L1 - Cartilage Flashcards
Where is cartilage found?
In articular joints of bones
In organs such as the trachea and bronchi
Costal cartilage connecting ribs to sternum
In the larynx
In the growth plate of long bones
In the nose, ears, epiglottis and Eustachian tubes
What are some properties of cartilage?
CT from mesenchymal stem cells Tough and resilient Contains 60-80% water No nerves or blood vessels Difficult to repair if damaged
Cartilage is covered with what?
Dense perichondrium which helps resist outer cartilage expansion when compressed
Contains stem cells
How do nutrients and gases travel through cartilage?
By diffusion
What are the main two cell types in cartilage?
Chondroblasts and chondrocytes
What are chondroblasts?
Forms initial cartilage (builds) and is located next to the perichondrium
Mitotic
Precursor to chondrocyte
What are chondrocytes?
Mature cells within spaces called lacunae
Separated from one another by ECM
Can proliferate to form clusters called isogenous groups
What is the amorphous component of cartilage?
ECM containing hyaluronic acid, proteoglycans and water
Which fibers are present in cartilage?
All have type II collagen but some have added elastin or type I collagen as well
What is perichondrium?
Layer of dense irregular CT covering hyaline and elastic cartilage
Essential for growth and maintenance of cartilage
Describe the outer/fibrous layer of perichondrium
Largely type I collagen and fibroblasts
Describe the inner/chondrogenic layer of perichondrium
Adjoins cartilage matrix
Contains mesenchymal stem cells serving as a source for new chondroblasts that will divide and differentiate into chondrocytes
What is the most abundant type of cartilage?
Hyaline cartilage
Describe characteristics of hyaline cartilage
ECM contains type II collagen fibrils, water, HA and proteoglycans (a very hydrated matrix)
Absorbs shock
Plays a key role in bone development and growth
Surrounded by a perichondrium
What is the surface appearance of hyaline cartilage?
Glassy, shiny and smooth
Where is hyaline cartilage located?
Joint surfaces, costal cartilage, larynx, trachea and bronchi, and nose
In moveable joints it is surrounded by a synovial fluid (glides easily)
List characteristics of elastic cartilage
Similar to hyaline but contains an abundant network of elastic fibers embedded in type II collagen
Elastic fibers allow for recoil/rebound —> retains shape after deformation
Flexible
Perichondrium present
Where is elastic cartilage located?
Auricle of the ear, walls of external auditory canals, auditory (Eustachian) tubes and epiglottis
List characteristics of fibrocartilage
Mix of hyaline cartilage and dense CT
Very tough and resistant to tension yet provides a cushioning support for bone
Chondrocytes arranged in singly in rows of isogenous groups
Sparse matrix of type II collagen with fibroblasts and dense buds of type I collagen
Where is fibrocartilage located?
Intervertebral discs, pubic symphysis and select joint capsules
Which types of cartilage lack a perichondrium?
Fibrocartilage and articular cartilage
List characteristics of articular cartilage
Remnant of original hyaline cartilage template used by the developing bone
Collagen fibers run perpendicular to the tissue surface but bend gradually to form an arc
Establishes 4 layers
Where is articular cartilage found?
On surfaces of moveable joints
Describe the orientation of fibers in fibrocartilage
Orientated in the direction of functional stress and provides extra tensile strength
Describe appositional growth
One layer on top of another
Chondroblasts next to the perichondrium form new cartilage on the surface
Describe interstitial growth
Expands within cartilage
Chondrocytes w/in cartilage divide forming clusters of cells called isogenous groups
They then deposit new ECM spreading themselves from one another thereby expanding the cartilage from within
What is territorial matrix?
Newly synthesized ECM adjacent to chondrocytes
Stains differently
Seen during interstitial growth
Why is cartilage repair slow after damage?
Due to its avascularity and low metabolic rate
How is cartilage repaired?
Very slow but more efficient in young children
Cells from the perichondrium invade damaged area and produce new cartilage or dense CT
May even replace it with bone
