Transcript Cartilage

WHERE AM I?
Online Anatomy Module 1
INTRO & TERMS
CELL
EPITHELIUM
CARTILAGE
MUSCLE
NERVOUS SYSTEM
AXIAL SKELETON
APPENDICULAR SKELETON
MUSCLES
EMBRYOLOGY
SKELETON & DISTINCT CARTILAGE ‘SKELETONS’
Ear cartilage
Nasal cartilage
Cartilage participates as pieces that
develop, and stay attached to the skeleton
Xiphoid process
an 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
CARTILAGE & ITS SITES
Ears
Nose
Airway
Cartilage is a firm, but flexible,
pressure-resisting tissue,
needed to support and connect
other tissues and structures
Ends of ribs
Spine disks
Joints
CARTILAGES: Technical names
Ears
Auricular cartilage
Nose Nasal/septal cartilage
Airway Laryngeal & tracheal cartilages
Ends of ribs
Costal cartilages
Spine disks
Intervertebral disks
Joints
Articular cartilages
CARTILAGE
Cartilage cells introduce to 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).
Chondrocytes make a Matrix of
Collagen II fibril meshwork trapping aggregated Proteoglycans PGs
PG
L
PGs bind
L - Link protein
L
L
H2O
aggregating
backbone of
HYALURONAN
PG
CARTILAGE
Cartilage cells introduce to 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 strength
vertebral endplate
to resist bursting and pull
fibrocartilage of
annulus fibrosus
nucleus pulposus
CARTILAGE
Fibrocartilage is dense fibrous tissue with
chondrocytes & their PGs substituted for fibroblasts
Intervertebral disk is under pressure, but has tensile strength
to resist bursting and pull
fibrocartilage of
annulus fibrosus
Fibril orientation
differs from one
fibrous layer to
nucleus pulposus
the next
CARTILAGE
Intervertebral disk is under pressure, but usually has
enough tensile strength to resist bursting and pull, however
fibrocartilage of
annulus fibrosus
nucleus pulposus
Herniated/ruptured disk pressing
on nerve leaving spinal canal,
e.g., causing sciatica
JOINT/ARTICULAR CARTILAGE
resilient, thin, lubricated,
attached, living, nourished,
modifiable,
vulnerable
Bone
Joint capsule
Muscle
JOINT TERMS
SYNOVIUM loose connective tissue
{
lining cells
Joint capsule
j
o
i
n
t
.
c
a
v
i
t
y
Joint cartilage Spongy subchondral
absorbs and
bone absorbs and
spreads load
directs load to shaft
SKELETON & CARTILAGE
Cartilage provides some flexibility &
recovery of shape at critical places
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
Facial and skull vault/dome bones form
with negligible cartilage present
SKELETAL DEVELOPMENT
Skeletal piece of
hyaline cartilage
Grows by internal expansion
and from the surface
Cell
enlargement/hypertrophy
Matrix calcification
Calcified cartilage can be
resorbed like bone, and
be attached to bone
selective erosion into
mineralized cartilage
LATER ENDOCHONDRAL OSSIFICATION
Articular cartilage
Growth/epiphyseal plate
Secondary ossification
centers
-
+
Shaft bone grows by
deposition on the outside,
with mild resorption on the
inside surface, plus
osteonal remodelling in the
interior
Bone would be larger
than in the previous view
JOINT CARTILAGE
Matrix
Chondrocytes in
holes/lacunae
layer of mineralized
cartilage for
attachment to bone
JOINT CARTILAGE
Chondrocytes make a Matrix of
Collagen II fibril meshwork trapping aggregated Proteoglycans PGs
PG
L - Link
protein
L
L
L
PGs bind H O
aggregating
backbone of
HYALURONAN
2
PG
PROTEOGLYCAN STRUCTURE & H2O-BINDING
Sugar side-chains of repeating
pairs (disaccharides)
SO4
SO4
}
H2O
SO4
-XL-GA-GU-GA-GU-GA-GU-GA-GUCore protein
Side chains bear
coo
H2O -binding
charged groups
which mutually repel, but cannot disperse because
of O2 bonds & anchorage to the core protein
ARTICULAR CARTILAGE NUTRITION
Nutrition
SYNOVIAL FLUID
Lubrication
Why via synovial fluid? #1
Load-bearing surface, therefore
vessels would not survive
Nutrition from marrow blocked by mineralized-cartilage layer
