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Tissues of the Body > Lecture 4.1: Cartilage and Bone > Flashcards

Lecture 4.1: Cartilage and Bone Flashcards

1
Q

What is Cartilage?

A

A form of connective tissue

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2
Q

Where is Cartilage found?

A

In nearly all joints

In structures that must be deformable and strong

Cartilage forms a template for the development of many bones in utero

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3
Q

General characteristics of Cartilage

A

Pliant
Resists compression
Avascular
Not innervated
Comprised of two cell types: chondroblasts and chondrocytes which produce
ECM

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4
Q

Types of Cartilage (3)

A

1) Hyaline Cartilage
2) Elastic Cartilage
3) Fibrocartilage

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5
Q

Hyaline Cartilage

A

ECM contains:
- Proteoglycans
- Hyaluronic acid
- Type II collagen

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6
Q

Elastic Cartilage

A

Similar to hyaline cartilage

But it also contains many elastic fibres

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7
Q

Fibrocartilage

A

Similar to hyaline cartilage

But matrix contains abundant type I collagen fibres

Comprised of dense regular connective tissue and hyaline cartilage

Contains fibroblasts and chondrocytes

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8
Q

Location of Hyaline Cartilage

A

Articular cartilage covers the ends of most bones and movable joints

Costal cartilages connect ribs to sternum

Larynx and trachea

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9
Q

Features of Hyaline Cartilage

A

It is is covered by a fibrous perichondrium (except at the articular surfaces of synovial joints)

Large amounts of hyaluronic acid means that hyaline cartilage is well hydrated

It is pliable and resilient under pressure

Large ratio of GAGs to collagen in the ECM facilitates diffusion of substances between chondrocytes and blood vessels surrounding the cartilage

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10
Q

Articular Cartilage has no perichondrium. Where does it get its nutrients from?

A

The surrounding joint fluid

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11
Q

The Extracellular Matrix (ECM) of Hyaline Cartilage

A

Comprised of type II collagen, water and ground substance (GAGs such as
hyaluronic acid and proteoglycans)

Hyaluronate proteoglycan aggregates are resistant to deformation

Negative charges on surface of GAGs strongly attract polarised H2O molecules forming a hydrated gel.

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12
Q

Appositional Growth

A

The increase in the diameter of bones by the addition of bony tissue at the surface of bones

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13
Q

Interstitial Growth

A

Interstitial growth is a bone growth which results in the lengthening of the bone

This growth occurs within the lacunae

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14
Q

Perichondrium

A

A dense layer of fibrous connective tissue that covers cartilage

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15
Q

Osteoarthritis

A

The most common form of arthritis, prevalence increasing with age

Results from focal and progressive hyaline articular cartilage loss with changes in underlying bone; Soft tissue structures in and around the joint also affected

Severe joint injury has a high likelihood of eventual osteoarthritis, likewise obesity increases the risk.

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16
Q

Growth Plates

A

Hyaline cartilage forms epiphyseal growth plates at the metaphysis of bones

This is where chondrocytes undergo a sequence of cell division and hypertrophy, followed by death and ossification by invading osteoblasts

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17
Q

Locations of Elastic Cartilage

A

External ear (pinna)
External acoustic meatus
Auditory tube
Epiglottis

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18
Q

Locations of Fibrocartilage

A

• Intervertebral discs
• Articular discs of the sternoclavicular and
temporomandibular joints
• Menisci of the knee
• Pubic symphysis
• Entheses (between tendon and bone)

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19
Q

Fibrocartilage in an Intervertebral Disc

A

Annulus fibrosus (tough circular exterior of the intervertebral disc), chondrocyes in lacunae are embedded in large bundles of type I collagen fibres

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20
Q

Meniscal Damage

A

The menisci of the knee are formed of fibrocartilage discs separating femur and tibia.

Menisci prevent degeneration of articular cartilage underneath

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21
Q

Meniscal Damage: Most Common Causes

A

Sports-related injuries are most common cause of meniscal lesions in young people

Long-term degeneration from use is most common cause of meniscal lesions from middle-age

22
Q

Features of Bones

A

• Strength and rigidity enables forceful muscle
contractions to result in movement
• Provides protection for internal structures
• Highly vascular and innervated
• Adapts to changing mechanical demands
• Regenerates following injury
• Mineral storage
• Blood cell formation

23
Q

Divisions and Classifications of Bones

A

1) Axial skeleton
2) Appendicular skeleton
3) Shapes of Bones

24
Q

Divisions and Classifications of Bones: Axial Skeleton

A

Skull
Vertebral column
Ribs
Sternum
Hyoid

25
Q

Divisions and Classifications of Bones: Appendicular Skeleton

A

Everything else except Skull, Vertebral column, Ribs, Sternum, Hyoid

26
Q

Divisions and Classifications of Bones: Shapes of Bones

A

Long
Short
Flat
Irregular
Sesamoid
Pneumatic

27
Q

Bone Composition

A

Inorganic: calcium hydroxyapatite crystals give strength

Organic: type I collagen confers flexibility and resistance to stress

28
Q

Types of Mature Bone Structure

A

Cancellous (spongy) bone is light and provides spaces for bone marrow

Compact (cortical) bone forms external surfaces and constitutes 80% of skeletal mass.

