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Body Logistics > Cartilage And Bone > Flashcards

Cartilage And Bone Flashcards

1
Q

What is Cartilage?

A

An avascular tissue that consists of an extensive extracellular matrix in which lie chondrocytes

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2
Q

What do chondrocytes do?

A

Produce and maintain the extracellular matrix

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3
Q

Explain the properties of extracelllar matrix in cartilage

A
  • large ratio of GAG’s to type II collagen permits ready diffusion of substances between chondrocytes and surrounding blood vessels
  • ECM is solid and firm but also pliable to is resilient to repeated pressure
  • large amount of hyaluronic acid in ECM attracts water
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4
Q

What are the three types of cartilage?

A

Hyaline
Elastic
Fibrocartilage

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5
Q

What cells are found in hyaline cartilage?

A

Chondrocytes only.

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6
Q

How are chondrocytes found in hyaline cartilage?

A

Present singly or in clusters called isogenous groups.

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7
Q

Why are chondrocytes found in isogenous groups?

A

If they have recently divided

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8
Q

Do chondrocytes in isogenous groups stay together?

A

No, they separate as they lay down ECM.

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9
Q

Hyaline cartilage is the model for what in early fetal development?

A

Bones which develop by echondral ossification.

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10
Q

Where can hyaline cartilage be found in the adult body?

A

Long bones retain some at their articulating surface and at the epiphyseal growth plate until growth ceases

It is also found in parts of the rib cage, nose, trachea, bronchi and larynx.

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11
Q

What is perichondrium?

A

A dense connective tissue which covers the margin of hyaline cartilage

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12
Q

What kind of cells does perichondrium contain?

A

Many elongate, fibroblast like cells which can develop into chondroblasts and then to chondrocytes.

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13
Q

What is appositional growth?

A

The fibroblast like cells of the perichondrium give rise to chondroblasts -growth from the periphery

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14
Q

What is interstitial growth?

A

Deposition of matrix by isogenous groups which causes the cells to separate.

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15
Q

What is the difference between territorial and inter territorial matrix?

A

Territorial surrounds isogenous groups and is more highly sulphated. Interterritorial is

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16
Q

What does each chondrocyte lie inside?

A

A lacuna

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17
Q

Where does new bone originate from in a non-adult?

A

The epiphyseal growth plate

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18
Q

What are the three parts of a long bone?

A

The epiphysis- region above EGP
metaphysis-region directly below the EGP
diaphysis-region along shaft of bone

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19
Q

What is the difference between elastic cartilage and hyaline cartilage?

A

Elastic cartilage contains many elastic fibres in the extracellular matrix giving it elasticity in addition to the resilience characteristic of hyaline.

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20
Q

Does elastic cartilage calcify?

A

No

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21
Q

Where is elastic cartilage found?

A

In the external ear (pinna), the external acoustic meatus, the epiglottis and the eustachian tube.,

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22
Q

Which cell types are found in fibrocartilage?

A

Chondrocytes and fibroblasts

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23
Q

What is fibrocartilage a mixture of?

A

Dense regular connective tissue and hyaline cartilage

24
Q

What is special about the arrangement of cells in fibrocartilage?

A

They are often seen to be distributed in rows

25
Q

Which cells are found in the perichondrium of fibrocartilage?

A

It has no perichondrium- trick question ;)

26
Q

Where can fibrocartilage be found?

A

Intervertebral discs, articular discs of the sternoclavicular and temporomandibular joints, the menisci of the knee joint and in the pubic symphysis.

27
Q

What are the properties of fibrocartilage relating to its role?

A

It has the resilience to act as a shock absorber and to resist shearing forces

28
Q

What is echondral ossification?

A

The replacement of a pre-existing hyaline cartilage template by bone and is the way in which most of the bones of the body develop

29
Q

How do long bones develop by echondral ossification?

A
  1. Inital cartilage model
  2. collar of periosteal bone in shaft
  3. central cartilage calcifies. Nutrient artery penetrates, supplying bone depositing osteogenic cells. Primary osification centre formed.
  4. Medulla becomes cancellous bone, cartilage forms EPG plates. Epiphyseal develop secondary centres of osification.
  5. epiphyses ossify and growth plates continue to move apart.
  6. epiphyseal growth plates replaced by bone. Hyaline articular cartilage persists.
30
Q

How does the shaft of a bone elongate?

A

Cartilage grows at the EPG plate and is replaced by bone in the metaphysis.

31
Q

How do bones lengthen?

A

At the epiphyseal growth plate exists a region of reserve cartilage with no cellular proliferation or active matrix production.
Below lies a zone of proliferation where cells actively divide to form columns. Cells also enlarge and secrete matrix
Below lie a zone of hypertrophy where cells enlarge greatly and matrix is compressed into linear bands between cell columns.
Below lies a zone of calcified cartilage where enlarged cells begin to degenerate and the matrix calcifies.
Below lies a zone of resorption where the calcified matrix is in contact with the marrow cavity. Small blood vessels and connective tissue invade the region occupied by the dying chondrocytes, leaving the cartilage as spicules between them. Bone is laid down on these cartilage spicules.

32
Q

What is the difference between osteoblasts and osteoclasts?

A

Osteoblasts lay down new bone- osteoclasts resorb bone by the release of enzymes and acid.

33
Q

What is a synovial joint?