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 in
lacunae
Nourished - From synovial vessels via synovial
fluid
Modifiable - Cells continue to make & selectively
destroy ECM
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 which
damaging 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
CARTILAGE TYPES
HYALINE
CARTILAGE
ELASTIC
CARTILAGE
Precursor to
bony skeleton
stays on as
Articular cartilage
Laryngeal
Airway
pieces
skeleton
Tracheal rings
like hyaline, but
reinforced with
elastic fibers
a few ‘vocal’ Laryngeal pieces
FIBROCARTILAGE
joins bones, e.g., vertebrae,
& tendons to bone
more like dense
fibrous tissue
Auricle (“ear’)
CARTILAGES: Technical names
Ears
Auricular cartilage elastic
Nose Nasal/septal cartilage
Airway Laryngeal & tracheal cartilages
Ends of ribs
Costal cartilages
Spine disks
Intervertebral disks
fibrocartilage
Joints
Articular cartilages
The rest are hyaline, as is most
of the embryonic skeleton
TYPICAL PIECE* OF CARTILAGE
PERICHONDRIUM ( dense irregular CT)
Chondrocytes
vessels
* Fibrocartilage does not occur as discrete pieces
CARTILAGE GROWTH
PERICHONDRIUM
Chondrocytes
Chondroblasts Appositional growth by
surface cell division &
differentiation
Interstitial growth by interior
cell division & matrix depostion
JOINT COMPONENTS
SYNOVIUM
Joint cartilage
absorbs and
spreads load
Spongy bone
with struts/
trabeculae
JOINT CAPSULE
LIGAMENT
Periosteum
Fibrous
Osteoblastic
JOINT CAPSULE & SYNOVIUM
SYNOVIUM
JOINT SPACE
Synovium lines
the joint capsule,
but it itself has a
lining or surface
JOINT CAPSULE
EASY SLIDING
FIRM ELASTIC SUBSTRATE
BOUNDARY
LUBRICANT
FLUID FILM
FIRM ELASTIC SUBSTRATE
EASY SLIDING: Synovial Joint
Articular layer
or Disc
Attached, polar
PHOSPHOLIPID molecules
Articular layer
WATER +
HYALURONAN
+ PROTEINS
Hydrophilic side
attaches to cartilage
Bond to
Hydrophobic side
lowers surface
energy for NONSTICK surface
SYNOVIOCYTE ROLES
SYNOVIAL FLUID
‘FIBROBLAST’
synthesizes hyaluronan
& glycoproteins
‘MACROPHAGE’
phagocytoses debris
in the joint space
SUB-INTIMA for inflammatory defensive
responses
ECM MOLECULAR INTERACTIONS - Pathology 2
Unwanted degradation by bystander inclusion in
cytokine signaling pathways of defensive cells
IL-1
MF
Lymphocytes of inner joint
synovium
IL-1
Articular
chondrocytes
Joint cartilage cells also
respond to the signal:
enzymes
enzyme inhibitors
proteoglycans
= an inappropriate response causing cartilage
matrix destruction - ARTHRITIS
JOINT PANNUS
SYNOVIUM
PANNUS is a overgrowth of
inflamed synovium onto & eating
into the articular cartilage
Joint cartilage
PTERYGIUM is a similar, but less inflamed
growth of conjunctiva onto the eye’s cornea
SKELETAL DEVELOPMENT
Skeletal piece of
hyaline cartilage
Grows by internal expansion
and from the surface
Cell
enlargement/hypertrophy
Matrix calcification
Calcified cartilage can be
resorbed like bone, and
be attached to bone
selective erosion into
mineralized cartilage
EARLY ENDOCHONDRAL OSSIFICATION
perichondrium
periosteum
Bony collar
provides support
as mineralized
cartilage is eaten
away
}
EPIPHYSIS
}
DIAPHYSIS/SHAFT
primary ossification
front
LATER ENDOCHONDRAL OSSIFICATION
Articular cartilage
Growth/epiphyseal plate
Secondary ossification
centers
-
+
Shaft bone grows by
deposition on the outside,
with mild resorption on the
inside surface, plus
osteonal remodelling in the
interior
Bone would be larger
than in the previous view
ZONES/LAYERS OF THE GROWTH
PLATE
}RESTING
}
PROLIFERATION
Expansion
}
HYPERYTROPHY
}
Matching erosion
Osteoclasts stop the
trabeculae from forever
extending
CALCIFICATION
}
OSSIFICATION
new bone on
calcified cartilage
Cartilage is replaced by bone. There is
no transformation of cartilage into bone
WHERE AM I?
Online Anatomy Module 1
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