Cartilage And Bone Flashcards
Which component of cartilage is responsible for conferring significant compression strength?
Chondroitin sulphate
Trabeculae are lined externally by a calliper layer known as what?
Endosteum
What physiological process drives osteoclastogenesis in conditions such as periodontitis and rheumatoid arthritis?
Inflammation
What cell type differentiates from immune cell lineage?
Osteoclasts
What cell type is involved in bone restoration?
Osteoclasts
Function of skeletal connective tissues.
Form skeleton
Form strong framework so support and protect body and facilitate movement.
Name and describe the 3 types of cartilage?
Hyaline = connects ribs to sternum
Contains articular cartilage. (lines bones at joints
Elastic = external ear or epiglottis (lap of tissue under tongue or back of throat)
Fibrocartilage = forms lad that connects and protects individual vertebrae
Describe the appendicular part of skeleton.
Function: facilitate movement
Contains bones of limbs (arms, legs)
Provide attachment site for muscles
When muscles contract they pull on bone
Describe the axial part of the skeleton?
Function: protect organs
Composed the head, vertebrae and ribs
Name the 3 main components of connective tissue
Ground substance
Fibres
Cells
GS+ fibres = extracellular matrix
Why is the extracellular matrix firm and glassy?
Due to predominance of chondroitin sulphites in GS
(Compression strength)
Function of chondroitin sulphates?
Provide resistance to compression
All cartilage are avascular.
What does this mean and what does it result in?
No blood vessels
Results in poor heeling or no heeling
All exchange of nutrients must occur by diffusion in and out of cartilage
What type of fibres does cartilage contain?
Collagen
Elastin fibres
What type of cells does cartilage contain?
What is there function?
Chondroblasts
Chondrocytes
Function: synthesise or secrete extracellular (cartilage) matrix
Also maintain it
Features of hyaline cartilage.
•Abundant GS
•Gives rise to smooth gel like tissue (lubricate joints)
•Tough but flexible (compression strength)
•Full of collagen fibres
What are lacunae?
Small chamber in matrix becomes occupied by one or more chondrocyte
Where does the chondrocytes live?
Lacunae
what type of cartilage is the outer perichondrium present?
hyaline
what is the function of the perichondrium?
growth and maintenance of cartilage
attach cartilage to other various tissue
what is the difference between hyaline and articular cartilage?
hyaline has an outer perichondrium and articular doesn’t.
where are chondroblasts found in cartilage?
the inner layer of perichondrium
what happens when chrondroblasts synthesise and secrete cartilage matrix?
they become completely embedded and surrounded by the matrix (essentially trapped)
what happens after chondroblasts become completely embedded in the matrix?
new ones synthesise new matrix and cells are pushed towards centre of cartilage, once they are encased they have to stop secreting new matrix as it has no where to go
this is mature chondrocytes and they maintain the matrix
what is a mature form of chondroblast called?
chondrocyte
what is elastic cartilage and what does it provide?
flexible, avascular connective tissue that provides support and resistance to compression.
what does elastic cartilage contain?
perichondrium, chondrocytes and lacunae
lots of elastic fibres
where is elastic cartilage found?
outer ear and epiglottis
where is fibrocartilage found?
in pads between spinal vertebrae
what does fibrocartilage do?
attach and connect vertebrae
limit movement of spine
features of fibrocartilage.
tough and durable
chondrocytes arranged in rows
donated by irregular dense collagen fibres
what does the ground substance of bone tissue contain?
chondroitin sulphate
hyaluronic acid etc
(GS is a small component in bone)
what are the fibres made up of in bone tissue?
type 1 collagen
in bone tissue, what does GS + fibres make?
osteoid
what is an osteoid?
un-mineralised organic component of ECM 28%
how does an osteoid become mineralised?
by decomposition of hydroxyapatite
what does hydroxyapatite do to bones and what is it like itself ?
gives them strength and hardness
in itself its extremely brittle
what do collagen fibres do for hydroxyapatite crystals?
provide framework which gives rise to very hard but flexible tissue
what is hydroxyapatite made of?
mineralised crystals of calcium phosphate
percentage composition of bone?
28% osteoid
2% cell
70% hydroxyapatite
bone consists of bone tissue and at least 1 other. name them (5)
- CT proper (periosteum) - dense irregular CT that wraps around external surface of bone
2.adipose tissue (fatty marrow) - at centre of bone - blood vessels
- nervous tissue
- articular cartilage - mod of hyaline cartilage lines external surface of bone where they form joint
name the 2 types of bone and describe them.
compact = cortical - dense tough outer layer of bone that goes round perimeter
spongey = trabecular - honeycomb structure
what makes bone heavy?
