Bone Flashcards
Why is bone classified as a specialized connective tissue?
Because it is mineralized and rigid
Does bone have cells, vessels and nerve fibers
Yes
True or false: bone is made once and is not reformed unless damage occurs
False-constantly being remodeled
What happens when pressure is applied to bone?
Bone resoption
Tension on bone results in what?
Bone deposition
What are the factors that contribute to orthodontic treatment on teeth that helps to reshape the bony tooth socket?
Tension and pressure
What are the four major functions of bone?
- Support and protection
- leverage for moement
- storage for minerals
- blood cell formation
What are epiphyeses?
the two bulbous ends of long bones
What covers the articulating surfaces of epiphyses?
hyaline cartilage
What do epiphyseal (growth) plates consist of?
hyaline cartilage that ossify at 18-20 y.o.
What is the metaphysis?
The articulation between the epiphysea place and the diaphysis
What is the diaphysis?
the loing, ylindrical shaft between the two epiphyses
What is at the core of the long shaft of bones?
Marrow
What is the external CT that covers bones capsules?
Periosteum
How many layers does the periosteum have? Which layer is growing/
Two layers–outer layer is active
What is the type of bone that lines our teeth sockets?
The primary immature bundle bone
What is the inner connective tissue of bone called?
The endosteum
True or false: periosteum encircles the entire long bone
False–the epiphyses do not have periosteum
What does the outer layer of periosteum contain?
- Dense, collagenous CT and fibroblasts
- blood vessels, lymph, nerves
- Anchoring “Sharpey’s fibers”
What anchors the periosteum to the underlying bone?
Sharpey’s fibers
The cellular layer of the periosteum contains what?
Osteoprogenitor cells (immature bone cells)
Where do the osetoprogenitor cells lie?
The inner cellular layer of bone
What is osteoid?
Soft, organic, non-mineralized bone that comes from osteoprogenitor cells, and is secreted into the inner cell layer
What is the difference between growing and non-growing bone?
The inner cell layer of growing bone will have osteoprogenitor cells, while mature bones will have periosteal cells
How do you differentiate between osetoprogenitor cells and osteoblasts?
Osteoid (pale staining area) will be presentin oseteoblasts, siince it is newly formed bone matrix
Is osteoid mineralized?
Not yet
The endosteum lines what three areas?
- Bone marrow cavity
- Haversian canals
- Volkman calanls
What is the function of the Haversian and Volkman canals?
allow small vessels and nerve fibers to reach deep into the bone tissue
What are trabeculae?
Prominent areas of developing bone that stain bright red with H&E
What are spicules?
Small areas of developing bone that stain bright red with H&E
The bone matrix has two major components. What are they?
Organic
Inorganic
What is the inorganic component of the bone matrix?
Mineral containing part of bone what forms about 65% of the dry weight of bones. Gives bone durability
What are the minerals that make up the inorganic component of the bone matrix (6)?
Hydroxapatite (CaPO4) crystals Bicarbonate Citrate Mg Na K
What is the organic component of the bone matrix?
Layer consisting of fibers and ground substance
This prevents bones from becoming brittle
What is the main type of collagen found in bones?
Type I collagen
Is type I collagen acidophilic or basophilic?
Acidophilic
What is the function of collagen I in the bone matrix?
Prevents bones from becoming brittle
What are the four major components of the ground substance of the organic component of the bone matrix?
- proteoglycans with GAGs
- Multiadhesive glycoproteins
- Bone specific Vit K dep proteins
- Growth factors and cytokines
What are the four types of glycoproteins found in the organic layer of bone matrix?
Osteonectin
Sialoproteins
psteopontin
osteocalcin
What is the function of the glycoprotein oseteonectin?
Glue between collagen and hydroxyapatite crystals
What is the function of the glycoproteins Sialoproteins and Osteopontin?
Anchor bone cells to the ECM
What is the function of the glycoprotein osteocalcin? What is it dependent on?
Traps Ca from the blood so that they can mineralize in the bone matrix, and stimulates ocetsoclsts to remodel bone
Dependent on Vit k
What is the function of growth factors in the bone matrix?
Stimulate the differentiation of mesenchymals cells to osteoblasts
Why are growth factors and cytokines used following surgery on long bones/
To induce mesechymal cells to differentiate into osteoblasts
What are osteoprogenitor cells?
Immature osteoblasts that are derived from the mesenchymal cells
What is the function of osteoblasts?
Synthesize the organic component of bone matrix
What is the distinguishing factor between osteoblasts and osteocytes?
Osteocytes are osteoblasts surounded by bone.
Where are osteoprogenitor cells found?
in the inner layer of mature periosteum and in the endosteum
The naming of osteoprogenitor cells change depending on their location. What are the two names/locations?
In the inner layer of the mature periosteum, they are called periosteal cells
In the endosteum, they are called endosteal cells
Can osteoprogenitor cells undergo mitosis?
Yes
Where do osteoblasts arise from?
osteoprogenitor cells
What shape are osteoblasts?
Cuboidal - columnar
Are osteoblasts acidophilic or basephilic?
Basophilic
What is the osteoid?
newly-formed non-mineralized bone, also referred to as “pre-bone”
It consists of collagen type I and bone matrix proteins (BMPs)
The cell membrane of osteoblasts have a high level of what?
alkaline phosphatase
What is the function of alkaline phosphatase in the formation of new bone?
splits pyrophosphate groups from the macromolecules of the matrix
How do osetoblasts communicate with other osteoblasts/cytes?