A

A moveable joint in which the juxtaposed bone ends are covered by hyaline or fibrocartilage and lie within lubricating synovial fluid, a synovial membrane and a fibrous capsule(continuous with the periosteum) which make up the articular capsule, reinforced with fibrous tissue and ligaments.

34
Q

Which cells can be found in the synovial membrane?

A

Macrophages-remove debris from the joint space

Fibroblast like cells-thought to secrete the synovial fluid.

35
Q

How do most flat bones develop?

A

Intracellular membranous ossification- in contrast to echondral ossification some bones develop directly from mesenchymal tissue.

36
Q

Which bones develop by intramembranous ossification?

A

Flat bones-skull, clavicle, scapula, pelvic bones (some echondral ossification here too)

The process also contributes to the thickening of long bones at their periosteal surfaces

37
Q

What are the different stages of intramembranous ossification?

A

A small cluster of mesenchymal stems cells (MSCs) form a tight cluster of cells ( a nidus)
The MSCs become osteoprogenitor cells (developing more GA and RER)
The osteoprogenitor cells become osteoblasts and lay down ECM containing type I collagen (osteoid)
The osteoid mineralises to form rudimentary bone tissue spicules which are surrounded by osteoblasts and contain osteocytes
The spicules join to form trabeculae which merge to from woven bone, which is finally replaced by the lamellae of mature compact bone.

38
Q

What is special about one of the organelles in osteoclasts?

A

They are multinucleated.

39
Q

What is a haversian canal?

A

A channel running through the centre of an osteon supplying it with blood, lymphatics and nerves

40
Q

What is a volkmanns canal?

A

A channel running in between adjacent osteons carrying blood vessels, lymph vessels and nerves.

41
Q

What is the difference between immature bone and mature bone?

A

Immature bone has osteocytes which are fairly randomly arranged, mature bone has osteocytes arranged in concentric lamellae of osteons.

42
Q

How do osteocytes connect to one another?

A

The have slender cytoplasmic processes which reach out to those of adjacent osteocytes via canaliculi. These processes connect via gap junctions so that nutrients can be passed between them.
The canaliculi are believed to connect with the central haversian canal.

43
Q

What is the difference between compact bone and spongy bone?

A

Osteocytes still lie between lamellae however are arranged into trabeculae rather than parallel aligned osteons and also have no haversian or volkmanns canals. Osteoblasts are arranged around the outside of the trabeculae with the occasional osteoclasts.

44
Q

What is a cutting cone?

A

Boring a tunnel through the bone by the action of osteoclasts- which release H+ ions and lysosomal enzymes

45
Q

What property of compact bone enables it to resist fracture?

A

It has great tensile and compressive strength but also a degree of flexibility- this is due to the lamellae being able to slip relative to each other before excessive load causes fracture.

46
Q

How is a haematoma formed?

A

Blood vessels in bone and periosteum break, forming a mass of clotted blood (haematoma)

47
Q

Why are macrophages present soon after haematoma formation?

A

Bone cells at the fracture edge die due to loss of blood supply, so swelling and inflammation occur
Phagocytic cells and osteoclasts begin to remove dead and damaged tissue
Macrophages will eventually remove the blood clot.

48
Q

How is a fibrocartilaginous callus formed?

A

New blood vessels infiltrate the fracture haematoma

A procallus of granulation tissue ( tissue rich in capillaries and fibroblasts) develops.

49
Q

What is the purpose of the procallus of granulation tissue?

A

Fibroblasts produce collagen fibres that span the break. Others differentiate into chondroblasts that give rise to a sleeve of hyaline cartilage
This matrix also splints the broken bone

50
Q

How is the bony callus formed?

A

Osteoblasts from the nearby periosteum and endosteum and multi potent cells from the bone marrow invade the fracture site and begin bone reconstruction by forming trabecular bone (spongy bone)

Hence new bone trabeculae begin to appear in the fibrocartilaginous callus- this in turn is converted into the bony callus of cancellous bone.

51
Q

How is bony callus replaced by cancellous bone?

A

Echondral ossification and intramembranous ossification

52
Q

What is the final stage of fracture repair and how does it work?

A

Bone remodelling- the callus of cancellous bone begins to be remodelled into compact bone especially in the cortical region.
The material bulging from the outside of the bone and inwards into the medullary activity is removed by osteoclasts

The final shape of the remodelled area is the sane as that of the unbroken bone because it responds to the same set of mechanical stressors.

53
Q

Bone graft types:-

A

Autograft-donor is recipient
Homograft-donor is different human (foreign rejection possible)
Heterograft-donor is different species

54
Q

What is osteoporosis?

A

A metabolic bone disease in which mineralised bone is decreased in mass to the point that it no longer provides adequate mechanical support

55
Q

What is the basic cause of osteoporosis?

A

More resorption by osteoclasts than laying down by osteoblasts- causes trabeculae to become attenuated

56
Q

What are the different types of osteoporosis?

A

Type 1- occurs in postmenopausal women and is due to an increase in osteoclasts number as a result of oestrogen withdrawal.

Type 2- occurs in elderly of both genders and is caused by attenuated osteoblast function

57
Q

Osteoporosis risk factors

A

Genetics- peak bone mass higher in blacks that in white or asians.

Insufficient calcium intake
Insufficient calcium absorption and vitamin D
Exercise-immobilization of bone leads to accelerated bone loss
Cigarette smoking in women

Body Logistics (6 decks)

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