Cartilage and bone Flashcards
the 4 types of tissue
epithelia, connective, muscle, nervous
function of skeleton
framework to support and protect body and facilitate movement
2 categories of skeleton
Appendicular skeleton and axial skeleton
function of appendicular skeleton
provide muscle attachment site to facilitate movement
What bones make up the appendicular skeleton?
Limbs - arms and legs
Function of axial skeleton
protect organs
what bones make up the axial skeleton?
Bones of head, vertebrae and ribs
3 types of cartilage
hyaline, elastic and fibrocartilages
locations of hyaline cartilage
connects ribs to sternum. includes articular cartilages which line bones in joints
Location of elastic cartilage
External ear and epiglottis
location of fibrocartilages
forms a pad that connects individual vertebrae in the spine
3 features common to all connective tissues
ground substance, fibres (elastin and collagen) and cells
Chemical found in ground substance of cartilage
Chondroitin sulphate
Function of chondroitin sulphate
Resistance to compression
Cells found in cartilage
Chondroblasts (synthesis and secrete ECM) and chondrocytes (maintain ECM)
Technical term referring to absence of blood vessels
avascular
How is waste/nutrients transported through cartilage? (as it is avascular)
diffusion
Hyaline cartilage characteristics
smooth and gel-like (lubricating joints), tough and flexible (compression strength)
What component of cartilage makes hyaline cartilage smooth and gel-like?
abundance of ground substance
Name of hyaline cartilage found in joints
articular cartilage
most abundant fibre in hyaline ECM
collagen
Name of dense, fibrous CT that surrounds hyaline cartilage
perichondrium
Structure of perichondrium
2 layers - outer layer is regular dense CT that attaches cartilage to other tissues, inner layer made of chondroblasts
Difference between hyaline cartilage and articular cartilage
Articular cartilage doesn’t contain fibrous outer perichondrium layer
Chain of events that cause chondroblasts to mature
Synthesise and secrete ECM until they are encased in matrix. Stop secreting ECM and form chondrocytes (maintain ECM)
Lacunae definition
small chamber in matrix that becomes occupied by one or more chondrocytes
Function of elastic cartilage
flexible, avascular CT that provides support and resistance to compression
Comparison of hyaline and elastic cartilage
similar histologically (perichondrium and lacunae). Elastic has more elastin fibres which makes it more flexible
Which stain is used to visualise elastin?
Van Gieson elastic stain (black= elastin)
Which cartilage type has no perichondrium?
Fibrocartilage
Physical features of fibrocartilage
extremely tough and durable
Structure of fibrocartilage
little ground substance, dominated by irregular dense collagen fibres, chondrocytes arranged in rows
Function of fibrocartilage
Found in pads between spinal vertebra which connect vertebrae to each other and limit spine movement
Composition of ground substance in bone
Chondroitin sulphate, hyaluronic acid. Ground substance is a very small component in bone.
Fibre in bone tissue
type 1 collagen
What percentage of bone is made of cells?
2%
Cells in bone tissue
osteogenic/osteoprogenitor, osteoblasts, osteocytes, osteoclasts
Osteoid definition
Unmineralised organic component of ECM (made of collagen and ground substance)
How do osteoids become mineralised?
Deposition of hydroxyapatite
What makes up hydroxyapatite?
Crystals of calcium and phosphate
function of hydroxyapatite
very brittle so gives bone strength and hardness
What percentage of bone is made of osteoids?
28%
What percentage of bone is made of hydroxyapatite?
70%
Why are bones organs?
Made of bone tissue and several other tissues: CT proper (periosteum), adipose, blood vessels, nervous, articular cartilage
Articular cartilage definition
modification of hyaline cartilage that lines the end of bones at joints
Where is red marrow found?
epiphysis (ends)
Where is yellow marrow confined?
Diphysis (shaft)
2 conformations of bone
Compact/cortical bone and spongy/trabecular bone
What is compact/cortical bone?
Dense, smooth, tough outer layer of bone (after periosteum)
What is spongy/trabecular bone?
Honeycomb structure toward medullar cavity made of interwoven network of bone plates.
Purpose of 2 bone confirmations
Allows optimum strength for least weight
Which is the only bone cell capable of cell division?
Osteogenic/osteoprogenitor cells
Function of osteogenic/osteoprogenitor cells
repair and maintain bone tissue. they are the bone cell precursors to osteoblasts.
function of osteoblasts
Synthesise and secrete bone tissue (osteoid). Give rise to osteocytes
How do osteoblasts mature?