Gap junctions
Where are ostepclasts derived from/
mononuclear hemopoitetic progenitor cells (from bone marrow)
What are bone lining cells made from? What is their function?
Osteoblasts
- Protect from osteoclasts
- nutritional support of osteocytes
- function in the uptake and release of Ca and PO4 by bone tissue
How do bone lining cells interact with osteocytes?
have extended gap junctions
What are osteocytes? What do they look like?
Osteobalsts surrounded in bone matrix.
Stellate shape with cytoplasma radiating from the cell, forming canaliculi
How do osteocytes interact with one another?
Their cytoplasmic processes contact those of near-by osteocytes and bone- lining cells via gap junctions (which permit ion exchange between cells
The space between the osteocyte cell membrane and the lacuna and
canaliculi is what? What is it filled with?
the periosteocytic space that hold ECF
How do osteocytes receive oxygen and nutrition?
From the ECM in the periosteocytic space
What will happen if bone matrix is not covered by bone lining cells?
Osteoclasts eat away
What are osteoclasts? How many nuclei? acido or basophilic? Why?
Are multinucleated (with up to 50 nuclei), motile, acidophilic (due to lysosomes containing acid phosphatase), enormous cells
Where do osteoclests lie?
In Howship’s lacuna (depressions on bone surface)
What are the three distinct histological regions that are found near osteoclsts?
- Ruffled border
- Clear zone
- Basolateral region
Are there lymphatic vessels in Haversian canals?
No
Where is the only area in the bone that has lymphatic vessels?
Periosteium
What is the function of the ruffled border on osteoclasts?
Increases cell surface area to allow for increase exocytosis of enzymes and endocytosis of broken down bone
What is the function of the clear zone in osteoclsts?
The actin filaments near the border of the cell allows for a tight fit between the osteoclast and the bone surface.
The clear part is d/tlack of organelles near the ruffled border
What is the baslolateral region of the osteoclasts?
The area that contains organelles that are used in the excretion of vesicles from the cell
What happens to osteoclasts once they complete bone resorption?
Apoptose
What can drug target to relieve osteoporosis?
Stimulate apoptosis of osteoclasts
What are the enzymes that are released by osteoclasts that break down the organic part of bone?
Lysosomal hydrolases and metalloproteinases
What is compact bone?
dense (solid) bone, that forms a shell around the exterior of long bones
What is cancellous bone?
spongy (porous) bone that lines the marrow cavity of long bones
contains mainly an irregular arrangement of bone lamellae (layers)
Every bone in the body has what two components?
A compact part, and a spongy part
What is the outer layer of compact bone of the calveria? The inner layer?
Outer layer = pericranium
Inner layer = periosteal layer of dura mater
Where is cancellous bone found?
fills the epiphyses of long bones
What type of bone forms the diploe between the inner and outer tables of the skull cap?
Cancellous bone
When does primary bone form?
During fetal development and during bone repair
What is primary bone made of?
irregular / interlacing bundles of collagen
Why is primary bone weaker than mature bone?
Has less mineral content than mature bone, and more ground substance
Is primary bone permanent?
No-it is a TEMPORARY tissue, it is reabsorbed by osteoclasts and then REPLACED by secondary bone (new bone formed by osteoblasts)
Why is orthodontic treatment feasible even in adults?
bone lining the alveolar sockets (tooth sockets) is referred to as “bundle” bone and remains immature throughout life
How are the collagen fibers arranged in primary/immature bone, compared to secondary/mature bone/
Immature is random and woven
Mature is straight and stronger
Which have concentric lamellae: haversian canals, volkman’s canals, or both?
Haversian canals
What are the bone lamellae?
consist of concentric, “wafer-thin” bone lamellae (layers) containing collagen fibers that are helically-arranged
These are found surrounding Haversian canals
What connects osteons to one another/
Volkmann canals
What is ankylosis?
a condition in which two articulating bones at a joint fuse, obliterating the joint so there is no movement. This is often seen with trauma
What is RA?
an autoimmune disease that attacks the synovial joints, damaging the articular cartilages, producing disfigurement of the joints and severe pain.
What is rickets?
a disorder that results from calcium deficiency during development, or from inadequate dietary supply of vitamin D which is necessary for calcium absorption form the GI tract. In this disorder, osteoid does not mineralize properly.
What is osteoporosis?
a condition characterized by a reduction in bone mass both in the
organic and inorganic components of its matrix
What are the three signals that regulate osteoclasts and are out of wack in osteoporosis?
Normally, osteoclast activity is controlled mainly by parathyroid hormone (PTH) and to a lesser extent by interleukin 1 and tumor necrosis factor. In women of child-bearing age, estrogens inhibit the production of these substances, restricting osteoclast activity.
Why are teeth more easily shaped than other types of bone?
Has a lot of primary bone
Do Sharpey’s fibers hold the outer fiberous layer to the inner or the inner to the matrix?
Anchors the outer fibrous layer to the inner layer
What type of cells are in not growing periosteium? What about growing?
Periosteal cells in non-growing, osteoprogenitor cells if growing?
What type of cells line the endosteum?
Osteoprogenitor cells
What are the an enzymatically-etched shallow depressions that osteoblasts lie in?
Howship’s lacuna
