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Questions and Answers
What is one primary function of connective tissue?
What is one primary function of connective tissue?
Which component contributes to the pressure forces within connective tissue?
Which component contributes to the pressure forces within connective tissue?
Why is bone considered a type of connective tissue?
Why is bone considered a type of connective tissue?
Which of the following is NOT a type of cell connection found in connective tissue?
Which of the following is NOT a type of cell connection found in connective tissue?
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How do fibroblasts interact with collagen fibers?
How do fibroblasts interact with collagen fibers?
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What structural property of the cornea contributes to its strength?
What structural property of the cornea contributes to its strength?
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Which type of collagen is primarily found in bone?
Which type of collagen is primarily found in bone?
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What characterizes James Morris's condition regarding collagen fibers?
What characterizes James Morris's condition regarding collagen fibers?
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What role do integrins play in cellular function?
What role do integrins play in cellular function?
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Which statement accurately describes fibronectin?
Which statement accurately describes fibronectin?
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How is integrin activity regulated?
How is integrin activity regulated?
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What is the primary function of proteoglycans in connective tissue?
What is the primary function of proteoglycans in connective tissue?
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What characterizes gap junctions between cells?
What characterizes gap junctions between cells?
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What is the function of tight junctions in epithelial tissue?
What is the function of tight junctions in epithelial tissue?
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Which type of cellular junction is primarily involved in resisting mechanical stress?
Which type of cellular junction is primarily involved in resisting mechanical stress?
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What characteristic is unique to hemidesmosomes?
What characteristic is unique to hemidesmosomes?
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What role do glycosaminoglycans (GAGs) play in tissue structure?
What role do glycosaminoglycans (GAGs) play in tissue structure?
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Which type of cell junction utilizes actin filaments for adhesion?
Which type of cell junction utilizes actin filaments for adhesion?
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What is the primary composition of the basal lamina?
What is the primary composition of the basal lamina?
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What effect does contraction of the adhesion belt have on epithelial tissue?
What effect does contraction of the adhesion belt have on epithelial tissue?
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What regulates the conductance of gap junctions?
What regulates the conductance of gap junctions?
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What is the primary function of the extracellular matrix (ECM)?
What is the primary function of the extracellular matrix (ECM)?
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Study Notes
Extracellular Matrix and Connective Tissue
- Multicellular organisms have various cell types and fluid spaces in between
- Connective tissue offers protection from stress and aids transport of oxygen and nutrients
- Examples include the layers of the gut and other tissues
Connective Tissue and Extracellular Matrix
- Collagen: Provides pulling forces
- Proteoglycans: Contribute to pressure forces and adhesion (along with laminin and collagen).
- Basal lamina: A region where collagen and laminin promote adhesion.
Cell Connections (extracellular matrix - cytoskeleton)
- Tight junction: Seals neighboring cells to prevent molecule leakage
- Adherence junction: Links actin bundles between cells
- Desmosome: Links intermediate filaments between cells
- Hemidesmosome: Connects intermediate filaments to the basal lamina
- Gap junction: Forms channels for small molecule transport between cells
Collagen Genes
- Collagen types vary in function and location throughout the body
- Different types are made from different genes and used in diverse areas of the body
- Mutations in collagen genes can result in various disorders
Bone as Connective Tissue
- Bone is a type of connective tissue
- It possesses a strong structure due, in part, to calcium phosphate deposits
- Collagen is a major component of bone's extracellular matrix
Collagen Structure
- Collagen is composed of a single polypeptide chain forming a triple-stranded molecule
- These molecules form fibrils and then fibers
- Fibroblasts secrete collagen molecules
Fibroblasts and Collagen
- Fibroblasts secrete collagen molecules
- Fibroblasts play a crucial role in organizing collagen fibers
Fibroblast and Matrix Contacts/Interactions
- Fibroblasts attach to the matrix via focal contacts via integrin proteins
- Actin cortex and lamelipodium play roles in these adhesions; integrins connect to the matrix and to the cytoskeleton.
- These adhesions can be formed or broken
Integrins
- Integrins are crucial to connecting the cytoskeleton to the extracellular matrix
- They connect with adapter proteins to extracellular components.
Fibronectin
- Fibronectin links between extracellular and intracellular components.
- It has collagen and cell adhesion binding sites
Two-way Communication Via Integrins
- Integrin activity can be regulated by intracellular signals
- Outside-in and Inside-out pathways
- This regulation enables cells to attach or detach from the extracellular matrix.
Regulating Integrin Activity
- Activity regulation of integrins can control cellular behavior
- Phosphorylation, protein modification involved
Glycosaminoglycans (GAGs)
- GAGs are negatively charged polysaccharides in tissues like cartilage
- Hyaluronic acid is a GAG, present in large amounts in cartilage
Proteoglycans
- Proteoglycans are large complexes formed from proteins and GAGs
- Aggregation occurs between core proteins, link proteins, and GAGs like chondroitin sulfate and keratin sulfate
- These structures provide resistance to compression and pressure
Protection Against Pressure
- GAGs and proteoglycans help protect against focal pressure, such as in the eye.
- The ability of tissues to resist forces
Epithelium and Basal Lamina
- Epithelial cells rest on a basal lamina
- The basal lamina is comprised of collagen IV and laminins
- Laminins are also linked to integrins on the cell surface
Polarized Orientation of Cells
- Epithelial cells have apical and basal surfaces
- These surfaces exhibit different properties
Polarized Cells in Gut Epithelium
- Intestinal cells have specialized functions based on their position
- Apical cells are involved in mucus secretion
- Basal sides are involved in nutrient absorption
Cell-to-cell Contacts in Epithelial Sheets
- Tight junctions, adherens junctions, desmosomes, and gap junctions connect neighboring cells
- The proteins that mediate these connections can be regulated
Tight Junctions
- Tight junctions are important for preventing leakage of molecules between cells.
- They use occludin and claudin proteins
Adherens Junctions
- Adherens junctions form a belt-like structure holding cells together.
- Cadherins bind actin filaments within cells
- These junctions also play an important role in cell movement/shape changes.
Desmosomes
- Desmosomes join intermediate filaments to connect cells
- The cadherin family of proteins are involved in these interactions.
Gap Junctions
- Gap junctions permit small molecule transport between cells
- They consist of connexon proteins, which form channels
- This process can be actively controlled by the cell
Hemidesmosomes
- Hemidesmosomal structures connect intermediate filaments to the basal lamina
- They resemble focal contacts, which help migrating cells to stick to a surface.
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Description
Test your knowledge on the structure and function of connective tissue and the extracellular matrix. This quiz covers essential elements such as collagen, proteoglycans, and various types of cell connections. Understand the roles these components play in multicellular organisms.
