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16 Cards in this Set
- Front
- Back
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Describe general characteristics of epithelial tissue.
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(1) Sheets or layers of cells held together by cell surface specializations.
(2) Cells are polarized (base, apex, lateral surfaces) (3) Cells are supported at the base by a basement membrane (basal lamina) and usually a layer of connective tissue (4) Constantly being replaced by new epithelial cells. |
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What are some of the fx's of epithelial tissues?
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(1) Covering and lining surfaces (skin, intestines)
(2) Protection (skin) (3) Secretion (glands) (4) Absorption (intestines) (5) Sensation (6) Contraction (myoepithelial cells) (7) Transcellular transport/Selective permeability |
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What is the lamina propria?
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It is a thin layer of loose connective tissue that lies beneath the epithelium and together with the epithelium constitutes the mucosa.
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Describe pseudostratified epithelial cells.
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1 layer of epithelial cells where all cells touch the basal lamina but not all of the cells contact the surface.
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Describe transitional epithelial cells.
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Can be 1 or more layers.
Domelike cells found in organs that stretch. When contracted - there several layers of cells. When distended - there are few layers of cells. |
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Explain how polarization affects the distribution of organelles in epithelial cells.
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Different parts of the cell can have different functions. So organelles and structures that support those functions will be found in different areas of the cell.
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What are microvilli?
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(1) Fingerlike projections that line many absorptive cells.
(2) They increase surface area to aid absorption. (3) They are covered by glycocalyx. (4) Within microvilli are actin microfilaments cross-linked together. |
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What are cilia?
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(1) Cylindrical, motile structures.
(2) Internally, they contain 2 central microtubules surrounded by 9 pairs of microtubules. (3) Inserted into a basal body at the apical pole below the membrane. (4) ATP is the source of energy for their back and forth motion. |
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What are Zona Occludens? Describe them.
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Tight Junctions
(1) Most apical of the junctions. (2) Forms a continuous band around the cell (3) It fuses neighboring cells together, creating a tight seal that prevents the flow of material b/t cells. |
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What are Zona Adherens? Describe them.
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Adhesion Plaques.
(1) Adhesive belt that encircles the cell and provides adhesion to neighboring cells. (2) Serves as an anchoring site for filaments. |
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What are Macula Adherns? Describe them.
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Desmosomes.
(1) Complex of proteins in a disc-like shape that match with an identical structure on neighboring cells. (2) Provides strong cell-to-cell adhesion. |
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What are gap junctions? Describe them.
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Cylindrical channels b/t cells whose primary functions are (1) containing damaged cells, (2) metabolic coupling, and (3) electrical coupling.
Each unit of gap junction is called a connexon and there are 10s to 100s of connexons per gap junction. Each connexon is made of 6 connexins that form a hydrophilic pore, creating a channel b/t cells. Opposing connexons made of 6 connexins that form a hypdrophilic pore. When open, these pores allow two to exchange ions and small molecules < 1200 MW, permitting communication as well as electrical and metabolic coupling between cells. |
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What is the purpose of infolding of the basal lamina? Where is it found?
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Purpose - increase surface area.
Found in ion-transporting cells to increase area for ion pumps or in tissues subject to stress (e.g. tongue & skin) |
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What are the subunits of the basal lamina? What are their functions?
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Subunits: Lamina lucida & Lamina densa.
Lamina lucida: comprised of laminin & anchors epi cell to basal lamina. Lamina densa: comprised of type IV collagen and heparan sulfate - an anion - giving basal lamina its negative charge |
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What are the overall functions of the basal lamina?
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(1) Physical support for epithelium
(2) Negatively charged permeability barrier (3) Differentiation of overlying epithelial cells |
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What are the functions of the epithelium?
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(1) Selective barrier, separating body into compartments
(2) Protection, resisting abrasion and dehydration (3) Secretion, synthesizing products released outside of the cell; form glands to increase number of secretory cells (4) Absorption, selectively controlling materials which can cross the barrier (5) Filtration PASS/F |
