101 Cartilage

8/8/2019 101 Cartilage

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WHERE AM I? Online Anatomy Module 1

APPENDICULAR SKELETON

CELL

INTRO & TERMS

EPITHELIUM

CARTILAGE

MUSCLE

NERVOUS SYSTEM

AXIAL SKELETON

MUSCLES

EMBRYOLOGY


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SKELETON & DISTINCT CARTILAGE SKELETONS

Cartilage participates as pieces that

develop, and stay attached to the skeleton

Nasal cartilage

Xiphoid processan extension to

the breast-bone

Other cartilages act as separate skeletal

elements in their own right: supporting the

larynx (voice-box) [feel its firmness on

yourself] and the trachea (windpipe) & bronchi

Ear cartilage


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CARTILAGE & ITS SITES

Cartilage is a firm, but flexible,

pressure-resisting tissue,needed to support and connect

other tissues and structures

Ears

Nose

Airway

Spine disks

Joints

Ends of ribs


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CARTILAGES: Technical names

Auricular cartilageEars

Nose

Airway

Spine disks

Joints

Ends of ribs

Nasal/septal cartilage

Laryngeal & tracheal cartilages

Costal cartilages

Intervertebral disks

Articular cartilages


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CARTILAGE

Cartilage cells introduceto the tissue resistance to

pressure & an ability to recover shape , principally by

aggregated proteoglycans able avidly to bind water.

The PGs themselves are held in place by a meshwork

of fine collagen fibrils (tiny fibers).

Matrix ofChondrocytes make a

Collagen II fibrilmeshwork trapping aggregated ProteoglycansPGs

aggregating

backbone of

HYALURONAN

PG

L

L

L

L

H2OPGs bind

PG

L - Link protein


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CARTILAGE

Cartilage cells introduceto the tissue resistance to pressure & an ability

to recover shape, principally by aggregated proteoglycans able avidly to

bind water. The PGs themselves are held in place by a meshwork of fine

collagen fibrils.

Fibrocartilage is dense fibrous

tissue with chondrocytes & their

PGs substituted for fibroblasts

Intervertebral disk is under pressure, but has tensile strengthto resist bursting and pull

nucleus pulposus

fibrocartilage of

annulus fibrosus

vertebral endplate


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CARTILAGE

Fibrocartilage is dense fibrous tissue with

chondrocytes & their PGs substituted for fibroblasts

Intervertebral disk is under pressure, but has tensile strengthto resist bursting and pull

nucleus pulposus

fibrocartilage of

annulus fibrosusFibril orientation

differs from one

fibrous layer to

the next


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CARTILAGE

Intervertebral disk is under pressure, but usually hasenough tensile strength to resist bursting and pull, however

nucleus pulposus

Herniated/ruptured disk pressing

on nerve leaving spinal canal,e.g., causing sciatica

fibrocartilage of

annulus fibrosus


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Joint capsule

Bone

Muscle

JOINT/ARTICULAR CARTILAGEresilient, thin, lubricated,

attached, living, nourished,

modifiable,

vulnerable


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JOINT TERMS

loose connective tissue

lining cells

{

Spongy subchondral

bone absorbs and

directs load to shaft

Joint cartilage

absorbs and

spreads load

SYNOVIUM

Joint capsule

j c

o ai v

n i

t t

. y


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SKELETON & CARTILAGE

Facial and skull vault/dome bones form

with negligible cartilage present

Cartilage participates as pieces that

develop, and stay attached to the skeleton

Other cartilage develops with bones

(indeed, it precedes the bone), then

remains at the ends to make the joint

surface or articular cartilage

Cartilage provides some flexibility &

recovery of shape at critical places


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SKELETAL DEVELOPMENT

Skeletal piece of

hyaline cartilageGrows by internal expansion

and from the surface

Cell

enlargement/hypertrophyMatrix calcification

selective erosion into

mineralized cartilage

Calcified cartilage can be

resorbed like bone, and

be attached to bone


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Secondary ossificationcenters

Growth/epiphyseal plate

Articular cartilage

Shaft bonegrows bydeposition on the outside,

with mild resorption on the

inside surface, plus

osteonal remodellingin the

interior

+-

LATER ENDOCHONDRAL OSSIFICATION

Bone would belarger

thanin theprevious view


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JOINTCARTILAGE

layer ofmineralizedcartilage for

attachment to

Spongysubchondralbone

Matrix

Chondrocytes inholes/lacunae


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JOINT CARTILAGE

Matrix ofChondrocytes make a

Collagen II fibrilmeshwork trapping aggregated ProteoglycansPGs

aggregating

backbone of

HYALURONAN

PG

LL

L

L

H2OPGs bind

PG

L - Link

protein


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PROTEOGLYCAN STRUCTURE & H2O-BINDING

Core protein

Sugar side-chains of repeating

pairs (disaccharides)

-XL-GA-GU-GA-GU-GA-GU-GA-GU-SO4

coo

Side chains bear -binding charged groups

which mutually repel, but cannot disperse because

ofO2 bonds& anchorage to thecore protein

H2O

H2O

} SO4SO4


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Nutrition

SYNOVIAL FLUID

Lubrication

Nutrition from marrow blocked by mineralized-cartilage

Load-bearing surface, therefore

vessels would not survive

ARTICULAR CARTILAGE NUTRITION

Why via synovial fluid? #1


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JOINT/ARTICULAR CARTILAGE

Resilient - Meshwork loaded with H2O-trapping

huge molecules

Lubricated - Synovial fluid & its special molecules

Attached - Via mineralized lowest layer to

subchondral bone

Living - Matrix allows diffusion to chondrocytes inlacunae

Nourished - From synovial vessels via synovialfluid

Modifiable- Cells continue to make & selectivelydestroy ECM


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JOINT CARTILAGE VULNERABILITIES

