Extracellular matrix Flashcards
Define the extracellular matrix (ECM)
Theextracellular matrix(ECM) is a three-dimensional network ofextracellular macromolecules, such as collagen, enzymes, and glycoproteins, that provide structural and biochemical support of surrounding cells
Identify the constituents of ECMs (6)
Collagen Elastin GAG Hyaluronic Acid (Type of GAG) Heparan Sulphate (Type of GAG) Proteoglycans
Describe the structure and function of collagen
Structure
• It is a major protein within the ECM
• In the body, it accounts for 25% of all protein
• They are rope like structures
• Since they are made intracellularly, a lot of pathological disorders regarding collagen can occur
• Collagen fibers are cross branded in a triple helix
• Every third amino acid is glycine in collagen, which enables tight coiling
Proline and Lysin in collagen enable the triple helix cross linkage of fibers
Function
* Rope like structures enable resistance of tension
Describe the structure and function of elastin
Structure
* Single molecule which are cross linked randomly with each other
Function
• Allows for stretching and recoiling
* It enables tissue to return to original shape after it has been stretched
Describe the structure and function of GAGs
Structure
• Are carbohydrate polymers
• Made up of long, unbranched polysaccharides which consists of a repeating disaccharide unit
• Repeating units consist of an amino sugar and uronic sugar
• Strong negative charge
• Sulphated
• Attracts and traps water due to its strong charge and traps cations
Function
* Resists compression and thus maintain hydration
Describe the structure and function of Hyaluronic Acid GAGs
Structure
• Manufactured on cell membrane by an enzyme complex
• Also made up of different disaccharides
• No sulphates
• Large polymer= excellent shock absorber
Binds many proteoglycans
Function
• Aids in water retention
* Thus, it is a major component in synovial fluid
Describe the structure and function of Heperan Sulphate GAGs
Structure
• Manufactured in the Golgi
• Similar to hyaluronic acid except it is highly sulfated
Sulfate groups enables it to be biologically active and participating in cellular signaling
Function
• Hydrates and aids in cushioning
* Regulates angiogenesis (making new blood vessels), blood coagulation and cellular signaling
What is a proteoglycan?
Proteoglycans are polysaccharide sugars attached to proteins.
GAGs are the polysaccharide components of proteoglycans.
What are the types of ECM? (5)
- Loose collagenous connective tissue
- Dense collagenous connective tissue
- Bone
- Cartilage
- Adipose tissue
Provide a description and example of loose collagenous connective tissue
Description:
• Blood vessels
• Higher amounts of proteoglycans and hyaluronic acid than collagen and elastin
* Role is to fill and hydrate intercellular spaces and enable travelling of cells
Example:
Small intestine mesentery
Provide a description and example of dense collagenous connective tissue
Description:
• Not many blood vessels hence white appearance macroscopically
* Lots of collagen thus very hard
Example:
Tendon
Provide a description and example of bone
Description:
• Highly vascular
• Calcified collagen (to ensure bone is flexible enough to not fracture easily)
• Osteoclasts, osteocytes and osteoblasts
• Soft tissue (marrow) in spaces
* Proteoglycans and glycoproteins although less, help in organization of collagen
Example:
Bone
Provide a description and example of cartilage
Description: • No blood vessel • Elastin (pharynx and epiglottis) • Collagen (counteracts tensile loads) * GAGs (dampen mechanical pressures)
Example:
Cartilage
Provide a description and example of adipose tissue
Description: • A lot of fat in it • Triglycerides • Structural cushioning thanks to high fat store * Stores water thus resists dehydration
Example:
• Hands
• Soles
* Enables body contour and thus indicates sexual morphology
Describe the process of adaptive ECM re-modelling with respect to various involved proteins
• The ECM is in a constant state of turnover; their synthesis is balanced by degradation
• Fibroblasts form collagen and elastin, but they can actually retract them with certain proteins
• They are degraded by enzymes
• Proteinases/ MMPS (metalloproteinases) digest proteins
* TIMPS (tissue inhibitors of metalloproteinases) inhibit these proteinases
