcium - [calcium] determined by rate at which calcium enters and leaves bone

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7
Q

cementing/reversal line

A

line of cementing substance put down by osteoblasts first - highly mineralized with little collagen

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8
Q

bone turnover in adults?

A

about 10% each year

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9
Q

what bones form by intramembranous bone formation?

A

flat bones: skull, facial bones, mandible, clavicle, pelvis - occurs in highly vascular mesenchymal tissue

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10
Q

what signaling patterns control intramembranous bone formation?

A

signals from polypeptides of Wnt, hedgehog, fibroblast growth factor (FGF), and transforming growth factor-Beta families

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11
Q

does intramembranous bone formation ever occur in endochondral bone?

A

yes - with healing of mild fractures

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12
Q

IBF - what forms primary ossification centers?

A

mesenchymal cells condense into primary os centers

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13
Q

what do mesenchymal cells in primary os centers differentiate into?

A

osteoblasts that begin secreting osteoid collagen

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14
Q

IBF- what happens after osteoblasts become trapped in matrix?

A

become osteocytes - small spicules of developing bone unite to form trabeculae

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15
Q

IBF- what does fusion of bony trabeculae form?

A

spongy bone

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16
Q

IBF- what happens once spongy bone is formed?

A

blood vessels invade and other undifferentiated mesenchymal cells give rise to bone marrow

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17
Q

IBF- where do the periosteum and endosteum differentiate from?

A

areas of mesenchymal tissues that do not undergo ossification

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18
Q

IBF- initial woven bone is turned into what in the outer and inner layers?

A

outer layer - converts to lamellar bone; inner layer -remains spongy (diploe)

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19
Q

what bones form by endochondral bone formation?

A

long bones

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20
Q

EBF- what is the purpose of hyaline cartilage?

A

serves as a small model for bone and as scaffold for bone development (bone follows cartilage)

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21
Q

EBF- what are the two stages?

A

development of primary and secondary ossification centers

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22
Q

EBF- Where does the primary os center develop?

A

at midriff of diaphysis of cartilaginous model

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23
Q

EBF- How is perichondrium turned into periosteum?

A

vascularization of perichondrium transforms chondrogenic cells to osteoprogenitor cells then osteoblasts (now periosteum)

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24
Q

EBF- what do osteoblasts first produce on surface of cartilaginous model?

