Week 5 Flashcards
What is cartilage?
A type of connective tissue
What is cartilage made of?
A dense network of collagen or elastin, and the associated matrix materials which will provide strength and resilience.
What is the cartilage extracellular matric deposited by?
Chondroblasts, which mature into chondrocytes
Where do the chondrocytes sit in the extracellular matrix?
The spaces - lacunae
What is the perichondrium?
A sheet of connective tissue that covers the surface of most cartilage throughout the body
What are the classifications of cartilage?
Hyaline cartilage, fibrocartilage, and elastic cartilage
What is hyaline cartilage composed of?
Fine type II collagen fibres bound together by a resilient gel like matrix material.
What is hyaline cartilage?
The most abundant yet weakest cartilage
Where is hyaline cartilage found?
All over the body
What is the function of hyaline cartilage?
to provide flexability and support, reducing friction, and absorbing shock. It covers the articular surfaces of joints and provides support to the resp system
What is the function of hyaline cartilage in the foetus?
It forms a temporary skeleton, which is then gradually ossified.
What else does hyaline cartilage form?
The epiphyseal plates in growing long bones
What is fibrocartilage composed of?
Thick bundles of collagen fibres interspersed with chondrocytes in their lacunae
What is fibrocartilage?
The strongest cartilage in the body
What is the function of fibrocartilage?
provides strength and rigidity
Where is fibrocartilage found?
Intervertebral discs, tendon attachment to bones, and the junctions between the flat bones of the pelvis
Does fibrocartilage have a perichondrium?
No
What is elastic cartilage?
Strong and elastic
What is elastic cartilage composed of?
A thread-like network of elastic and collagen fibres interspersed with chondrocytes in their lacunae
What is the function of elastic cartilage?
provides and maintains the shapes of various structures
Where is elastic cartilage found?
The auricle of the ear, the walls of the external auditory meatus, and the epiglottis of the larynx
How is cartilage nourished?
Its avascular so is nourished through diffusion. There is no nerves in cartilage
What is bone?
A specialised type of connective tissue which has a mineralised extracellular component
What is the periosteum?
A layer of connective tissue that surrounds bone
What is the function of periosteum?
To nourish the tissue and provide an interface for attachment of tendons and ligaments
What are the two types of bone?
Compact bone and spongy bone (trabecular or cancellous)
What are the differences between the two types of bone?
depend on the relative amount of solid matter and the number and size of the spaces they contain
What do all bones have?
A superficial thin layer of compact bone around a central mass of spongy bone (except where the spongy bone is replaced by a medullary cavity)
What happens in the medullary cavity and spicules of spongy bone of adult bone?
Blood cells and platelets are formed
What is the function of compact bones?
Provide strength for weight bearing in long bones, designed for rigidity and attachment of muscles and ligaments
Where is most of the compact bone found?
Near the middle of the shaft (body) of the bone, where it has the most risk of buckling
What is the rigidity and elasticity of living bones like?
A little bit of elasticity (flexibility) and great rigidity (hardness)
What are the different shapes of bones?
Long bones, short bones, flat bones, irregular bones and sesamoid bones
What are long bones?
Tubular structures (e.g. humerus and femur)
What are short bones?
Cuboidal structures (e.g. bones of the wrist and ankle)
What are flat bones?
Serve protective functions - consist of two compact bone plates separated by spongy bone (e.g. skull)
What are sesamoid bones?
round or oval bones that develop in tendons
When do bone markings appear?
Wherever tendons, ligaments and fascia are attached or where arteries lie adjacent to or enter bones
How do other bone formations occur?
In relation to the passage of a tendon or to control the type of movement occurring at a joint
What are the 4 main types of bone cells responsible for?
the formation, repair, development and destruction of bone
What are the 4 main types of bone cells?
osteogenic cells, osteoblasts, osteocytes, osteoclasts
What are osteogenic cells?
Unspecialised mesenchymal cells.
where are osteogenic cells found?
Predominantly alongside membranes that surround the bones and the blood vessels in bone canals
What do osteogenic cells do?
The only bone cells that undergo cell divisions with the resulting cells becoming bone producing cells
What is a mesenchymal cell?
A tissue from which most connective tissue is derived
what are osteoblasts?
