Connective Tissue Flashcards
Describe the cellular contact with each other in CT
Cells have few contacts with each other
How much ECM is there in CT
Large amount of ECM
Where is CT located in relation to epithelium and basal lamina?
CT is under the basal lamina which is under epithelium
What is the ECM?
Spaces between cells composed of a complex array of molecules
What is the ECM composed of?
Tough fibrous proteins embedded in a polysaccharide gel like material
What is the polysaccharide gel like material in the ECM called?
The ground substance
How is there a variety of CTs?
Different composition and arrangement of ECM
Describe the ECMs in Tendon, Bone and Cartilage CT
Tendon (muscle to bone CT) - numerous fibrous proteins, little ground substance
Bone - calcified ground substance and fibrils
Cartilage - large amount of polysaccharide gel
Name some of the roles the ECM plays?
Structural support and regulation of cellular activities
How is the ECM produced?
By cells within it, so the cells produce, secrete and organize components of ECM
what is one of the most abundant proteins in the ECM?
Collagen and must be correctly aligned and organised
Different cells produce ECM depending on the tissue. Name the cells that produce the ECM in the following tissues;
1) Loose connective tissues
2) Bone
3) Cartilage
4) Basement membrane in epithelia
1) Fibroblasts
2) Osteoblasts
3) Chondroblasts
4) Epithelial cells
ECM is composed of what two main things?
Proteins and proteoglycans
What proteins are in the ECM and examples of them
Fibrous/Structural (Collagen and Elastin)
Adhesive (Laminin)
What does collagen provide?
Provides tensile strength
What amino acids is Collagen rich in?
Proline and Glycine arranged in repeats as a helical polypeptide chain
What is the collagen structure of an alpha chain
Gly-X-Y triplets
X= Proline or Lysine
Y = HydroxyProline or Hydroxylysine
What does a collagen molecule consist of?
3 alpha chains into an alpha helix, 1.5nm diameter
Alpha collagen chain is what handed and why?
Left handed due to dihedral angle of prolines
What are collagen fibrils?
Collagen molecules assembled, outside of the cell, together via covalent cross linking
Regular packing of collagen molecules in fibrils leads to what?
Cross stations
Collagen fibrils pack together to form what?
Fibres
Name the type of collagen formation that doesnt form fibres?
Fibril Associated Collagens
Describe the structure of the FAC
Triple helix interrupted by non-helical domains which gives flexibility
Is FAC cleaved after secretion?
No, retains propeptides
Do FACs aggregate to form fibrils?
No
Describing the binding of FACs
Bind periodically to other collagen fibrils.
Type IX binds Type II fibrils. Type XII binds Type I fibrils
Name the 8 stages in collagen synthesis?
1) Synthesis of pro alpha chain
2) Hydroxylation of selected prolines and lysines
3) glycosylation of selected hydroxylysines
4) self assembly of 3 pro alpha chains
5) procollagen triple helix formation
6) secretion
7) cleavage of propeptides
8) self assembly into fibril
Where does the synthesis of Pro Alpha Chain/ Procollagens take place?
Outside of the ER lumen
N and C terminal ends of the pro alpha chain have what?
the propeptide
Intrachain disulfide bonds between the N and C terminal propeptide sequences do what?
Align chains to form triple helix in ER
Procollagen is modified where and secreted by what?
Modified in ER and Golgi
Secreted by exocytosis
Where is the assemblied 3pro-alpha-chain secreted into?
Extracellular space
Name the extracellular enzymes and the function of them in relation to the 3pro-alpha-chain
Procollagen peptidases remove N and C terminal propeptides
After the removal of propeptides, what occurs?
Self polymerises into fibrils
What do the collagen pro-peptides prevent?
Premature assembly of collagen in side cells
After secretion, what happens in terms of covalent bonding?
Covalent bonds (lysine resides) cross link the collagen molecules
How is tensile strength of collagen determined?
Extent of cross linking.
High cross linking gives high tensile strength which occurs in tendons
What are the 3 defects in collagen?
Collagen I - Otsteogensis imperfecta (brittle bones), variety of mutations - failure to form triple helices
Collagen II - Achondrogensis - Abnormal bone and joint formation
Collagen III - Fragile skin, blood vessels and hypermobile joins, elastic skin
What is scurvy caused by?
Failure to hydroxylate prolines and lysines in fribrillar collagen due to reduced levels of ascorbate (vitamin c)
