Chapter 8 - Bone Flashcards
How do bone cells develop?
MSC > osteoprogenetors > osteoblast make matrix > encased in matrix and mineralization = osteocyte
What causes the differentiation from chondrocytes to osteocytes?
An increase in O2
What is bone made of?
Osteocytes
Type I and V collogen
Little ECM/group dubstant
What functions does bone provide?
Support
Protection of internal organs
Produces hormones: parathyroid and calcitonin
Does bone get high or low diffusion of nutrients? Why?
Low diffusion because it has very little ground substance
What two types of mulitadhesive glycoproteins are found in bone? What are their functions?
- Osteonectin - adhesive bewtwwen collagen and hydroxyapatite crystals
- Osteopontin - attaches cells to bone matrix
What fibers so you find in bone? What are their functions?
Type I collagen - structure
Type V collagen - support
Traces of other collagens
What GAGs and Proteoglycans can you find in bone? What do they contribute to?
Hyaluronan Chondroitin sulfate
Keratin sulfate
All contribute to compressive strength
What are canaliculi?
Rays extending from osteocytes toward the center of the osteon
Tunnels between adajent osteocytes
Connect by gap junctions
What are the 4 bone associated cell types?
- Osteoprogenitor cells
- Osteoblasts
- Bone-lining cells (remain when bone isn’t growing)
- Osteoclasts
What are the two types of bone tissue?
- Compact (dense)
- Spongy (cancellous)
What are the 4 types of bone?
- Long bone
- Short bone
- Flat bone (ex skull, sternum)
- Irregular (vertebrae)
Characteristics of compact bone?
Highly organized , dense
What are the holes in spongy tissue filled with?
Marrow
What are the three regions of the long bone?
- Epiphysis - on either end, spongy bone
- Metaphysis - where flairing occurs. Contains epiphysial plate
- Diaphysis - shaft, dense bone
What surrounds the entire bone execept on the very ends?
Periosteum
What is the periosteum?
outer layer: dense fibrous CT
inner layer: osteogenic layer
What is the endosteum?
Lines compact bone facing marrow cavity and trabeculae (plates?) of spongy bone
Houses osteoprogenitor cells
What does the marrow cavity consist of?
Blood cells and netowk of fibers
Red marrow vs yellow marrow
Red marrow is found in kid, more hematopoietic cells and RBC
Yellow marrow is found in adults, more adipose tissue
Osteon
Concentric lamallae that surround the haversian canal
Canaliculi
Passage for substances between osteocytes and blood vessels also tunnels connecting osteocytes
Interstitial Lamellae
Result from bone remodeling
Volkman’s canals
connect perioteal and endosteal surfaces to the haversian canal (middle of the osteon)
Is bone vascular or avascular?
Bone is highly vascular
What are nutrient foramina?
Openings in bone that allow blood vessels access to marrow
Of epiphysis, metaphysis, and diaphyses which are the most rich is vasculature?
Diaphysis
Epiphysis
How do osteoclasts develop?
Granulocyte/monocyte progenetor > osteoclast
Similar in function to macrophages
What two types of cells can osteoblasts differentiate into?
Osteocyte
Bone-lining
Where are osteoprogenitor cells located?
Inner layer of perioesum
Lining of marrow cavities, haversian canals, Volkmann’s cannals
What is the function of osteoblasts?
Bone-forming cell
Secrete osteiod
Secrete ALP
What do osteoblasts look like?
Cuboidal in shape
What is osteoid?
unmineralized bone matrix
What is ALP? What does it do?
Alkaline phophatase Initiate bone mineralization
What do osteocytes do?
Maintain bone matrix
Respond to mechanical forces applied to bone
What are osteocytes encased in?
Lacuna
How do osteocytes respond to different pressure??
Weighlessnes = reabsoption > decreased matrix
Quiescent = low matrix turn over, low rough ER
Formative = high rough ER and golgi bodies > creation of matrix
What do osteocytes do during reabsorption?