Bone producing cells
Where are osteoblasts found?
regions of bone formation such as the surface of growing bones or areas undergoing active bone remodelling
What is the function of an osteoblast?
to synthesize and secrete collagen fibres and other organic components.
What are the components synthesized by osteoblasts used for?
To build the extracellular matrix of bone tissue and to initiate calcification
What happens when the matrix is formed by osteoblasts?
the osteoblasts become trapped in their own secretions and eventually are turned into osteocytes
What are osteocytes?
the major cell type found in mature bone
What are osteocytes derived from?
osteoblasts
Where are osteocytes found?
within the matrix of the bone
What is the function of osteocytes?
Maintain the daily metabolism of bone tissue, which includes the exchange of nutrients and waste within the blood
What are osteoclasts?
large cells derived from the fusion of monocytes present within the bone marrow or from other blood producing tissue
Where are osteoclasts present?
in close contact with the bone surface in bone surface resorption bays and are mainly concentrated within the layer of connective tissue on the inside of the bone
What is the function of osteoclasts?
local removal of bone growth and the subsequent remodelling of the bone surface.
What is resorption?
local removal of bone growth and the subsequent remodelling of the bone surface.
Where is resorption commonly seen?
The normal development, maintenance and repair of bone
How do osteoclasts carry out resorption?
They release HCL
What is the organic part of the bone matrix composed of?
Osteoid
What is osteoid produced and secreted by?
Osteoblasts
What is osteoid maintained by?
osteocytes
What is osteoid made up of?
Predominantly type 1 collagen fibres and a small proportion of ground substance
How much of bone is made up of inorganic mineral?
approximately 50%
What is the inorganic mineral in bone called?
Hydroxyapatite
What is hydroxyapatite formed from?
Mineral salts which combine with additional salts on the matrix (calcium and phosphate)
What is the process that forms hydroxyapatite called?
Calcification
what is a joint?
Where two or more bones articulate
What does articulate mean?
Where two or more bones meet
what three categories are joints put into structurally?
Fibrous, cartilaginous and synovial?
What are fibrous joints?
connected by dense connective tissue, have no joint cavity. Most are synarthrotic or amphiarthrotic
What are cartilaginous joints?
Connected by hyaline cartilage and have no joint cavity
What are synovial joints?
Have a synovial, fluid filled cavity that surrounds the articulating bones
what three categories are joints put into functionally?
synarthrosis, amphiarthrosis, diarthrosis
What are synarthrosis joints?
joints that don’t provide any movement
What are amphiarthrosis joints?
Joints that provide only a small degree of movement
What are diarthrosis joints?
Joints that allow free movement
How can joints be classified?
By their structural components, the tissue that holds the bones together, their functions or the degree of movement that they provide
What are the three types of fibrous joints?
suture, gomphosis and syndesmosis
Where are suture joints found?
between the plate bones of the skull
Where are gomphosis joints found?
the tooth junction
What are syndesmosis joints?
two bones are held together by an interosseous ligament. These joints are amphiarthrotic
What does an interosseous ligament consist of?
long collagenous fibres
What are the two types of cartilaginous joints?
Synchondrosis and symphyses
What types of bone are there?
long bone
short bone
irregular bone
flat bone
sesamoid bone
give an example of a long bone
humerus
give an example of a short bone
carpal bone
give an example of an irregular bone
vertebra
give an example of a flat bone
sternum
give an example of a sesamoid bone
patella
Describe the diaphysis of a bone
main shaft-like portion
hollow and cylindrical shape with thick compact bone on the outside
strong but not too heavy
describe the epiphysis of a bone
both ends of a long bone
bulbous shape which provides space for muscle attachment
red marrow fills the spaces of cancellous bone
describe the metaphysis of a bone
the region where the epiphysis and diaphysis meet
describe the periosteum
dense, white, fibrous membrane
covers bone except for joint surfaces
periosteum fibres penetrate the underlying bone
tendon fibres and periosteum fibres interlace to attach muscle to bone
contains bone remodelling cells and blood vessels
Describe articular cartilage
thin layer of hyaline cartilage that covers the articular surfaces of bones
resilient material that cushions jolts and blows
describe the medullary cavity
hollow space in diaphysis of long bone.
