Lecture 1: Cartilage (Wronski) Flashcards
Name the 3 types of cartilage recognized
- hyaline cartilage
- elastic cartilage
- fibrocartilage
which type of cartilage is most common?
hyaline cartilage
define chrondroblast
cells that are capable of producing cartilage-specific extracellular matrix
define lacunae
celullar compartments surrounded and isolated by extracellular matrix produced by chondroblasts
define chrondrocyte
chondroblasts that have become embedded in matrix within luncunae.
they maintain the ability to divide and produce extracellular matrix
define perichondrium
a fibrous covering formed by by mesenchymal cells at the margins of the centers of chondrification.
name the two different layers of cells recognized within the perichondrium.
- fibrous layer = most external, developed by differentiated fibroblasts. looks like dense irregular connective tissue
- chondrogenic layer or cellular layer - generates new chondroblasts.
does perichondrium persist in adults?
yes, but its chondrogenic capacity decreases and eventually ceases.
which type of cartilage lacks perichondrium?
articular cartilage
Name the two different types of cartilage growth.
- appositional growth
2. interstitial growth
define appositional growth
the deposition of new cartilage at the surface (perichondrium) by chondroblasts.
define interstitial growth
the division of chrondrocytes within lacunae and the production of matrix, resulting in expansion by new cartilage from within.
explain the development of isogenic clusters of chondrocytes
when chondrocytes divide, new matrix is produced that separates the daughter cells into separate lacunae. this division results isogenic clusters of chondrocytes - the progeny of a single chondrocyte
what type of collagen dominates in hyaline cartilage?
type II collagen!
what type of cell produces type II collagen in hyaline cartilage?
chondrocytes within the growth plate
define aggregans
extremely large proteoglycan aggregates that contains embedded collagen fibers.
what properties does the extracellular matrix provide to hyaline cartilage?
strength and resiliency of cartilage
what properties do the collagen fibers provide to hyaline cartilage?
tensile strength and shape of cartilage
what properties do the proteoglycans provide to hyaline cartilage?
ability to absorb compressive forces
define chondronectin
a fibronectin-like connecting glycoprotein that specifically binds collagen fibers and proteoglycans to chondrocytes.
territorial matrix
the matrix immediately surrounding lacunae (newest formed).
- more basophilic
- more peripherally placed
interterritorial matrix
outlying matrix
what provides the firm gel-like quality of cartilage?
the high concentration of very large proteoglycan aggregates
explain what creates the compressive strength of cartilage
it is due to its high water content and negatively charged glycosaminoglycan side chains. when compressed, water is displaced. with the displacement of water, the repelling forces of the like negative charges are left to resist any further compression.
is cartilage vascular or avascular?
avascular
how do metabolites pass from capillaries to chondrocytes?
long distance diffusion
explain the effect of deposition of insoluble salts in the matrix
this is the process of mineralization. it impedes diffusion and leads to degenerative changes because viable chondrocytes are essential for maintenance of cartilage matrix.
what treatments for hyaline cartilage have been reasonably successful and why
allografts because it prevents large molecules (like immunoglobulins and CTL cells from coming into contact with chondrocytes due to its avascular nature.
what type of cartilage is present in the external ear, auditory tube, and epiglottis?
elastic cartilage
what are areas of degenerative cartilage replaced with?
fibrous connective tissue
what is the main difference between elastic cartilage and hyaline cartilage?
elastic cartilage has elastic fibers rather than collagen that comprise the fibrillar component of the extracellular matrix.
define fibrocartilage
a specialized connective tissue where tendons and ligaments insert on bone or cartilage
what type of collagen is dominant in fibrocartilage?
type I collagen fibers
what other substances are found in fibrocartilage other than collagen?
amorphous ground substance composed of chondroitin sulfate and dermatan sulfate
where is fibrocartilage most commonly found?
the annulus fibrosis of the intervertebral discs and menisci of the stifle joint
what are articular surfaces composed of?
articular cartilage supported by underlying subchondral bone
what is articular cartilage composed of?
hyaline cartilage that is not covered by a perichondrium
how is growth of articular cartilage achieved?
interstitial growth
what happens at cessation of growth of articular cartilage?
chondrocytes are no longer able to divide but are capable of producing additional cartilage matrix
what are the 4 zones of articular cartilage?
- tangential zone (most superficial)
- transition zone of chondrocytes
- radial zone of chondrocytes
- deep zone of calcified cartilage
describe the tangential zone of articular cartilage
it is superficial, narrow and consists of a zone of small, flattened chondrocytes aligned parallel to the articular surface
describe the transition zone of chondrocytes in articular cartilage
consists of an ovoid morphology
describe the radial zone of chondrocytes in articular cartilage
they are aligned in longitudinal rows perpendicular to the articular surface
describe the deep zone of calcified cartilage in articular cartilage
it interlocks with subchondral bone to anchor the articular cartilage
define tidemark
the junction between the radial zone and the calcified cartilage
how does the tidemark appear on x-ray? why?
appears as the “joint surface” because it is the junction between non-calcified (radial zone of articular cartilage) and calcified tissues
how does articular cartilage receive nutrients? what is its main source?
by diffusion and the main source is synovial fluid of the joint cavity
what is osteroarthritis or degenerative joint disease characterized by?
the degeneration of articular cartilage
what are the 8 stages of osteoarthritis?
- proteoglycan and hyaluronic acid content of they hyaline cartilage matrix decreases
- fat is deposited in the interterritorial matrix and chondrocyte numbers decrease
- chondromalacia
- fibrillation
- brood capsules form at the margins of fissures to try and repair the damage
- resorption of cartilage matrix by chrondroclasts
- underyling subchondral bone is exposed
- osteophytes form at the periphery of the degenerative joint
define chondromalacia
articular cartilage becomes soft
define fibrillation
the formation of small fissures on the surface of the articular cartilage
define brood capsules
clusters of chondrocytes
define osteophytes
bony outgrowths
what breed has particular issues with herniated intervertebral discs?
dachshunds
what is the outer part of the intervertebral disc called? what type of cartilage is it composed of?
the annulus fibrosis. it is composed of fibrocartilage
what happens in the early stages of herniated disc development?
the proteoglycan content within the fibrocartilage matrix of the annulus fibrosis is decreased AND the collagen content of the nucleus pulposus increases which results in fibrosis and dehydration causing loss of shock absorbency.
what happens in time to a herniated disc?
- collagen fiber bundles become disorganized in the fibrocartilage of the annulus fibrosis and fissures develop.
- the nucleus pulposus extrudes through these fissures in the annulus fibrosis and compresses the spinal cord.
what should be done if the patient is unresponsive to conservative therapy?
laminectomy
what is done in a laminectomy?
certain parts of the bony vertebra are removed to expose the spinal cord within the vertebral canal, followed by removal of the extruded nucleus pulposus
