Vet histology lectures 14 & 15
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Describe the vasculature in cartiledge?
Is there any nerves or lymph in the cartilage?
What are the 2 main cartiledge forming cells?
Chondroblasts and chondrocytes
Cartilage is composed of cells and ground substance, why can we see any fibers in cartilage?
Same refractive index as ground substance so blends in
What is cartilage that covers bone where it articulates another bone called?
Why cant we have nerve blood vessels or lymphatics in cartilage, especially articular cartilage?
Because often high pressure tissue and could damage those structures
Other than articular portions of bone where else do we find cartilage?
Place that need strong but flexible reinforcement such as the trachea and esophagus
What is the space the chondrocyte sits in called?
Chondrocytes we would expect to see a large number of what intracellular organelle? Why?
- Producing lots of proteins
Cartilage is composed of what type of collagen? Does this collagen form bundles?
- No only fibrils never fibers or bundles
Why do we often see a halo around chondrocytes in tissue?
Because when we process the tissue we often shrink the chondrocytes for some reason
the ECM of cartilage is formed of? (2)
- Type 2 collagen
- Ground substance
As cartilage cells get older and bigger they get bigger and deeper within the cartilage. Why do we see a decline in health down there? What adaptation is meant to negate this? Is cartilage still limited?
- Hard to get nutrients in and waste out because avascular
- High water content of ground substance
- Yes it cant get too big or it dies
Agrecans in cartiledge are formed by what binding to what
proteoglycan to hyaluronic acid
Do we see perichondriuym in articular cartilage? Why?
- Too vascular for the pressure and would be ruined
Perichondrium has 2 layers?
- Inner cellular layer
- Outer fibrous layer
Chndroblasts originate from what other cell?
Fibroblasts of the connective tissue
What layer makes the cartilage?
What are 3 types of cartilage? Briefly describe each?
- Hyaline - glassy looking generic cartilage
- Elastic - has elastic fibers imbedded in it
- Fibro - Halfway between cartilage and tendon
Where do we see most fibrocartilage?
At the most stressful points of a tendon
Where do we see hyaline cartilage?
- Respiratory system
- i.e. trachea etc
How do we make elastic cartilage? What are its properties? Where do we see it? Can we normally see it?
- Adding elastic fibers into type 2 collagen
- elasticity and flexibility
- Places like epiglottis
- Not without special staining
Do we find vasculature in the fibrocartilage?
No not at all
How does fibrocartilage appear?
As small rows of cartilage cells between tendon spaces
Essentially how is fibrocartilage formed?
Some fibroblasts decide to turn into cartilage
So all chondroblasts start from? But can they go backwards?
Describe the development of cartilage?
- Cells derived from mesenchymal cells
- Withdraw their processes
- Secrete amorphous substance and type 2 collagenv(causes them to spread apart)
How do chondrocytes get nutrition?(2) (physically what 2 places does it come from) What happens if the chondrocyte is >3mm inside
- Through diffusion, cappiularies outside perichondrium, synovial fluid
- vascular canals form
Where other than deep cartilage do we see vasculkar canals to bring nutrition to tissue?
In the development of fetal bone and therefore later in bone
is bone vascular or avascular?
Is bone a dynamic or static tissue?
What is the main cell of the bone?
What is the name of the non mineralized matrix of the bone? it contains what?
- Type 1 collagen and proteoglycans
Where osteoblasts nucleus located? What colour under H&E are they? They form the bones?
- Basophillic (with prominent rER)
What happens to bone with old age or with mineral deficiencies?
THey get bendy and weak because of nutrient deposition issues
OSteoblasts release 2 kinds of things?
- Ground substance and collagen fibers are produced
- Also release secretory vesicles containing alkaloid substance
What happens to the alkaloid vesicles that are released from the osteoblasts ask they get older and older?
Ca and P are deposited and they become hydroxyappetitie crystals eventually fusing to form the mineralized layer
While osteoblasts create bone osteocytes? What about osteoclasts?
- Maintain bone
- Eat and turnover bone
Osteocytes are where?
Completely surrounded by their own minerilization in the bone
How do osteocytes get nutrition?