in adults filled with yellow marrow
Describe the endosteum
thin, fibrous membrane that lines the medullary cavities and spaces of cancellous bone
contains bone cells and their precursors
Describe compact bone
cylindrical-shaped osteons or haversian systems
each osteon surrounds a canal which runs longitudinally through the bone
Describe cancellous bone
no osteons
tiny needle-like branches called trabeculae
nutrients and waste products diffuse via tiny canaliculi that extend to the surface of the very thin bony branches
Describe osteoclasts
large cells with many nuclei
share lineage with blood cells (macrophages)
Precursors circulate in blood and bone marrow
When RANK-ligand (from osteoblasts) binds with RANK receptors - mature osteoclast form from fusion of progenitor cells
osteoclasts resorb bone
release acids and enzymes
then undergo apoptosis
What is OPG?
osteoprotogerin
binds to RANK-ligand so can regulate osteoclast activity
Describe osteoblasts
cuboidal and columnar shape with central nucleus
found on bone surface
from mesenchymal stem cells
osteoblasts make proteins to form the organic matrix of the bone and regulate mineralisation
Receptors for vitamin D, oestrogen and parathyroid hormone
secrete RANK-ligand to activate osteoclasts
can differentiate into osteocytes, lining cells or undergo apoptosis
Describe osteocytes
long branches that allow them to contact each other and the lining cells at the bone surface
sense mechanical strain
secrete growth factors to activate lining cells or osteoblasts
Describe lining cells
flat and pancake-shaped
responsible for immediate release of calcium
Protect bone from chemicals that dissolve crystals
receptors for hormoes and factors that effect bone remodelling
What are BMPs?
bone morphogenetic proteins
produced in bone or bone marrow
bind to BMP receptors on mesenchymal cells
cells produce cbfa1 - a transcription factor
cells mature into mature osteoblasts
Describe IGFs in regards to bone
Insulin-like growth factors
produced by osteoblastic cells in response to parathyroid hormone, oestrogen or BMPs
released from matrix during bone remodelling and stimulate osteoblastic cell replication
Describe RANK-ligand
a cytokine that is produced in response to systemic hormones such as 1,25dihydroxyvitaminD3 and other cytokines such as IL6
Induces osteoclast development
What hormones increase bone resorption?
parathyroid hormone
glucocorticoids
thyroid hormone
vitamin D metabolites
What hormones decrease bone resorption
calcitonin
gonadal steroids
what hormones increase bone formation?
growth hormone
vitamin D metabolites
gonodal steroids
What hormones decrease bone formation?
glucocorticoids
what are the main type of inorganic salts found in bone?
hydroxyapatite crytals
What is the organic matric of bone composed of?
collagenous fibres and “ground substance”
name features of a synovial joint
articular cartilage
synovial cavity
synovial membrane
joint capsule
what are the two names for the three kinds of joints?
synarthroses (fibrous)
ampiarthroses (cartilaginous)
diarthrosis (synovial)
Describe synarthrosis movement
immovable
describe ampiarthoses movement
slightly moverable
Describe diarthrosis movement
freely moveable
What types of fibrous joints are there?
Syndesmoses
sutures
gomphoses
What are syndesmoses joints?
e.g. distal end of radius and ulna
ligament connects bones
What are sutures?
only found in the skull
interlocking teeth-like projections
What are gomphoses?
found at the root of the teeth
periodontal membrane
What type of cartilaginous joints are there?
synchondrosis
symphyses
What are synchondroses?
e.g. between first rib and sternum
hyaline cartilage between articulating surfaces
What are symphyses?
e.g. pubic symphysis
fibrocartilage disk
What kinds of synovial joints are there?
uniaxial - hinge, pivot
biaxial - saddle, condyloid
multiaxial - ball and socket, gliding
Describe the uniaxial joints
hinge - e.g. elbow, flexion and extension
pivot e.g. between C1 and C2, rotation
Describe the biaxial joints
saddle - e.g thumb joint. flexion, extension, adduction and abduction
condyloid - between radius and carpal bones - flexion, extension, adduction and abduction
Describe the multi axial joints
ball and socket - e.g. shoulder - wide range
gliding - e.g between articulating facets of vertebrae. Gliding
what are the three types of cartilage?
hyaline cartilage
elastic cartilage
fibrocartilage
How do chondrocytes get their nutrients?
