Flashcards in Cartilage and Bone Deck (72)
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Is cartilage vascular or avascular
-Avascular
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In general, what two components make up cartilage?
-Chondrocytes
-Extensive ECM
2
What is the function of the chondrocytes within cartilage?
-To produce and maintain ECM
3
What is the ECM of cartilage made up of?
-Hyaluronic acid and proteoglycan aggregates
-Proteoglycan monomers have a core protein with gags attached
-Collagen fibres
4
What are the characteristic features of cartilage?
-Resilience to repeated applied pressure
-Non-compressibility
-Solid but pliable
-Elasticity
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What does the gag:collagen ratio of the ECM ensure?
-The ratio permits diffusion of nutrients to the chondrocytes from the surrounding blood vessels
6
Which type of collagen is predominantly found in cartilage?
-Type 2
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What type of tissue is cartilage?
-Connective tissue
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Name the three type os cartilage
-Hyaline
-Elastic
-Fibrocartilage
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What is the ECM of hyaline cartilage made of?
-Hyaluronic acid and proteoglycan aggregates bound to type II collagen
-Proteoglycan monomers have a core protein with gags attached
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What is the main characteristic feature of hyaline cartilage?
-Resilience to repeated pressure loads
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What occurs when pressure loads are applied to hyaline cartilage?
-Creates mechanical, electrical and chemical signals which direct the synthetic activity of the chondrocytes
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What cell type is found in hyaline cartilage?
-Chondrocytes
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Where in the body is hyaline cartilage found?
-larynx, trachea, bronchus
-ear and nose
-ribs
-articulating surfaces of joints
-At the epiphyseal growth plate
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What surrounds cartilage?
-Perichondrium
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What is particular about the hyaline cartilage at articulating surfaces of joints?
-No perichondrium as would be damaged, needs to be smooth and thus cannot repair itself, gets nutrients from surrounding fluid
-Also contains type III collagen
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Why does hyaline cartilage at articulating surfaces have irregular boundaries?
-To prevent shearing off
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Describe how chondrocytes are distributed in hyaline cartilage
-Lie in lacunae, separated by ECM that they secrete or in isogenous groups if just recently divided, which eventually become to lie separately
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Why does hyaline cartilage remain at the epiphyseal growth plates?
-To allow elongation of long bones
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What is interstitial growth in cartilage?
-Growth which occurs as a result of isogenous groups secreting matrix and becoming single cells laying in separate lacuna
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What is appositional growth?
-Growth from the periphery
-The perichondrium contains elongate fibroblast-like cells which develop into chondroblasts and then into chondrocytes, laying down ground substance as they develop
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What is the territorial matrix?
-The highly sulphated deeply staining matrix immediately surrounding chondrocytes
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What is the interterritorial matrix?
-The matrix which lies in between chondrocytes and their lacunas
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How is the ECM of elastic cartilage similar/different from that of hyaline cartilage, and what extra feature does this add?
-ECM made of hyaluronic acid and protein aggregates providing resilience
-Contains many elastic fibres conferring elasticity upon the cartilage
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What colour is elastic cartilage in FRESH tissue?
-Yellowish
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Where is elastic cartilage found in the body?
-Pinna of the ear
-Eustachian tube
-Epiglottis
-Auditory meatus
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Does hyaline cartilage or elastic cartilage have more abundant chondrocytes?
-Elastic
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What cell type(s) does fibrocartilage contain?
-Chondrocytes and fibroblasts (in relatively low numbers)
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Why is fibrocartilage different from hyaline and elastic cartilage?
-It is a mixture of dense irregular connective tissue and hyaline cartilage
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Does fibrocartilage have a surrounding perichondrium?
-No
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Describe the distribution of cells within fibrocartilge
-Often found in rows or isogenous groups
-Few
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What fibres does fibrocartilage contain?
-TI and TII collagen
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How are the fibres arranged in fibrocartilage? Relate the structure to its function
-Fibres run in parallel with direction of force exerted upon it
-Provides high tensile strength and non-compressibility
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What is the main function of fibrocartilage?
-Shock absorber and resistance of shearing force
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Where is fibrocartilage located in the body?
-Intervertebral discs
-Sternoclavicular and temperomandibular joints
-Menisci of the knee joing
-Pubic Synthesis
-Ethesis
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What is ethesis?
