Cartilage Flashcards
What is cartilage a key tissue in?
Fetal development and growing bones
What is the cartilage matrix made of?
Chondrocyte cells and an extensive extracellular matrix
What function does the extracellular matrix account for?
Resilience in cartilage
How does the chondrocytes obtain their nutrients?
Diffusion by ECM, ECM is crucial for survival of chondrocytes
What is the extracellular matrix composed of?
Mostly collagen fibers, and Ground substance (proteoglycan aggregates)
What is glycosaminoglycan?
Complex polysaccharides containing amino groups
What are proteoglycan aggregates?
Glycosaminioglycans GAGs, linked to a core protein
Example of glycosaminoglycan?
Chondroitin sulfates
Proteoglycan aggregates permit the diffusion of nutritive substances from?
Blood vessels in surrounding connective tissue to chondrocytes
What is most of ECM made of?
Water
What components of cartilage makes it an excellent shock absorber?
Extracellular water, resilient and shock absorber
What component of cartilage binds extracellular water?
Glycosaminoglycans
Which proteoglycan is primarily present in hyaline cartilage?
Aggrecans
Which cartilage has Type 1 collagen?
Fibrocartilage
What do chondrocytes secrete?
Type II Collagen
What does Hyaline cartilage ECM contain?
Type II collagen, proteoglycans in form of aggrecans, multiadhesive proteins
What does Elastic cartilage ECM contain?
Elastic fibers, elastic lamellae, type II collagen, proteoglycans, and multiadhesive proteins
What does Fibrocartilage ECM contain?
Type I collagen, Type II collagen, proteoglycans, multiadhesive proteins
What do fibroblasts secrete?
Type I Collagen
What does type I collagen provide?
Tensile strength
Where is hyaline cartilage found?
Nose, articular joints, costal cartilage, trachea ring, larynx, bronchi of lung, epiphyseal plate of long bone
Where is elastic cartilage found?
Pinna of ear, epiglottis, external acoustic meatus, auditory tube
Where is fibrocartilage found?
Meniscus, pubic symphasis, intervertebral discs, temperomandibular joint, triangular complex of wrist
Where do chondrocytes live in?
Lacunae
Chondrocytes produce what?
Extracellular matrix
Chondrocytes are formed in what type of arrangement?
Hexagonal arrangement of fibrils
What does type X collagen do?
Organizes fibrils into three dimensional hexagonal lattice
What does type XI collagen do?
Regulates fibril size
What does type IX collagen do?
Facilitates fibril interaction with matrix proteoglycan
Clusters of isogenous groups indicates?
Cells are dividing and increase size of cartilage
Multiadhesive glycoproteins are what?
Branches oligosaccharides or Non proteoglycan linked glycoproteins
What does multiadhesive glycoproteins do?
Influence the interaction between chondrocytes and matrix molecules
Anchorin CII does what?
Helps anchor chondrocytes to the matrix, functions as a collagen receptor on chondrocytes
What is clinical value of multiadhesive glycoproteins?
Used as markers to detect cartilage turnover and degeneration
Collagen fibrils (15%) provide?
Tensile strength and shape, bind aggrecans and support them, *provides a framework to resist swelling pressure caused by aggrecans
Aggrecans (9%) provide?
Bind water molecules with high affinity
(60-80% of water)
What does a hydrated ECM provide?
Resilience and diffusion of metabolites
Functions of type II collagen in hyaline cartilage?
Provides shape, tensile strength, provides framework to resist swelling pressure
Hyaline cartilage ECM can undergo calcification and cause what?
Leads to chondrocytic cell death, seen with aging process
What characteristics does sulfated ground substance of matrix show?
Basophilia, metachromasia (similar to mast cell), and variable stain intensity- provides info about distribution and relative concentration of sulfated proteoglycans
More ground substance in ?
Dark areas of cartilage
What is pericellular matrix?
Ring of densely staining matrix around chondrocytes
What does pericellular matrix contain?
Highest concentration of proteoglycan hyaluronan and multiadhesive glycoproteins
What type of collagen is found in pericellular matrix?
ONLY type VI collagen, anchors chondrocytes to matrix
What does territorial matrix contain?
Randomly arranged type II collagen fibrils, lower concentration of sulfated proteoglycans than pericellular matrix
What does interterritorial matrix contain?
Type II collagen, lowest concentration of proteoglycans
Where does type II collagen assemble?
