SPECIAL PROJECTING CELLS Flashcards
(24 cards)
In epithelia specialized for absorption the apical cell surfaces are often filled with an array of projecting ______ (L. villus, tuft), usually of uniform length.
microvilli
In cells such as those lining the ______, densely packed microvilli are visible as a ______ or ______ projecting into the lumen.
small intestine, brush, striated border
The average microvillus is about ______ μm long and ______ μm wide, but with hundreds or thousands present on the end of each absorptive cell, the total surface area can be increased by ______- or ______-fold.
1, 0.1, 20, 30
The thick ______ covering microvilli of the intestinal brush border includes membrane-bound proteins and enzymes for digestion of certain macromolecules.
glycocalyx
Each microvillus contains bundled ______ capped and bound to the surrounding plasma membrane by actin-binding proteins.
actin filaments
Although microvilli are relatively stable, the ______ arrays are dynamic and undergo various myosin-based movements, which help maintain optimal conditions for absorption via numerous channels, receptors, and other proteins in the plasmalemma.
microfilament
The actin filaments insert into the ______ of cortical microfilaments at the base of the microvilli.
terminal web
______ are a much less common type of apical process, best seen on the absorptive epithelial cells lining the male reproductive system.
Stereocilia
Like microvilli, ______ increase the cells’ surface area, facilitating absorption.
stereocilia
More specialized stereocilia with a motion-detecting function are important components of ______ cells.
inner ear sensory
______ resemble microvilli in containing arrays of microfilaments and actin-binding proteins, with similar diameters, and with similar connections to the cell’s terminal web.
Stereocilia
Stereocilia are typically much ______ and less ______ than microvilli, and may show branching ______.
longer, motile, distally
______ are long, highly motile apical structures, larger than microvilli, and containing internal arrays of ______ not microfilaments.
Cilia, microtubules
In addition to cilia on epithelial cells, most (if not all) other cell types have at least one short projection called a ______, which is not ______ but is enriched with receptors and signal transduction complexes for detection of light, odors, motion, and flow of liquid past the cells.
primary cilium, motile
Motile cilia are abundant on ______ or ______ cells of many epithelia.
cuboidal, columnar
Typical cilia are ______-______ μm long and ______ μm in diameter, which is much ______ and ______ times wider than a typical microvillus.
5, 10, 0.2, longer, two
Each cilium has a core structure consisting of nine ______ (in which a few tubulin protofilaments are shared) arrayed around two ______. This 9 + 2 assembly of microtubules is called an ______.
peripheral microtubule doublets, central microtubules, axoneme
Cilia
As with other microtubules, ______ and ______ motors move along the peripheral microtubules for the transport of molecular components into and out of these structures.
kinesin, cytoplasmic dynein
Cilia
Microtubules of axonemes are continuous with those in ______, which are apical cytoplasmic structures just below the cell membrane.
basal bodies
Cilia
Basal bodies have a structure similar to that of ______, with triplets of microtubules and dynamic tubulin protofilaments forming rootlets anchoring the entire structure to the cytoskeleton.
centrioles
______ exhibit rapid beating patterns that move a current of fluid and suspended matter in one direction along the epithelium.
Cilia
______ motion occurs through successive changes in the conformation of the axoneme, in which various accessory proteins make each cilium relatively stiff, but elastic.
Ciliary
Cilia
Complexes with ______ bound to one microtubule in each doublet extend as “arms” toward a microtubule of the next doublet. With energy from ATP dynein-powered sliding of adjacent doublets relative to each other bends the axoneme and a rapid series of these sliding movements produces the beating motion of the cilium.
axonemal dynein
Cilia
The long ______ that extends from each fully differentiated sperm cell has an axonemal structure like that of a cilium and moves with a similar mechanism.
flagellum
