Cartilage and Bone Flashcards
(59 cards)
1
Q
Three types of cartilage
A
- Hyaline 2. Elastic 3. Fibrocartilage
2
Q
Cartilage functions
A
- support of soft tissues 2. as a shock absorber 3. Free sliding surface for joints 4. as a template for growth of long bones
3
Q
Cartilage lacks
A
blood vessels lymphatics nerves
4
Q
Cartilage Composition
A
water: 70-80% of ECM Collagen: 10-20% of ECM (collagen type II) Proteoglycans: 10-15% composed of glycosaminoglycans *Sulfated GAGs have a negative charge, makes them absorb (mainly) Na+ ions and water follows
5
Q
Formation of Cartilage during Embryonic Development
A
- At the site of chondrogenesis, mesenchymal cells round out and proliferate, and differentiate into chondroblasts 2. Chondroblasts synthesize and secrete matrix into the extracellular space, entrapping themselves within lacunae *they become further separated by more matrix, now called chondrocytes 3. mesenchymal cells of the periphery condense to form a fibrous sheath around the newly formed cartilage, PERICHONDRIUM
6
Q
Isogenous group
A
cluster of chondrocytes originating from a single progenitor
7
Q
Territorial matrix
A
a thin rim around lacunae more basophilic due to high GAGs. Stains dark
8
Q
Interterritorial matrix
A
More eosinophilic. Stains light
9
Q
Perichondrium
A
-a dense layer of DCT that covers cartilage -outer cells are fibroblasts and closest to cartilage are chondroblasts - rich in: fibroblasts, undifferentiated mesenchymal stem cells, blood vessels, nerves, lymphatic vessels *this is the vascular supply for avascular cartilage -Two layers: 1. Fibrous layer 2. Chondrogenic layer
10
Q
Hyaline Cartilage
A
-Most common type of cartilage in the adult - basophilic matrix - fibroblast-like cells change properties and help form matrix. Rounding up and enlargement depicts this
11
Q
A
12
Q
A
Hyaline Cartilage
13
Q
Cauliflower Ear
A
- External ear suffers a blow
- This seperates the cartilage from the overlying perichondrium that supplies its nutrients, causing the cartilage cells to die and resulting in the formation of fibrous tissue (scar tissue) in the overlying skin
14
Q
Synovial Joint
A
- a joint in which the opposing bony surfaces are covered with a layer of hyaline cartilage or fibrocartilage
- This articular hyaline cartilage is bathed in synovial fluid
- Articular hyaline cartilage lacks a perichondriumand receives nutrients from the synovial fluid
15
Q
A
- C= chondrocytes
- cc= calcified cartilage
16
Q
Osteoarthritis
A
- inflammation of the joints
- breakdown of joint cartilage underlying bone
17
Q
Elastic Cartilage
A
- Found in structures subjected to repeated deformation or vibration
- external ear
- epiglottis
- larynx
- random coil domains which expand and contract
- Type II collagen
- perichondrion
*
18
Q
A
Elastic Cartilage
19
Q
Fibrocartilage
A
Combination of:
- Dense regular CT
- Type I collagen
- blood vessels
- Hyaline Cartilage
- Type II collagen
- No perichondrium (only cartilages that don’t have perichondrium are fibrocartilage and articular hyaline cartilage)
- Locations: intervertebral discs, pubic symphysis, menisci of knee joint
20
Q
A
Fibrocartilage
21
Q
Interstitial Growth of Cartilage
A
- occurs when chondrocytes divide mitotically into clusters of daughter cells each secreting a small amount of matrix
- occurs at epiphseal plates of long bones
- increases length
- Also occurs at articular cartilage (growth comes from within because there is no perichondrium
22
Q
Appositional Growth of Cartilage
A
- results from the differentiation of perichondrial cells
- chondrogenic cells in the inner layer of the perichondrium undergo mitotic division and synthesize matrix
- Eventually, chondroblasts become chondrocytes
23
Q
Repair of Damaged Cartilage
A
- except in young childer, damaged cartilage undergoes slow and often incomplete regeneration
- mainly because it is avascular
- if it is repaired it is from chondrogenic cells in the perichondrium
- produces a scar of dense CT
24
Q
Endochondral Ossification
A
- During embryonic development, most of the skeleton is cartilage
- capable of dividing
- grows rapidly like the fetus
- gradually replaced by bone
25
Bone
* Bones are organs largely composed of bone tissue that also contains:
* bone marrow
* arteries
* veins
* lymphatics
* nerves
* fibrous tissue
26
Functions of Bone
1. provides protection for internal organs
2. provides supporting framework for body
3. enables movement
4. produces blood cells
5. calcium and phosphorous reserve
6. detoxification
7. sound transduction in the middle ear
\*bone is a dynamic tissue that is constantly changing shape in relation to the stress placed on It
27
Bone is specialized CT
Cells:
1. osteogenic cell
1. differentiate into osteoblasts
2. osteoblast
1. secrete matrix
3. Osteocyte
1. when surrounded by matrix osteoblasts become osteocytes
4. Osteoclast
1. bone resorption and remodeling
Fibers:
* Collagen type I
Ground substance:
* hydroxyapatite
28
Trabeculae
anastomosing bony spicules in cancellous bone which form a meshwork of intercommunicating spaces that are filled with bone marrow
## Footnote
\*Spicule: a slender, pointed usually hard body
29
Typical long bone
* Diaphysis:
* the shaft of a long bone, compact bone, medullary cavity
* Epiphyses
* long bone's bulbous end
* contains cancellous bone
* joints with other bones
* Metaphysis
* between the two
* extends to epiphyseal line
* during childhood, the metaphysis consists of cartilage and is the part that grows
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Bone Structure
Steel bars are collagen type I (33%) cement is hydroxyapatite (67%)
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Osteoid
organic component of bone before it is mineralized. Contains fibers and ground substance
