Cartilage & Bone Flashcards
What do chondrocytes manufacture and secreate?
Collagenous precurser procollagen–> modified in the ECM into tropocollagen
latter forms various cross-links to form a collagen FIBRIL
Can you see fine fibrillar matrix of cartilage under LM?
No
What is the amorphous ground matrix composed of
AGGRECAN
Where is the entire amorphous matrix contained?
within the spaces between the type 2 collagen fibers
Fibers and amorphous ground substance form a alttice
What is function of collagen and aggrecan?
Collagen- provides tensile strength
Aggrecan contains high concentration of negative ions to bind large quantities of water molecules
What is function of cartilage ECM
space-holding network ,formed of immobilized water
Serves as a shock absorber, releasing water when under compression and attracting water when the compressive force is removed
Where does cartilage tissue develop from?
mesenchymal cells that migrate, aggregate, cndense, and give rise to chondrogenic (precursor) cells
Mesenchymal cells?
develop into chondrblasts –> chondroblst secrete ECM around itself –> now completed embedded in ECM in a space called a lacuna!
Mature cell is called?
Chondrocyte!
Contain large amounts of RER b/c they manufacture large amounts of collagen
What are the function and location of Hyaline Cartilage? (5)
- Fetal Skeleton
- Anterior Portion of the Ribs (costal cartilage)
- Structural support of the trachea and bronchi
- Articular surfaces of synovial joints
- Epiphyseal (growth) plate in long bone
What is a synovial joint composed of?
Fibrous Capsule
synovial membrane (whcih secretes synovial fluid)
Articular surface of hyaline cartilage
Does articular surface have perichondrium?
No! It gets diffusion of oxygen and nutrients from synovial fluid
Perichondrium surrounds all cartialge exept where?
Articular surfaces
What is the composition of Elastic Cartilage?
Type 2 collagen & elastic fibers
Provide an increased amt of flexibility designed to withstand repeated flexiosn and extensions
Where can you find Elastic Cartilage?
In structures that must withstand repeated bending,
such as auricle of ear,
external auditory canall,
Estachian tube, epiglottis,
and the larynx
What kind of stain is needed to see Elastic fibers?
Not with H&E
Specific Stain is required to definitely identify this tissue, bye staining elastic fibers BLACK
Describe what Elastic cartilage looks like?
Covered by perichondrium and contains chondroblasts and chondrocytes in lacunae.
IT also contains the same ECM components as allohter cartalge
Type II colalge, minor colalgens, same amorphous ground substance`
What two components make up elastin fibers?
Fibrillin fibers with an elastin core
What kind of fibers are in Fibrocartilage
Usual ECM components, also contains TYpe I Colalgen Fibers
Presence of Type I colalgen in fibrocartilage ECM makes it tougher than hyaline or elastic cartilage, but also makes it resistant to compressive forces
Where can you find Fibrocartilage?
symphysis pubis
intervertebral disks
menisci of knee joint
attachment points of tendons to bones
Provides resistance to particularly strong forces beign exerted at these locations and it also provides flexibility
What color does it stain?
Presence of Type I colalgen fibers makes fibrocartilage stain pink with H&E
Does it have a perichondrium?
No
Describe the layers of the intervertebral disck
acts as shock abosrber between vertebrae
oval-shaped disk has 2 parts
1. center- nucleus pulposus that contins mesenchymal cells in viscous fluid of hyalaurinc acid
- outer regularly arranged concenetrc fibrocartilage layers = annulus fibrosus
In young, how is cartilage repaired?
repair form damage occurs through replacement of chondroblasts generated from chondrogenic layer of perichondrium
IN adults, ?
Cartilage repair occurs poorly or not at all
Hwne cartilage in kenee is torn, natural healing process favors either formatino of scar tissue (Fibrous CT, generated from fibrous layer of perichondrium) or bone deposition
Under what conditions favor cartilage formaiton?
when oxygen pressure is low,
usually not the case in a wound where blood is bing delivered quickly as part of normal immune and healing repsonses
High oxygen concentrations favor development of bone
What is a consequence of cardiothoracic surgery?
costal cartilage is severed to open chest ccavity for heart repair– ribs have to be wired back to sternum
one after-effect can be arthritis of rib cage
What is bone?
Specialized CT and organ
What kind of tissue types are in bone (the organ?)
CT fibers, hemopoietic tissue, nerves, vasculature, lymphatics, fat, cartialge, bone tissue
Bone as organs are classified as (4)
- long bones (upper and lower extremities)
- short bones (hands and feet)
- flat bones (skullbones, breastbone)
- Irregular oones (vertebrae, mastoid bone)
What are the functions of bone?
