ANATOMY AND PHYSIOLOGY - Cartilage and Bone Flashcards
What are the three structural components that make up connective tissue?
Cells
Fibres
Ground substance
What are the three types of cartilage?
Hyaline cartilage
Elastic cartilage
Fibrocartilage
What are the two cell types found in cartilage?
Chondroblasts
Chondrocytes
What is the function of chondroblasts?
Chondroblasts produce the extracellular matrix (ECM) which makes up cartilage
What is the function of chondrocytes?
Chondrocytes maintain the extracellular matrix (ECM) which makes up cartilage
(T/F) Cartilage is a vascular connective tissue
FALSE. Cartilage is an avascular connective tissue
Which type of fibre is found in hyaline cartilage?
Type II collagen
Which type of proteoglycans are found in the hyaline cartilage extracellular matrix (ECM)?
Aggrecan proteoglycans
What is the function of aggrecan proteoglycans in the hyaline cartilage extracellular matrix (ECM)?
Aggregan proteoglycans provide hyaline cartilage with resistance to mechanical load through generating a swelling pressure
What are the two regions of the body where elastic cartilage is found?
Ear pinnae
Epiglottis
Which type of fibres are found in elastic cartilage?
Elastin
Type II collagen
Which type of fibre is found in fibrocartilage?
Type I collagen
What are the two methods of cartilage growth?
Appositional growth
Interstitial growth
What is the perichondrium?
The perichondrium is a layer of connective tissue which covers the surface of cartilage which undergoes appositional growth
Describe briefly the process of appositional growth
Chondroblasts within the perichondrium produce extracellular matrix (ECM) along the existing surfaces of the cartilage causing the cartilage to expand and widen
Which types of cartilage undergo appositional growth?
Hyaline cartilage
Elastic cartilage
What are isogenous groups?
Chondrocytes can be reactivated into their chondroblast form within the extracellular matrix (ECM) where they will divide to form daughter cells which form 2-4 cell clusters known as isogenous groups
Describe briefly the process of interstitial growth
Isogenous groups produce extracellular matrix (ECM) within the existing cartilage causing the cartilage to expand and widen
Which types of cartilage undergo interstitial growth?
Hyaline cartilage
Elastic cartilage
Fibrocartilage
Why is the articular hyaline cartilage of synovial joints incapable of undergoing appositional growth?
There is no layer of perichondrium covering the surface of articular hyaline cartilage in synovial joints due to the presence of synovial fluid - preventing the cartilage from undergoing appositional growth
What are the three functions of synovial fluid?
Lubrication
Anti-concussive function
Nutrient transport
What are the three components of synovial fluid?
Interstitial fluid
Hyaluronan
Lubricin
Which cell type produces the hyaluronic acid present in synovial fluid?
Synoviocytes
Which cell type produce the lubricin present in synovial fluid?
Chondrocytes
What colour and consistency should normal synovial fluid be?
Normal synovial fluid should have a viscous, egg-white like colour and consistency
List three changes in synovial fluid which can indicate joint pathology?
Cloudy synovial fluid
Blood in synovial fluid
Excess synovial fluid
What are the two layers of the synovium?
Intima
Subintima
What are the two cell types found within the intima layer of the synovium?
Synoviocytes
Macrophages
What are the two components which make up the subintima layer of the synovium?
Loose connective tissue
Capillaries
What are the two types of bone?
Lamellar bone
Woven bone
What are the two types of lamellar bone?
Compact bone
Trabecular bone
What is the main difference between lamellar bone and woven bone?
Lamellar bone has a specific orientation of collagen fibres whereas woven bone has a random orientation of collagen fibres
What are the three cell types found within bone?
Osteoblasts
Osteocytes
Osteoclasts
What is the function of osteoblasts?
Osteoblasts produce the organic component of the extracellular matrix known as osteoid
What is the function of osteocytes?
Osteocytes maintain the extracellular matrix (ECM)
What is the function of osteoclasts?
Osteoclasts carry out enzymatic digestion of the extracellular matrix (ECM) which is essential for bone remodelling
Which cell type are osteoclasts derived from?
Osteoclasts are derived from monocytes
What are the four main components of the osteoid component of the bone extracellular matrix (ECM)?
Type I collagen
Chondroitin sulphate
Keratin sulphate
Osteocalcin
What are the four main components of the inorganic component of the bone extracellular matrix (ECM)?
Hydroxyapatite crystals
Sodium (Na)
Magnesium (Mg)
Iron (Fe)
Which type of lamellar bone makes up the walls of the diaphysis?
