Cartilage Histology Flashcards
What are the three types of cartilage?
hyaline cartilage
elastic cartilage
fibrocartilage
important featuers of hyaline cartilage
most prevalent type, has basic features common to all three types
homogeneous matrix makes it one of the most readily identifiable tissues in the body
What type of collagen is in hyaline cartilage?
Type II cartilage - protein fibers in the matrix
other types help interconnect and stabilize the matrix components
What is the role of proteoglycans and glycosaminoglycans (GAGs) in cartilage?
form large molecular complexes with negative charges
this causes binding with water and gives the matrix its viscosity, strength, and flexibility
examples of hyaline cartilage
epiphyseal growth plates
articular cartilage
costal cartilage (where ribs join the sternum)
cartilages of the larynx
rings int he trachea and bronchi
What kind of collagein is in elastic cartilage?
type II collagen - elastic fibers
embedded in the gyaline cartilage matrix
examples of elastic cartilage
external ear (pinna)
epiglottis of the larynx
auditory (Eustacian) tube
What type of collagen is in fibrocartilage? What are the important histological features?
Type I and type II in the matrix
much greater density of fibers in the matrix compared with elastic cartilage
there is cartilage matrix around the chondrocytes and fibroblasts among the collagen fibers
may appear similar to dense regular connective tissue
distinguishing feature is the round appearance of chondrocytes due to the lacunae
examples of fibrocartilage
the annulus fibrosis of intervertebral discs
the pubic symphysis
articular discs within the sternoclavicular, temporomandibular, and knee joints
Describe the sequence of endochondral bone formation.
starts of as hyaline cartilage models
cartilage is eventually replaced by bone
ends of the bone remains hyaline cartilage at the end
What are the components of a typical synovial join?
synovial membrane
articular cartilage (hyaline)
synovial cavity
periosteium becoming the fibrous joint capsule
there is no perichondrium on articular cartilage
What are the components of the pericondrium?
fibrous layer
chondrogenic layer
perichondrium
surrounds the cartilage
it has an outer fibrous and inner chondrogenic layer
a perichondrium is absent on the articular surface of cartilage and around fibrocartilage
chondrogenic layer
source of new stem cells that will differentiate into chondroblasts
cells secrete cartilage matrix around them
isogenous groups
newly formed clusers of chondrocytes
contain chondrocytes that have recently divided - cells produce new matrix
capsular matrix
a thin, very dark staining rim that surrounds each chondrocyte
it contains type IV collagen that connects the chondrocytes to the matrix
territorial matrix
consists of newly secreted matrix around isogenous groups that is darker staining because of a higher concentration of matrix molecules and fibers
interteritorial matrix
older matrix between chondrocytes/isogenous groups and is lighter staining
What are the components of cartilage?
matrix is 60-80% water
the rest is cells, collagen, and long hyaluronic acid (GAG) chains with proteoglycan monomers
What are the two modes of cartilage growth?
interstitial grown from isogenous groups
appositional growth from perichondrium
Does cartilage have a blood supply?
no, no nerves or vessels enter the cartilage
cartilage will not heal if injured
lacunae
chondrocytes and chondroblasts reside here
“little lakes”
glycoproteins bind cells to the matrix
What are the types of GAGs and their side chains in cartilage?
chondroitin sulfate (side chain)
keratin sulfate (side chain)
hyaluronic acid (GAG)
hyaluronic acid
the largest glycosaminoglycan
a very long, repeating disaccharide that is the core of the complex
connected by link proteins to ~80 proteoglycan monomers consisting of a protein core with GAG side chains of chondroitin sulfate and keratan sulfate
Where is elastic cartilage found in the body?
laryngeal epiglottis
ear and nasal cartilages
What are the defining features of fibrocartilage?
dense bundles of type I collagen fill the hyaline matrix
has chondrocytes and fibroblasts
**note **presence of lacunae **with round cells
unlike hyaline and elastic cartilage, there is no pericondrium
look for round, clear cells - baseline of hyaline cartilage matrix
What is the purpose of fibrocartilage?
to help the cartilage resist shear forces in addition to compression
What are changes in cartilage with age?
replaced by bone, which is lighter-staining
fatty marrow cavity
hyaline cartilage almost always becomes calcified with age
What happens in wear and tear osteoarthritis?
the surface of articular cartilage shreds
cartilage erodes until very little is left and bone is exposed on the joint surface
What does cartilage develop from?
develops from mesenchymal cells that differentiate into chondroblasts that secrete matrix
mesenchymal cells from from somite sclerotomes and the lateral plate in somatopleure
Where does cartilage develop from?
the mesoderm of the gastrula
most mesoderm is initially in the form of loose embryonic connective tissue called mesenchyme
What sources of mesenchyme does cartilage develop from?
the sclerotome of somites that gives rise to the endochondrial bone of the ribs and vertebral column
the lateral plate mesoderm of somatopleure that gives rise to the bones and connective tissues of the extremities
What are the steps in the development of cartilage?
condensation of mesenchyme by mitosis to produce a very cellular primordium of the organ
differentiation of mesenchymal cells into chondroblasts that begin secreting matrix, this early stage of cartilage is also very cellular
secretion of cartilage matrix and the cartilage grows in size, the cells become separated within the matrix to become chondrocytes
dispersion of cells within the matrix forms isogenous groups of cartilage cells surrounded by newly-formed territorial (capsular) matrix
