Bone Tissue II

Question 1

classification of bone tissue

Answer 1

WOVEN BONE
- randomly oriented collagen fibres
- first step in making bone (in embryo, in repair)
- eventually remodelled

LAMELLAR BONE
- mature bone organized in sheets (LAMELLAE)
-2 types
1. SPONGY/CANCELLOUS/TRABECULAR
- inside of bones
- less matrix, more space
- 20% of skeleton mass
2. COMPACT/CORTICLE
- outside of bones
- dense
- 80% of skeleton mass

Question 2

trabeculae

Answer 2

• rod structures that connect spongy bone
• spaces between filled with marrow and vessels
• oriented along lines of stress

Question 3

where are different cell types found within bone?

Answer 3

osteocytes: inbetween lamellae

osteoclasts & osteoblasts: surface of bone

Question 4

tissue type that surrounds all bone

Answer 4

periosteum

Question 5

space on inside of bone

Answer 5

medullary cavity
contains trabecular/spongy bone

Question 6

3 different types of lamellae

Answer 6

• concentric
• circumferential
• interstitial

Question 7

2 layers of periosteum

Answer 7

OUTER FIBROUS LAYER
- dense fibrous connective tissue
INNER OSTEOGENIC LAYER
- osteoblasts, osteoclasts, osteochondro progenitor cells

Question 8

lining of medullary cavity

Answer 8

ENDOSTEUM
- only has ONE LAYER
- only cell component, no dense connective tissue

Question 9

Blood in bone

Answer 9

• PERIOSTEAL VEINS AND ARTERIES enter via outer periosteum
• then enter into bone via PERFORATING/VOLKMANN CANALS (perendicualr to bone)
• enter CENTRAL CANALS (parallel to bone)

Question 10

concentric lamellae

Answer 10

• circles around blood vessels that make up central canal
• form OSTEONS

Question 11

osteons

Answer 11

circular units of bone compressed towards each other and compacting bone

Question 12

movement of nutrients in spongy vs compact bone

Answer 12

spongy bone
- nutrients move IN through lamellae layers

compact bone
- nutrients move OUT from central canals to reach lamellae

Question 13

circumferential lamellae

Answer 13

OUTER
- run around outside of bone (before periosteum)
- bundle all osteons together
INNER
- surrounds medullary cavity

Question 14

interstitial lamellae

Answer 14

• fill spaces between osteons
• made of leftover broken down osteon

Question 15

other name for osteon

Answer 15

Haversian system

Question 16

other name for central canal

Answer 16

Haversian canal

Question 17

canals that connect central canals

Answer 17

perforating/Volkmann canals

Question 18

shaft of long bone

Answer 18

DIAPHYSIS

Question 18

end region of long bone

Answer 18

EPIPHYSIS
(proximal or distal)

Question 19

connection between diaphysis and ephiphyses in long bone

Answer 19

METAPHYSIS

Question 20

surrounding outside of epiphyses in long bones

Answer 20

ARTICULAR CARTILAGE (hyaline)

Question 21

contents of medullary cavity in long bones

Answer 21

bone marrow
red in children, yellow in adults

Question 22

epiphyseal line in long bones

Answer 22

ossified epiphyseal plate (cartilage line used to separate epiphysis from diaphysis growth)

Question 23

what areas of long bones retain red marrow?

Answer 23

proximal epiphyses of long bones

Question 24

when does bone formation begin in embryo? Why?

Answer 24

8 weeks
- blood stimulates MESENCHYME CELLS (stem) to become osteochondral progenitor cells

Question 25

2 types of bone formation

Answer 25

INTRAMEMBRANOUS OSSIFICATION
- connective tissue ossified (skull, mandible, part of clavicle)

ENDOCHONDROL OSSIFICATION
- cartilage ossification (base of skull, other part of clavicle, remainder of bones)

Question 26

process of intramembranous ossification

Answer 26

• mesenchyme cells create collagen membrane
• osteochondral progenitor cells -> osteoblast cells
• membrane ossified

Question 27

process of endochondral ossification

Answer 27

• mesenchyme cells -> osteochondro progenitor cells -> chondroblasts
• chondroblasts form hyaline cartilage skeleton
• blood vessels enter perichondrium, stimulate ostrochondro progenitor cells -> osteoblasts
• perichondrium -> periosteum
• osteoblasts remodel cartilage

Question 28

why can’t bone undergo interstitial growth?

Answer 28

matrix needs to remain solid. can’t have osteocytes pushing against each other.

Question 29

2 types of bone growth

Answer 29

growth in
length
thickness

Question 30

regions within epiphysel plate

Answer 30

epiphyseal side
1. ZONE OF RESTING CARTILAGE
- slowly dividing chondrocites (interstitial growth)
- anchor for epiphyses
2. ZONE OF PROLIFERATING CARTILAGE
- rapid chrondrocyte division
- new cells on resting side
3. ZONE OF HYPERTROPHIC CARTILAGE
- chondrocytes mature + enlarge
- secrete hydroxyapatite to calcify
4. ZONE OF CALCIFICATION
- matrix calcified, condrocytes die
5. OSSIFIED BONE

Question 31

growth in bone thickness

Answer 31

1. osteblasts beneath periosteum lay down bone near blood vessel - ridge forms
2. ridges meet, tunnel forms. Periosteum becomes endosteum of tunnel
3. osteoblasts from edosteum form new concentric lamellae
4. osteoblasts from periosteum form new circumferential lamellae

Question 32

bone remodelling

Answer 32

How bone is broken down and built across the lifespan

in youth
- medullary cavity broken down, outside of bone built
- growth of epiphyses

other causes of remodelling
- stress (injury or use in sport)

Question 33

Fetal bone tissue that has collagen fibers randomly oriented in many directions is ______
bone, and after it is remodeled it becomes ______
bone

Answer 33

woven
lamellar