Session 7: Cartilage, Bone and Bone Fractures Flashcards
Cartilage is a connective tissue secreted by what cells?
Chondrocytes
Chondrocytes are derived from the same precursor cells as what other cell type?
Fibroblasts
Chondrocytes create fibrous material such as what two important proteins?
Collagen
Elastin
Collagen and elastin provide cartilage with what two features?
Strength
Flexibility (Elasticity)
Is cartilage innervated?
No
Is cartilage vascular?
No, it is avascular
If cartilage is not innervated and is avascular, how does it receive its nutrients and immune protection?
From surrounding fluid
What are the three main types of cartilage found in the body?
Hyaline cartilage
Elastic cartilage
Fibrous cartilage
Where is hyaline cartilage found?
Larynx, trachea, throat, nose
Joints where the surfaces are articulating each other
Where would you find elastic cartilage in the body?
The outer ear
The epiglottis
The Eustachian tube
Where would you find fibrous cartilage in the body?
Intervertebral discs
Pelvis symphysis
The menisci of the knee joint
What is the function of hyaline cartilage?
Reduce friction
Absorb shock
What is the function of elastic cartilage?
Provide shape and support
What is the function of fibrous cartilage?
Provide rigidity
Absorb shock
Bone is formed through which process?
Ossification
Ossification can take on two forms depending on which type of bone is forming. What forms can bone take?
Flat bone
Long bone
Short bone
Irregular bone
What are 4 examples of flat bone?
Skull, scapula, ribs, pelvis
Where would you find long bones?
Arms
Legs
Ossification that forms flat bones is known as what?
Intramembranous ossification
What is the type of ossification that forms long, short and irregular bone?
Endochondrial ossification
What cells differentiate in intramembranous ossification to give osteoblasts?
Where are these cells found?
Mesenchymal Stem Cells
In the embryonic fibrous connective tissue
Osteoblasts lay down what?
Osteoid
What happens to osteoblasts once they are surrounded by osteoid?
They become osteocytes
What are formed when the osteoid calcifies?
It forms spicules which fuse to form trabeculae
What is the periosteum? How is it formed?
The fibrous sheet that covers the outer surface of bone and lays down connective tissue
Formed by condense mesenchyme
Intramembranous ossification also contributes to what important aspect of long bone formations?
What kind of growth is this?
Thickening
Appositional growth
After the formation of what structure are endochondrial and intramembranous ossification much the same?
Spicule
Osteoblasts and osteoclasts are important for which process?
Osteoblasts are responsible for what?
Osteoclasts are responsible for what?
Bone remodelling
Depositing new bone
Reabsorbing/break down already formed bone
Osteoclasts release what two things to contribute to the break down of bone?
Hydrogen ions
Lysosomal enzymes
What is the endosteum?
The fibrous sheet that lines the inner surface of all bones and lays down connective tissue
What kind of bone forms the external surfaces of bones?
Compact or cortical bone
What kind of bone forms a network of fine bony plates that combine strength with lightness?
Spongy or cancellous bone
Spaces within spongy bone are filled with what?
Bone marrow
What are the canals that run through the lamellae called?
Are they orientated longitudinally or transversely?
Haversians canals orientate longitudinally
Volkmann’s canals orientate transversely
What do Haversians and Voklsmann’s canals carry?
Blood vessels, lymph and nerves
How does immature bone differ from mature bone?
Immature bone has randomly arranged osteocytes
Mature bone has osteocytes arranged within the concentric lamallae of osteons
Where do reabsorption canals run in mature bone?
Parallel with the osteons’ long axis
What do you call the functional unit of compact bone?
An osteon
Osteocytes have slender cytoplasmic processes called what?
What is their function?
Canaliculi
Connect adjacent osteocytes via their gap junctions to allow nutrients to pass between them
Spongy (cancellous) bone does not have what structures that compact (cortical) bone does?
Haversian canals
Volksmann’s canals
Bone is composed of: 65% \_\_\_\_\_\_\_\_\_\_ 23% \_\_\_\_\_\_\_\_\_\_ 10% \_\_\_\_\_\_\_\_\_ 2% \_\_\_\_\_\_\_\_\_\_\_
mineral
type 1 collagen
water
non-collagen protein
What features of bone help them to resist fractures?
Great tensile and compressive strength
Degree of flexibility
The lamellae of bone are thought to be able to do what before excessive load causes fracture?
Slip relative to each other
What are the 4 stages of bone fracture repair?
- Haematoma formation
- Fibrocartilaginous callus formation
- Bony callus formation
- Bone remodelling
What happens to form the haematoma in the initial stage of bone fracture?
Blood vessels in the bone and periosteum break and a clot forms
What happens during stage two of bone fracture repair?
Fibrocartilagenous callus forms
New blood vessels infiltrate the fracture haematoma
The bony callus is made up of what type of bone?
Spongy (Cancellous) bone
What type of ossification occurs during the final stages of fracture repair?
