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MSS Weeks 3-5 > Cartilage > Flashcards

Cartilage Flashcards

1
Q

Physical Characteristics of Cartilage:

A
  • Specialized connective tissue that provides resilient support to specific areas of the body
  • Hydrated nature of cartilage matrix allows it to resist compressive forces
  • When it is deformed by an external pressure, cartilage has the capability of regaining its shape and size
    • i.e. resilience
  • Also can provide a smooth “cushioned” surface for the movement of articulating bones
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2
Q

What type of cartilage is found in synovial joints?

A

Articular cartilage

  • specialized hylaine cartilage
  • covers the articulating surfaces of opposing bones of the joint
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3
Q

Cartilage consists of cells called __________ that are embedded within an extensive extracellular matrix termed ________ ______

A

Cartilage consists of cells called Chondrocytes that are embedded within an extensive extracellular matrix termed Cartilage Matrix

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4
Q

What are the three components of cartilage?

A
  1. fibers
  2. ground substance
  3. noncollagenous multiadhesive glycoproteins
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5
Q

What gives mechanical stability to the ground substance?

A

fibers

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6
Q

What is the primary fiber in the cartilage matrix?

What fiber predominates in the cartilage matrix?

A
  • Cartilage-Specific Collagens are the primary fiber type found in cartilage matrix
  • Of these, Type II Collagen is the predominant isoform
    • Collagen types IX, X & XI are also associated with cartilage
    • Type VI Collagen is found at the periphery of the chondrocyte and facilitates the link between the chondrocyte and the cartilage matrix
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7
Q

Describe the function:

  • Type II collagen
  • Type IX collagen
  • Type X collagen
  • Type XI collagen
A
  • Type II:
    • Most abundant of the cartilage-specific collagens
    • Provides mechanical stability for the cartilage matrix
  • Type IX:
    • Stabilizes type II collagen fibrils network by
      facilitating collagen fibril-proteoglycan interaction
  • Type X
    • Associated with hypertrophic regions in cartilage where it organizes collagen fibrils into a 3D lattice
  • Type XI
    • Regulates type II collagen fibril size
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8
Q

What is the predominant component of cartilage matrix?

A

ground substance

  • It exists as a hydrated gel composed of water, ions and proteoglycans
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9
Q

What is aggrecan?

A

predominant proteoglycan monomer

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10
Q

Describe how Multimolecular Proteoglycan Aggregates are formed.

What is their significance to the cartilage matrix?

A
  • Aggrecan monomers are bound to a central hyaluronate backbone forming large Multimolecular Proteoglycan Aggregates
  • Sulfate and carboxyl groups on the chondroitin and keratin sulfate subunits of the proteoglycan monomers give them a dense negative charge
  • Proteoglycan aggregates remain expanded due to repulsion of the negatively charged proteoglycan monomers
  • Water and sodium ions attracted to the negatively charged ion groups hydrate the cartilage matrix
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11
Q
  • What are Noncollagenous Multiadhesive Glycoproteins?
  • What are 3 examples?
  • What is their clinical significance?
A
  • consist of small regulatory and structural proteins that influence interactions between chondrocytes and the ECM
  • Examples:
    1. ​Chondronectin
    2. Tenascin
    3. Anchorin CII
  • ​Clinical Significance:
    • markers of cartilage turnover and degeneration
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12
Q

Cells of Cartilage:

Chondrocytes

A

cells embedded within the cartilage matrix

  • oval to round cells with basophilic cytoplasm that can divide and often are found in clusters called Isogenous Groups or Cell Nests
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13
Q

What is a lacunae?

A

space within the cartilage matrix that is occupied by the chondrocyte

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14
Q

What is the function of chondrocytes?

A
  • produce and secrete the components of cartilage matrix
  • secrete enzymes that can degrade cartilage matrix
  • prime function:
    • maintain the integrity of the cartilage matrix
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15
Q

Cells of cartilage:

Chondroblasts

A

cartilage forming cells

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16
Q

Cells of cartilage:

Chodroclasts

A

multinucleated cells that degrade calcified cartilage

  • derived from monocytes
  • similar to osteoclasts
17
Q

Chondroma & Chondrosarcoma come from which cells of cartilage?

A

chondrocytes

18
Q

Hormones Affecting Sulfated GAG Synthesis by Chondrocytes

  • Increase Synthesis
  • Decrease Synthesis
A
  • Increase Synthesis:
    1. Growth Hormone
    2. Thyroxin
    3. Testosterone
  • Decrease Synthesis:
    1. Cortisone
    2. Hydrocortisone
    3. Estradiol
19
Q

Cartilage elements are often enclosed within a perichondrium:

  • outer part:
  • inner part:
A
  • outer part:
    • fibrous connective tissue, primarily type I collagen
    • secreted by fibroblasts
    • contains a capillary plexus, nerves and lymphatics
  • inner part:
    • ​contains flattened Chondrogenic Cells that have the potential to become Chondroblasts
    • once a chondroblast surrounds itself with cartilage matrix, it becomes a chondrocyte
20
Q

Since cartilage is avascular, how is it nourished?

