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Connective Tissue Overview
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Connective Tissue Overview
Connective Tissue Overview
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1
Question
What are the fibers of connective tissue?
Answer
1. Collagen 2. Procollagen 3. Collagen Fibrils 4. Crossbanding 5. Collagen Bundles 6. Matrix Metalloproteinases (MMPs) 7. Reticular Fiber 8. Elastic Fibers
2
Question
What are the 3 main types of fibers in connective tissue?
Answer
1. Collagen Fibers 2. Reticular Fibers 3. Elastic Fibers, which are mainly formed by Elastin.
3
Question
What is collagen?
Answer
Collagen constitutes a family of proteins selected during evolution for their ability to form various extracellular fibers, sheets, and networks, all of which are extremely strong and resistant to normal shearing and tearing forces.
4
Question
What is the role of collagen in connective tissues?
Answer
Collagen is a key element of all connective tissues as well as epithelial basement membranes and the external laminae of muscle and nerve cells.
5
Question
What cell type primarily produces collagen?
Answer
Collagen is a major product of fibroblasts, but it is also secreted by several other cell types.
6
Question
How many types of collagen exist in vertebrates?
Answer
A family of 28 collagens exists in vertebrates, numbered in the order they were identified.
7
Question
What are fibrillar collagens?
Answer
Fibrillar collagens have polypeptide subunits that aggregate to form large fibrils.
8
Question
Which type of collagen is the most abundant?
Answer
Collagen type I is the most abundant and widely distributed, forming collagen fibers.
9
Question
What are collagen fibers?
Answer
Collagen fibers are large, eosinophilic bundles that densely fill the connective tissue, forming structures such as tendons, organ capsules, and dermis.
10
Question
What are network or sheet-forming collagens?
Answer
These collagens have subunits produced by epithelial cells and are major structural proteins of external laminae and all epithelial basal laminae.
11
Question
What are linking and anchoring collagens?
Answer
Linking and anchoring collagens are short collagens that link fibrillar collagens to one another, forming a larger fiber.
12
Question
What is the role of type VII collagen?
Answer
Type VII collagen binds type IV collagen and anchors the basal lamina to the underlying reticular lamina in basement membranes.
13
Question
Where does collagen synthesis occur?
Answer
Collagen synthesis occurs in many cell types but is a specialty of fibroblasts.
14
Question
What are procollagen chains?
Answer
Procollagen chains are polypeptides made in the Rough Endoplasmic Reticulum (RER) with different chains of variable lengths and sequences synthesized from collagen genes.
15
Question
How are procollagen chains aligned in the ER?
Answer
In the ER, three chains are selected, aligned, and stabilized by disulfide bonds at their carboxyl terminals, and folded into a triple helix.
16
Question
What happens to the procollagen molecule after exocytosis?
Answer
The procollagen molecule undergoes cleavage to become a rod-like collagen molecule, which is the basic subunit from which fibers or sheets are assembled.
17
Question
What is the difference between homotrimeric and heterotrimeric procollagen?
Answer
Homotrimeric has all three chains identical, while heterotrimeric has two or all three chains having different sequences.
18
Question
What is required for collagen synthesis?
Answer
An unusually large number of posttranslational processing steps are required to prepare collagen for its final assembly in the ECM.
19
Question
What role do hydroxylase enzymes play in collagen synthesis?
Answer
Hydroxylase enzymes in the ER add hydroxyl groups to amino acids, requiring oxygen, ferrous sulfate, and ascorbic acid.
20
Question
What are procollagen peptidases?
Answer
Procollagen peptidases are specific proteases outside a fibroblast that remove terminal globular peptides, converting procollagen molecules to collagen molecules.
21
Question
What is the function of lysyl oxidase?
Answer
Lysyl oxidase catalyzes the process that allows collagen to withstand forces and remain secured outside of the cell.
22
Question
What is collagen cross-linking?
Answer
A process where the fibrillar structure is reinforced, and disassembly is prevented by the formation of covalent cross-links between collagen molecules.
23
Question
What happens to collagen fibrils after exocytosis?
Answer
The nonhelical ends of procollagen subunits are removed, forming trimeric collagen molecules that aggregate and become covalently bound in large collagen fibrils.
24
Question
What is crossbanding in collagen?
Answer
The highly regular assembly of collagens in the fibrils produces a characteristic pattern of crossbanding visible ultra structurally along some collagen types.
25
Question
What is the stability of collagen in different organs?
Answer
In some organs, such as tendons and ligaments, collagen is very stable, whereas in others, like the periodontal ligament surrounding teeth, the collagen turnover rate is high.
26
Question
What are collagenases?
Answer
Collagenases are enzymes that initiate collagen degradation and are members of the matrix metalloproteinases (MMPs).
27
Question
What is a keloid?
Answer
A keloid is a local swelling caused by abnormally large amounts of collagen that form in scars of the skin.
28
Question
Who is most at risk for keloids?
Answer
Keloids occur most often in individuals of African descent and can be a troublesome clinical problem to manage.
29
Question
What is the difference between hypertrophic scars and keloids?
Answer
Hypertrophic scars remain confined to the original wound boundary, while keloids extend beyond the original wound area, growing into surrounding healthy skin.
30
Question
What are reticular fibers?
Answer
Reticular fibers consist mainly of type III collagen and are found in delicate connective tissue of many organs, notably in the immune system.