Term
| What is the function of bone? |
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Definition
skeleton
supports and protects
contains bone marrow
stores calcium
muscles attach |
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Term
| What are the components of bone? |
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Definition
Cells
Fibers
Ground substance
Mineral
Very little water |
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Term
| What is an osteoblast and what is its function? |
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Definition
It is a bone cell that "builds" bone. osteoBlast = Build
they synthesize and secrete the organic components of bone - osteoid
characteristics
have well-developed rER and Golgi complex
located at surface of bone tissue
cells lined up side by side
are cuboidal in shape, but polarized
nucleus on side away from matrix
basophilic cytoplasm |
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Term
| What are osteocytes/function of osteocyte? |
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Definition
Osteocytes are osteoblasts that have been surrounded by bone matrix (osteoid)
incapable of mitosis
maintain bone matrix, not actively synthesizing matrix
less rER and Golgi than osteoblasts
contain filopodial processes- extensions of the cell
cells make contact with each other with gap junctions
lies in a lacuna
filopodial processes lie in extensions of the lacuna called canaliculi |
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Term
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Definition
Osteoclasts are bone cells responsible for bone resorption
osteoClast = cut
Derived from blood monocytes- mononuclear phagocyte system
Contain many nuclei (multinucleate) (2-50)
Acidophilic cytoplasm, abundant mitochondria, well-developed Golgi complex
Surface that faces bone matrix has a ruffled border- provides large surface area
Lie in an enzymatically etched depression called Howship’s lacunae
Contain proteolytic enzymes, and acids, numerous lysosomes
Respond to PTH via signal from osteoblast- increase activity
Have receptors for calcitonin- decrease activity |
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Term
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Definition
connective tissue capsule surrounding bone
Provides blood supply for nutrition of cells
Provides continuous supply of new osteoblasts |
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Term
| What are the two layers of the periosteum? |
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Definition
Fibrous layer- outermost layer
collagen and fibroblasts
Dense regular CT
Osteogenic layer- inner layer,very cellular
Contains osteoprogenitor cells- have ability to divide and differentiate into osteoblasts
Contain Sharpey’s fibers (collagen fibers that penetrate bone matrix and bind periosteum to bone) |
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Term
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Definition
Lines all internal surfaces of bone
Lines marrow cavity and extends into Haversian canals
Composed of reticular tissue
Contains osteoprogenitor cells
Thinner than periosteum |
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Term
| What is the bone matrix composed of? |
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Definition
Fibers
-Type I Collagen
Ground Substance
-GAGs
-Proteoglycans
-Glycoproteins
Mineral
-Calcium
-Phosphate
-Hydroxyapatite crystals |
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Term
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Definition
It is the organic material secreted by bone
50% of the bone matrix
Provides resistance to tension
Type I collagen
Ground substance
GAGs
GP (bone sialoproteins, osteonectin, osteopontin)
PG (Chondroitin 4 & 6 sulfate, keratan sulfate)
Removal of organic material results in structure with same shape, but very fragile and breaks easily |
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Term
| What is the inorganic portion of bone matrix? |
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Definition
the mineral portion which composes 50%
Provides resistance to compression
Provide hardness and rigidity
It is mostly calcium and phosphate but there are also small amounts of bicarbonate, citrate, Mg, K, Na
Hydroxyapatite crystals form along collagen fibrils from calcium and phosphate |
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Term
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Definition
Proteins (osteocalcin and osteonectin) in osteoid that bind Ca++
Matrix vesicles containing alkaline phosphatase bud off from osteoblasts
Alkaline phosphatase liberates phosphate groups
Calcium and phosphate precipitate into an insoluble salt called hydroxyapatite
Hydroxyapatite crystals associate closely with collagen fibrils- this association results in hardness and resistance of bone |
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Term
| What is calcium mobilization? |
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Definition
Physical mechanism
rapid mobilization- along a concentration gradient
physical transfer of ions into interstitial fluid, then to blood
Parathyroid hormone
acts on osteoblasts (have receptors)
osteoblasts secrete cytokines which stimulates osteoclasts (the osteoclasts lack the hormone receptor)
increased bone resorption
Calcitonin-
acts directly on OC (on calcitonin receptors)
inhibits resorption activities of OC
stimulates bone deposition by osteoblasts |
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Term
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Definition
Location
Epiphyses
Interior of bones
Flat bones of skull, (between plates of compact bone)- called diploë
Characteristics
Forms trabeculae (bone spicules)
Interconnecting cavities
3-D lattice with many open spaces
loosely organized layers of bone
It can be primary or secondary bone
other names are cancellous bone and trabecular bone |
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Term
| What/where is compact bone? |
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Definition
Location
Covers spongy bone in epiphyses
Diaphysis
Flat bones of skull
Characteristics
No open spaces or trabeculae
Contains Haversian systems (osteon)
Organized into lamellae (layers of bone)
contains Haversian canals and Volkman's canals
always secondary bone
other names are cortical, dense, or lamellar bone |
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Term
| What is a Haversian canal? |
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Definition
a canal in compact bone
parallel to long axis of diaphysis
lined by endosteum
contains blood vessels, nerves, lymphatic vessels
lamella farthest from blood vessel forms first
a haversian system (or osteon) is concentric layers (lamellae) surrounding a Haversian canal
Haversian canals are how bones are highly vascularized |
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Term
| What is a Volkman's canal? |
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Definition
a canal in compact bone
run perpendicular to Haversian canals
link Haversian canals
do not have concentric lamellae- perforate Haversian lamellae
lined with endosteum |
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Term
| What are characteristics of lamellae? |
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Definition