Compact bone
What is the name of the membrane surrounding the outer surface of compact bone?
Periosteum
What is the name of the membrane surrounding the inner surface of compact bone?
Endosteum
Which cell type is found within the periosteum and endosteum?
Osteoblasts
What are the main structural units of compact bone involved in compact bone remodelling?
Haversian systems
Describe the structure of a Haversian system/osteon
Haversian systems consist of blood vessels within a central Haversian canal surrounded by concentric rings of mineralised extracellular matrix (ECM) known as lamellae. Osteocytes are contained between the lamellae in spaces known as lacunae
What is the function of the blood vessels contained within the central Haversian canal?
Blood vessels within the central Haversian canal provide a blood supply to the osteocytes
How do osteocytes within the mineralised extracellular matrix (ECM) communicate with adjacent osteocytes?
Cellular extensions known as canaliculi extend from the lacunae to form the lacunar-canalicular system which allows osteocytes to communicate with adjacent osteocytes
What are Volkmann’s canals?
Volkmann’s canals are transverse canals formed from the inversion of periosteum and endosteum which connect adjacent Haversian systems
Which type of lamellar bone makes up the epiphyses and metaphyses?
Trabecular bone
Describe the basic structure of trabecular bone
Trabecular bone is made up of spicules covered in endosteum with haematopoietic tissue in between the spicules
What are the two methods of skeletal development?
Intramembranous ossification
Endochondral ossification
What is intramembranous ossification?
Intramembranous ossification is the formation of bone directly from osteogenic connective tissue
Which two skeletal structures are formed due to intramembranous ossification?
Skull bones
Mandible
What is endochondral ossification?
Endochondral ossification is the replacement of a hyaline cartilage template with bone
Describe the six steps of endochondral ossification
- Chondrocytes in the centre of the hyaline cartilage template undergo hypertrophy and alter the content of the extracellular matrix (ECM) to enable mineralisation
- Hypertrophied chondrocytes secrete vascular endothelial cell growth factor to induce the sprouting of blood vessels from the perichondrium
- Chondrocytes undergo apoptosis due to decreased nutrient provisions as a consequence of extracellular matrix (ECM) mineralisation
- Blood vessels from the perichondrium invade and transport osteoprogeniter cells which form the periosteal collar and bud, and transport osteoblasts which deposit osteoid
- Primary centre of ossification forms in the diaphyseal region
- Cartilage continues to proliferate at either end of the bone. These proliferative regions become the epiphyseal growth plates
- After birth, this process repeats in the epiphyseal regions to form the secondary centres of ossification
How do epiphyseal growth plates allow for bone growth after birth?
Epiphyseal growth plates allow for expansion of cartilage toward the epiphysis with simultaneous replacement of cartilage with bone at the diaphysial end of the growth plate
What are the five zones of epiphyseal growth plates?
Resting zone
Proliferative zone
Hypertrophy zone
Apoptotic zone
Vascular invasion zone
What occurs within the resting zone of epiphyseal growth plates?
Quiescent chondrocytes secure the epiphyseal plate to the secondary centre of ossification (i.e. the epiphysis)
What occurs within the proliferative zone of epiphyseal growth plates?
Chondrocytes actively proliferate
What occurs within the hypertrophy zone of epiphyseal growth plates?
Chondrocytes undergo hypertrophy which expands the epiphyseal growth plate towards the epiphysis - lengthening the bone. The hypertrophied chondrocytes also alter the content of the extracellular matrix (ECM) to enable mineralisation
What occurs within the apoptotic zone of epiphyseal growth plates?
Chondrocytes undergo apoptosis due to decreased nutrient provisions as a consequence of extracellular matrix (ECM) mineralisation
What occurs within the vascular invasion zone of epiphyseal growth plates?
Blood vessels from the diaphysis invade the spaces left behind by the apoptotic chondrocytes and transport osteoblasts which deposit osteoid within the remaining spaces between the mineralised extracellular matrix (ECM)
What is bone remodelling?
Bone remodelling is the change of shape of bone in response to normal growth, altered mechanical use or disease
Describe briefly the process of compact bone remodelling
Osteoclast precursors are recruited to the Haversian canal where they differentiate into osteoclasts and begin resorption of the lamellae. Osteoblasts reverse this resorption by depositing osteoid to form new lamellae. These osteoblasts eventually become trapped between the lamellae and differentiate into osteocytes - forming a new Haversian system
How does trabecular bone remodelling differ from compact bone remodelling?
Trabecular bone remodelling occurs on the bone surface rather than within Haversian systems