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Ground substance
* hydroxyapatite crystal nucleation sites
* glycosaminoglycans
* glycoproteins
33
Osteoprgenitor Cells
* Derived from mesenchymal cells of bone and bone marrow
* when new bone is not required, these cells are quiescent
* osteoprogenitor cells are activated following fracture, growth or various disorders
34
Periosteum
the exterior of long bones is covered with a connective tissue membrane called the periosteum which consists of:
1. outer layer of dense fibrous connective tissue
2. inner cellular layer containing osteoprogenitor cells
Nutrition, repair, growth
35
Endosteum
the lining of internal marrow cavity and trabeculae
Composed of:
1. a monolayer of osteoprogenitor cells
2. osteoblasts
nutrition, repair, growth
36
Osteoblasts
* exclusively on the surface of bone
* flattened (inactive)
* cuboidal (active)
* Synthesize and secrete the organic matrix of bone
* collagen type I
* binds osteocalcin and osteonectin
* alkaline phosphatase (ALP)
* responsible for crystallization of CaPO4
* ALP used as a marker of osteoblast activity
* proteoglycans
* GAGs
* Glycoproteins
37
Osteoblasts
38
Osteocytes
* mature bone cells derived from osteoblasts that become trapped in lacunae
* reduced RER and Golgi
* Canaluculi radiate from lacunea
* live as long as the organism itself
* do not divide
* involved in the routine turnover of bony matrix
* respond to reduced mechanical stress by secreting matrix metalloproteinases that degenerate bone (osteocytic osteolysis)
39
Gap junctions
bone needs gap junctions to transfer oxygen and ions through osteocytes
40
* Osteon
* L= lacunae
* C= canaliculi
* H= haversion canal
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Osteon
* consists of concentric layers or lamellae
* surround a central haversian canal
* haversian canal provides the nutrient supply
42
Volkmann's Canals
carry blood horizontally or obliquely
(compared to haversian canals that carry blood vertically)
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Sharpey's Fibers
* Connective tissue consisting of bundles of strong collagenous fibers (Type I) connecting periosteum to bone
* They are part of the outer fibrous layer of the periosteum
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Osteoclasts
* Bone resorbing cells
* in the macrophage family with 5-50 nuclei derived from monocytes
* lots of lysosomes
* lots of mitochondria
* well developed rER and Golgi
* within Howship's lacunae (etched depressions)
* Uses carbonic anhydrase to acidify the mineralized bone
* hydrolytic enzymes from lysosomes digest organic
45
* Fetal bone
* Ob= osteoblasts
* BM= bone matrix
* Ocl= osteoclasts
* Os= Osteocytes
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Two varieties of bone
1. Primary bone (immature, woven)
* The first bone tissue to appear in embryonic development and bone repair.
* abundant osteocytes
* Haphazard organization of collagen fibers
* Low mineral content
2. Secondary bone
* replaces primary bone
* found in adults
* composed of parallel or concentric lamellae of collagen
* Calcified matrix
47
Formation of bone in embryo
1. intramembranous ossification
1. flat bones of skull and mandible
2. soft spots later become ossified forming the skull
2. Endochondral ossification
1. replacement of cartilage by bone
2. most bones are formed this way
\*Cartilage develops from chondrogenic precursors where oxygen is low. Bone develops from osteogenic precursors in high oxygen. Blood vessels must already exist close to newly formed bone.
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Bone Fracture
* A break of any size is called a fracture
* in the healing of a bone fracture, fibrocartilage forms, then bone
* In embryological endochondral ossification hyaline cartilage forms the template for bone formation
50
Calcitonin
* Released by the thyroid gland
* binds to the calcitonin receptor on osteoclasts and reduces the activity of their bone resorbing function
51
Parathyroid hormone
* Released by the parathyroid glands
* Binds to the PTH receptor on osteoblasts
* They stop production of osteoid and instead secrete factors that promotes osteoclastic resorption of bone, raising calcium
52
Osteoporosis
* Occurs when the rate of bone resorption exceeds the rate of bone formation
* Loss of bone mass leads to loss of strength, making the bones brittle and weak
* the leading cause is decrease in estrogen and testosterone which are osteoclast inhibitors
53
RANK/RANKL
* RANKL is secreted by osteoblasts
* RANK receptor is on osteoclasts
* If RANKL is allowed to bind, it will cause immature osteoclasts to mature and proliferate and become activated
* This leads to bone resorption
54
Osteopetrosis
* Stone bone disorder
* caused by defective osteoclast function
* overgrowth thickening and hardening of bones
* deficiency in carbonic anhydrase
55
Rickets/Osteomalacia
* deficiency of vitamin D
* Vit D stimulates osteocalcin and osteopontin which bind hydroxyapatite to collagen type I and integrins on bone cells
* In children this is rickets
* In adults this is osteomalacia
* Bowing of femurs and decreased bone opacity
56
Gigantism/Acromegaly
* Overproduction of pituitary growth hormone causes excessive growth at the epiphyseal plate
* in children this is gigantism
* great stature
* In adults, after the growth plates have closed, it is called acromegaly
* deformed bones
57
Dwarfism
1. Growth hormone deficiency can be treated through replacement therapy
2. Achondroplasia
1. without cartilage formation
2. mutation in fibroblast growth factor receptor 3 (FGFR3) which has a negative regulatory effect on bone growth
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