Epithelial Tissue Flashcards
A simple epithelium has how many cell layers?
one
Which of the following structures is not commonly found on the apical surface of epithelial cells?
a. Microvilli
b. Cilia
c. Stereocilia
d. Desmosomes
d. Desmosomes
Epithelial cells that function mainly to produce and secrete various macromolecules may occur in epithelia with other major functions or comprise specialized organs called?
Glands
This is the connective tissue that underlies the epithelia lining the organs of the digestive, respiratory, and urinary systems.
Lamina propria
What does “keratinized” mean in stratified squamous cells?
Dry
Where do stratified columnar cells line?
Conjunctiva
How much sodium ions should be present inside the cell compared to potassium ions?
more potassium ions inside, more sodium ions outside
These are the shapes of Epithelial Cells, except:
a. Cuboidal
b. Squamous
c. Spherical
d. Columnar
c. Spherical
Scattered secretory cells, sometimes called as ______.
Unicellular glands
These are the Apical Structures of Epithelial Cells, except:
a. Cilia
b. Celiac
c. Microvilli
d. Stereocilia
b. Celiac
______ tissue is a type of tissue that covers body surfaces, lines cavities, and forms glands.
Epithelial
It serves as a protective barrier, involved in absorption, secretion, and sensation.
Epithelial tissue
The cells in Epithelial tissue are tightly packed, forming layers that can be ______ (one layer) or ______ (multiple layers), and vary in shape, including ______ (flat), ______, and ______ (tall) forms.
simple, stratified, squamous, cuboidal, columnar
______ tissue is crucial for protecting the body and supporting essential functions.
Epithelial
______ (Gr. epi, upon + thele, nipple) line all external and internal surfaces of the body and all substances that enter or leave an organ must cross this type of tissue.
Epithelia
Epithelial tissues are composed of ______ adhering strongly to one another and to a thin layer of ECM, forming cellular sheets that line the cavities of organs and cover the body surface.
closely aggregated polyhedral cells
Shapes of Epithelial cells
columnar
Cuboidal
squamous
Shapes of Epithelial cell nuclei
elliptic (oval)
spherical
flattened
Functions of epithelial tissues
Covering, lining, and protecting surfaces (eg, epidermis)
Absorption (eg, the intestinal lining)
Secretion (eg, parenchymal cells of glands)
This is the connective tissue that underlies the epithelia lining the organs of the digestive, respiratory, and urinary systems.
lamina propria
These are Small evaginations that increases the area of contact between the epithelial and connective tissues.
Papillae
______ occur most frequently in epithelial tissues
subject to friction, such as the covering of the skin or tongue.
Papillae
Most epithelia are adjacent to ______ tissue containing blood vessels from which the epithelial
cells receive nutrients and O2. Even thick epithelia do not themselves normally contain blood vessels.
connective
Epithelial cells generally show ______, with organelles and membrane proteins distributed unevenly within the cell.
polarity
The region of the cell contacting the ECM and connective tissue is called the ______ and the opposite end usually facing a space is the ______.
basal pole, apical pole
The two poles differing significantly in both structure and function. Regions of cuboidal or columnar cells that adjoin neighboring cells comprise the cells’ ______; ______ here often have numerous folds which increase the area and functional capacity of that surface.
lateral surfaces, cell membranes
This is a thin extracellular, felt-like sheet of macromolecules where the basal surface of all epithelia rests on.
Basement Membranes
This is a semipermeable filter for sub stances reaching epithelial cells from below.
Basement Membranes
This always lies at the interface of epithelial cells and connective tissue.
Basement Membranes
Nutrients for epithelial cells must diffuse across the ______.
basement membrane
Glycoproteins and other components in the ______ can often be stained and visualized with the light microscope.
basement membrane
It is Nearest the epithelial cells.
Basal lamina
It is a thin, electron-dense, sheet-like layer of fine fibrils.
Basal lamina
It is Beneath the basal lamina and More diffused and fibrous.
Reticular lamina
The terms “basement membrane” and “basal lamina” are sometimes used interchangeably, but “______” usually denotes the fine extracellular layer seen ultra-structurally and “______” the entire structure beneath the epithelial cells visible with the light microscope.
basal lamina, basement membrane
ECM components of the Basal lamina:
Type IV collagen
Laminin
Nidogen and perlecan
Monomers of ______ self assemble into a two-dimensional network of evenly spaced subunits resembling the mesh of a window screen.
type IV collagen
These are large glycoproteins that attach to transmembrane integrin proteins in the basal cell membrane and project through the mesh formed by the type IV collagen.
Laminin
Respectively a short, rod-like protein and a proteoglycan, both of these cross-link laminins to the type IV collagen network, helping to provide the basal lamina’s three-dimensional structure, to bind the epithelium to that structure, and to determine its porosity and the size of molecules able to filter through it.
