connective tissue adaptation Flashcards

1
Q

What are the 4 tissue types?

A
  • epithelial
  • connective tissue
  • nervous tissue
  • muscle
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2
Q

What is connective tissue made up of?

A
  • relatively few cells
  • mostly made up of ECM (proteins such as elastin and collagen, ground substance)
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3
Q

How is ECM formed?

A
  • formed by the cells of the connective tissue
  • which secrete macromolecules in the ECM
  • components vary between different connective tissues
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4
Q

What does ECM do?

A
  • separates and holds the cells in place
  • maintains tissue and cell integrity
  • mediate the exchange of nutrients and waste
  • transmits chemical signals to the cells to regulate migration, growth, differentiation
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5
Q

Describe the structure of collagen fibres

A
  • composed of protein collagen
  • triple helix of polypeptide chains
  • hierarchal structure ( microfibril, fibril, fibre)
  • great tensile strength
  • compliant due to arrangement of fibrils and crimp
  • 29 forms, five common sub-types found in different areas of the body
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6
Q

Describe the structure of elastic fibres?

A
  • composed of the protein elastin
  • coiled structure
  • cross-links between molecules
  • ability to stretch
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7
Q

What is ground substance?

A
  • gel-like material
  • transparent
  • fills spaces between cells and fibres
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8
Q

What is ground substance made up of?

A
  • made of large molecules called glycosaminoglycans (GAGS)
  • GAGS linked via proteins into even larger proteoglycans
  • hydrophilic (90% is water)
  • high water content and inflexible molecules mean very good at resting compressive forces
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9
Q

What cells does the ECM contain?

A
  • fibroblasts
  • adipocytes
  • immune cells
  • other specialised cells e.g.. osteocytes and blasts, chondrocytes and blasts
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10
Q

What are fibroblasts?

A
  • least specialised cells, secrete collagen and ground substance
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11
Q

What are adipocytes?

A
  • fat cells
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12
Q

Name immune cells found in ECM?

A
  • macrophages
  • mast cells
  • plasma cells
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13
Q

What is a tendon?

A
  • A type of fibrous connective tissue (dense regular connective tissue)
  • comprised of collagen fibres tightly packed and running in the same direction
  • excellent tensile strength in one direction
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14
Q

What are the components of a tendon?

A
  • cells such as tenocytes (specialised fibroblast)
  • fibres, predominantly collagen type 1 and a small amount of elastin
  • ground substance ( proteoglycans and water)
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15
Q

What is a ligament?

A
  • Dense regular connective tissue
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16
Q

What is the structure of a ligament?

A
  • similar to a tendon
  • slightly less ground substance
  • fibrils not as uniformly orientated to cope with multiaxial loading patterns
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17
Q

What is cartilage?

A
  • A specialised type of connective tissue
  • three types of cartilage
18
Q

What are the general components of cartilage?

A
  • cells, chondrocytes (chondroblasts that get trapped)
  • fibres - collagen type 2
  • ground substance - proteoglycan aggrecan (10%) takes up lots of water (75%)
  • composed of GAGS (hyaluronic acid, chondroitin sulphate, keratin sulphate)
19
Q

What is a hyaluronic acid/hyaluronan?

A
  • very large GAG molecule
  • very hydrophilic
  • increases tissue viscosity when bound
  • excellent lubricative properties
  • important in tissue repair (linked to tumour progression)
20
Q

What is chondroitin sulphate and keratin sulphate?

A
  • highly charged sulphate groups repel (anti-compression)
  • link up with proteins to form proteoglycans (e.g. aggrecan)
21
Q

What is hyaline cartilage?

A
  • most common kind of cartilage
  • glassy appearance
  • specialised by collagen type 11
  • weakest type of cartilage
22
Q

Where is fibrocartilage found?

A
  • found if certain regions of the body undergoing tension as well as compression
  • e.g., intervertebral disc, joint capsules, ends of ligaments
23
Q

How is fibrocartilage specialised?

A
  • abundant collagen bundles sandwiched in between cartilage layers
  • strongest type of cartilage
24
Q

Where is elastic cartilage found?

A
  • areas that need to be flexible but return to a certain shape
  • e.g. pinna ( external part of ear) , epiglottis (tissue beneath tongue) , larynx
25
How is elastic cartilage specialsed?
- many elastin fibres - strong and flexible
26
Describe the ECM in hyaline cartilage at articular surfaces?
- surface has tight collagen sheets parallel to to surface - middle zone has random and less dense arrangement to accommodate proteoglycans and water - deep zone has radial fibres that penetrate into calcified cartilage and bone to anchor the cartilage - chondrocytes also have different shape and distribution
27
What is bone?
- A specialised type of connective tissue
28
What are the components of bone?
- cells - osteoblasts, osteocytes, osteoclasts - fibres - predominantly collagen type 1 - ground substance - inorganic hydroxyapatite (calcium phosphate crystals) - organic GAGs
29
Forces and movements are applied to locomotory structures - what do they produce?
- compression - shear - tension - bending - torsion
30
What is tissue stiffness?
- how much the tissue deforms when loaded
31
What happens if continual stress is applied to a tissue?
- There is a move from elastic region to plastic region (permanent deformation) - e.g., microfractures, tears and eventual failure (breaking)
32
Describe a brittle material
- will not deform/ change length - doesn't absorb much energy before failing - high failure strength
33
Describe ridge and tough materials
- deform a bit - absorb quite a lot of energy
34
Describe compliant materials
- deform a lot under relatively low loads
35
How does the ECM respond to loading?
- ECM transmits force to cells - cells surface receptors activate intracellular signalling pathways - there is a continuous ECM turnover by cells (secrete enzymes to break down ECM) (secrete components of ECM) - cells increase matrix turnover in response to load
36
What is Wolff's law?
- bone is laid down where needed and reabsorbed where not needed
37
Remodelling of bone is regulated by what stresses and strains?
- magnitude - frequency - rate - loading cycles - distribution
38
What does exercise lead to in tendons?
- increased number of fibroblasts - increased collagen synthesis - increased tendon cross-section
39
What does exercise lead to in cartilage?
- increased size and number of chondrocytes - increased ECM
40
what does disuse of cartilage lead to?
- reduced proteoglycan synthesis
41
What does excessive loading of cartilage lead to?
- synthesis rate decreases - degradation rate increases