Cartilage Histology

Question 1

What are the three types of cartilage?

Answer 1

hyaline cartilage

elastic cartilage

fibrocartilage

Question 2

important featuers of hyaline cartilage

Answer 2

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

Question 3

What type of collagen is in hyaline cartilage?

Answer 3

Type II cartilage - protein fibers in the matrix

other types help interconnect and stabilize the matrix components

Question 4

What is the role of proteoglycans and glycosaminoglycans (GAGs) in cartilage?

Answer 4

form large molecular complexes with negative charges

this causes binding with water and gives the matrix its viscosity, strength, and flexibility

Question 5

examples of hyaline cartilage

Answer 5

epiphyseal growth plates

articular cartilage

costal cartilage (where ribs join the sternum)

cartilages of the larynx

rings int he trachea and bronchi

Question 6

What kind of collagein is in elastic cartilage?

Answer 6

type II collagen - elastic fibers

embedded in the gyaline cartilage matrix

Question 7

examples of elastic cartilage

Answer 7

external ear (pinna)

epiglottis of the larynx

auditory (Eustacian) tube

Question 8

What type of collagen is in fibrocartilage? What are the important histological features?

Answer 8

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

Question 9

examples of fibrocartilage

Answer 9

the annulus fibrosis of intervertebral discs

the pubic symphysis

articular discs within the sternoclavicular, temporomandibular, and knee joints

Question 10

Describe the sequence of endochondral bone formation.

Answer 10

starts of as hyaline cartilage models

cartilage is eventually replaced by bone

ends of the bone remains hyaline cartilage at the end

Question 11

What are the components of a typical synovial join?

Answer 11

synovial membrane

articular cartilage (hyaline)

synovial cavity

periosteium becoming the fibrous joint capsule

there is no perichondrium on articular cartilage

Question 12

What are the components of the pericondrium?

Answer 12

fibrous layer

chondrogenic layer

Question 13

perichondrium

Answer 13

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

Question 14

chondrogenic layer

Answer 14

source of new stem cells that will differentiate into chondroblasts

cells secrete cartilage matrix around them

Question 15

isogenous groups

Answer 15

newly formed clusers of chondrocytes

contain chondrocytes that have recently divided - cells produce new matrix

Question 16

capsular matrix

Answer 16

a thin, very dark staining rim that surrounds each chondrocyte

it contains type IV collagen that connects the chondrocytes to the matrix

Question 17

territorial matrix

Answer 17

consists of newly secreted matrix around isogenous groups that is darker staining because of a higher concentration of matrix molecules and fibers

Question 18

interteritorial matrix

Answer 18

older matrix between chondrocytes/isogenous groups and is lighter staining

Question 19

What are the components of cartilage?

Answer 19

matrix is 60-80% water

the rest is cells, collagen, and long hyaluronic acid (GAG) chains with proteoglycan monomers

Question 20

What are the two modes of cartilage growth?

Answer 20

interstitial grown from isogenous groups

appositional growth from perichondrium

Question 21

Does cartilage have a blood supply?

Answer 21

no, no nerves or vessels enter the cartilage

cartilage will not heal if injured

Question 22

lacunae

Answer 22

chondrocytes and chondroblasts reside here

“little lakes”

glycoproteins bind cells to the matrix

Question 23

What are the types of GAGs and their side chains in cartilage?

Answer 23

chondroitin sulfate (side chain)

keratin sulfate (side chain)

hyaluronic acid (GAG)

Question 24

hyaluronic acid

Answer 24

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

Question 25

Where is elastic cartilage found in the body?

Answer 25

laryngeal epiglottis ear and nasal cartilages

Question 26

What are the defining features of fibrocartilage?

Answer 26

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

Question 27

What is the purpose of fibrocartilage?

Answer 27

to help the cartilage resist shear forces in addition to compression

Question 28

What are changes in cartilage with age?

Answer 28

replaced by bone, which is lighter-staining fatty marrow cavity hyaline cartilage almost always becomes calcified with age

Question 29

What happens in wear and tear osteoarthritis?

Answer 29

the surface of articular cartilage shreds cartilage erodes until very little is left and bone is exposed on the joint surface

Question 30

What does cartilage develop from?

Answer 30

develops from **mesenchymal cells** that differentiate into chondroblasts that secrete matrix mesenchymal cells from from **somite sclerotomes** and the **lateral plate** in somatopleure

Question 31

Where does cartilage develop from?

Answer 31

the mesoderm of the gastrula most mesoderm is initially in the form of loose embryonic connective tissue called mesenchyme

Question 32

What sources of mesenchyme does cartilage develop from?

Answer 32

**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

Question 33

What are the steps in the development of cartilage?

Answer 33

**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