Interterritorial matrix
Where does interstitial growth take place?
In isogenous groups of chondrocytes
What do active chondrocytes display?
Basophilic cytoplasm (indicating active protein synthesis), lots of golgi and rER
What do older chondrocytes display?
Lipid droplets, stores of glycogen
What are the functions of chondrocytes in hyaline cartilage?
Secrete collagens type II, VI, IX, X, and XI, glycosaminolycans, multiadhesive glycoproteins
Hyaline cartilage is covered by?
Perichondrium, connective tissue cover
What is perichondrium?
Layer of dense connective tissue that surrounds hyaline and elastic cartilage
Where is the chondrogenic layer located?
Layer closest to chondrocytes
What is perichondrium rich in?
Blood vessels, permits diffusion of nutrients and waste products between perichondrium and cartilage matrix
The perichondrium has two layers?
Chondrogenic layer (inner cellular layer) and the outer fibrous layer
What is appositional growth?
Chondrogenic layer deposits extracellular layer from the outside
What cells are present in the chondrogenic layer?
Progenitor cells
Where is perichondrium absent in?
Articular cartilage
Articular cartilage is ?
Hyaline cartilage covering articular surface of synovial joints
What is Osteoarthritis?
Disease of articular cartilage, ECM is degraded by metalloproteinases
What happens when matrix metalloproteinase enzyme activity enhances?
Results in breakdown of proteoglycans and collagen, loss of cartilage, bone on bone contact
What does elastic cartilage matrix contain?
Dense network of branching and anastomosing elastic fibers and sheets of elastic material
What does elastic material provide?
Cartilage elasticity
T or F: Elastic cartilage can undergo calcification?
False
What is fibrocartilage?
Combination of dense regular connective tissue and hyaline cartilage
In fibrocartilage, chondrocytes are dispersed among collagen fibers in?
Single rows or isogenous groups
What does fibrocartilage consist of?
Chondrocytes that produce type II collagen, and fibroblasts that produce type I collagen
Is fibrocartilage covered with perichondrium?
No
What is chondrogenesis?
Process of cartilage formation
What is a chondrogenic nodule?
Chondroprogenitor mesenchymal cells aggregate into a mass of rounded cells
What does expression of transcription factor SOX-9 trigger?
Chondrogenic nodule to differentiate into chondroblasts
What do chondroblasts secrete?
Cartilage matrix
Where does cartilage arise from in the head region?
Ectomesenchyme, derived from embryonic neural crest cells
Chondroblasts move around while?
Matrix is being deposited
When completely surrounded by matrix, chondroblasts are called?
Chondrocytes
Multiplication of chondrocytes within matrix forms?
Isogenic cell clusters surrounded by territorial matrix
Mesenchymal tissue immediately around chondrogenic nodule forms?
Perichondrium
What is appositional growth?
New cartilage forms on surface of existing cartilage
Where are new cartilage cells derived from?
Inner portion of perichondrium, chondrogenic layer
What is interstitial growth?
New cartilage arises from the division of chondrocytes within lacunae
What happens with continued matrix secretion of cells?
Cells continue to move farther apart
Where does major interstitial growth take place?
Growth plates of bones
Why does cartilage repair have limited ability?
Avascularity, immobility of chondrocytes, limited ability of chondrocyte proliferation
What cartilage repair complications happen in adults?
New blood vessel formation at site of healing wound, blood vessels stimulate bone formation instead of cartilage repair
What is hyaline cartilage calcification?
Calcium phosphate crystals become embedded in the cartilage matrix
When does calcification occur?
Growing and adult bones, endochondrial ossification during growth, aging process
What happens when cartilage is calcified?
Diffusion is impaired and chondrocytes swell and die. Results in removal of calcified matrix and replaced by bone tissue.
Removal of calcified cartilage matrix is done by?
Phagocytes (chondroclasts, osteoclasts)
Aggrecan hyaluronan aggregates have what features?
Chondroitin sulphate, keratan sulfate, connected to core protein, all 3 linked to hyaluronan sulfate
What best describes hyaline cartilage?
Surrounded by perichondrium, except at articular surfaces
A breakdown of nasal cartilage would release primarily which collagen type?
Type II collagen
Where is fibrocartilage found?
Annulus Fibrosus
Stain intensity differences in an H&E stained hyaline cartilage is attributed to ?
Concentration of GAGs
What best describes the cartilage?
Often occurs in the thin plates or sheets
