chapter 5 Flashcards
What are the 3 principal characteristics of the cells that make up epithelium?
-closely apposed and adhere to one another/cell junctions
-functional and morphologic polarity/distinct surface domains
-basal surface attached to underlying basement membrane
Why is epithelioid not considered epithelium?
they lack a free surface
Epithelium functions as a ______________________that facilitates or inhibits the passage of specific substances between the exterior environment and the underlying connective tissue compartment.
selective barrier
when epithelium is one cell layer thick
simple
when epithelium has two or more cell layers
stratified
when the width of the epithelial cell is greater than its height
squamous
when the width, depth, and height of the epithelial cell are approximately the same
cuboidal
when the height of the epithelial cell appreciably exceeds the width
columnar
type of epithelium that appears stratified, although some of the cells do not reach the free surface; all rest on the basement membrane
pseudostratified epithelium
a term applied to the epithelium lining the lower urinary tract, extending from the minor calyces of the kidney down to the proximal part of the urethra
transitional epithelium or urothelium
-the epithelial lining of the blood and lymphatic vessels
-consists of highly specialized simple squamous cells that regulate and monitor cellular transport, vascular smooth muscle tone, immune responses, and synthesis and secretion of variety of hormone and active metabolites
endothelium
the epithelial lining of ventricles and atria of the heart
endocardium
the epithelium that lines the walls and covers the contents of the closed cavities of the body
mesothelium
What are the different functions performed by epithelium?
secretion
absorption
transportation
mechanical protection
receptor function
In some pseudostratified epithelia, basal cells are the ___________________that give rise to the mature functional cells of the epithelium, thus balancing cell turnover.
stem cells
Which domain is always directed toward the exterior surface or the lumen of an enclosed cavity or tube?
apical
Which domain communicates with adjacent cells and is characterized by specialized attachment areas?
lateral
Which domain rests on the basal lamina, anchoring the cell to underlying connective tissue?
basal
finger-like cytoplasmic projections on the apical surface of most epithelial cells that increase the free cell surface area
microvilli
In general, the number and shape of the microvilli of a given cell type correlate with the cell’s _________________________.
absorptive capacity
The microvilli of the _____________________epithelium are the most highly ordered and are even more uniform in appearance than those that constitute the brush border of kidney cells.
intestinal
Microvilli contain a conspicuous core of about 20 to 30 __________________.
actin filaments
The barbed (plus) ends are anchored to ___________, a 95 kDa actin-bundling protein located at the tip of the microvillus.
villin
Name the actin-bundling proteins:
fascin, espin, and fimbrin
a molecule that binds the actin filaments to the plasma membrane of the microvillus
myosin I
The terminal web is composed of actin filaments stabilized by____________, which also anchors the terminal web to the apical cell membrane.
spectrin
What proteins decrease the diameter of the apex of the cell, causing the microvilli to spread apart and increase the intermicrovillus space?
myosin II and tropomyosin
-unusually long, immotile microvilli
-limited to the epididymis, proximal part of the ductus deferens, and sensory cells of the inner ear
stereocilia
What are the unique features of stereocilia?
-an apical cell protrusion from which they arise
-thick stem portions that are interconnected by cytoplasmic bridges
How do stereocilia develop from microvilli?
by the lateral addition of actin filaments to the actin bundle as well as by elongation of the actin filaments
What protein of stereocilia anchors the actin filaments to the plasma membrane?
ezrin
The stem portion of the stereocilium and the apical cell protrusion contain the cross-bridge-forming molecule _________________.
α-actinin
What is the striking difference between microvilli and stereocilia?
the absence of villin at the tip of the stereocilium
The internal structure of stereocilia of the sensory epithelium is characterized by high density of actin filaments extensively cross-linked by________________.
espin
Cilia are hair-like extensions of the apical plasma membrane containing an __________________, the microtubule-based internal structure.
axoneme
The axoneme extends from the basal body, a centriole-derived ________________________located in the apical region of a ciliated cell.
microtubule-organizing center (MTOC)
Which type of cilia function as chemosensors, osmosensors, and mechanosensors, and mediate light sensation, odorant, and sound perception in multiple organs of the body?
primary cilia (monocilia)
Which type of cilia are found in the embryo on the bilaminar embryonic disc at the time of gastrulation and are concentrated in the area that surrounds the primitive node? They are distinct in their ability to perform rotational movement.
nodal cilia
cilia that are capable of moving fluid and particles along epithelial surfaces
motile cilia
internal core of microtubules
axoneme
motor protein that uses ATP hydrolysis to move along the surface of the adjacent microtubule
dynein
Name the basal body-associated structures:
alar sheets, basal feet, and striated rootlets
-tethers the basal body to the apical plasma membrane
-a collar-like extension between the transitional zone of a basal body and the plasma membrane
alar sheet
-accessory structure that may function in coordinating ciliary movement
-most likely involved in adjusting basal bodies by rotating them to the desired position
basal foot
-composed of longitudinally aligned protofilaments containing rootletin
-projects deep into the cytoplasm and firmly anchors the basal body within the apical cytoplasm
striated rootlet
What is the only mechanism for delivering proteins required for cilia assembly and growth?
intraflagellar transport
-also called tight junctions
-establishes a barrier between different compartments of the body and allow epithelial cells to function as a barrier
-maintains cell polarity
occluding junctions
provide mechanical stability to epithelial cells by linking the cytoskeleton of one cell to the cytoskeleton of adjacent cells
anchoring junctions
allow direct communication between adjacent cells by diffusion of small molecules
communicating junctions
represents the most apical component in the junctional complex
zonula occludens
-forms backbone of ZO strands
-forms and regulates aqueous channels used for paracellular diffusion
Claudin
-present in most occluding junctions
-maintains barrier between apical and lateral cell surface
Occludin
-present in most occluding junctions in endothelial cells
-mediates interactions between endothelial cells and monocyte adhesions
JAM
-important link in transduction of signals from all transmembrane proteins
-interacts with actin filaments
-has tumor-suppressor actin
ZO-1
required in the epidermal growth factor-receptor signaling mechansim
ZO-2
interacts with ZO-1, occludin, and actin filaments of cell cytoskeleton
ZO-3