Both endochondrial ossification and intramembranous ossification
If a fracture involves loss of bone fragments, then what is not possible? What can be done in this case?
Bony callus formation
Bone graft
What is osteoporosis?
A metabolic bone disease in which mineralized bone is decreased in mass to the point that it can no longer provide mechanical support
Osteoporosis associated with ageing results from what?
Incomplete filling of bays formed by osteoclasts
Osteoporosis is a risk factor for what in the elderly?
Bone fractures
Primary osteoporosis exists in two types, what are they?
Type 1: Postmenopausal women, increased osteoclast number as a result os oestrogen withdrawal
Type 2: Elderly individuals, attenuated osteoblast function occuring after the age of 70
Name 5 risk factors for osteoporosis
Genetics Insufficient calcium intake Insufficient calcium absorption and vitamin D Exercise Cigarette smoking
Cartilage is an avascular tissue make up of what?
Extracellular matrix
Chrondrocytes
Cartilage contains a large ratio of what in relation type I collagen which means that it is able to readily diffuse substances between chondrocytes and blood vessels surrounding the cartilage?
Glycosaminoglycans (GAGs)
There is a large amount of what substance in the ECM of cartilage which aids its resilience to repeated application of pressure?
Hyaluronic acid
A proteoglycan monomer is made up of what?
Approximately 100 glycosaminoglycans joined to a core protein
Describe the structure of the cartilage ground substance based on the arrangement of proteoglycan momomers, hyaluronic acid and collagen fibrils
The proteoglycan monomers are attached to hyaluronic acid molecules which form linear aggregates and are interwoven with a network o collagen fibrils
What feature of the hyaluronate proteoglycan aggregate enable it to form a hydrated gel?
The high density of negative charges on the GAGs which attracts water
Which type of cartilage is the most abundant in the body?
Hyaline cartilage
What is the composition of hyaline cartilage?
In terms of matrix proteins
A matrix containing:
proteoglycans
hyaluronic acid
Type II collagen
The hyaluronate proteoglycan aggregates are bound to the fine collagen matrix fibres
What is the composition of elastic cartilage?
A matrix like hyaline cartilage with the addition of many elastic fibres and elastic lamellae
What is the composition of fibrocartilage?
The same matrix material of hyaline cartilage with abundant Type I collagen
Fibrocartilage is a cross between what and what?
Dermis and hyaline cartilage
Hyaline cartilage contains what type of cells?
Only chondrocytes
Briefly describe hyaline cartilage development
Chondrocytes form isogenous groups and lay down extracellular matrix as they separate and elaborate
In early fetal development hyaline cartilage is the precursor for what? What process creates this?
Bone
Endochondrial ossification
As long bone develops some hyaline cartilage remains where?
At the articulating surface (end of bones)
At the epiphyseal plate until growing ceases
What covers the margin of hyaline cartilage?
Perichondrium
What is the perichondrium made up of?
Fibroblast-like cells which can develop into chondroblasts and further develop into chondrocytes
The perichondrium is a _______ connective tissue
dense
Growth from the periphery is known as what?
Appositional growth
Chondrocytes deeper in the cartilage may divide and give rise to isogenous groups which deposit matrix that results in what kind of growth?
Interstitial growth
Interstitial growth is growth in ________
Length
Appositional growth is growth in _________
Thickness
Each chondrocyte lies in a ________. The pleural or this is ________
Lacuna
Lacunae
What will determine how much ECM the chondrocyte lay down?
Forces applied to them (Pressure loads)
In developing bones, hyaline cartilage will do what?
Ossify
In developing bones, what is there at the non-articulating surfaces that there is a lack of at the articulating surfaces
Perichondrium
The end of a long bone is known as the what?
Epiphysis
The shaft of a long bone is known as the what?
Diaphysis
What is the portion of the bone in-between the epiphysis and diaphysis known as?
Metaphysis
Unlike hyaline cartilage, elastic cartilage does not do what with age?
Calcify
What cell types are found in fibrocartilage?
Chondrocytes
Fibroblasts
Fibrocartilage is a combination of what?
Dense regular connective tissue and hyaline cartilage
There is no ___________ in fibrocartilage
perichondrium
Fibrocartilage contains type ___ cartilage which is not found in hyaline and elastic cartilage
Type I
What is the name given to the process in which a hyaline cartilage template is replaced by bone
Endochondrial ossification
What is the synovial joint?
A moveable joint in which the opposed bone ends are:
- Covered in hyaline cartilage
- Within lubricating synovial fluid bounded by an articular capsule, lined by a synovial membrane and reinforced with fibrous tissue and ligaments
The synovial membrane consists of what cells which remove debris from the joint space?
Macrophages
Which cells are responsible for secreting synovial fluid in the synovial joint?
Fibroblast-like cells
The fibrous capsule of the synovial joint is continuous with what structure of bone?
Periosteum
What is the difference between osteoporosis and osteomalacia?
Osteoporosis is loss of bone density whereas osteomalacia is loss of bone mineral leading to softening of the bone