- Form jointed skeletal system of the bond-
ligaments and provide attachemtn sites for sk muscle - protect vital organs-
skull encase brain, thoracic cage, pelvis protects reproductive - Contain bone marrow
- new blood cells formed - provide reservoir for Ca and Pi ions
growth facotrs and other minerals
What is the ECM of bone composed of?
- organic portion that forms template for mineratlized protein
What is organic protion called? what does it contain?
What kind of fibers ?
Osteoid- contains amorphous ground substance and fibers
ground substance is composed of proteoglycans
fibers are predominatly Type I collagen
Where does their assembly take place?
Extracellulary from precursor molecuels syntehsized and secreted by osteblasts
What is the principla mineral component of EC in bone?
Calciumm Phosphate (hydroxyapetite) , present in crystalline form
What two methods are used to prepare bone from LM examination?
- Ground bone method
2. Demineralization (decalcification)
What is the Ground Bone Method?
Bone is thinly sliced and finely ground
Calcified matrix is preserved but cellsa re lost
What is the Demineralized Method?
bone is fixed, calcium phosphate is removed, and remianing material is embedded, sectioned, and stained with H&E stained
Fixation process preserves cells and organic portion of ECM (mostly collagen fibers)
What are osteoblasts? waht do they produce?
Basophilic, cuboidal cells taht secrete organic componetn of ECM.
Produce ALKALINE Phosphatase, procolalgen, and non-collagenous proteins that have a role in calcification.
What stimulates Osteoblasts?
Vitamin D, Calcitonin, estrogen, and grotwht factors
The also contain receptors for parathryoid hormone, which inhibits their activity and stimulates osteoclast activity
When does calcification begin?
When osteoblast’s secretions lower pH around teh cell
Alkaline phosphatase rleases free phosphate ions; these combinde with calcium ions and ppt as crystlas of calcium phospahte
low pH is required for this step
What cells do osteoblasts originate from? Where are they found?
osteoblasts originate from OSTEOPROGENITOR CELLS in teh periosteum and in BM
capabe f active cell division
Found ining endosteal and periosteal surfaces of actively-growing one and maintain communication with each other by means of gap junction
How doe osteoblasts stay in contact? What is prominent in their structure?
Communicate with each otehr thorugh gap unctions and have a prominent Golgi apparatus and rER since they make a lot of cells and rlease large amounts of proteins
What are osteoclasts? Function?
Multinucleated macrophae
under hormonal control, osteoclast uses low pH and preoteases to digest bone
Resorbs bone
what do osteoclasts secete?
H+ ions to raise extracellular pH, then secrete acid phosphatase–> dissolves calcium phospahte matrix of bone
Also release collagenase which digests old collagen fibers
What stimulates osteoclasts?
Stimulated indirectly by Parathyroid hormone (PTH), and inhibited directly by CALCITONIN, which binds to specific receptors on their surface
Do osteoclasts begin digestive process extracellulary or intracellulary?
Extracellulary by secreting lysosomal-like enzymes like acid phsophatase and collagenase nto lumen adjacent to their ruffled border
What happens during bone remodeling and when does it occur?
Osteoclast resorption, osteoblast activity (matrix formation steoid), mineralization, resting phase
Remodleling takes palce during normal bone maintenance, repair of bone fractures and in response to increased bone loading (lifting weights leads to thicker, stronger bones)
What are contained in Haversian canacls and Volksmann’s canals?
Veins, arteries, lymphatics, nerve processes
Broken bones are painful and bone breakage always involves bleeding
what are canaliculi
canaclas taht extend between lacunae
processes of adjacent osteocytes communicate via gap junctions
all osteocytes are conencted to Haverisan canal which provides their nourishemnt
What is PERIOSTIEUM
outer covering with two layers,
outer, fibrous layer (similar to dense CT0 and inner cellular layer
covers external surface of bone, contains a reservoir of osteoblasts for new appositional bone formation
attachemtn point for muscles, tendons and ligaments
what are Shaerpye’s fibers
Type I colalgenous fibers that exend into bone, anchioring it firmly’ fibers are found wherever a strong aattachemnt to bone is required
attachemtn if furtehr strengthened by thickening of the periosteum wherever bones, tendons, or laigament attach
what kind of cellsa re in teh inner layer of periostieum?
contain osteoprogenitor ells which give rise to osteoblasts
What are two types of ossificaiton? Two ossficaiton differ with respect to starting material
1 can be mesenhyme
2. oe XERILfw
What does low oxygen levels favor?
development of cartialge
What does high oxgyen levels favor?
development of bone
What is intramembranous ossification?
bone forms direclty within layer of condensed mesenchyme
bone generated from within the MEMBRNAE
CARTILAGE is NOT invovled in this process at all
Mesencymal cells differentiate directly into OSTEOPROGENITOR celsl (bone precursr ) cells –> osteoblast
Periosteal layer
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