Bone and Cartilage Flashcards
(133 cards)
0
Q
What does cartilage consist of?
A
Chondrocytes and extracellular matrix
1
Q
What is cartilage?
A
Avascular and aneural tissue
2
Q
Where are chondrocytes located?
A
Within the ECM lacunae
3
Q
True/False: Chondrocytes can divide and generate matrix.
A
True
4
Q
What are chondrocytes replenished by?
A
surrounding perichondrium
5
Q
What is perichondrium?
A
Connective tissue layer
6
Q
What does the inner layer of perichondrium differentiate into?
A
Chondroblasts (i.e. growing cartilage (GC) cells)
7
Q
When does a chondroblast become a chondrocyte?
A
When they stop dividing
8
Q
ECM is richly hydrated. What leads to this?
A
- High Gylcosaminoglycans (GAGs) to collagen ratio
- Creates a 60-80% level of hydration
9
Q
GAG binds ______ tightly to confer resilience
A
Water
10
Q
GAG bind some water loosely which permits what?
A
Diffusion of substances to and from the blood
11
Q
What are characteristics of hyaline cartilage?
A
Contains homogeneous and amorphous matrix
12
Q
Resilience makes hyaline cartilage useful for which type of surfaces?
A
Articular
13
Q
What type of cartilage is the earliest form of cartilage in embryogenesis?
A
Hyaline
14
Q
What does the hyaline cartilage become as a person grows?
A
Growth plates of growing bones
15
Q
What are 3 functions of hyaline cartilage?
A
- Supports
- Reinforces
- Resists compressive stress
16
Q
Hyaline cartilage has been used as a model for what?
A
Endochondral ossification of bone
17
Q
Hyaline cartilage covers the articular surfaces of moveable bone and forms what structures?
A
Costal cartilages
18
Q
What is the difference between elastic cartilage and hyaline cartilage?
A
Elastic cartilage has more elastic fibers and contains a perichondrium
19
Q
Where is elastic cartilage found?
A
- Epiglottis
- External ear
- Auditory (Eustachian) tube
20
Q
What is the function of elastic cartilage?
A
Maintains the shape of a structure while allowing great flexibility
21
Q
What makes up fibrocartilage?
A
Combination of hyaline cartilage and dense regular CT
NO perichondrium
22
Q
What two cell types are present in fibrocartilage? What do they generate?
A
Chondrocytes and fibroblasts; ECM
23
Q
The CT component of fibrocartilage resists compression and shearing in which areas?
A
- Intervertebral disc
- Pubic symphysis
- Articular discs in TMJ
- Menisci in the knee
24
Where is cartilage originally formed from?
Mesenchyme
25
True/False: Mesenchymal cells are differentiated into chondroblasts
True
26
Cartilage growth occurs up to the end of adolescence in which two phases?
- Appositional growth
| - Interstitial growth
27
Both phases of cartilage growth are common, but which one becomes more predominate with age?
Appositional growth
28
At what period of growth does growth cease? Why?
Late teens; chondrocytes stop dividing
29
What is interstitial growth and were does it take place?
Division of the chondrocytes; within the distensible matrix
30
When does most interstitial growth occur?
Embryogenesis
31
What is taking place during interstitial growth during embryogenesis?
Mesenchymal cells aggregate and differentiate into chondroblasts
32
Once mesenchyme cells differentiate into chondroblasts, what do they secrete, form, and become?
ECM; lacunae; chondrocytes
33
Chondrocytes divide one or more times to form what groups?
Isogenic groups
34
Each chondrocyte lays down ______ causing it to form its own _______ and spread apart.
matrix; lacunae
35
As chondroblasts differentiate into chondrocytes, they form clusters that secrete what? Causing what?
secrete matrix; pushing cells apart
36
Where does appositional growth occur? During which stage of development?
On the surface of cartilage; later stages of development
37
Which cells of appositional growth differentiate into chondroblasts and what do they initiate?
Perichondrial cells; cartilage matrix formation
38
Matrix formation increases what type of mass?
Cartilage; making it more rigid
39
Cells of appositional growth mature into what type of cell and where are they embedded?
Chondrocytes; rigid matrix
40
The high water content of the matrix permits what action? To and from which structures, in what area?
Diffusion of nutrients and waste products; to and from the blood vessels; in the perichondrium
41
What are 3 reasons cartilage ceases growing in adulthood?
- Avascularity
- Immobility of chondrocytes
- Limited ability of chondrocytes to proliferate
42
Repair following injury only occurs under what circumstances, involving which type of cells?
If the defect involves the perichondrium; which can provide new chondrocytes, but mostly dense CT.
43
In appositional growth, what happens to some damaged cartilage?
It is calcified and vascularized leading to bone substitution.