only through diffusion from the periosteum or synovial fluid - cartilage is avascular unlike bone
Describe hyaline cartilage
most common
both collagen and elastic fibres
articular surfaces of bones, tracheal rings, bronchi of lungs, tip of the nose
Describe elastic cartilage
large numbers of elastic fibres
gives form to external ear, epiglottis, eustachian tubes
Describe fibrocartialge
small quantities of matrix and abundant fibrous elements
strong, rigid
pubis symphyses, IV disks, near site of attachment of some large tendons to bones
what are the main changes seen in an osteoarthritic joint?
thickened capsule
cyst formation and sclerosis of subchondral bone
fibrillated cartilage
osteophytic lipping
synovial hypertrophy
altered contour of bone
What causes damage to cartilage in OA?
decreases in water content, proteoglycan synthesis, collagen cross linking, size of GAGs and hyaluronic acid
traumatic damage
What is osteoarthritis?
progressive disorder of the joints caused by gradual loss of cartilage and resulting in the development of bony spurs and cysts and the margin of the joint
What are the causes of OA?
primary - degenerative
secondary - trauma, hip dysplasia, infection, diabetes
who is most affected by OA?
women over 45
What is seen in an X-ray of an OA joint?
joint space narrowing
osteophytes
subchondral bone sclerosis
cyst formation
What is ECM?
extracellular matrix
a complex network of proteins and polysaccharides
secreted locally
provides structural, adhesive and biochemical signalling support
What makes up ECM?
fibres - collagen and elastin
ground substance - proteoglycans, glycosaminoglycans, glycoproteins
What are the functions of ECM?
mechanical and structural support
tensile strength
determines cellular movment
what are the five classes of macromolecules found in ECM?
collagens
elastin
proteoglycans
glycosaminoglycans
other glycoproteins
where is type I collagen found?
dermis, tendons, ligaments, bones
where is type II collagen found?
hyaline cartilage
Where is type III collagen found?
liver, bone marrow, lymphoid organs
Where is type IV collagen found?
basement membrane
Where is type V collagen found?
linker to basement membrane
Describe GAGs
also called mucopolysaccharides
chains of repeating disaccharide units
carbohydrate component of proteoglycans
What GAG is found in the synovial fluid?
hyaluronic acid
What GAGs are found in cartilage?
chondroitin sulphate and keratan sulphate
What GAG is found in the basement membrane?
Heparin sulphate
what makes aggrecan and where is it found?
chondroitin sulphate and keratan sulphate
cartilage
What is perlecan made from and where is it found?
heparan sulphate
basement membrane
What is syndecan made from and where is it found?
chondroitin sulphate and keratan sulphate
cartialge
What is decorin made from and where is it found?
chondroitin sulphate and dermatan sulphate
wide spread
Give examples of 5 glycoproteins
fibrillar
fibronectin
laminin
entactin
tenascin
What does fibrillin do?
controls deposition and orientation of elastins
what does fibronectin do?
linker role in BM
What does laminin do?
primary organiser in BM
What does entactin do?
linker role in BM
What does tenascin do?
linker role in connective tissue
How is collagen made?
synthesised as pro collagen
post-translational modification - glycosylation and hydroxylation
assembled as triple helix
How is elastin made?
synthesised as tropo elastin
post-translational modification - hydroxylation
assembled in fibrillin scaffold, cross-linked fibres
What are the three layers of the basement membrane?
lamina lucida
lamina densa
lamina fibroreticularis
what is the basement membrane composed of?
collagen
laminin
perlecan
entactan
what are the functions of the basement membrane?
support
binding to underlying connective tissues
mediates signalling
determines cell polarity
permits flow of nutrients
path for cell migration
barrier to downward growth
Give examples of disorders of BM
cancer - epithelial tumours malignant when breach BM
Diabetes - thickening of BM of glomerulus alters function
epidermolysis bullosa - attachment of epidermis to BM
Good pastures syndrome - autoantibodies to collagen IV destroy BM in lung and glomerulus
A condition caused by problem in elastin
supravalvular aortic stenosis
A condition causes by a problem with fibrillin I
Marstan syndrome
A condition caused by a problem with collagen
etlers danlos syndrome
a condition caused by problem in keratan sulphate
macular corneal dystrophy
a condition caused by problem with perlecan
Silverman-Handermaker type of dyssegmental dysplasia (DDSH) lethal dwarfism