Become encased in ECM so they stop secreting. Trapped in lacunae. Mature to become osteocytes
Function of osteocytes
maintain mineralised bone tissue
Which is the only bone cell from a different lineage? (not derived from osteogenic/osteoprogenitor cells)
Osteoclasts
Which lineage are osteoclasts derived from
Monocyte/macrophage lineage
Function of osteoclasts
reabsorbs and recycles bone (phagocytic cells)
How are osteoclasts formed?
Fusion of many monocyte/macrophage-like cells to form large, multinucleate cells
What is the periosteum?
Outer layer of dense CT in bone
What comprises the two layers in periosteum?
Outer dense fibrous layer, inner osteogenic/osteoprogenitor layer
Name of layers of bone tissue that compact/conical and spongy/trabecular bone is arranged in
lamellae
How is the lamellae arranged in compact/cortical bone?
Beneath periosteum - parallel layers known as circumferential lamellae. but majority is in concentric circles (osteons) with interstitial lamellae between
Name of the functional unit of compact/cortical bone / unit of concentric lamellae
Osteon (haversian system)
What exists at the centre of each osteon?
Central canal / Haversian canals
What direction do the central canals run in?
Longitudinally along entire bone length
What is each central canal made up of?
Network of blood vessels, nerves, lymphatic vessels
Name of smaller canals that connect central canals to the periosteum?
Perforating (volkmann’s) canal
Function of Perforating/Volkmann’s canal?
Supply bone tissue with nutrients
Name of layers of bone directly beneath periosteum
Circumferential lamellae
What is interstitial lamellae?
Areas of compact bone that lies between osteons. Remnants of old osteons that have been partially reabsorbed and remodelled.
How is a new osteon formed?
Osteoclasts migrate to resorb an area of weakened bone (e.g. interstitial lamellae between 3 osteons) to form a channel. New central canal is created. Osteoblasts begin to lay down new bone tissue in concentric circles to form a new osteon. Surrounding osteons may be partially resorbed to create the new, large osteon and the remnants becomes interstitial lamellae.
Name of chamber which osteoblasts become trapped in and therefore mature to form osteocytes
lacunae
how do osteocytes communicate
They have numerous extensions in canaliculi (tiny canals which osteocytes reach out to each other).
Why can diffusion not occur in bone (unlike cartilage)?
Due to presence of hydroxyapatite
Structure of spongy/trabecular bone
Contains lamellar bone (layered - like cortical/compact bone). Not osteons due to absence of central canal. Woven network of plates.
What are trabeculae?
Spikes in spongy/trabecular bone
What occupies the spaces between trabeculae?
red and yellow marrow, nerves, blood vessels, lymphatics
Endosteum definition
cellular layer containing osteogenic/osteoprogenitor cells that line each trabeculae
term for bone formation
osteoblastogenesis
term for bone resorption
osteoclastogenesis
term used to describe balance between bone formation and bone resorption
coupled
factors that influence bone remodelling
growth, mechanical stress (e.g. exercise), hormones, immunological
examples of hormones that affect bone remodelling
oestrogen, parathyroid hormone, calcitriol
Effect of periodontitis
Loss of periodontal ligament attachment in alveolar bone (causes gingival recession), alveolar bone loss, inflamed gums
How does periodontitis arise?
Chronic immune response to oral bacteria creates inflammation which increases the presence of immune cells. Inflammatory molecules in the tissue cause monocytes to fuse and differentiate into osteoclasts. no longer balanced numbers of osteoclasts and osteoblasts - immune-mediated uncoupling of bone remodelling. Increased osteoclastogenesis.
What is arthritis?
disease that causes inflammation and pain in joints.
Name of fluid that bathes joints
synovial fluid
Two most common forms of arthritis
osteoarthritis and rheumatoid arthritis
What does osteoarthritis affect?
Smooth cartilage lining joints roughens and thins out causing bone-on-bone friction. May alter shape of joint.
What is rheumatoid arthritis?
Autoimmune disease that initially affects synovial fluid. Immune-mediated uncoupling of bone remodelling. Increased osteoclastogenesis, decreased bone volume
What is osteomalacia?
Failure of osteoid to mineralise adequately by hydroxyapatite deposition
Causes of osteomalacia
Lack of calcium and/or phosphate, lack of vit D
Effects of osteomalacia
Flexible bones (bowlegged shape), weakened bones more prone to fracture, dental abnormalities - enamel hypoplasia and delayed tooth eruption.
What is enamel hypoplasia?
insufficient enamel on the teeth which is not straight creating a rough surface