Permeates through small canals called canaliculi because bone is obviuously not permeable
Osteoblasts are single nucleated cells, while osteoclasts are? And do what? and are derived from what?
- multi nucleated
- eat and turnover bone
Does the body leave the bone for long?
No bone is constantly being turned over
no osteocytes is > than ____ microns from a blood vessel. The cell cytoplasm of the osteocyte can extend into the?
How do osteoclasts change their shape to efficiently eat away bone?
They get little indentations into themselves on the surface of the bomne where they are eating, it is hear they release the enzymes to degrade bone, by making this tight packet of space inbetween the bone and the cell it doe snot loose its enzymes friverously and can be more efficient (see picture in lecture 14 page 3 slide 6)
Bone matrix is made of?
Type 1 collagen and ground substance
Bone can act as a storehouse for what? IT can be mobilized when?
- Calcium and phosphorous
- Whenever needed
Calcium and phosphorous are stored in bone in the form of ?
The out layer of a long bone that is solid and gives rigidity is reffered to as? What about the inner softer lighter bone? Why is all bone this solid bone all the way through?
- trabecular (cancellous)
- Because it would be far too heavy
What are two ways you can prepare bone slides? Why are these so unique?
- Decalcified bone
- Ground bone into thin slice
- Because you cant simply slice bone
What is the name of the system of organization that bone is in?
The haversian system of bone is based off of what unit that includes the blood vessels?
In the middle of the osteon is the?
Central (haversion) canal
What surround the central canal of an osteon?
Concentric or haversian lamellae
What is located between the concentric lamellae? which holds? and spreads out via?
- The lacuna
WHat are the interstitial lamellae?
Lammalae facing the inside of the bone but not compleeltey surrounding an osteon, almost cut off bu end of compact bone
THe haversion system applies to compact bone or cancellous bone?
What surrounds all the osteons on the outside of the bone?
The external circumferential lamellae
Do we see lacuna in the external circumferential lamellae and the interstitial as well as the concentric?
What surrouns the external circumferential lamellae? which is connected to the comnpact bone via? And has 2 layers which are the? And is vascular or avascular?
- perforating fibers
- cellular layer, and fibrous layer
Blood vessels in the compace bone run longitudinal or transverse?
What do we find in the central canal spaces of the trabecular bone?
What do we call the actual branches of trabecular bone?
Describe the anatomy of a trabeculae starting from outside layer in
- Endosteum (made up of osteoblasts aligned on outside) (often find osteoclasts eating away here too)
- Parallel lamellae
- Inbetween the parallel lamellae is lacunas similar to the compact bone
parallel lamellae in the trabecular bone are also called?
IF YOU ARE HAVING ANY TROUBLE WITH MICROSCOPIC STRUCTURE OF BONE THERE IS GREAT BIG LARGE SLIDES PRINTED OFF ON THE BACK OF LECTURE 14
What type of preparation allows you to see cannaliculi? Can you distinguish cells? Why?
- Ground preparation
- Cause they are all ground up and distorted, can only see spaces between
Periosteum has 2 layers? Which layer is more prominent in young?
- Inner osteogenic layer
- Outer fibrous layer
- Innter osteogenic layer in young
What is the endosteum? It is contrasted to the?
- Layer of osteoblasts in trabecular bone
Name 2difference from cartilage to the bone
- Bone has
- Presence of canalicular system
- Direct vascular supply
Canaliculi travel from where to where and open up where?
Lacuna to lacuna and open up on bone surface to get into connective tissue close to capillaries
What process does the healing of a fracture resemble?
Formation of new bone
What are the extremities of a long bone called? What about the more central portion?
- Epiphysis = extremities
- Diaphysis = centre
What is immature fetal bone called? Why is it weaker and more bendy?
- Woven bone
- Because not near as organized or compact, no osteocytes, so quite weak
What are the 2 ossification methods? Which is most common? Where are both found?
- Intramembranous - flat bones
- Endochondrial - long bone
What is the growth plate? What is its technical name?
