Cartilage
-what is it?
form of supportive connective tissue with extra cellular matrix that has high concentration of GAG’s and proteoglycans interacting with collagen and elastic fibers
Cartilage ECM
- function
- components
- firm consistency
- allows for tissue to bear mechanical stress without permanent distortion; supportive framework of soft tissue (ears, nose) & cushioning sliding regions for bone movement
- collagen (type II); glycoprotein (chondronectin); proteoglycan (contains GAGS-most common is aggrecan)
Chondrocytes
- function
- location
- synthesize and maintain ECM
- located in matrix cavities call lacunae
How do chondrocytes receive nutrients?
-From surrounding tissue, the nutrients will travel through ECM until they reach the chondrocyte
Perichondrium
- what is it
- what does it do
- what lacks it
- sheath of dense connective tissue surrounding cartilage
- harbors blood supply and small neural component in cartilage
- not in articular cartilage
3 types of cartilage
-Hyaline, Elastic, fibro
Hyaline
- prevalence
- where it is found?
- special feature-embryo
- most common
- located in articular surfaces of movable joints, walls of larger respiratory passages (nose, larynx, trachea, bronchi), ventral ends of ribs (where they articulate with the sternum) and in the epiphyseal plates of long bones (makes possible longitudinal bone growth).
- In the embryo, hyaline cartilage forms the temporary skeleton that is gradually replaced by bone.
Matrix of hyaline cartilage
-consists of?
-type II collagen, abundant aggrecan, and various other proteoglycans and GAGS
What does water bind to in hyaline cartilage?
-GAGS attached to proteoglycans
Chondronectin
-function
-allows for chondrocytes to adhere to ECM
Chondrocytes in hyaline cartilage
- where
- shape
- form
- metabolism
- located at periphery
- elliptical in shape with long axes
- form isogenous aggregates: group of 2-8 cells that come from same chondrocyte: cells separate by producing collagen OR in lacunae
- metabolism: anaerobic
Perichondrium in hyaline cartilage
- surrounds all hyaline cartilage except in articular joints
- contains fibroblasts, mesenchymal cells, blood vessels and small nerves
Elastic cartilage
- what is it
- where is it
- similar to hyaline but contains more elastin
- More flexible: found in auricle of the ear, the walls of the external auditory canals, the auditory (Eustachian) tubes, the epiglottis, and the upper respiratory tract
Elastic cartilage matrix and cells
- type II collagen and elastin
- abundant aggrecan and various other proteoglycans and GAGS
- -chondroblasts, chondrocytes, and fibroblasts in perichondrium; kept in lacunae or isogenous groups
Perichondrium of elastic cartilage
- surrounds all hyaline cartilage except in articular joints
- contains fibroblasts, mesenchymal cells, blood vessels and small nerves
Fibrocartilage
- what is it made out of
- where is it found?
- hyaline cartilage intermingled with dense connective tissue
- found in IV discs and pubic symphysis
Fibrocartilage chondrocytes
- chondrocytes and fibroblasts
- occur singly and in aligned isogenous aggregates
Fibrocartilage matrix
-collagen tupe I and II, aggrecan, very few proteoglycans
Fibrocartilage perichondrium
-lacks perichondrium
Chondrogenesis
-precursor and collagen types
-mesenchyme (collagen I, III, V) to chondroblasts (II,IX, XI) to chondrocytes (collagen X and calcification of matrix)
Chondroblast
- phase
- stimulated by
- location
- nutrients/respiration
- name of cell during rapid proliferation phase
- Sox9
- located on outside
- glucose, anaerobic
Chondrocyte
- phase
- stimulated by
- special
- location
- nutrients/respiration
- name of cell during hypertrophy-calcification
- Runx2/Runx3
- cells are then enclosed in lacunae by excreting ECM
- located on inside
- glucose, anaerobic
Interstitial growth
- how?
- where?
- Mitotic division of pre-exiting chondrocytes
- Used in long bone growth
- Used in articular cartilage since they do not have perichondrium
Appositional growth
- how?
- time frame?
- Chondroblast differentiation from mesenchymal cells in inner membrane of perichondrium
- More important after birth
