Bone and Bone Development Flashcards
2 ways to visualize
• Ground bone = unpreserved bone is ground down so thin light can pass ____
– ____ & ____ matrix do not survive, but general architecture (____, lacunae, ____ {narrow tunnels}) are visualized
• ____ bone = cells are fixed and inorganic matrix is removed by decalcification
– Good detail of ____ material
through cells organic matrix lamellae canaliculi decalcified organic
Bone is a connective tissue. Types: • \_\_\_\_ connective tissue – Mesenchyme (stem cells!) – Mucous • Connective Tissue Proper – \_\_\_\_ – \_\_\_\_ • Specialized connective tissue – Cartilage – \_\_\_\_ – Hematopoetic
embryonic
loose
dense
bone
Bone is a ____ connective tissue
What is connective tissue made of?
• Extracellular matrix
– Fibers = proteins made of long peptide chains
produced by fibroblasts (____!)
– ____ substance = gel-like matrix where cells and fibers are embedded
• Cells
– Mesenchymal stem cells form:
– Osteoprogenitor cells
– Osteoblasts, Fibroblasts, Chondroblasts, Myofibroblasts, Adipose cells
– ____, mast cells & basophils
– ____, plasma cells, eosinophils, monocytes & ____
specialized
collagen
ground
macrophages
lymphocytes
neutrophils
Classification of Bone
• Compact/dense forms ____
• ____ forms inside consists of trabeculae
– Spaces within have marrow & blood vessels
• Woven = ____ (Immature bone)
• More ____ per unit of area & cells are ____ arranged, More ____
- Lamellar (Mature bone)
- ____ arrangement of collagen fibers
outside spongy/cancellous non-lamellar cells randomly ground substance
regular
Bone Classification (cont’d)
- Bone tissue
- –by ____
- –(trabecular = spongy = cancellous, ____ = ____ = compact)
— by stage in formation
(primary = ____/____, scondary = ____/____)
architecture
cortical
dense
woven/immature
lamellar/mature
Bone develops in two ways from mesenchymal stem cells:
- endochondral ossification from a ____ precursor
- intramembranous ossification directly from ____
Immature bone matrix formed by either process looks the ____
Facial bones arise from ____
hyaline cartilage
mesenchyme
same
intramembranous
Bone matrix is formed by Osteoblasts
Osteoblasts are derived from
____
(have potential to ____ and capacity to ____)
These cells arise from ____ mesenchymal stem cells that can become fibroblasts, osteoblasts, adipocytes, chondrocytes or muscle cells.
Found on the ____ and ____ of bones. Look flattened and ____ with elongate or ovoid nuclei.
osteoprogenitor stem cells
proliferate
differentiate
multipotent
external (periosteum)
internal surface (endosteum)
squamous
Mesenchymal Stem Cells:
Give rise to ____ cells, but can also form fibroblasts, chondroblasts, adipocytes and muscle cells.
Osteoblasts: derived from osteoprogenitor cells
secrete ____ then form osteocytes.
Osteoblast formation is controlled by members of the ____
osteoprogenitor
bone matrix (osteoid)
bone morphogenetic protein family
Difficult to differentiate ____ from osteocytes histologically
Mesenchymal stem cells sittwithin the connective tissue; induced to form OPC, which are then ____ to giving rise to osteoblasts
progenitor cells
committed
Bone formation by osteoblasts
Four step process:
1. ____ deposition
forms a collagen (mainly ____) fibril matrix like steel bars in concrete
- secretion of ____
amorphous matrix of GAGs, PGs, glycoproteins, salt and water. ____ is the combination of steps 1 and 2 - ____ seeding
osteoblasts saturate ground sustance with ____ and phosphate which precipitate as ____ crystals - mineralization and ____
calcium phosphate crystals are modified to form ____
crystals tethered to collagen by ____, this provides strength for the bone
collage
type I
ground substance
osteoid
crystal
calcium
calcium phosphate
maturation
hydroxyapatite
proteoglycans
Components of the bone matrix
(Osteoid)
____% organic, ____% inorganic
Organic: Fibers: \_\_\_\_ collagen Ground substance: previous slide Non Collagenous proteins: Important! 1. \_\_\_\_ a ligand to induce formation of osteoclasts 2. \_\_\_\_ stimulating factor (M-CSF) 3. \_\_\_\_ 4. \_\_\_\_
Inorganic:
Calcium phosphate deposits with crystalline characteristics of ____.