-Point of attachment of tendon to bone
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Which type of cartilage calcifies with age?
-Hyaline
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Which cartilage is the most common?
-Hyaline
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In general, what are the three constituents of bone?
-Cells
-ECM
-Fibres
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What is specific about the ECM of bone?
-Integrated with mineral salts, particularly calcium phosphate for rigidity and hardness
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How is bone specialised for its function?
-High mechanical strength with minimal weight
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Name the different groups of bones
-Long bones
-Short bones
-Flat bones
-Sesamoid bones
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What are the two types of bone?
-Compact
-Spongy (Cancellous/trabecular)
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What is the macroscopic histiological appearance of compact bone?
-Dense bone with no cavities
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Where is compact bone found?
-External surfaces of bones
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Microscopically, into what is compact bone arranged?
-Into osteons
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What are osteons?
-Concentric lamellae of bone arranged around a central haversian canal, joined to other osteons, periosteum and bone marrow by volkmann canals
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What do haversian canals carry?
-Blood vessels, lymphatics and nerves
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What is cementing substance?
-A thin homogenous layer of amorphous material between osteons
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Are volkmann canals surrounded by concentric lamellae?
-No
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What are interstitial lamellae?
-Remnants of lamellae which used to be concentrically arranged around an osteon have been remodelled
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What is the macroscopic structure of cancellous bone?
-Interconnecting network of cavities, filled with bone marrow separated by numerous irregular trabeculae
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What is the microscopic structure of trabeculae?
-No haversian systems
-Lamellae not arranged in concentric circles but irregularly
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How does trabecular bone receive nutrients?
-By diffusion from the marrow
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What is periosteum?
-Vascular connective tissue which surrounds bone
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What cell types are found in bone?
-Osteoblasts (which develop into osteocytes)
-Osteoclasts
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What is the function of osteoblasts?
-Lay down new osteiod in bone remodelling
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What is the function of osteoclasts?
-To resorb bone during bone remodelling
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How do osteoclasts exert their action?
-Through H+ and lysosomal enzymes
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In what do osteocytes lie?
-Lacunae
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How are osteocytes arranged in immature and mature bone?
-Immature-> fairly randomly arranged
-Mature-> in the concentric lamellae
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What is different about the lacunae of bone to lacunae of cartilage?
-Radiate canaliculi which anastomose with canaliculi of other lacunae
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What is the function of canaliculi?
-Permit osteocyte cytoplasmic processes and passage of ions and nutrients to those osteocytes which lay far away from the artery
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What is the sheath of neumann?
-fine fibrous tissue which lines lacunae and canaliculi
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What must happen to bone in order for it to be histologically viewed?
-Decalcified which kills organic material
or
-Ground
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Describe the action of bone remodelling
-Osteoclasts resorb bone through H+ and lysosomal enzymes which forms a cutting cone which runs parallel to the direction of the haversian canal creating a resorption cavity, osteoclasts lie in the resulting depression
-Osteoblasts deposit osteoid in sucessive lamellae creating a closing cone, filling the resorption cavity with new bone
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Why can the bone resist fracture until a certain point?
-High tensile strength
-Degree of flexibility- lamellae can slip relative to one another before excessive force causes fracture
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What are the four stages of bone repair following a fracture?
-Haematoma formation
-Fracture repair
-Bony callus formation
-Bone remodelling
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Describe haematoma formation following a fracture
-Blood vessels in bone and periosteum break
-Haematoma (mass of clotted blood) forms
-Cells at periphery of fracture die due to lack of blood supply
-Removed by macrophages
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Describe fracture repair following haematoma in a bone fracture
-New blood vessels infiltrate haematoma
-Procallus of granulation tissue (tissue rich in fibroblasts and capillaries) forms
-Fibroblasts produce collagen fibres which span the break, others differentiate into chrondrocytes and form a sleeve of hyaline cartilage across the break
-An externally buldging fibrocartilagineous matrix splints the bone
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Describe bony callus formation after procallus formation following a fracture
-Trabeculae develop and a spongy callus is formed
-Edochondral ossification replaces cartilage with bone
-Fibrocartilagineous callus is know a hard bony callus of cancellous bone
-Continues for 2 months until hard union is formed
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