Epithelium Glands II Flashcards
1
Q
name the lateral surface specialization of cells
A
- Junctional complexes:
- Occluding junctions
- Tight junction (zonula occludens)
- Anchoring junctions
- adhering junctions (zonula adherens)
- desmosomes (macula adherens)
- Communicating junctions
- Gap junctions
- Occluding junctions
2
Q
Name these junctions
A
- zonula occludens
- zonula adherens
- maculae adherens (desmosomes)
3
Q
describe zonula occludens
A
- Occluding junctional complex (cell to cell)
- Zonular occludens = tight junctions
- Localized sealing of the PM of adjacent cells
- Network of anastomosing strands that completely surround the apical cell borders
- Transmembrane proteins = claudins & occludins
- Interaction with actin cytoskeleton via ZO-1
4
Q
describe how zonula occludens affects movement of stuff
A
- Zonula occludens separates the luminal space from the intercellular space and connective tissue compartment
- Paracellular pathway
- Across the zonula occludens between 2 cells
- Transcellular pathway
- Across the PM of the epithelial cell
- Establishes functional domains in the PM
- apical
- lateral
- basal
5
Q
describe zonula adherens
A
- Anchoring junctional complex (cell to cell)
- Lateral adhesion between epithelial cells
- Continuous band or belt that surrounds the entire cell, found just beneath the tight junction
- Transmembrane protein = E-cadherin
- Ca+ dependent
- Helps to attach adjacent cells (15-20 nm apart)
- Interaction with actin cytoskeleton
6
Q
describe macula adherens
A
- Macula adherens = desmosomes
- Lateral, localized, spot adhesion between epithelial cells about 30nm apart
- Focal dense spots (macula)
- Found beneath the zonula adherens of cells
- Transmembrane protein = desmocollin and desmoglein
- Cadherin family, calcium dependent
- Intercellular plaque = plakoglobins and desmoplakins
- Interaction with intermediate filaments of cytoskeleton
7
Q
describe gap junctions
A
- Communicating junctional complex (cell to cell)
- Present in a variety of tissues
- Epithelium
- Smooth and cardiac muscle
- Nerve
- Help coordinate activity of adjacent cells
- Connexin
- transmembrane protein subunits
- Connexon
- half channel formed by 6 connexins
- Connexons align to form a communicating channel connecting the cytoplasm of adjacent cells
8
Q
describe lateral interdigitations
A
- Lateral interdigitations
- infoldings (plicae) of cytoplasmic processes of adjoining cells
- Increase lateral cell surface area
- Common in cells engaged in fluid and electrolyte transport
- Ex: gall bladder, small intestine
- Sodium ions are pumped out of cytoplasm by Na/K/ATPase localized there
- Fluid accumulates in intercellular space until driven into underlying connective tissue
- Tight junctions prevent fluid escape in apical direction
9
Q
describe focal adhesions
A
- Anchoring junctional complex
- Cell to ECM junctions
- Helps to anchor epithelial cells to basment membrane
- Transmembrane proteins = integrins
- Link between actin microfilaments of cytoskeleton and ECM
- Important role during cell migration
10
Q
describe hemidesmosomes
A
- Anchoring junctional complex
- Cell to ECM junctions
- Helps to anchor epithelial cells to BM
- Half the component of desmosomes
- Transmembrane proteins = integrins
- Interaction with IFs of cytoskeleton
11
Q
what is a bollus pemphigoid
A
- Blisters between epidermis and BM caused by incorrect hemidesmosomes
- Bullous pemphigoid
- Disease characterized by blister formation at epithelium attachment to BM
- antibodies directed against BP230 and type XVII collagen
12
Q
describe basal infoldings
A
- Significantly increase the surface area of the basal domain
- Allow for more transport proteins and channels to be present
- Well developed in cells performing active transport of molecules
- Kidney tubule
- Striated ducts of exocrine glands
13
Q
describe the basal lamina
A
- Visualized by EM
- Structural attachment site for overlying epithelial cells and underlying connective tissue
- Called “external lamina” in nonepithelial cells
- Composed of fine filaments
- Laminins
- Type IV collagen
- Proteoglycans and Glycoproteins
- 2 layers
- Lamina lucida (just an artifact, not real)
- Lamina densa: electron dense
14
Q
name the 2 major groups of glands, and the 3 release mechanisms of the first one
A
- Exocrine
- Secrete onto a surface directly or through ducts that are connected to surface
- 3 release mechanisms
- Merocrine
- Apocrine
- Holocrine
- Endocrine
- secrete products (hormones) into the connective tissue and then enter blood stream
- paracrine = nearby cells
- autocrine = same cell
15
Q
describe merocrine secretion
A
- Exocytosis of membrane-bound vesicles
- most common