35 65 type I RANKL macrophage colony osteoprotegrin osteopontin hydroxyapatite
Osteocytes: Are osteoblasts that became trapped in ____
Maintain ____ quality
Transmit ____ signals
Linked by ____ to each other and to bone lining cells
Periosteal and Endosteal cells: ____ Osteoblasts
matrix bone mechanical gap junctions inactive
Cannot distinguish between ____ and ____
Osteoblasts are larger and more ____
OPC
endosteal cells
cuboidal
Osteocyte • Completely surrounded by bone matrix • Maintain \_\_\_\_ homeostasis • \_\_\_\_ is the space this cell inhabits • Cytoplasmic processes in canaliculi are linked by \_\_\_\_ • States – \_\_\_\_ – Formative deposits matrix – Resorptive- has \_\_\_\_
• ____ than osteoblast precurser and usually highly distorted by ____ in routine preps
calcium lacuna gap junctions quiescent lysosomes smaller shrinkage
Bone-lining cells: Periosteal and endosteal cells
• Derived from ____
• Cover bone that is not ____
• Flat cells with few ____, have ____ join processes of adjacent cells
• Function in maintenance and nutritional support of ____ in underlying bone
osteoblasts remodeling organelles gap junctions osteocytes
What transforms non-lamellar/woven bone to mature/lamellar bone and continues to remodel bone throughout life?
____
Osteoclasts
BONE REMODELING: forms lamellar bone and continues ____ life
- Activation: ____ are activated and recruited to the bone surface. (____)
- Resorption: Osteoclasts ____ bone. (____).
- ____: Process is reversed
- Formation: Osteoblasts deposit new ____ and mineralize it. (____)
throughout
osteoclasts
weeks
resorb
weeks
reversal
osteoid
months
Where do osteoclasts come from and how are they activated??
Osteoclasts: develop from ____
bone marrow monocytes
Osteoclastogenesis is triggered by ____ and by RANKL produced by ____.
M-CSF binds to a ____ and induces it to form a ____.
The Macrophage expresses RANK. RANK = Receptor Activator of ____
RANKL on the ____ or ____ binds to RANK and commits the macrophage to ____.
macrophage colony-stimulating factor (M-CSF)
osteoblasts
monocyte
macrophage
nuclear factor kappaB (NF-kB)
osteoblast
stromal stem cell
osteoclastogenesis
- Resorption
Osteoclasts become active when ____ bind to ____ and seals the area for absorption. Osteopontin and integrins keep osteoclasts attached to bone surface.
____ degrades hydroxyapatite and ____ break down collagen. Calcium and phosphate are released into the ____
integrins
osteopontin
acid
proteases
blood
Ruffled border of osteoclasts increase ____
Osteoclasts are ____, have a ____ cytoplasms due to the acidic matrix
surface area
multi-nucleated
pink
- Reversal
____ determine when sufficient bone has been resorbed. They release ____ that acts as a decoy receptor that binds to RANKL on stromal cells and prevents ____ of additional Osteoclast precursors.
Osteoclasts undergo ____.
osteoblasts
osteoprotegerin (OPG)
activation
apoptosis
Mature bone consists of:
• Compact lamellar bone (outer)
– Haversian systems/osteons are ____ units
• A central canal is the ____
• ____ lamella of bone matrix surround the canal
– ____ are channels through which blood vessels and nerves travel from one surface to another
• Spongy bone (inner)
– ____ or spicules have numerous
interconnecting marrow spaces
• Blood supply
– Blood travels from the marrow, into & through bone to the ____ veins
cylindrical
osteonal (haversian) canal
concentric
volkmann’s canals
trabeculae
periosteal
____ allows the osteoblast to form a much more well-organized version of the osteiod
Volkmann’s canals are ____ to haversian canals
remodeling
perpendicular
Compact bone contains Haversian systems/osteons:
they consist of ____ and surrounding ____
haversian canal
lamellae
Formation of lamellar bone
LOOK OVER THE SLIDE
OKAY
Regulation
The balance between bone resorption and formation is regulated by ____.
____ binds to receptors on Osteoblasts and ____ pool of RANKL. More RANKL available to bind to RANK on ____
____ and ____ decrease Ca++ release
hormones
parathyroid hormone (PTH)
increase
osteoclast precursors (macrophages)
calcitonin
vitamin D
Regulation
____ and ____ are required to maintain stable skeletal mass in males. Both ____ osteoprotegerin (OPG) synthesis and ____ RANKL availability
estrogens
androgens
stimulate
reduce