- It is a cartilaginous layer between the epiphysis and diaphysis
- Epiphysial plate
Describe the formation of a flat bone in 4 steps, also describe the name of this process
- Intramembranous ossification
- normal connective tissue
- turn into osteoblasts
- Calcification forming, mesenchyme condenses to form periosteum
- Calcification points around osteoblasts start to fuse and make a structure
What is the best way to kill a cartilage?
mineralize its matrix and starve it to death
When you mineralize the matrix around cartilage cells what does it leave behind? What fills this?
- Holes and spaces where cells were
- Osteoblasts and vasculature
Describe the dfifference between the first bone formed and more refined bone
- Refinement is the key word here
- 1 bone formed Is essentially old cartilage remanant mineralized,
- future bones are replaced by osteoclasts and have proper bone structures and mineralization
How many centers of ossification do we normally have in a long bone? What is it?
- Generally we consider it to be the point where ossification begins within the bone
Where is the primary center of ossification? What about secondary?
Describe how we go from mesenchyme to bone
- hyaline cartilage (all chondrocytes)
- Bone formation begins in the shaft
So how does the vasculature and cells actually get within the bone?
Osteoblasts form collar around diaphysis, when the cartilage dies the osteoblasts and vessels move in
Which center of ossification is the first to be invaded
Cartilage lining joint point of long bone
Does the epyphysial plate grow towards the shaft or the end
Toward the shaft,Constantly growing that direction, makes sense because growing on a curve would be strange
What is the name of the area within the epiphyseal plate where the bone is actually being formed?
Why do we see irregular shapes of the cartilage in the bone at the extremity end of the epiphyseal plate
So that the bone and the cartilage attach together well
Describe the steps of the cartilage as it goes downwards towards the diaphysis and the changes in job it goes through (6)
- deposite and build up strength
What is the prolioferation zone called? What about growing zone? Why would these cells what to grow so big?
- Zona proliferation
- zona hypertrophy
- to make as big of cavities as possible
1st model of bone what will come of it?
Eaten away at a later date and relayed more efficiently and more organized
In the transition from cartilage to bone at the epiphyseal plate all the cartilage cells must die, how do they die?
All extra cellular space between them is calcified thus shutting down the diffusion of nutrients
So during formation of bone when dead cells are absorbed they leave behind
What closes the epiphyseal plate? What gender shuts down bone growth first?
- Testosterone and estrogen, or steroid hormones
What leads the remodeling?
Cutting edge of osteoclasts
What follows the cutting edge of the osteoclasts when they drill into bone for remodeling
Osteoblasts and blood vessels
What remodels faster young or old bone?
What ends up happening to the pattern of osteons seen by the 3rd generation
ends up overlapping old osteons and lookinging like an old pattern of unfisnished osteons
Going farther back from the cutting edge of the osteoclasts what happens to the cavity?
Gets thinner and thinner as osteoblasts fill it up
In the remodeling of spongey bone how does it differ?
An entire leaflet of osteolasts moves at once followed by a whole leaflest of osteoblasts
Describe the 4 steps of fracture repair
- Blood vessels fill the fracture with a hematoma which turns into a big clot
- clot is overgrown by periosteum, makes cartilage
- cartilage is invaded by first bone, making a hard callus (not as hard as strong bone) then the bone is drilled out in remodelling and becomes bone again
What is the latin term for joint?
Describe syndesmosis, Synchondrosis, Synostosis and symphysis
All of them are joints of a sort
- Syndesmosis = glued together by dense connective tissue like young skull
- Synchondrosis = cartilage attaching the joint together such as ribs to sternum
- Synostosis = Eventually when joint truly fuses together with bone, like an adult skull
- Symphysis = attached via connective tissue, cartilage to cartilage ie. vertebra
What is a diarthroses?
A joint with a capsule or cavity
What happens with the articular cartilage when you get closer and closer to the surface of the articular cartilage?
The cells get smaller and smaller
The compression near the surface of the articular cartilage in a diarthrosis changes what structure
Thje fibers of the articular cartilage vear off to the side
Why is it rare to have to epithelium within the diarthrotic capsules?
Cause it is one of the only capsules to not be lined with epithelium
What is the inside of a diarthrotic capsule lined with?
- Blood vessels
- Fibroblasts - secreting fluid
- Macrophages - cleaning fluid
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