Bone and Cartilage Flashcards

1
Q

What are the two different skeletons?

A

Axial skeleton: skull, rib cage, vertebrae of the spine

Appendicular skeleton: limbs and pelvis

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2
Q

What are the types of bones and what is their specific function?

A

Flat: protect organs and haemopoeisis
Long: framework for movement and haemopoeisis

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3
Q

What are the two types of bone marrow and what are their specific functions?

A

Red: haemopoeisis
Yellow: fat storage

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4
Q

What are the layers of the outer shell of bone?

A

Outer shell: (compact bone)
Periosteum (vascular connective tissue)
Circumferential lamellae
Osteons (made of concentric lamellae)
Interstitial lamellae (lamellae between osteons)
Volkmanns canal (connect Haversian canals in osteons)
Forms compact bone

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5
Q

What is the inner trabeculae made of?

A

Network of bone fibres (osteocytes between lamellae)
Marrow
Forms cancellous (spongy) bone

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6
Q

What are osteons made of?

A

Concentric lamellae:
Osteocytes occupy spaces called lacunae
Osteocytes extend processes through canaliculi (microcanals) to communicate with each other (connect via gap junctions)
Haversian canals:
Arteries, veins, lymph vessels and nerve fibres

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7
Q

What is bone matrix made of and what are their specific functions?

A
Osteoid - Organic for tensile strength:
Proteins (osteocalcin and osteopontin)
Type I collagen
Hydroxyapatite - Inorganic for rigidity and density:
Calcium phosphate crystals
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8
Q

What are the functions of the various bone cells?

A

Osteoprogenitor: become osteoblasts (osteoclasts come from monocytes)
Osteoblasts: secrete type I collagen, proteins, alkaline phosphatase (becomes hydroxyapatite)
Osteoclasts: secrete tartrate resistant acid phosphatase (resorbs bone)

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9
Q

What are the hormones that control bone development?

A

Resorption: (increases osteoclast activity)
Parathyroid hormone (PTH) and Calcitriol:
Increases the absorption of Ca2+ in intestines and kidneys
Build-up: (increases osteoblast activity)
Calcitonin:
Decreases the absorption of Ca2+ in intestines and kidneys

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10
Q

What is cartilage and what are some of it’s main features?

A

Connective tissue in which chondrocytes lie
Avascular
Aneural
High ratio of GAG’s : Type II collagen (readily diffuses)

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11
Q

What are chondrocytes and what are their specific function?

A
Fibroblast-like cells in the perichondrium become chondroblasts and eventually chondrocytes (lying in lacunae)
Secretes and maintains Extracellular matrix
Secretes collagen (strength) and elastin (flexibility)
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12
Q

What is the main components of cartilage?

What are the three types of cartilage and their specific function?

A

Extracellular Matrix and Type II collagen
Hyaline: reduce friction and absorb shock (articulated/non-articulated)
Elastic: provide shape and support (mix of hyaline and many elastic fibres)
Fibrocartilage: rigidity, absorb shock and resist shearing (mix of hyaline and dense regular CT - contains fibroblasts secreting type I collagen)

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13
Q

What are:
Ligaments
Tendons
Joints

A

Ligaments: connections between bones
Tendons: connections between bone and muscle
Joint: point where bones articulate

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14
Q

What is perichondrium?

Where is it absent?

A

Dense, irregular connective tissue that acts as a membrane around cartilage
Absent in fibrous and articulated hyaline

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15
Q

What directs the synthetic activity of chondrocytes?

A

Pressure loads applied to cartilage create: mechanical, electrical, chemical signals

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16
Q

What is endochondrial ossification?

What is intramembrous ossification?

A

Endochondrial:
Replacement of cartilage with bone

Intramembrous:
Formation of bone from mesenchymal cells

17
Q

What are the stages in endochondrial ossification and what bones are developed in this way?

A

Long bone development:

1) Collar of peristeal (pre-periosteum) bone develops from perichondrium around the cartilage model
2) Primary ossification centre forms in the diaphysis and a nutrient artery penetrates to deposit osteogenic cells (which differentiate into osteoblasts and secrete osteoid)
3) Chondrocytes switch from secreting collagen/elastin and ECM and start secreting alkaline phosphatase
4) Alkaline phosphatase begins to calcify the osteoid forming trabeculae of spongy bone (medulla becomes inner cancellous bone)
5) Secondary ossification centres form in the epiphysis and nutrient arteries penetrate (ossification begins in the epiphytes)
6) Cartilage between epiphysis and diaphysis is now the epiphyseal growth plate and is ossified when the ossification centres meet
7) Hyaline cartilage persists at the ends

18
Q

What are the five zones of the epiphyseal growth plate and what is happening at each of them?