Thin and easily worn away (osteoarthrosis)

Relies on very indirect nutrition

A few cells look after extensive matrix

Has nearby a loose CT (synovium) in whichdamaging defensive responses occur, e.g., to

crystals (gout), virus? (rheumatoid arthritis)

Inflammatory synovial cells release damaging

enzymes into synovial fluid, or cytokine signals

turning on chondrocyte ECM destruction

Large ECM molecules (PGs & Collagen) easily

cleaved by enzymes into useless shorter pieces


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HYALINE

CARTILAGE

Airway

skeletonTracheal rings

Laryngeal

pieces

Precursor to

bony skeleton

stays on as

Articular cartilage

like hyaline, but

reinforced with

elastic fibers Auricle(ear)

more like dense

fibrous tissue

CARTILAGE TYPES

ELASTIC

CARTILAGE

FIBROCARTILAGE

a few vocal Laryngeal pieces

joins bones, e.g., vertebrae,

& tendons to bone

CARTILAGES T h i l


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CARTILAGES: Technical names

Auricular cartilage elasticEars

Nose

Airway

Spine disks

Joints

Ends of ribs

Nasal/septal cartilage

Laryngeal & tracheal cartilages

Costal cartilages

Intervertebral disks

fibrocartilage

Articular cartilages

The rest are hyaline, as is most

of the embryonic skeleton

TYPICAL PIECE* OF CARTILAGE


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TYPICAL PIECE* OF CARTILAGE

PERICHONDRIUM ( dense irregular CT)

Chondrocytes

* Fibrocartilage does not occur as discrete pieces

vessels

CARTILAGE GROWTH


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PERICHONDRIUMAppositionalgrowth by

surface cell division &differentiation

Chondrocytes

Interstitialgrowth by interior

cell division & matrix depostion

Chondroblasts

CARTILAGE GROWTH

JOINT COMPONENTS


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JOINT CAPSULE

PeriosteumFibrous

Osteoblastic

Spongy bonewith struts/

trabeculae

Joint cartilage

absorbs and

spreads load

JOINT COMPONENTS

SYNOVIUM

LIGAMENT


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JOINT CAPSULE

JOINT CAPSULE & SYNOVIUM

SYNOVIUM

Synovium lines

the joint capsule,but it itself has a

lining or surface

JOINT SPACE

EASY SLIDING


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EASY SLIDING

FIRM ELASTIC SUBSTRATE

FIRM ELASTIC SUBSTRATE

BOUNDARY

LUBRICANT

FLUID FILM


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EASY SLIDING: Synovial Joint

orDisc

Attached, polar

PHOSPHOLIPID molecules

WATER +

HYALURONAN

+ PROTEINS

Articular layer

Hydrophilic side

attaches to cartilage

Hydrophobic side

lowers surface

energy for NON-

STICK surface

Bond toArticular layer

SYNOVIOCYTE ROLES


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SYNOVIOCYTE ROLES

FIBROBLAST

synthesizes hyaluronan& glycoproteins

MACROPHAGEphagocytoses debris

in the joint space

SUB-INTIMA for inflammatory defensive

responses

SYNOVIAL FLUID

ECM MOLECULAR INTERACTIONS P th l 2


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Unwanted degradation by bystander inclusion in

cytokine signaling pathways of defensive cells

M

Lymphocytes of inner jointsynovium

IL-1

Articular

chondrocytes

IL-1

Joint cartilage cells alsorespond to the signal:

enzymes enzyme

inhibitors proteoglycans

= an inappropriate response causing cartilage

matrix destruction - ARTHRITIS

ECM MOLECULAR INTERACTIONS - Pathology 2

JOINT PANNUS


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JOINT PANNUS

SYNOVIUM

Joint cartilage

PANNUS is a overgrowth ofinflamed synovium onto & eating

into the articular cartilage

PTERYGIUM is a similar, but less inflamed

growth of conjunctiva onto the eyes cornea



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Skeletal piece of

hyaline cartilageGrows by internal expansion

and from the surface

Cell

enlargement/hypertrophyMatrix calcification

selective erosion into

mineralized cartilage

Calcified cartilage can be

resorbed like bone, and

be attached to bone

EARLY ENDOCHONDRAL OSSIFICATION


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EARLY ENDOCHONDRAL OSSIFICATION

EPIPHYSIS

}

}DIAPHYSIS/SHAFTprimary ossification

front

perichondrium

periosteum

Bony collar

provides support

as mineralized

cartilage is eatenaway



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Secondary ossificationcenters

Growth/epiphyseal plate

Articular cartilage

Shaft bonegrows bydeposition on the outside,

with mild resorption on the

inside surface, plus

osteonal remodellingin the

interior

+-


Bone would belarger

thanin theprevious view

ZONES/LAYERS OF THE GROWTH PLATE


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ZONES/LAYERS OF THE GROWTH PLATE

}

}}}

RESTING

PROLIFERATION

HYPERYTROPHY

CALCIFICATION

}OSSIFICATION

Expansion

Osteoclasts stop the

trabeculae from forever

extending

Matching erosion

new boneoncalcified cartila e


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Cartilage is replaced by bone. There is

no transformation of cartilage into bone

WHERE AM I?


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WHERE AM I? Online Anatomy Module 1

APPENDICULAR SKELETON

CELL

ORIENTATION

EPITHELIUM

CARTILAGE

MUSCLE

NERVOUS SYSTEM

AXIAL SKELETON

MUSCLES

EMBRYOLOGY

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101 Cartilage