Session 4 : Cartilage and bones Flashcards
1
Q
What are bone and cartilage examples of?
A
Specialised connective tissue
2
Q
What is cartilage an example of?
A
Cartilage is a form of connective tissue.
3
Q
Where can cartilage be found?
A
It can be found at nearly all joints and in structures which must be deformable and strong.
4
Q
What are some of the qualities of cartilage?
A
Cartilage is pliant (flexible) and resistant to compression.
5
Q
Describe some of the general features of cartilage.
A
- Avascular and not innervated
- Chondroblasts & chondrocytes
- Pliant & resistant to compression, deformable but strong
6
Q
Cartilage forms a _____ for the development of many _____ in utero.
A
Cartilage forms a template for the development of many bones in utero.
7
Q
List the three types of cartilage.
A
Hyaline, elastic, fibrocartilage (HEF)
8
Q
What type of collagen is found in hyaline cartilage?
A
Type II collagen
9
Q
What type of collagen is found in fibrocartilage?
A
BOTH type I and type II collagen fibres
10
Q
What is one quality of elastic cartilage?
A
Contains many elastic fibres
11
Q
Where can hyaline cartilage commonly be found?
A
- Articular cartilages of joints
- Nose
- Costal cartilages
- Trachea
- Larynx
12
Q
Where can elastic cartilages commonly be found?
A
- External ear (pinna)
- Epiglottis
13
Q
Where can fibrocartilages commonly be found?
A
- Intervertebral discs
- Pubic symphysis
- Meniscus of knee
14
Q
What are some features of hyaline cartilage?
A
* Covered by perichondrium (fibroblasts & mesenchymal stem cells)
* Type II collagen in ECM
* Cells = chondroblasts & chondrocytes & fibroblasts in perichondrium
* Function = sliding of joints, model for bone growth in utero
15
Q
What does the ECM of the hyaline cartilage contain?
A
- **Type II collagen **
- Water
- Ground substance (GAGs such as hyaluronic acid & proteoglycans)
16
Q
What component of the ECM gives hyaline cartilage a feature which makes it ‘resistant to deformation’?
A
The hyaluronate proteoglycan aggregates
17
Q
Describe the structure of hyaline cartilage GROWTH (appositional and interstitial).
A
Appositional growth: Chondroblasts secrete new matrix along existing surfaces = expand and widen.
Interstitial growth: Chondrocytes secrete new matrix within the cartilage = grows in length.
18
Q
What is the difference between chondrocytes and chondroblasts?
A
- Chondroblasts = immature cartilage cells found **near the perichondrium **
- Chondrocytes = mature cartilage cells found embedded within the ECM
19
Q
Pressure and ___ applied to the cartilage - creates mechanical, electrical and chemical signals that ____ chondrocyte activity.
A
Pressure and stress applied to the cartilage - creates mechanical, electrical and chemical signals that increase chondrocyte activity.
20
Q
Which cartilage cells are involved in appositional growth of hyaline cartilage?
A
Chondroblasts in the perichondrium
21
Q
Which cartilage cells are involved in interstitial growth of hyaline cartilage?
A
Chondrocytes embedded in the ECM
22
Q
What is osteoarthritis (OA)?
A
- Most common type of arthritis.
- Results from focal and progressive hyaline articular cartilage loss with changes in the underlying bone.
23
Q
What are some risk factors for osteoarthritis (OA)?
A
- History of joint injury (e.g. fractures of articular surfaces, tears of menisci)
- Obesity
- Increasing age
24
Q
What condition is the most common reason for total knee and total hip replacement surgeries?
A
Osteoarthritis (OA)
25
What are epiphyseal growth plates in hyaline cartilage?
Location on hyaline cartilage where **chondrocytes** undergo **cell division and hypertrophy** - followed by **death** and **ossification by invading osteoblasts**.
26
What does ossification mean?
Bone formation
27
What type of epithelium is found in the epiglottis?
**Stratified squamous non-keratinised epithelium** lines one side of the epiglottis while **pseudostratified columnar epithelium** lines the other side of the epiglottis.
The elastic cartilage can also be found here.
28
What is the function of the elastin fibres within the elastic cartilage in the epiglottis?
These elastin fibres lying in the ECM of the elastic cartilage of the epiglottis confer elasticity as well as increased resilience.
29
What is the function of fibrocartilage?
- Cushioning
- Strength
- Resistance to tearing and compression
30
What is fibrocartilage comprised of (tissue, cartilage, cells)?
* Tissue: dense, regular connective tissue
* Collagen:** type I and type II** collagen
* Cells: fibroblasts, chondrocytes
* **NO perichondrium**
31
Does the fibrocartilage have a perichondrium?
No
32
What components of fibrocartilage give it the tensile shock-absorbing structure/strength?
Bundle of type I collagen fibres provide tough, shock absorbing structure
33
What type of cartilage are the discs of the menisci (knee joint) made from?
Fibrocartilage
34
What is the function of the menisci?