44
Why is it that articular cartilage cannot be regenerated?
It has no perichondrium on either the free or bone-facing surfaces
45
In what types does bone come?
Long, short, flat, irregular
46
All bone is formed by an outer layer of what type of bone, surrounding what type of interior layer?
compact (dense) bone; spongy (cancellous, trabecular) bone
47
Long bones illustrate which 5 structures within bone?
- Diaphysis
- Epiphysis
- Metaphysis
- Marrow (medullary) cavity
- Outer bone surface
48
What is the diaphysis of a long bone?
The shaft
49
What is the epiphysis of a long bone?
Expanded end
50
What is the metaphysis of long bone?
It extends from diaphysis to the epiphyseal line
51
What does the marrow (medullary) cavity of the long bone form? What lines the the inner cavity?
The inner space (most bones are hollow); endosteum
52
What covers the outer bone surface of long bone?
Periosteum or articular cartilage
53
What is the periosteum?
Outer bone surface
54
Which area of bone is innervated, thus sensing pain?
Periosteum
55
What two layers make up the periosteum?
Fibrous layer and cellular layer
56
The outer fibrous layer of the periosteum is made up of what type of tissue and is the site for what structure?
Dense irregular CT; tendon attachment
57
The inner (deep) cellular osteogenic layer on the compact bone contains what type of cells?
Osteoprogenitor
58
The endosteum (inner/trabecular surface) is made up of an epithelial layer that produces what type of bone cells and is lacking which type of layer?
Progenitor cells; no fibrous layer
59
From where do osteoprogenitor cells originally differentiate?
Embryonic mesenchymal stem cells
60
Where, in mature bone, are osteoprogenitor cells located?
On the internal and external bone surfaces
61
In mature bone, what two areas do the osteoprogenitor cells form?
- Endosteum
| - Inner layer of the periosteum
62
From where do the osteoblast differentiate?
Osteoprogenitor cells
63
What function does the osteoblast retain after differentiation from osteoprogenitor cells?
Ability to divide
64
Due to their ability to divide, what are the two directions an osteoblast can take?
- Generate new bone cells
| - Remain dormant in periosteum or endosteum
65
What does the osteoblast secrete?
- Bone matrix proteins (osteoid)
| - alkaline phosphatase
66
What is the purpose of osteoblast secretion of bone matrix proteins (osteoid) and alkaline phosphatases?
Promote matrix mineralization
67
With what does alkaline phosphatase combine to form crystalization?
Calcium
68
When enclosed in mineralized matrix, osteoblasts become which type of cell?
Osteocytes
69
From which type of cells are osteocytes derived? Where are they contained?
Osteoblasts; lacunae
70
What is lacunae?
Enclosed matrix spaces
71
Osteocytes send cytoplasmic extensions through what structures leading to adjacent lacunae?
Canaliculi
72
What is the purpose of the osteocyte sending out cytoplasmic extensions through the canaliculi to adjacent lacunae?
Permits contact with osteoblasts via gap junctions
73
Osteocytes are able to respond to what type of forces applied to the bone?
mechanical
74
What are two roles that osteocytes play with regard to structure of bone matrix?
- Synthesizes
| - Break down
75
What causes osteocytes to synthesize new matrix or break it down?
Blood-calcium homeostasis (not so much with bone remodeling)
76
From which type of cells are bone-lining cells derived?
Osteoblasts
77
Where are bone-lining cells found?
- Where bone is quiescent (not building or resorbing)
- Periosteum
- Endosteum
78
What is the function of bone-lining cells?
Maintenance and nutritional support for osteocytes
79
What is a regulatory action of bone-lining cells?
Regulate movement of calcium and phosphate in and out of the bone.
80
What area of bone is the major source of blood?
Bone marrow
81
Where do blood vessels enter bone?
Through epiphyseal and diaphyseal nutrient foramen
82
Blood that nourishes bone tissue moves from what location, through bone tissue, and out via which veins?
Marrow space; periosteal veins
83
Which marrow consists of blood cells in different stages of development?
Red marrow
84
Red marrow is enmeshed in a network of which type of cells and material?
Reticular cells and fibers
85
When does red marrow form blood cells and what happens over time?
Early years; diminishes with time and is replaced with yellow marrow.
86
In adults, where is red marrow restricted? What are these reserves used for?
-Sternum
-Iliac crest
Available for bone marrow transplant
87
What is the main consistency of yellow marrow?
Mostly fat cells
88
In extreme cases of blood loss, what can happen to yellow marrow?
It can revert to red marrow
89
What are other names for compact (dense) bone and what type of matrix does it contain?
Cortical bone or lamellar bone; high density matrix
90
What are cylindrical layerings of concentric lamellae enclosing a central canal?
