Cartilage Tissue Flashcards
What 4 types of tissue are focused on in histology?
Epithelium
Muscle
Connective
Nervous
What are the characteristics of cartilage in general?
Semirigid supporting tissue - strong but slightly flexible
Withstands compressive forces incurred by locomotion and weight bearing
Avascular - no lymphatics or blood vessels
Aneural
How many types of cartilage are there?
Three
What is the location of hyaline cartilage?
Nose, articular surfaces, costal cartilage, respiratory system
• translucent blue-white appearance in fresh samples
Fetal skeleton (to be replaced eventually by bone)
What is the matrix composition of hyaline cartilage?
Type II collagen
Chondroitan sulfate
What is type II collagen?
Organizes and anchors ground substance
Only found in cartilage and thinner than type I cartilage
What is chondroitan sulfate function?
Binds water and resists compression
Provides a shock absorbing quality to cartilage matrix
This matrix is non-fibrous in appearance with routine light microscopy
What are chondrocytes?
Relatively mature cells located throughout matrix
• relatively large round cells living in lacuna
What is the lacuna?
Spaces in the matrix
In what configurations can chondrocytes be located?
Maybe located individually or within isogenous groups (clusters)
What is the function of chondrocytes?
responsible for some growth and most maintenance of cartilage matrix
What are chondroblasts?
Relatively immature cells located at the periphery of the matrix
Relatively small ovoid cells at the edge of the cartilage matrix
What is the function of chondroblasts?
Contribute to the growth and repair of cartilage matrix
What is the perichondrium?
Transition tissue at the periphery of the cartilage
Contains the vasculature and provides for growth
What are the two components of perichondrium?
Chondrogenic perichondrium
Fibrous perichondrium
What does Chondrogenic perichondrium contain?
inner layer containing chondroblasts and type II collagen
What does Fibrous perichondrium contain?
outer layer containing fibroblasts and type I collagen
Is the perichondrium present in articular cartilage?
no it is absent
Where is elastic cartilage found?
external ear, auditory tube, epiglottis, parts of larynx
What is elastic cartilage made of?
Type II collagen, chondroitan sulfate
What is the function of elastic fibers in elastic cartilage?
Provide greater elasticity than hyaline cartilage exhibits
Appear as short, sinusoidal lines in matrix (usually densely packed)
Fresh samples are more yellowish than hyaline cartilage
Are chondrocytes, chondroblasts and a perichondrium present in elastic cartilage?
Yes the only difference is elastic fibers
Where is fibrocartilage located?
intervertebral disks, pubic symphisis, articular disks, menisci of knee
what is the function of fibrocartilage?
present where tough support or tensile strength is required
what type of collagen does fibrocartilage contain?
Contains both type I and type II collagen
This matrix has a uniformly fibrous appearance
What type of cartilage is the strongest?
Fibrocartilage due to the type I collagen present
Are condrocytes present in fibrocartilage?
Yes, Chondrocytes tend to be grouped and separated by bundles of collagen fibers
Is there a true perichondrium in fibrocartilage?
no true perichondrium is present
type I collagen blends with the type I collagen of bone
what are the two types of cartilage growth mechanisms?
Intersititial growth
Appositional growth
What is interstitional growth?
Growth from inside out
Process:
1) chondrocytes divide inside their lacunae
2) they separate by secreting matrix between themselves
3) this method of growth works well early on but slows as cartilage matures
4) isogenous groups are more prevalent as interstitial growth becomes less effective
What is appositional growth?
Depends on the presence of a functional perichondrium
the process:
1) perichondrial chondroblasts secrete new matrix on the existing cartilage
2) perichondrium pushes outward as a result
3) as chondroblasts lag behind the outward moving perichondrium they
become chondrocytes
Does growth mechanisms occur simultaneously?
yes both can occur simultaneously
Where does endochondral ossification occur?
in all bones except for flat bones and facial bones
What is endochondral ossification?
Hyaline cartilage replacement in the development of most long bones
What are mesenchymal cells?
Essentially stem cells that exist in the fetal areas where these bones will form.
These are multipotential cells capable of becoming a variety of cell types
what do some fetal mesenchymal cells initially differentiate into to start the endochrondal ossification process?
Chondrogenic cells
What do chondrogenic cells divide into?
chondroblasts
what do chondroblasts initially produce ?
a hyaline cartilage model of bone
Chondroblasts have a peripheral perichondrium (both chondroblasts and mesenchymal cells)
will grow in size by both intersitial and appositional growth
where do blood vessels start developing?
In the surrounding mesenchyme at the same time as hyaline cartilage
what changes do the developing vasculature cause to the periphery of the cartilage model?
Cartilage cells start dying and are replaced by bone cells
Results in a conversion of the peripheral cartilage matrix into bone matrix
do blood vessels eventually grow through the perichondrium? if yes, where?
yes, they grow through the perichondrium at about the mid-diaphysis
What creates the primary ossification center in the diaphysis?
when blood vessels grow through the perichondrium at about mid-diaphysis