- **Shock absorption**
- Menisci **prevent degeneration of articular cartilage** underneath it
35
What are some common causes of meniscal damage?
1) Young people = sports-related injuries
2) Middle-aged people = long-term degeneration from extended use
36
What are some general features/functions of bone?
* **Strength & rigidity** = enabling forceful muscle contractions for movement
* **Protection** = internal structures are protected e.g. ribs protecting lungs
* **Highly vascular/innervated**
* Adapts to changing mechanical demands
* **Regenerates following injury **
* **Mineral storage** = calcium and phosphate
* **Blood cell formation in the bone marrow**
37
What are the divisions/classifications of bone?
* **Axial skeleton** = skull, vertebral column, ribs, sternum, hyoid
* **Appendicular skeleton **= everything else
38
Inorganic and organic component of bone
**Inorganic: Calcium hydroxyapatite** = strength
**Organic: Type I collagen** = flexibility & resistance to stress
39
What are the two types of mature bone structure?
**Cancellous (spongy) bone**: Light, provides space for bone marrow
**Compact (cortical) bone**: Forms external surfaces and constitutes 80% of skeletal mass
40
What are the different shapes of bones?
Long, short, flat, irregular, sesamoid, pneumatic
41
Give an example of a long bone?
Femur
42
Give an example of a sesamoid bone?
Patella
43
Give an example of an irregular bone?
Vertebral column
44
Give an example of a flat bone?
Sternum and skull
45
Give an example of a short bone?
Wrist and ankle (hands)
46
Describe the organisation of compact (cortical) bone.
**Osteon/Haversian systems** = functional unit of compact/cortical bone
**Haversian (central) and Volkmann's (perforating) canals** = carry blood vessels, lymph vessels and nerves
Cortical bone is surrounded by layer of fibrous connective tissue called the '**periosteum**'.
47
What is one feature of the osteons (functional unit in compact bone) that allow for degree of deformation?
**Lamellar structure of osteons** provides **SLIPPAGE PANES** which allows for a degree of deformation.
48
What are canaliculi in bone?
**Small canals running through the bone solid matrix **= hosting osteocyte's slender cytoplasmic processes (dendrites) and saturated by interstitial fluid rich in ions.
49
What is the name of the junction that allow adjacent osteocyte processes to connect, enabling the passage of nutrients between them?
**Gap junctions**
50
What are some features of spongy (cancellous) bone?
* No Haversian or Volkmann's canals
* Osteocytes reside in lacuna (gaps) between lamellae
* The lamellae are more irregular in spongy bone
51
What are the function of osteoblasts and osteoclasts in spongy (cancellous) bone?
Remodelling is provided by osteoblasts and osteoclasts, located on the surface of the trabeculae.
52
What stain can be used on decalcified spongy (cancellous) bone?
H&E stain as type I collagen is left behind
53
What can be found in the marrow of the spongy (cancellous) bone?
Adipose (yellow marrow)
Haematopoietic cells (red marrow)
54
What does a bone remodelling unit consist of?
**1) A cutting cone** = of osteoclasts
**2) A reversal zone **= containing osteoprogenitors
**3) A closing cone** = of osteoblasts which secrete organic components of bone (osteoid)
55
What is the function of osteoclasts?
Resorption (break down) of bone
56
What is the function of osteoblasts?
Build bone
57
What are osteocytes?
Mature osteoblasts that are embedded and maintain the bone matrix = but remain metabolically active
58
Cutting cone (H&E) photomicrograph
Note: the closing cone is smaller
59
What factors change the rate of bone remodelling?
• Mechanical loading applied to the bone (sensed by osteoclasts & their dendrites/processes) = higher the load = higher the bone remodelling rate
• Increased age = decreased rate
• Increased sport activity = bone hypertrophy, increasing cortical bone thickness (increased bone growth)
60
Why do bones resist fractures in general?
The balance between the **flexibility and rigidity of bone** allow it to resist fractures.
The **lamellae are able to 'slip' relative to each other to help DISPERSE forces applied to bone** (slippage planes).
However, when the forces applied are too strong - fractures can occur.
61
What are the stages of bone fracture repair?
1) **Haematoma **= Blood clot formed
2) **Soft fibrocartilage callus** = **clot removed by macrophages**, replaced by mass of **procallus tissue** (made up of fibroblasts & collagen)
3) **Hard/bony callus (callus ossification)** = callus invaded by blood vessels & osteoblasts. Fibrocartilage **gradually replaced by woven bone**.
4) **Bone remodelling** = the woven bone is remodelled as **compact and spongy bone**
62
What type of cartilage can be found in trachea?
Hyaline
63
What type of cartilage can be found in articulating surfaces of bones?
Hyaline
64
What type of cartilage can be found in menisci?
Fibrocartilage
65
What type of cartilage can be found in intervertebral discs?
Fibrocartilage
66
What type of cartilage can be found in epiglottis?