Osteons
91
What feature of lamellae increases resistance to twisting forces?
Alternating direction of collagen fibers
92
What is at the center of an osteon?
Central canal
93
What structures run through the central osteonal (Haversion) canal?
- Artery with capillaries
- Vein
- Nerve fiber
94
Periosteal blood vessels cary blood to the osteocytes via which canals?
Perforating (Volkmann's) canals
95
Spongy (cancellous) bone is organized into _________ separated by _____ _______, but otherwise has many similarities to compact bone.
trabeculae; marrow spaces
96
True/False: Spongy bone contains osteon (Haversion systems)
FALSE!!! Spongy bone does NOT have osteon - Haversion systems are ONLY found in compact bone!!
97
Spongy bone lays down in which structure?
Lamellae
98
Trabeculae are surrounded by ___________ which also contains which two types of cells?
endosteum; osteoblasts and osteoclasts
99
True/False: Osteocytes are found within lacunae of spongy bone, interconnected by canaliculi.
True
100
True/False: Spongy bone is the precursor to compact bone during bone development.
True
101
Spongy bone trabeculae are organized along force lines in order to...?
Maximally resist tension or compression forces
102
Homeobox genes signal what structures to form somites?
Paraxial mesoderm segments
103
Somites establish early spinal levels (cervical, thoracic, etc.) of what three structures?
- Bones
- Muscle
- Dermis
104
In somite differentiation, sclerotome surround neural tube to form what two structures?
Vertebrae and ribs
105
In somite differentiation, dermatome becomes...
dermis of the skin
106
In somite differentiation, myotome becomes...
muscles of the body below the neck
107
Fusion of dense and loose tissue of adjacent somites forms what?
the intersegmental vertebra
108
The notochord of somites eventually becomes what structure within vertebral bodies?
Nucleus pulposus
109
Due to resegmentation of somites myotomes span...
adjacent vertebrae (touching the one above and one below, i.e. bottom half of T5 and top half of T6)
110
Due to resegmentation of somites, spinal nerves get interposed....
Between vertebrae (which is why we have a C8 nerve root, but no C8 vertebrae)
111
How is it that we have 8 cervical nerves but only 7 cervical vertebrae? (Hint: what makes up the "8th" cervical vertebrae)
A proatlas anlage that separates into portions of the basioccipital bone and the dens of the axis bone
112
Limb development comes from?
Local limb bud tissue
113
What is the first major tissue of limb to differentiate from mesenchyme?
Bone
114
True/False: In limb development, CT (tendons and fascia) are laid out along bone segments.
True
115
True/False: Cells of each somite region begin forming specific tissues prior to arriving at their destination.
FALSE!!! Cells of each somite region migrate separately to target destinations before forming specific tissue
116
Sclerotome cells migrate ________ to form what?
medially; bones (vertebrae and ribs)
117
Dermatome cells migrate in which direction in relation to ectoderm to form what?
under; connective tissue of skin (dermis)
118
Myotome cells migrate to form what structures, within which areas?
skeletal muscle; within body and limbs
119
Which part of mesoderm expands to form limb buds?
Lateral plate mesoderm
120
Myotomal cells differentiate into muscle and follow what structures during migration?
tendons
121
From what tissue does the epidermis derive?
ectoderm
122
In bone pattern formation, what does the AER (apical ectodermal ridge) determine, where, and using which factor?
growth of bones; along proximal-distal axis; using fibroblast growth factor (FGF)
123
In bone pattern formation, what does the ZPA (zone of polarizing activity) determine and using which factor?
Pattern of bones (which bones: radius, ulna, etc.) using sonic hedgehog (Shh)
124
True/False: Shh and FGF mutually enhance each other through feedback control
True
125
What determines the differentiation of digits?
Concentration gradient of Shh factor
126
Where is the highest concentration of Shh?
On the side of the 5th digit (digiti minimi)
127
Where is the lowest concentration of Shh?
Technically, the 2nd digit, because there is no Shh present at the pollus.
128
What process induced by Shh produces fingers?
Interdigital apoptosis
129
Disruption of interdigital apoptosis by Shh results in what condition? Which areas are most affected?
Syndactyly; most often affecting digist 3, 4, and/or 5
130
True/False: Hox genes are turned on all at once creating bones along the limb
FALSE!!! Sets of Hox genes are turned on SEQUENTIALLY, each set producing specific bones along the longitudinal axis of the limb.
131
What is the condition, phocomelia?
Absence of proximal segments, but normal distal segements (hands coming from the shoulder - no humerus, radius, or ulna)
132
What drug was associated with increased phocomelia, and what seemed to be causing the problem?
Thalidomide; blocks angiogenesis leading to reduction of FGF release.