29
Q

Organisation of Cortical Bone

A

Osteon (lamellar structure provides slippage panes, allowing a degree of deformation)

Haversian (central) and Volkmann’s (perforating) canals carry blood vessels, lymph vessels and nerves

Cortical bone is surrounded the periosteum

30
Q

Structures within an Osteon

A

Osteocyte in lacuna

Canaliculi (Osteocytes have very slender cytoplasmic processes that reach out to adjacent osteocytes)

Haversian (or central) canal

Lamella of adjacent osteon

31
Q

Cancellous (Spongy) Bone

A

Osteocytes reside in lacuna between lamellae (which are more irregular)

Arranged in trabeculae

Space for Adipose (yellow marrow) and haemopoietic cells (red marrow) between trabeculae

Type 1 Collagen

32
Q

Internal Trabeculae Structure

A

Osteocytes

Osteoclasts

Interstitial Lamellae

Osteoblasts aligned along trabeculae of new bone

33
Q

How much bone is turned annually?

A

5-10% of adult bone turns-over annually

34
Q

Bone Remodelling Unit Components

A

A cutting cone of osteoclasts

A reversal zone containing osteoprogenitors

A closing cone where osteoblasts secrete the organic components of bone (osteoid)

This process is accompanied by angiogenesis (formation of new blood vessels)

35
Q

What factors affect bone remodelling?

A

Largely dictated by the mechanical loading applied to bone

Bone resorption increases when gravitational forces are reduced

Age (rate of remodelling decreases)

Increased sport activity (can cause bone hypertrophy)

36
Q

How can bones resist fracture?

A

Due to balance between flexibility and rigidity

Lamellae are able to “slip” relative to each other to help disperse forces

Fractures occur when the forces applied are too strong

37
Q

Stages of Fracture Repair (4)

A

1) Haematoma: Torn vessels bleed, forming a blood clot

2) Soft (fibrocartilage) callus: Clot is removed by macrophages and replaced
by a mass of procallus tissue comprised of fibroblasts and collagen

3) Hard (bony) callus: Callus is invaded by blood vessels and osteoblasts.
Fibrocartilage is gradually replaced by woven bone.

4) Remodelling: Woven bone remodelled as compact and spongy bone

38
Q

Osteogenesis/ Ossification

A

It is when new bone is formed

39
Q

Endochondral Ossification

A

A pre-existing hyaline cartilage template is replaced by bone

Osteoblasts from circulating osteoprogenitors invade the cartilage, depositing
osteoid (protein matrix) as a substrate for calcification

Most of the bones of the body develop in this way

40
Q

What is the Osteoid?

A

The organic component of bone

Largely comprised of type I collagen (secreted by osteoblasts)

Undergoes calcification as hydroxyapatite crystals become embedded between collagen fibres

41
Q

Intramembranous Ossification

A

Bone formation takes place within condensations or “membranes” of mesenchymal tissue

Osteoblasts differentiate from local mesenchymal stem cells and deposit osteoid

Most flat bones develop in this way

42
Q

Bone formation in a 14 week foetus: what stain?

A

Alizarin Red

43
Q

Diaphysis

A

Shaft or central part of a long bone

44
Q

Epiphysis

A

The expanded end of the long bones in animals

45
Q

Metaphysis

A

The wide portions of long bones and the regions of the bone where growth occurs

46
Q

Medullary Cavity

A

The hollow part of bone that contains bone marrow

47
Q

Epiphysis of an adult long bone

A

Epiphyseal growth plates of long bones are no longer visible after the cessation of growth

48
Q

Endochondral Ossification in Utero (1ary)

A

1) Skeletal elements are initially composed of hyaline cartilage

2) Late in the 1st trimester, a bone collar develops around the diaphysis long bone, with degeneration of underlying cartilage

3) Invasion of capillaries and osteoprogenitors create a
primary ossification centre; Osteoid undergoes calcification to form woven bone

49
Q

Endochondral Ossification in Adolescence (2ndary)

A

4) Secondary ossification centres appear in the epiphyses around the time of birth

5) In childhood, primary and secondary ossification centres are separated by the epiphyseal growth plate that allows elongation

6) No further elongation can occur when the growth plates close, but an osteoblast reservoir in the periosteum allows thickening

50
Q

Appositional Growth

A

Occurs when chondroblasts secrete new matrix along existing surfaces and this causes the cartilage to expand and widen

51
Q

Interstitial Growth

A

Chondrocytes secrete new matrix within the cartilage and this causes it to grow in length

Tissues of the Body (18 decks)

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