A

subperiosteal bone collar by intramembranous bone formation

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25
EBF- what causes cartilage matrix in diaphysis to begin to calcify?
chondrocytes become hypertrophic and secrete collagen X and VEGF
26
EBF- how does cartilage calcification affect chondrocytes?
calcified cartilage matrix inhibits nutrient diffusion and hypertrophied chondrocytes die
27
EBF- what forms the primitive marrow cavity?
lacunae becoming confluent when hypertrophied chondrocytes die due to inhibited nutrient diffusion
28
EBF- what do osteoclasts do with the bone collar?
create perforations in it, permitting periosteal buds to enter primitive marrow cavity in cartilage model - cartilage in walls of these spaces now becomes calcified
29
EBF- what are contained in periosteal buds?
blood vessels, osteoprogenitor cells, mesenchymal cells
30
EBF- where is osteoid/bone matrix made?
made/calcified on surface of calcified cartilage, forming a calcified cartilage-calcified bone complex
31
EBF- what happens after formation of the calcified cartilage-calcified bone complex begins to form?
subperiosteal bone collar thickens and elongates toward epiphyses
32
EBF- how do osteoclasts affect the calcified cartilage-calcified bone complex?
they begin to resorb the complex and enlarge the marrow cavity
33
EBF- describe the direction of bone formation
spreads from primary os center towards epiphyses
34
how does calcified cartilage stain
basophilic
35
how does calcified bone stain
acidophilic
36
EBF- Where and when do the secondary os centers form?
at epiphyses after diaphyseal os centers well established - when osteoprogenitor cells invade epiphyses and differentiate into osteoblasts
37
EBF- How do secondary os centers form?
similarly to primary ossification
38
EBF- where is cartilage located after the epiphyses are filled with bone tissue?
articular surfaces and epiphyseal plates
39
Epiphyseal plate growth?
new cartilage added to epiphyseal end while being replaced at diaphyseal end
40
How does articular cartilage contribute to bone growth?
it doesn't
41
closing of growth plates
diaphyseal and epiphyseal bone become continuous, connecting the two epiphyseal marrow cavities - around 20 y/o
42
zone of reserve?
small, randomly arranged, inactive chondrocytes at the front edge of growth
43
zone of proliferation?
interstitial growth - region of rapid mitotic divisions that gives rise to rows of isogenous cell groups
44
zone of hypertrohpy and maturation?
region where the chondrocytes are enlarged
45
zone of calcification?
region where remnants of cartilage matrices become calcified and chondrocytes die
46
zone of ossification/resorption?
where bone is made upon the calcified cartilage, followed by resorption of calcified bone-calcified cartilage complex
47
signaling molecule in epiphyseal growth plate?
type 10 collagen
48
what does bone fracture damage?
bone matrix, bone cells, and blood vessels
49
what is bone fracture accompanied by?
localized hemorrhaging and blood clot formation
50
what is the first step of fracture healing?
proliferation of osteoprogenitor cells from periosteum and endosteum surrounding fracture
51
what do the osteoprogenitor cells produce at the fracture site?
cellular tissue surrounding fracture and penetrating b/w ends of damaged bone - forms callus internally and externally
52
what forms in fracture zone after callus?
fibrous CT and hyaline cartilage
53
what replaces cartilage at the fracture zone?
bone from endochondral bone formation replaces cartilage w/ mostly woven bone to form a bony callus
54
what is the fate of the bony callus?
it is resorbed and replaced with secondary/lamellar bone as the fracture heals
55
how do hairline fractures heal?
via intramembranous bone formation that occurs at the periosteal surface - tends to be a slower process
56
synarthroses
immovable joints composed of CT, cartilage, or bone
57
synarthroses locations
unite first rib to sternum and connect skull bones
58
amphiarthroses
joints with slight movement
59
amphiarthroses locations
IV discs
60
diarthroses
synovial joints - permit maximum movement
61
diarthroses locations
unite long bones
62
what are diarthroses surrounded by?
2-layered capsule that encloses and seals articular cavity - external capsular layer and internal capsular layer
63
what is contained in the capsule of diarthroses?
synovial fluid
64
synovial fluid
colorless, viscous fluid that lubricates joints
65
what does synovial fluid contain?
rich in hyaluronic acid and proteins
66
external/fibrous capsular layer composition
fibrous layer of dense CT
67
internal/synovial capsular layer composition
3-4 cell deep layers of type A and B cells
68
what is the internal capsular layer lined by?
squamous to cuboidal cells on internal surface
69
is internal capsular layer true epithelium?
no
70
internal capsular layer function?
permits diffusion of nutrients to hyaline cartilage from synovial fluid
71
what do cells in the synovial fold produce?
synovial fluid
72
type A cells
phagocytic cells w/ well-developed golgi and many lysosomes
73
type B cells
cells resembling fibroblasts w/ well-developed rER - probably secrete synovial fluid
74
osteopetrosis
hereditary disease - abnormal osteoclast fxn leads to brittle and easily broken bones, lack of remodeling, undeveloped marrow cavity
75
what type of bone is present most in osteopetrosis?
woven (lack of remodeling)
76
albers-schonberg disease
marble bone disease - deficiency in CA II -> osteoblasts can't accumulate H+ in Howship's lacunae to activate lysosomal enzymes
77
osteoporosis
loss of bone mass - primarily trabecular
78
osteoporosis in PMS women: rates of resorption vs formation?
mainly normal rate of resorption and decreased bone formation
79
how does rheumatoid arthritis begin?
inflammatory rxn in synovial tissue
80
what does rheumatoid arthritis pathology involve?
activation of CD4+ T cells (unknown antigen)
81
what do T-cells produce in rheumatoid arthritis?
IL-15 - stimulates synovial macrophages to produce proinflammatory cytokines and metalloproteases
82
what proinflammatory cytokines does IL-15 stimulate production of in rheumatoid arthritis?
TNF-a, IL-1, IL-6

Histology - Exam 2 (6 decks)

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