Increase the breakdown of calcium phosphate
What do bone-lining cells do?
Function in maintainence and nutritional support of osteocytes
Where do you find bone-lining cells?
Located on a bone surface where remodelign is NOT occuring ex) Periosteal cell (external bone surface)
ex) Endosteal cell (internal bone surface)
What is the function of osteoclasts?
Bone reabsorption
When remodeling what type of bone cell increases?
Osteoclasts
What cell make the resorption bay / Howship’s lacuna?
Made by osteoclasts
What are the three regions of the resorption bay and what do they do?
- Ruffled Boarder; microvilli extentions that release protons to increase the acidity which then causes bone demineralization and releases digestive fluid which breaks down collagen and matrix
- Basolateral region; excytosis the minerals and broken down collagen and matrix
- Clear zone; forms tight seal that allows osteoclasts to tightly fix to bone
What are the two types of bone formation?
- Intramembrounous ossification
- Endochondral ossification
Intramembrounous ossifcation
MSC > osteoblasts
Flat bones, peripheral long/short bones
Endochondral ossification
Hyalin cartilage replaced with bone
Bones of extrematies and weight-bearing axial skeleton
Intramembranous Ossification (5 steps)
- Ossification center forms (MSC > osteoprogenitor cells)
- Osteoblasts secrete bone matrix, forming trabeculae
- Trabeculae become interconnected (woven)
- Periosteum form
- Lamellar bone replaces immature bone
When does intramembranous ossification occure?
During the 8th week of gustation
Talk me through intramembranous ossification in your own words
Ossification center forms > osteogenetor cells > grow in size and become rounder > produce matrix > osteoblasts > calcification > osteocytes > trabeculae islands of bone > eventually become interconnected = woven, but irregular > periostieum forms creating fibrous cap around immature bone > llamellar bone replaces immature bone
What is an example of intramembranous ossification?
The growth of the skull in a newborn to replace the soft spots on its head 1-2 month = mesynchyme tissue 7
-19 months = intramembraneous ossification
What is endochrondral ossification?
Bone growth within hyaline cartilage
What are the 6 steps to endochronral ossification?
- Bony collar forms
- Chondrocytes hypertrophy and initiate calcifications
- Calcified cartialege degenerates adn becomes invaded by a periosteal bud
- Osteoblasts deposit bony matrix on surface of calcified cartilege
- Secondary ossification center forms in epiphysis
- Hyaline cartilige only remains in epiphyseal plates and articular cartilages
When does endrochrondrial ossification occur?
Begins at 12 weeks of gustation
External and internal remodeling maintain proper proportions and shape of bone
True
What two types of cones does the bone remodeling unit consist of?
- Advancing cutting cone / resoption canal
- Closing cone
What is the cutting cone in the bone remodeling unit consist of? (cell type)
Osteoclasts
What is the closing cone in the bone remodeling unit consist of? (cell type)
Ostoblasts
How is the bone remodeled? What is the process?
The advancing cutting cone creates a hole in existing bone the size of the osteon > osteoclasts (cutting cone) leave > ostoblasts (closing cone) attach and release osteoid > calcification > osteocytes Repeat until osteonal canal forms
What is the purpose of the endosteal layer during bone remodeling?
The endosteal layer is full of osteoprogeneter cells which can give rise to new cells as needed
What are the two parts of naming bone?
- Compact or Spongy
- Woven or llamelar
What is the periosteum?
Outer, fibrous layer Inner, cellular layer
What is the endosteum?
Single cell layer next to the marrow
What happens when you get a fracture?
Facture > immune response > hematoma > stabalizes fracture for the time being Macrophages chew at necrotic bone and decrease the blood clot > create soft callous (type I and II collagen) = bainaid to hold the bone together > recruitment > intramembranous ossification in two locations >>>
What is osteopetrosis? Symptoms? What causes it?