Lamellae are layers of bone tissue. The collagen fibers are arranged in parallel fashion in each lamella, but are perpendicular to the fibers in adjacent lamellae
Lamellae surround Haversian canals |
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Term
| What is cementing substance? |
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Definition
amorphous material surrounding each Haversian system
consists of mineralized matrix with few collagen fibers
helps anchor osteons |
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Term
| What are the three types of lamellae? |
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Definition
Outer circumferential lamellae
“Rings” of bone tissue lining the outer portion of the bone, immediately beneath the periosteum
Inner circumferential lamellae
“Rings” of bone tissue surrounding the marrow cavity
lined by endosteum
Interstitial lamellae
partial lamellae between osteons- parts of old osteons |
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Term
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Definition
immature or woven bone
The first bone to appear during formation and repair
Formed by intramembranous or endochondral bone formation
Is temporary, replaced by secondary (except in tooth sockets and near sutures of flat bones)
Collagen fibers arranged in irregular array
Smaller content of mineral- more easily penetrated by x-rays
Higher proportion of osteocytes
ALWAYS SPONGY BONE |
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Term
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Definition
mature bone
more organized than primary bone
Collagen fibers arranged in lamellae parallel to each other in spongy bone
Collagen fibers in lamellae arranged concentrically around a vascular canal in compact bone
it can be spongy bone or compact bone |
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Term
| How is compact bone remodeled? |
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Definition
1. Osteon (usually only parts of an osteon) resorbed by osteoclasts.
2. Resorbed areas invaded by osteoblasts and new blood vessel growth.
3. A new osteon forms.
Bone continuously remodeled throughout life
Bone responds to stress on the tissue |
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Term
| How do bones grow in girth? |
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Definition
overall pts
-bone marrow cavity expands
-thickness of compact bone stays the same
breakdown
Growth in girth- resorption of osteons and formation of new osteons
Differentiation of cells in periosteum and new osteoid deposited in outer portion of the bone.
The thickness of the bone stays the same- the inner marrow cavity expands in size.
The marrow cavity expands into the space that was occupied by bone tissue. |
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Term
| What do growth hormone, estrogen, calcium, Vit A, Vit C, and Vit D have in common? |
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Definition
| They are important hormones and vitamins related to bone and bone growth |
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Term
| What is intramembranous ossification? |
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Definition
direct synthesis of bone
No cartilage model formed
Mesenchyme differentiates directly into osteoblasts to form bone
Bones of the head form this way (derived from neural crest-Ectoderm)
Layer of spongy bone (diploe) between compact bone |
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Term
| What is endochondral ossification? |
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Definition
the way long bones form
Mesenchyme condensations formed
Mesenchyme cells differentiate to form chondroblasts
Cartilage model of each skeletal structure formed
Cartilage model has the same shape as future bone
Chondrocytes become more specialized
“Zones” of chondrocytes form which form the epiphyseal plate (where cartilage turns into bone) |
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Term
| What is the epiphyseal plate? |
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Definition
It is formed from the zones of chondrocytes
It is where cartilage turns into bone
It is responsible for the growth in length of the bones |
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Term
| What are the zones of chondrocytes? |
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Definition
In sequence
The Resting Zone
Zone of Proliferation - intense proliferation occurs
Zone of Hypertrophy - chondrocytes become much larger
Zone of calcification - strips of cartilage matrix begin to calcify
Zone of ossification - where the final steps occur including osteoid deposition and mineralization
The zone of hypertrophy and zone of calcification form the bridge between cartilage and mineralized tissue |
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Term
| What is the primary ossification center? |
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Definition
- the first area in the bone to begin the ossification process.
-near the middle of the diaphysis in long bones |
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Term
| What is the secondary ossification center? |
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Definition
begin after primary centers.
in the epiphyses of long bones |
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Term
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Definition
| the region between a primary and secondary ossification center |
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Term
| What is the tertiary ossification center? |
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Definition
form the tubercles and ridges to which large muscle groups attach
only on some bones |
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Term
| What are the two types of bone slide preparation? |
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Definition
Ground Section
cut piece of bone with a saw
attach bone piece to slide with glue
grind bone until only thin piece left
stain with ink
cells not preserved
ink fills spaces, can see arrangement of bone tissue
Demineralized Section
demineralize bone tissue in acid
fix tissue, embed in paraffin or plastic
section on microtome, stain
Cells are fixed and remain in tissue |
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Term
| What are the main concepts behind bone fracture repair? |
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Definition
- blood clot forms after damage to the vessels that vascularize bone
-Osteoprogenitor cells in periosteum and endosteum differentiate into fibroblasts, chondroblasts, and osteoblasts
-after macrophages break down clot, CT and cartilage are formed (the callus)
-primary bone replaces the callus and then secondary bone replaces that |
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Term
| What are pituitary dwarfism, gigantism, chondrodysplasia, and arthritis? |
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Definition
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Term
| What are osteogenesis imperfecta, osteopetrosis, scurvy, osteomalacia, rickets, osteoporosis, and acromegaly? |
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Definition
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