A

Zone of reserve (resting cartilage): no cellular proliferation or matrix production
Zone of proliferation: chondrocytes undergo Mitosis to produce stacks and secrete matrix
Zone of hypertrophy: chondrocytes grow, secrete alkaline phosphatase while the matrix is compressed between the stacks
Zone of calcification: chondrocytes degenerate leaving lacunae and spicules
Zone of resorption: osteogenic cells invade region, differentiate into osteoblasts and secrete osteoid forming bone

19
Q

What is appositional growth and what is interstitial growth?

A

Appositional growth: fibroblasts in the perichondrium develop into chondroblasts and widen the cartilage
Interstitial growth: chondroblasts divide and form isogenous groups, secrete ECM and separates becoming chondrocytes

20
Q

What are the stages in intramembrous ossification and what bones are developed in this way?

A

Mesenchymal Stem Cells (MSC’s) form a tight cluster (nidus)
MSC’s differentiate into osteoprogenitor cells which become osteoblasts (with more Golgi and ER)
Osteoblasts secrete osteoid and mineralisation causes them to form spicules
Further growth fuses the bone spicules to form trabeculae
Trabeculae interconnect to form woven bone which is eventually replaced by lamellar bone to form compact bone

21
Q

What is the difference between mature bones and immature bones?

A

Mature:
Osteocytes arranged in concentric lamellae (osteons)
Resorption canals (Haversian canal) run parallel to osteons
Immature:
Osteocytes arranged randomly
Resorption canals run through gaps in matrix

22
Q

What is the structure of the cutting cone?

A

Osteoblasts sit behind the osteoclasts in the closing cone, the osteoclasts in the closing cone:
Osteoblasts secrete osteoid forming new bone
Osteoclasts secrete H+ and lysosomal enzymes

23
Q

How do osteons branch and terminate?

A

Successive generations of Haversian systems made by cutting cones misalign the osteons forming branches and eventually terminating

24
Q

What are the three types of joints?

A

Synarthroses (immovable)
Amphiarthroses (slightly moveable)
Diarthroses (moveable/synovial)

25
Q

How do bones resist breaking?

A

Bone has great tensile strength due to collagen fibres
Bone can be compressed because of the ECM
Bone has some degree of flexibility
Bone can resist shearing because the lamellae can slip next to each other

26
Q

What happens when bone breaks?

A

Haematoma forms where the periosteum and blood vessels break, causing inflammation
Bone tissue at fracture die (no blood supply) and is removed by phagocytes and osteoclasts
Blood vessels infiltrate the haematoma and soft callus of granulation tissue (rich in capillaries + fibroblasts) forms
Fibroblasts form chondroblasts which secrete collagen to form a fibrocartilage splint
Osteoblasts from the inner endosteum and outer periosteum form a hard callus from new trabeculae (by endochondrial and intramembrous ossification)
The bone then undergoes remodelling by the osteoclasts and osteoblasts replacing lamellar bone with compact bone and any swollen material is removed by osteoclasts

27
Q

What is osteoporosis?

A

Decrease in bone mass due to resorption > formation (incomplete filling of osteoclast resorption bays)
Increasing the likelihood for fractures and providing inadequate mechanical support

28
Q

What is Type I osteoporosis?
What is Type II osteoporosis?
What are some other risk factors?

A

Type I: post-menopausal women (increase in the number of osteoclasts due to oestrogen withdrawal)
Type II: elderly (decrease in the osteoblast activity)
Genes
Intake of Ca2+
Inactivity

29
Q

What is the structure of a synovial joint?

A

Surrounded by articular capsule (continuous periosteum)
Synovial Membrane surrounds synovial cavity (filled with synovial fluid)
Synovial Membrane contains macrophages and cells that secrete synovial fluid
Hyaline articulated cartilage surrounds the ends of articulating bones

30
Q

Describe what osteoarthritis is and rheumatoid arthritis

A

Osteo: degeneration of the (hyaline) articular Cartilage and loss of the synovial cavity (bone rubs against bone)

Rheumatoid: autoimmune inflammation of the synovial Membrane causing swelling of the capsule