cartilage and bone 1&2 Flashcards
cartilage and bone consist of cells within a ____ that they have produced
matrix
what does matrix contain
fibers and in bone insoluble calcium salts
in cartilage matrix is a firm gel composed of
proteoglycans
for cartilage what lays down the matrix
chondroblasts
what are the mature cell type of chondroblasts
chondrocytes
chondrocytes are isolated in small chambers called
lacunae
is there nerves or blood supply in cartilage
no: chondrocytes maintained via diffusion through matrix
poor healing properties of cartilage
what forms the fetal skeleton
cartilage
fetal cartilage skeleton is largely replaced by
bone
cartilage is surrounded by a tough dense fibrous capsule called
perichondrium
(has 2 layers)
- outer; irregular dense connective tissue
- inner; cellular layer; chondroblasts; involved in growth
where is the perichondrium NOT found
at joint surfaces
describe the 2 layers of the perichondrium
- outer; irregular dense connective tissue
- inner; cellular layer; chondroblasts; involved in growth
name the 2 mechanisms by which cartilage grows
- interstitial growth
- appositional growth
describe intersitital growth of cartilage
- GROWTH FROM WITHIN
- chondrocytes divide isogenous groups
- daughter cells produce matrix pushes cells apart
describe appositional growth of cartilage
- GROWTH BY ADDING TO OUTSIDE
- chondroblasts divide
- inner layer of the perichondrium
- produce matrix
- differentiate into chondrocytes
name the 3 types of cartilage
- hyaline: closely packed w collagen fibers
- fibrocartilage; interwoven collagen fibers
- elastic; elastic fibers
what is the most common type of cartilage
hyaline
describe perichondrium of hyaline cartilage
dense except at joints
matrix of hyaline cartilage contains
closely packed collagen fibers
what type of cartilage forms the skeletal template which later ossifies in the fetus
hyaline
where is hyaline cartilage found in an adult
- sternal end of ribs
- articular surfaces of joints
- nasal septum, larynx, tracheal rings
fibrocartilage has characteristics that are intermediate between
dense connective tissue and cartilage
describe how chondrocytes are in fibrocartilage
aligned in rows between layers of interwoven collagen fibers
where is fibrocartilage found
- menisci of stifle
- intervertebral discs (annulus fibrosus)
fibrocartilage ____ compression and ____ shock
resists
absorbs
elastic cartilage contains numerous
branching elastic fibers in the matrix
other than elastic fibers, the matrix of elastic cartilage also contains
collagen
elastic cartilage is extremely
resilient and flexible
where is elastic cartilage found
- pinna of ear
- auditory (eustachian) tube
- epiglottis
- larynx
describe matrix of bone
- calcified
- CaPO4 and CaCO3
- hard
- calcium store
- contains collagen fibers; relatively flexible, tolerates tension and compression, light
2 types of bone
compact and cancellous (spongy)
compact bone
- located on surface of bones
- sturdy protective layer
- thickest where stresses greatest
cancellous bone
- located in interior of bones
- open network of bone plates (trabeculae)
ratio of compact: cancellous bone varies with
shape of bone
long bones consists of what parts
- diaphysis; hollow shaft that contains marrow
- epiphyses; ends that may be surrounded by cartilage
- metaphyses; narrow region between diaphysis and epiphyses
what kind of bone do long bones consist of
both cancellous (spongy) on interior of bone and compact bone (outer layer)
central space in diaphysis that contains the marrow is called
medullary cavity
diaphysis has outer layer of compact bone called the
cortex
epiphyses has a ___ cortex of compact bone
and central area of ____
thin
cancellous bone
out of these flat bones:
skull
ribs
sternum
scapulae
which are formed from mesenchyme and which are formed via endochondral ossification
skull formed from mesenchyme
rest formed via endochondral ossification
flat bone structure
Centre of cancellous bone sandwiched between two thick layers (tables) of compact bone
do flat bones have a medullary cavity
No medullary cavity, but
marrow is dispersed within
cancellous bone
periosteum
- Covers the outer layer of compact bone
- not at articular surfaces
- becomes interwoven with tendons
- Fibrous outer layer
- Cellular inner layer; osteogenic properties, functions in bone growth & repair
where is periosteum NOT found
not at articular surfaces
describe 2 layers of periosteum
- Fibrous outer layer
- Cellular inner layer; osteogenic properties, functions in bone growth & repair
endosteum
- Thin, cellular layer
- Lining of medullary cavity, trabeculae of cancellous bone
- Osteogenic properties
- Functions in bone growth & repair
4 types of bone cells
- osteoprogenitor cells
- osteoblasts
- osteocytes
- osteoclasts
osteoprogenitor cells are derived from
mesenchymal stem cells
how do osteoprogenitor cells divide
- divide to produce daughter cells