Elastic
67
What type of cartilage matrix is composed of type II collagen fibres with abundant GAGs to allow for diffusion of nutrients?
Hyaline
68
What type of cartilage matrix is composed of type II collagen, GAGs and elastic fibres?
Elastic
69
What type of cartilage matrix contains both type I and II collagen fibres?
Fibrocartilage
70
Identify the zones in this photomicrograph of a region of the epiphyseal growth plate.
Zone 1 = resting/reserved cartilage
Zone 2 = proliferating cartilage
Zone 3 = hypertrophing cartilage
Zone 4 = calcifying cartilage
Zone 5 = ossification
71
What is shown in the image?
Bone marrow
72
What is shown in the image?
Hyaline cartilage
73
What is shown in the image?
Decalcified bone (H&E)
74
What is shown in the image?
Elastic cartilage
75
What is shown in the image?
Mesenchyme
76
What is shown in the image?
Fibrocartilage
77
Does fracture repair occur by intramembranous ossification, endochondral ossification, or both?
Both
78
Does development of long bones occur by intramembranous ossification, endochondral ossification, or both?
Endochondral
79
Does development of flat bones (e.g., parietal) occur by intramembranous ossification, endochondral ossification, or both?
Intramembranous
80
Does development of skeleton in utero occur by intramembranous ossification, endochondral ossification, or both?
Both
81
Does development of vertebrae occur by intramembranous ossification, endochondral ossification, or both?
Endochondral
82
Immediate progenitors of cells that deposit cartilage?
Chondroblasts
83
Stem cells for all connective tissue (other than blood)?
Mesenchymal
84
Progenitors for macrophages?
Monocytes
85
Cells trapped in lacunae in cartilage?
Chondrocytes
86
Mature bone cells trapped in lacunae?
Osteocytes
87
Cells that deposit osteoid?
Osteoblasts
88
Fused macrophages that destroy bone?
Osteoclasts
89
Are the following features of compact bone, spongy bone, or both?
* Highest turnover rate = spongy bone
* Composed of type I collagen & calcium hydroxyapatite = both
* Covered by endosteum = spongy bone
* Lamellar organisation = both
* Covered by periosteum = compact bone
* Comprised of osteons = compact
* Niche for bone marrow = spongy bone
* Remodelled by action of osteoclasts & osteoblasts = both
* Contains osteocytes trapped in lacunae = both
* Trabecular organisation = spongy bone
90
Identify the following features of a sectioned long bone.
Section A = spongy bone
Section B = cortical bone
Section C = medullary cavity
91
(Immature) chondroblasts found in the...
Perichondrium
92
(Mature) chondrocytes found in the...
ECM
93
For what structures do Haversian canals provide channels?
The osteocytes
94
What name is given to the transverse canals that connect Haversian canals?
Volkmann's canals - transverse/horizontal or oblique canals. **Volkmann's canals interconnect Haversian canals**.
95
How are interstitial lamellae created?
It is laid down by the remnants of the old osteomyelitis cells and by osteoblasts which secrete matrix.
96
How does lamellar structure contribute to bone strength?
Organic and inorganic materials such as **collagen provide tensile strength** and **hydroxyapatite crystals with compressive strength**.
97
Tumours of the bone cells (osteosarcomas) are rare; however, tumours are commonly found in bone. Why is this?
Tumours constantly metastasise to bone.
98
Identify the bones provided and organise them by classification.
Flat - Sternum, cranial bones in the skull
Irregular - Vertebrae, sacrum, coccyx, ethmoid, hyoid
Long - Tibia, Fibula, Femur
Sesamoid - patella
Short - carpal bones in the hand that allow movement of the wrist
99
Identify the features A-C on this sectioned long bone.
In the following diagram of ground bone, which letter indicates a feature that provides channels for osteocyte communication? A = Canaliculi
During bone formation, osteocytes get connected with each other via a dense network of canaliculi within the mineralised bone matrix.
100
List the main differences between hyaline cartilage and fibrocartilage.
Hyaline cartilage has an extracellular matrix containing proteoglycans, hyaluronic acid and type II collagen.
101
What is the patella?
The patella is a short bone located in the knee joint.
102
What are carpal bones?
Carpal bones are short bones in the hand that allow movement of the wrist.
103
What feature provides channels for osteocyte communication in bone?
A = Canaliculi
## Footnote
Canaliculi are small channels that connect osteocytes within the mineralised bone matrix.
104
What are the main differences between hyaline cartilage and fibrocartilage?
Hyaline cartilage has an extracellular matrix containing proteoglycans, hyaluronic acid, and type II collagen. Fibrocartilage contains abundant type I collagen fibers in addition to these components.
105
What are the two features of fibrocartilage in a stained photomicrograph?
A = Chondrocytes
B = Type I collagen fibres
106
Compare spongy (cancellous) bone and compact (cortical) bone.
Spongy bone is lighter and contains a network of trabecular structures, while compact bone is denser and forms the outer layer of bones.