Hydroxyapatite
name the 4 cells of brain tissue?
osteogenic/ osteprogenitor
osteoclast
osteoblast
osteocyte
what are osteogenic/ osteprogenitor cells?
only found in bones
capable of cell division
bon cell precursor (enables bone formation)
important: repair and maintenance = divide and give rise to osteoblasts
describe order of bone cell lineage.
osteocytes were one osteoblasts that differentiated from different osteogenic cells
what is an osteoblast involved in?
synthesising and secreting new bone matrix before maturing into and osteoclast
function of an osteocyte?
maintain mineralised bone tissue
function of an osteoclast?
resorb bone (recycle)
where do osteoclasts derived from and how do they form?
immune cell lineage
fusion of many monocytes or macrophages
what are osteoclasts?
phagocytic cells that can ingest and dissolve bone matrix
have many nuclei (multinucleate)
what is a trabeculae?
each spike on an interwoven network of bone plates
what is the periosteum?
outer layer of fibrous connective tissue in bones
(like perichondrium in cartilage)
what do you find in inner osteogenic layer of bones?
osteogenic cells that give rise to osteoblasts
what is under the osteogenic layer in bone?
thick layer of compact and spongey bone towards medullary cavity.
what is the lamellae?
layers of compact and spongey bone
- can be arranged in concentric circles
what is an osteon and what is it made up of?
functional unit of bone
made up of concentric lamellae
what is at the centre of an osteon and what is it made up of?
centre (aversion) canal
- run longitudinally
blood vessels, nerves, lymphatics
what is a Volkmann’s canal?
extends from centre canal and connects it to periosteum
function of volksmann’s canal?
supply tissue with nutrients
what are circumferential lamellae?
layers of bone not in concentric circles directly below the periosteum
- run around circumference of bone
“compact bone that lies between osteons that are remnants of previous remodelled osteons”??
interstitial lamellae
what migrates into interstitial lamellae and why?
osteoclasts to resorb and recycle large channel into bone tissue
what are remnants of old osteons called?
interstitial lamellae
why do osteocytes lay in the lacunae?
to maintain the material they previously laid down as osteoblasts.
“tiny canals which osteoclasts reach out to neighbours”
canaliculi
what do canaliculi allow?
osteocytes to maintain contact, communication with neighbours and receive nutrients
features of spongey bone.
contains lamellar bone.
lined externally by endosteum
don’t have centre canal so not an osteon
no blood vessels, nerves, lymphatics at centre
what are the spaces between tabeculae in spongey bone occupied by?
red/yellow marrow
blood vessels
nerves
lymphatics
what is spongey bone externally lined by?
endosteum
what happens in the healthy activity of osteoclasts and osteoblasts?
they coordinate so that bone formation (osteoblastogenesis) is coupled with bone resorption (osteoclastogenesis)
describe the 4 factors of bone remodelling?
growth = expertise builds bone too
mechanical stresses
hormonal = calcium homeostasis
immunological
what hormones influence bone remodelling?
- sex hormones (oestrogen)
- parathyroid control bone/ calcium metabolism (stimulates osteoclastogenesis)
what do we require for calcium uptake from diet?
hormone calcitriol (active form of vit D) produced from sun exposure
(precursor for calcitriol)
what type of of control is bone remodelling under
immunological
what does inflammation do in inflammatory diseases in bone?
disrupt balance of bone resorption and bone formation
lead to increased ossteoclastogensis and loss of bone
what is periodontitis?
loss of attachment of periodontal ligament (gingival recession)
- destructive inflammatory disease
- chronic immune response to oral bacteria leads to destruction of host tissue
- immune mediated uncoupling of bone remodelling
- increased osteoclastogenesis
- destruction of alveolar bone and subsequent tooth loss
what is arthritis (2 types) ?
osteoarthritis - affects smooth cartilage around joint (changes shape)
rheumatoid arthritis - autoimmune, body attacks own tissue
- initially affects synovium (outer joint covering)then inflammation spreads changing joint shape
what causes osteomalacia? (rickets in children)
-Failure of osteoid to mineralise adequately
-Lack of vit d/ calcium are most common cause
what happens if there is no decomposition of of hydroxyapatite in bone?
bones become flexible (bow legged)
aren’t rigid enough to maintain normal stance
what percent of hydroxyapatite in bone and enamel?
bone = 70%
enamel = 95%
what leads to enamel hypoplasia?
lack of vit D leads to lack of calcium absorption leads to enamel hypoplasia as enamel isnt strengthened enough
plays role in delayed tooth eruption
