Bone Tissue II Flashcards
classification of bone tissue
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
trabeculae
- rod structures that connect spongy bone
- spaces between filled with marrow and vessels
- oriented along lines of stress
where are different cell types found within bone?
osteocytes: inbetween lamellae
osteoclasts & osteoblasts: surface of bone
tissue type that surrounds all bone
periosteum
space on inside of bone
medullary cavity
contains trabecular/spongy bone
3 different types of lamellae
- concentric
- circumferential
- interstitial
2 layers of periosteum
OUTER FIBROUS LAYER
- dense fibrous connective tissue
INNER OSTEOGENIC LAYER
- osteoblasts, osteoclasts, osteochondro progenitor cells
lining of medullary cavity
ENDOSTEUM
- only has ONE LAYER
- only cell component, no dense connective tissue
Blood in bone
- 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)
concentric lamellae
- circles around blood vessels that make up central canal
- form OSTEONS
osteons
circular units of bone compressed towards each other and compacting bone
movement of nutrients in spongy vs compact bone
spongy bone
- nutrients move IN through lamellae layers
compact bone
- nutrients move OUT from central canals to reach lamellae
circumferential lamellae
OUTER
- run around outside of bone (before periosteum)
- bundle all osteons together
INNER
- surrounds medullary cavity
interstitial lamellae
- fill spaces between osteons
- made of leftover broken down osteon
other name for osteon
Haversian system
other name for central canal
Haversian canal
canals that connect central canals
perforating/Volkmann canals
shaft of long bone
DIAPHYSIS
end region of long bone
EPIPHYSIS
(proximal or distal)
connection between diaphysis and ephiphyses in long bone
METAPHYSIS
surrounding outside of epiphyses in long bones
ARTICULAR CARTILAGE (hyaline)
contents of medullary cavity in long bones
bone marrow
red in children, yellow in adults
epiphyseal line in long bones
ossified epiphyseal plate (cartilage line used to separate epiphysis from diaphysis growth)
what areas of long bones retain red marrow?
proximal epiphyses of long bones
when does bone formation begin in embryo? Why?
8 weeks
- blood stimulates MESENCHYME CELLS (stem) to become osteochondral progenitor cells
2 types of bone formation
INTRAMEMBRANOUS OSSIFICATION
- connective tissue ossified (skull, mandible, part of clavicle)
ENDOCHONDROL OSSIFICATION
- cartilage ossification (base of skull, other part of clavicle, remainder of bones)
process of intramembranous ossification
- mesenchyme cells create collagen membrane
- osteochondral progenitor cells -> osteoblast cells
- membrane ossified
process of endochondral ossification
- 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
why can’t bone undergo interstitial growth?
matrix needs to remain solid. can’t have osteocytes pushing against each other.
2 types of bone growth
growth in
length
thickness
regions within epiphysel plate
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
growth in bone thickness
- osteblasts beneath periosteum lay down bone near blood vessel - ridge forms
- ridges meet, tunnel forms. Periosteum becomes endosteum of tunnel
- osteoblasts from edosteum form new concentric lamellae
- osteoblasts from periosteum form new circumferential lamellae
bone remodelling
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)
Fetal bone tissue that has collagen fibers randomly oriented in many directions is ______
bone, and after it is remodeled it becomes ______
bone
woven
lamellar
