ECM Flashcards
(37 cards)
What is the composition and arrangement of the tissue surrounding the gut epithelium? What cell types make up the gut epithelium?
(1)
Layer of ECM
Smooth muscle (circularly and longintudinally)
More ECM
Distinguish among the functions of the different cell junctions found in epithelial sheets in animal tissues. How do some interact with the cytoskeleton? Distinguish among occludin/claudin, connexon, cadherin, etc.
Tight junctions
- hold cells together near apical surface
- prevents leakage
- maintains polarity of epithelial cells
- important in intestinal epithelia
- formed from claudins and occludins
Adherens junctions
- cadherin
- connect to actin filaments
- forms adhesion belt (located near apical end) in small intestine
Desmosomes
- cadherin
- connect to keratin filaments (intermediate filaments found in epithelial cells)
Gap junctions
- near basal end
- allows small, intracellular, water-soluble soluble molecules to pass from cell to cell
- Important for spreading electrical waves of excitation through cardiac muscle tissue
- connexons (form water-filled channels between adjacent cells)
What is the difference between desmosomes and hemidesmosomes?
Desmosomes:
- linkage mediated by cadherins
Hemidesmosomes:
- anchor epithelial tissue to underlying connective tissue via integrins
- do not interact with other cells
- interact with basal lamina
- bind epithelial cells to basal lamina
- linkage mediated by integrins
Which cell junctions facilitate direct communication (metabolic/electrical) between cells? How is this
achieved? What protein(s) are involved?
(1) Gap junctions
(2)
(3) Connexons
(1) How does the actin cytoskeleton interact with the ECM (e.g., collagen, elastin)? (2) What components of the ECM contribute to strength vs. flexibility?
(1) Integrins
(2) Collagen (strength) and elastin (flexibility)
Describe four different cellular arrangements found in epithelial sheets. How are the arrangements similar vs.
different? In what type of tissues are they found?
- Columnar
- e.g., intestine - Squamous (flat)
- e.g., primordial ovarian follicles - Cuboidal
- e.g., glandular tissue - Stratified (layers)
- e.g., epidermis
What is the difference between lamin and laminin?
Lamin - intermediate filaments
Laminin - helps form the basal lamina (part of ECM); provides adhesive sites for integrins
How is mechanical strength achieved differently within the intestinal epithelium vs. the epidermal epithelium?
Intestinal epithelium - adherens junctions (actin filaments)
Epidermal epithelium - desmosomes intermediate filaments)
How are epithelial tubes formed during embryogenesis?
• Adhesion belt tightens apical domain
• Tube forms through apical constriction/contraction
• Structures:
- Neural tube
- Lens
What are the four categories of tissue?
- Nerve tissue
- Muscle tissue
- Epithelial tissue
- Connective tissue
Tissue is further organized into _______.
Organs
Where is procollagen proteinase located?
ECM
Compare the structure of collagen and elastin.
Collagen:
* Triple helix of peptides (triple stranded helical structure)
* Rich in glycine (every 3rd aa is a glycine)
* Adds strength
Elastin:
* Relatively loose and unstructured peptide chains
* Cross-linked by disulfide bonds
* Add flexibility
Oxidative environment (in ER)
Compare the function osteoblasts and fibroblasts.
Osteoblasts - produces ECM in bone
Fibroblasts - produces ECM in skin, tendons, and connective tissue
Describe the assembly of collagen
Procollagen -> collagen -> collagen fibrils -> collagen fibers
What causes hyperextensible skin?
Defects/mutations in extracellular proteinases
Describe integrins. What is their structure and how do they function? How does it perform this function?
Structure: Single-pass transmembrane proteins that form a-B dimers
Function: Couple matrix outside cell to interior cytoskeleton
* Extracellular domain binds to components of matrix
- Intracellular domain interacts with adapter proteins connecting to actin cytoskeleton
What is the role of fibronectin?
- One region binds to collagen
- Another region binds to integrins
Which domain of integrin binds to fibronectin? Which domain binds to actin filaments?
Extracellular domain - binds to fibronectin
Intracellular domain - binds to actin filament
What are the two faces of the epithelial sheet?
- Apical - free and exposed
- Basal - attached to basal lamina
What is the basal lamina composed of?
Type IV collagen and laminin
What keeps apical and basal domains separate?
Tight junctions
What are the two major cell types that make up the intestinal epithelial lining?
- Absorptive - import food molecules through apical surface and export them through basal surface
- Secretory - allow things to go into lumen; secrete mucus
- Synthesize mucus and then discharge it from apical domain only
