Lecture 7: Histology I: Cartilage

Question 1

bone and cartilage are specialized CT formed from ?

Answer 1

mesecnchyme derived from mesoderm

Question 2

what does the lateral plate mesoderm form

green arrow

Answer 2

limb skeleton and sternum

Question 3

what does the paraxial mesoderm form

light blue arrow

Answer 3

vertebrae, ribs and some of the skull

Question 4

what does the neural crest form

Answer 4

parts of the skull

Question 5

perichondrium cartilage is composed of how many layers and what are they

Answer 5

2 (outer fibrous and inner cellular)

Question 6

what is the outer fibrous layer of cartilage composed of ?

Answer 6

• dense CT
• type I collagen
• fibroblasts
• vasculature

Question 7

what it the inner cellular layer of cartilage composed of ?

Answer 7

chondrogenic cells = cartilage stem cells
- impt for appositional growth, maintenance and some repair

Question 8

what cell type is arrow pointing to

Answer 8

chondrogenic cell = cartilage stem cell, a specialized fibrocyte producing cartilage ECM

Question 9

characteristics of the chondrogenic cells

Answer 9

• narrow and spindle shaped
• ovoid nucleus w/ one or two nuclei

Question 10

function of chondrocytes

Answer 10

secrete ECM

Question 11

characteristics of Chondrocytes?

Answer 11

• ovoid to rounded shape
• large nucleus with prominent nucelolus

Question 12

what cells are the blue arrows pointing to

Answer 12

chondrocytes

Question 13

what type of cell is this?
what do the colored arrows each refer to

Answer 13

Chondrocyte

• blue = euchromatin
• pink = golgi
• yellow = rER

Question 14

term for chondrocytes that are actively secreting ECM

Answer 14

chondroblasts

Question 15

As ECM forms around a chondroblast, it forms a ______, a fluid filled space where the inactive chondrocyte resides

Answer 15

lacuna

Question 16

what is the blue arrow pointing to ? yellow arrow? green arrow?

Answer 16

Blue = chondrocyte in lacuna
Yellow = empty lacuna
green = ECM

Question 17

what is the composition of the extracellular matrix (ECM) of cartilage?

Answer 17

mostly water, supported by collagen fibers

Question 18

Why is all cartilage avascular

Answer 18

• helps cartilage regulate fluid content to resist compression

Question 19

where does cartilage receive its blood supply since it is avascular itself?

Answer 19

from nearby CT, diffusion from periphery

Question 20

what are proteoglycan aggregates (PGAs)

Answer 20

very large aggregates of proteoglycans non-covalently bound to hylauronic acid

• they create internal pressure (turgor) that allows cartilage to resist compression without inhibiting its flexibility

Question 21

what regions of matrix does each arrow point to

Answer 21

red = capsular matrix
- around chondrocytes
- many PGs
- very dark staining
blue = terrirorial matrix
- near chondrocytes
- type II fibrils, PGs
- dark staining
green = inter-territorial matrix
- away from chondrocytes
- few PGs
- pale staining

Question 22

ECM components exist to help regulate water content in order to resist ______

Answer 22

compression

Question 23

what cartilage type do these images depict

Answer 23

hyaline cartilage

• no visible fibers
• ECM stains pink or purple depending on the abundance of collagen
• NEVER has elastic or type I collagen fibers in its ECM

Question 24

what cartilage type is this

Answer 24

elastic cartilage
- has elastic fibers in its ECM

Question 25

What do these images depict

Answer 25

fibrocartilage - type I collagen fibers - no perichondrium - chondrocytes of fibrocartilage are much larger and rounder than those in dense CT

Question 26

physical difference b/w chondrocytes found in fibrocartilage vs in dense CT

Answer 26

- fibrocartilage chondrocytes are larger and rounder - dense CT chondrocytes are flatter and elongated

Question 27

what type of cartilage is this?

Answer 27

articular cartilage

Question 28

what is cartilage comprised of

Answer 28

- large amount of functional ECM - small amount of chondrocytes

Question 29

what is articular cartilage and where is it found

Answer 29

a type of hyaline cartilage found on the surface of synovial joints

Question 30

what type of cartilage is this

Answer 30

hyaline - has isogenous group - no fibers

Question 31

what is this ?

Answer 31

subchondral bone - bone supporting articular cartilage - entirely covered by cartilage - lacks chondrocytes

Question 32

explain the steady state of cartilage

Answer 32

- maintained by chondrocytes - steady state allows for normal anabolic processes - synthesis of ECM components - equilibrium w/ normal catabolic processes - normal turnover of matrix molecules

Question 33

how does injury to the cartilage matrix affect the steady state balance

Answer 33

injury causes chondrocytes to release cytokines that inhibit ECM secretion and enzymes that digest the ECM instead of factors to produce more matrix this results in cartilage degeneration

Question 34

fibrocartilage has no?

Answer 34

perichondrium

Question 35

# p

Question 36

proteogylcans contain _________, which are molecules that attract water

Answer 36

Glycosaminoglycans (GAGs)

Question 37

what binds proteogylcans to eachother, forming proteoglycan aggregates

Answer 37

hylauronic acid

Question 38

ECM components of hyaline cartilage

Answer 38

* PGAs, MGPs, type II collagen

Question 39

ECM components of elastic cartilage

Answer 39

* PGAs, MGPs, type II collagen AND elastic fibers

Question 40

ECM components of fibrocartilage

Answer 40

* PGAs, MGPs, type II collagen AND type I collagen for resistance to tension

Question 41

what is missing from articular cartilages that inhibits its ability to repair or scar

Answer 41

no perichondrium