A
  • Chondrocytes are nourished by Diffusion through the cartilage matrix
  • Important that the matrix remains completely hydrated
    • some of the water is loosely bound to proteoglycans ⇒ diffusion of small molecules
  • In spite of being surrounded by an avascular matrix, chondrocytes have a high metabolic rate
  • Note: Cartilage matrix also has no lymphatics or nerve endings
21
Q

What are the 3 types of cartilage?

Which is the most common?

A
  1. hyaline
  2. elastic
  3. fibrocartilage
  • ​Most common: hyaline
22
Q

LM Characteristics of Hyaline Cartilage:

  • Shape:
  • Pericellular Matrix:
  • Territorial Matrix:
  • Interterritorial Matrix:
  • Perichondrium present?
A
  • Shape:
    • oval at the periphery and round centrally
  • Pericellular Matrix:
    • surrounds the chondrocyte acting as a biochemical buffer between the cell and the
      adjacent Territorial Matrix
  • Territorial Matrix:
    • ​contains thin collagen fibers
  • Interterritorial Matrix:
    • ​remaining cartilage matrix between lacunae
  • Perichondrium present?
    • ​usually present
23
Q

What are the special types of hyaline cartilage?

A
  1. articular
  2. epiphyseal plate
24
Q

**Articular Cartilage: **

Structure (zones)

A

covers the articular surfaces of most bones

  1. Adjacent to the surface:
    • ​​chondrocytes are flattened
    • collagen fibers are parallel to the surface
  2. Second zone:
    • ​​round, randomly oriented chondrocytes
    • collagen fibril bundles oriented obliquely
  3. Third zone:
    • collagen fibrils oriented perpendicular to the surface
    • chondrocytes stacked in vertical columns parallel to the collagen fibrils
  4. Deepest zone
    • ​​adjacent to the subchondrial bone contains mineralized cartilage matrix
25
Q
  1. What is the Tidemark?
  2. What is the advantage of having the collagen fibers arranged in different zones?
  3. What is a major difference about articular cartilage compared to normal hylaline cartilage?
A
  1. Tidemark:
    • boundary between the deepest zone and the three unmineralized zones above
  2. arrangement of collagen fibers within the zones enables them to distribute compressive forces
  3. articular cartilage has NO PERICHONDRIUM
    • enables a smooth surface
26
Q

Elastic cartilage:

  • Appearance:
  • LM characteristics:
  • Perichondrium present?
A
  • Appearance:
    • yellowish in appearance when fresh because the matrix contains a predominance of elastin
  • LM characteristics:
    • chondrocytes that are randomly distributed within the cartilage matrix
    • hyaline-like matrix that surrounds the chondrocytes
  • Perichondrium present?
    • usually present
27
Q

Fibrocartilage:

  • Appearance:
  • LM characteristics:
  • Perichondrium present?
A
  • Appearance:
    • white and opaque in the fresh state because the cartilage matrix has a predominance of Type 1 collagen
  • LM characteristics:
    • bundles of collagen fibers are observed within the cartilage matrix
    • chondrocytes are ovoid and arranged in a linear fashion parallel with the bundles of collagen fibers
  • Perichondrium present?
    • no perichondrium
28
Q

What are the two ways cartilage can grow?

A
  1. Interstitial growth
  2. Appositional growth
29
Q

Describe interstitial growth:

What is it important for?

A

growth from within

  1. As chondrocytes divide, they separate because of new matrix production
  2. Cartilage element expands from within
  3. This type of growth generally occurs in young cartilage where matrix plasticity is greater
  • Interstitial Growth of epiphysial cartilage is important for the growth of long bones
30
Q

Describe appositional growth:

A

growth from the surface

  1. inner layer of the perichondrium contains Chondrogenic Cells having the potential to become Chondroblasts which express SOX 9
  2. chondroblasts secrete cartilage matrix
    • become enclosed within it
  3. new cartilage is added to the surface of existing cartilage element
31
Q

What are the general effects of aging on cartilage?

A

Aging affects matrix organization, matrix mechanical properties and chondrocyte function

32
Q

Osteoarthritis

A

Family of degenerative joint diseases characterized by:

  1. chronic pain
  2. joint deformity
  3. eventual disability
  • Patients experience progressive loss of articular cartilage
  • Cartilage degeneration may eventually expose the bone
33
Q

Rheumatoid Arthritis

A

inflammatory reaction against the synovium of the joint:

  • chronic inflammatory disease
  • can lead to destruction of the joint
34
Q

Describes what happens if articular cartilage is injured:

A
  • Injury that does not extend across the tidemark:
    • usually does not heal due to lack of influx of chondrogenic cells, fibrin clot or growth factors
  • If the injury extends into the bone:
    • repair is incomplete
    • does not restore the normal composition or mechanical properties to the cartilage matrix
35
Q

What degenerative changes affect intervertebral discs?

A
  1. Aging decreases the water content of the nucleus pulposis while the content of proteoglycans that do not bind water increases
    • size of the aggrecan molecules also decreases
  2. Increase in collagen and other proteins cause the nucleus to become firm
  3. Tears also appear in the annulus fibrosis
  4. Collectively, these changes affect alignment of the spine and disk flexibility.
  5. Increase the probability of mechanical failure
    • may lead to disk herniation
36
Q

What can cause cartilage to lose its resilience?

A

mineralization

  • due to aging or pathologic change

MSS Weeks 3-5 (22 decks)

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