histo bone and osteogenesis 1
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- -highly specialized CT
- -has cells and ECM, just like any other CT
Bone has what type of collagen fiber bundles?
hyaluronic acids, chondroitin 4-SO4, keratan SO4
Bone also has?
- -INORGANIC COMPOUNDS
- -Ca & PO4 in the form of HYDROXAPATITE CRYSTALS
Collagen fibers and inorganic materials make bone extremely?
- -relatively light weight
- -somewhat resilient
What is osteonectin?
structural proteins that bind things together
What are the structural things that bind things together in cartilage?
What are the structural proteins that bind things together in CT?
Enamel is __% inorganic & ___% organic & water.
Dentin is ___% inorganic, ___% organic, & ___% water.
Bone and Cementum are __%inorganic & __% organic+water
The %percentage of inorganic material gets less and less as it gets closer to the pulp.
Because of mineral deposition, bones become ?
- -can bear more weight
- -form rigid skeleton
- -for muscle attachments
- -highly hydrated
- -higher water content
- -much more flexible than bone
In x-ray. what tooth is the most white?
-What tooth tis the most gray?
- white= enamel
- gray= pulp (soft)
For an XRAY ID:
- dentin= gray HARD TISSUE
- enamel= white on top
- pulp= most gray SOFT TISSUE
Functions of BONE:
- -enables SKELETON to maintain the body shape
- -for PROTECTION, cranium protects the brain, thoracic cage protects the heart, lungs...
- -serve as LEVERAGE for muscle action, mobility
- -act as RESERVOIR for ions, especially Ca, released from bone when too low in blood & vice versa
- -has BONE MARROW for formation of blood cells
Problems occurs because bone is hard:
- -impossible for diffusion of nutrients/wastes
- -impossible to grow interstitially from within
- -impossible to cut section, demineralized first teeth also
- -miss important parts in DEMINERALIZED OR DECALCIFIED SECTION
Problems occur because bone is hard: ( continued)
-miss cells/other organic components in DRY GROUND SECTIONS
A long bone:
- -shaft or DIAPHYSIS, compact bone
- -ends or epiphyses
(small pieces) of SPONGY or CANCELLOUS BONE
(bigger pieces) of SPONGY or CANCELLOUS BONE
where cancerous bone is located
Trabeculae and spicules?
-look different but both have the SAME IDENTICAL cells, fibers, and ground substance
covers bone, has 2 layers
Periosteum and Endosteum?
-both provide blood supply
What is the Osteon/Haversian system?
collagen fibers arranged in lamellae/layers concentrically organized around a canal= whole complex
hole in the middle that contains blood vessels & nerves
Where is the OUTER CIRCUMFERENTIAL LAMALLAE located?
just beneath the periosteum outside
Where is the INNER CIRCUMFERENTIAL LAMELLAE located?
around the marrow cavity
Intersitial lamellae is?
irregular lamellae, bits/pieces left after remodeling
communicates between osteons together and to the peri/endosteum
- -lay down Harversian systesms
- -lay down ECM
- -trapped in own matrix
- -become OSTEOCYTES located in lacunae
Where are osteocytes found?
Short/irrgular bones (mandible/maxillary)?
spongy bone surrounded by compact bone
2 plates seperated by dipole
PRIMARY, IMMATURE, OR WOVEN BONE is?
the first bone formed in embryo and in fracture repair
Primary bone is?
Secondary bone is?
Secondary bone is also called?
- -mature bone
- -LAMELLAR BONE
Dry Bone qualities
- -osteons, lamellae
- -Haversian/Volksmann canals
- -canalliculi, calcified matrix
NO CELLS, FIBERS, NEUROVASCULAR OR LYMPHATICS
3 types of bone cells are?
- 1. osteoblasts
bone forming cells
Osteoblasts are derived from?
Where are osteoblasts located?
located at the surfaces of bone tissue, once cell layer like simple epithelium
Osteoblasts have what type of cytoplasm?
Basophilic cytoplasm, active protein producing cells
What do osteoblasts lay down?
lay down organic components (type 1 collagen fiber bundle, GAGS, proteins) of bone matrix first
Osteoblasts add what type of components later?
What is an OSTEIOD?
bone like, later of newly formed bone but NOT yet mineralized
Bone can grow by what type of growth?
by appositional growth ONLY
-adds on the surface not by interstitial growth
Once surrounded and trapped in their own matrix, osteoblasts stop forming bone, they become?
Osteoblasts have receptors for?
-when activated, will activate and increase the number of osteoclasts
Parathyroid hormone promotes?
bone RESORPTION, more Calcium in the blood
What happens in MINERALIZATION in both types of bone formation:
- -decrease in water content
- -increase in inorganic content
- -collagen content stays the same, NO CHANGE
Osteocytes are located?
in lacunae between lamellae
Only __ osteocyte in each space.
Cells contact each other via cytoplasmic processes in ____, molecular exchange/communication via _____.
- 1. canaliculi
- 2. gap junctions
In osteocytes, how does the bone get blood supply?
-not by diffusion like cartilage
osteocytes look like?
-flat, almond shaped cells
Osteocytes activity compared to osteoblasts?
osteocytes are LESS ACTIVE than osteoblasts, never inactive
Osteoclasts are still actively involved in?
Cells get rid of wastes via?
gap junctions between them!
Osteoclasts are derived from?
cells that break down bone (resorption)
- -multi nucleated cells with Ruffle border
- -located at Howship's lacunae
How do osteoclasts attack bone surfacr or resop bone by?
acid phosphatase enzyme reaction
Osteoclasts have receptors for?
-secreted by parafollicular of C cells of thyroid gland, which INHIBITS OSTEOCLAST ACTIVITY AND BONE RESORPTION
What is bone remodeling?
continuously being removed/replaced in both young and old bones
Sharpeys fibers are?
-Type 1 collagen fiber bundles inserted into the bone
Sharpeys fibers are seen as?
-anchoring to the bony tooth socket, or where tendon attached to the bone
Collagen fiber bundles in the matrix give bone its?
made up of all the cells lining the marrow cavity
-osteoprogenitor cells, osteoblasts, osteoclasts
A bone spicule is formed by?
intramembranous formation from head/neck mesenchyme
Intramembranous ossification is?
direct mineralization of matrix secreted by osteoblasts
Intracatilaginous/endochondral ossification is?
by deposition of bone matrix on pre-existing cartilage model
In intramembranous ossification and intracartilaginous ossification the first bone tissue is?
primary bone (immature or woven) then replaced by secondary bone (mature or lamellar)
In intramembranous ossification trapped cells become?
What bones are formed from intramembranous ossification?
-flat bones of skull and irregular bones, maxilla & mandible (except sphenoccipital join & condyles of mandibles)
In endochondral/intracartiliaginous ossification it occurs within?
pre-existing catilage model
Endochondral ossification is found in the formation of?
long/short ones, the condyles of the mandible, sphenocciptial joint
Hyaline cartilage models acts as fetal skeleton, is NOT harden and become bone
Bone collar is produced?
at local perichondrium
Primary ossification center is?
at the center
Secondary ossification centers is at?
Articular cartilage ?
persists thru out adult life, does not contribute to bone growth in length
Epiphyseal plate or growth plate is responsible for bone growth in?
-disappears in adults, strop growing in height, remnants= epiphyseal lines
Step/Zones in endochondral osteogenesis:
- 1. Resting zone
- 2. Zone of proliferation
- 3. Zone of hypertrophy
- 4. Zone of calcification
- 5. Zone of ossification
- 6. Resorption
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