- differentiate into osteoblasts
where are osteoprogenitor cells located
located in cellular layer of periosteum & endosteum
osteoprogenitor cells function
important in repair of fractures
osteoblasts produce
the matrix
osteoblasts form an epithelial layers in areas of
active growth
Osteoblasts nucleolus and cytoplasm
prominent nucleolus, basophilic cytoplasm
osteocytes develop from
osteoblasts
osteocytes
mature bone cells
most abundant cell type in bone
osteocytes
how do osteocytes divide
they CANNOT divide
where do osteocytes reside in formed bone
lacunae
how osteocytes contact one another
- cytoplasmic extensions through narrow tunnels called canaliculi
canaliculi
cytoplasmic extensions through narrow tunnels through which osteocytes contact one another
osteocytes maintain the ____ and _____ content of the matrix
protein and mineral
can osteocytes de-differentiate into osteoblasts and osteoprogenitor cells
yes
contribute to repair of damaged bone
osteoclasts are syncytia of cells with over ___ nuclei
50
osteoclasts are involved in
- bone resorption
- acids & proteolytic enzymes: collagenase
- dissolve matrix
roles of osteoclasts
- bone resorption: acids & proteolytic enzymes: collagenase, dissolve matrix
- Ca2+ & PO4
regulation - bone remodelling: growth, changed stresses balance between activity of
osteoclasts & osteoblasts
osteoclasts are derived from
monocytes (circulating macrophages)
where are osteoclasts found
found in areas of resorbed bone, called Howship’s lacunae, at junction of bone & endosteum
bony matrix laid down in
lamellae
radiating from lacunae are
canaliculi
In Compact Bone
Lamellae are laid down in 3 forms:
- Haversion systems (osteons)
- Interstitial lamellae
- Circumferential lamellae
Haversion systems (osteons) (a way lamella is laid down in compact bone)
- osteocytes arranged in concentric lamellae around a
central Haversian canal - Haversian canal contains one or more blood vessels
- aligned parallel to long axis of bone
- Volkmann’s canals at right angles to Haversian canals
interstitial lamella (a way lamella is laid down in compact bone)
- between Haversian systems
- non-concentric lamellae
Circumferential lamellae (a way lamella is laid down in compact bone)
- encircle bone
- beneath periosteum & endosteum
in cancellous bone how are lamellae arranges
- Lamellae are not arranged into Haversian systems
- Matrix forms trabeculae
- Nutrients reach osteocytes via diffusion along canaliculi
that open onto surface of trabeculae
2 ways bones are formed
- endochondral ossification: from a cartilage model, most bones
- intramembranous ossification: directly from mesenchyme
what bones are formed via intramembranous ossification (ie directly from mesenchyme)
- membrane bones such as:
- flat bones of skull
- mandible
- clavicle
steps of intramembranous ossification
- Embryonic mesenchymal cells cluster, secrete matrix
- Mesenchymal cells differentiate into osteoblasts: ossification centre
- Developing bone extends from ossification centre as
spicules: osteoblasts become trapped –> osteocytes - Blood vessels grow into developing bone
- Matrix calcified
- Initially formed as cancellous bone
- Remodelled later into compact bone
steps of endochondral ossification
- In the diaphysis, chondrocytes hypertrophy & die as the
surrounding matrix calcifies = primary centre of ossification - Cells of perichondrium differentiate into osteoblasts & lay down a thin bony collar around the surface of the cartilaginous diaphysis
- Blood vessels grow into perichondrium & invade spaces left by dying chondrocytes
- Fibroblasts migrate into areas left by dying chondrocytes
- Fibroblasts differentiate into osteoblasts and lay down cancellous bone
- Secondary centres of ossification in the epiphyses form cancellous bone; cartilage remains on articular surfaces & at the level of the metaphyses (epiphyseal plates; growth plates)
zones of endochondral ossification
- zone 1; zone of resting cartilage
- zone 2; zone of proliferating cartilage
- zone 3; zone of hypertrophic cartilage
- zone 4; zone of calcified cartilage
- zone 5; zone of ossification
continues growth in long bones steps: growth in length
- Chondrocytes multiply at epiphyseal plate
- Chondrocytes mature & hypertrophy at diaphyseal end & lay down calcium
- Chondrocytes then die, capillaries and osteoprogenitor cells fill the spaces that remain and lay down bony matrix on the calcified cartilage spicules
- Bone at diaphyseal end is eroded by osteoclasts, enlarging the marrow cavity
- Chondrocyte proliferation equals rate of osteoclast
remodelling –> epiphyseal plate remains a constant length until growth has ceased
continues growth of long bones: growth in diameter
- Appositional growth
- Osteoblasts in periosteum lay down new bone: form circumferential lamellae
- Osteoclasts remove bone from inside the bony collar to expand the medullary cavity: medullary cavity enlarges as bone increases in diameter