Bones are extremely dense and lack marrow cavity = very brittle
Weaker because they lack O2 and nutrients
Defective osteoclasts
What is rickets? Symptoms? Cause? Who does it effect?
Abnormal bone calcification in growing bone
Short, bowed legs
Caused by poor dietary calcium or vitamin D
Defficeint Ca and Vitamin D > lack of calcification
Effects children
Osteomalacia; symptoms? cause? who does it effect?
Weakend bones
Unusually thick uncalcified matrix
Poor dietary Calcium or Vitamin D
Effects Adults
Osteoporosis; symptoms? cause? who does it effect?
Osteoclasts are messed up
More bone loss than bone formation
Extensive spongy bone inside
It can occur in post-menopausal women (decrease in Estrogen > decreased bone formation because osteoclasts need pro-inflammatory cytokines to form?)
5 zones of epiphysial/growth plate?
- Reserve cartilage; osteocytes are NOT undergoing interstitial growth
- Porliferation; bigger cells and interstitial growth > isogenous groups (stacks of coints)
- Hypertrophy; bony collar on outside
- Calcified cartilage; even bigger cells, cells start to die > gives osteoblasts (?) a place to attach
- Reabsroption; cartilage disappear and is entirely bone
Identify the image
Osteocytes and Bone-Associated Cells
Identify the image
Compact bone
Spongy bone
Identify the image
- Epiphysis
- Metaphysis
- Diaphysis
- Metaphysis
- Epiphysis
- Articular cartilage on articular surface
- Epiphyseal line
- Spongy bone
- Marrow cavity
- Periosteum
- Compact bone
- Spongy bone
- Epiphyseal line
- Articular cartilage on articular surface
Identify the image
- Osteonal artery
- Collagen fibers
- Interstitial lamellai
- Osteon
- Outer circumferential lamellae
- Periostuem
- Osteocyte and lacuna
- Haversian canal
- Osteonal endosteum
- Lamellae of bone
- Volkmann’s canal
- Inner circumferential lamellae
- Endosteum
Identify the image
(Just top box and 3 on the right)
Articular cartilage
Epiphysis
Metaphysis
Diaphysis
Identify the image
Cartilage
Bone-lining cells
Osteocytes
Osteoblasts
Osteoprogenitor cells
Mesenchymal stem cells
Granulo/monocyte progenitor
Inactive osteoclast
Active osteoclasts
Endosteal cells
Identify the image
Osteoprogenitor Cells
Identify the image
Osteoblasts
Identify the image
Osteocytes
Quiescent
Formative
Resorptive
Identify the image
Bone-lining cells
Identify the image
Osteoclasts
Identify the image
Osteoclast
Clear Zone
Ruffled Border
(top section is basolateral region)
Identify the image
Instramembraneous Ossification
Identify the image
Intremembranious ossification
- Ossification center forms
- Osteoblasts secrete bone matrix, froming rabeculae
- Trabeculae become interconnected (woven bone)
- Periosteum forms
Identify the image
Dark pink = trabeculli
Osteoblasts - line the trabeculli
Bone froms around blood vessels
Identify the image
Endochondral Ossification
Identify the image
- Reserve cartilage
- Proliferation
- Hypertrophy
- Calcified Cartilage
- Resorption
Identify the image
- Zone of reserved cartilage
- Zone of proliferation
- Zone of hypertrophy
- Zone of calcified cartilage
- Zone of resorption
Identify the image
Bone Formation - bone remodeling unit
Identify the disease - bowed legs
Rickets
Identify the disease/injury
Repair of a bone fracture
Identify the disease
Osteopetrosis
Identify the disease
Osteopetrosis
Identify the image
Condrocytes
Repair of a bone fracture
Identify the image
Osteocytes
Repair of a bone fracture
Identify the disease
Osteomalacia
Identify the disease
Osteoporosis
Identify the disease
Osteoporosis
Identify the disease
Epiphysial / growth plate