Nidogen and perlecan
The ______ helps to provide structural support for epithelial cells and attach epithelia to underlying connective tissue.
Basement Membrane
______ components help organize integrins and other proteins in the plasma membrane of epithelial cells, maintaining cell polarity and helping to localize endocytosis, signal transduction, and other activities.
Basal lamina
______ proteins also mediate many cell-to-cell interactions involving epithelia and mark routes for certain cell migrations along epithelia.
Basement membrane
The ______ also serves as a scaffold that allows rapid epithelial repair and regeneration.
basement membrane
Intercellular Adhesion and Other Junctions
Tight or occluding junctions
adherent or anchoring junctions
gap junctions
lateral surfaces of epithelial cells have complexes of several specialized intercellular junctions with different functions:
______ junctions form a seal between adjacent cells.
Tight or occluding
lateral surfaces of epithelial cells have complexes of several specialized intercellular junctions with different functions:
______ junctions are sites of strong cell adhesion.
Adherent or anchoring
lateral surfaces of epithelial cells have complexes of several specialized intercellular junctions with different functions:
______ junctions are channels for communication between adjacent cells.
Gap
In many epithelia, these junctions are present in a definite order at the ______ end of the cells.
apical
Tight junctions, also known as ______, are located at the ______ end of epithelial cells.
zonulae occludens, apical
The term “______” indicates that these junctions form a continuous band around each cell.
zonula
In transmission electron microscopy (TEM), ______ junctions appear as fused or tightly apposed adjacent membranes.
The seal between cell membranes is created by interactions between transmembrane proteins, specifically ______ and ______.
tight, claudin, occludin
______ junctions are clearly visible after cryofracture of epithelia, appearing as a band of branching strands around each cell’s apical end.
Tight
______ junctions ensure that molecules crossing an epithelium do so through the cells (______ path) rather than between them (______ pathway).
Tight, transcellular, paracellular
Permeability (Tight Junctions)
Epithelia with fewer fused sealing strands (e.g., proximal renal tubule) are ______ permeable to water and solutes.
more
Permeability (Tight Junctions)
Epithelia with many fused strands (e.g., lining of the urinary bladder) are ______ permeable.
less
______ junctions also serve a related purpose: these continuous zones within cell membranes serve as fences restricting movements of membrane lipids and proteins at the apical cell surface into the lateral and basal sur faces, and vice versa.
Epithelial tight
The tight junctions thus maintain two distinct membrane domains (______ and ______) with different sets of components, which allows these two sides of the epithelium to display different receptors and other proteins and to function differently.
apical, basolateral
______ cell membranes of epithelia are part of the luminal compartment of a tissue or organ, while the ______ domains are part of a basal compartment that also encompasses the underlying connective tissue.
Apical, basolateral
Proteins of tight junctions provide the targets for certain common bacteria of medical importance. The ______ secreted by Clostridium perfringens, which causes “food poisoning,” binds claudin molecules of intestinal cells, prevents insertion of these proteins during maintenance of tight junctions, and causes loss of tissue fluid into the intestinal lumen via the paracellular pathway. Similarly, ______, which is important in the etiology of gastric ulcers, binds the extracellular domains of tight-junction proteins in cells of the stomach and inserts a protein into these cells, which targets ZO-1 and disrupts signaling from the junction.
enterotoxin, Helicobacter pylori
The ______ Junction (______) Encircles the epithelial cell, usually just below the tight junction. It Anchors a cell to its neighbors.
Adherens, Zonula Adherens
Adherens Junction (Zonula Adherens)
Cell adhesion is mediated by ______, transmembrane glycoproteins of each cell that bind each other in the presence of Ca2+.
cadherins
Adherens Junction (Zonula Adherens)
At their ______ ends, cadherins bind catenins that link to actin filaments with actin-binding proteins.
cytoplasmic
The actin filaments linked to the adherens junctions form part of the “______,” a cytoskeletal feature at the apical pole in many epithelial cells.
terminal web
Together, the ______ and ______ junctions encircling the apical ends of epithelial cells function like the plastic bands that hold a six-pack of canned drinks together.
tight, adherent
Another anchoring junction is the ______ (Gr., ______, binding and ______, body) or ______ adherens (L. ______, spot).
desmosome, desmos, soma, macula, macula
The ______ Resembles a single “spot-weld” and does not form a belt around the cell.
Desmosome
______ are disc-shaped structures at the surface of one cell that are matched with identical structures at an adjacent cell surface.
Desmosomes
Desmosomes contain larger members of the cadherin family called ______ and ______. The cytoplasmic ends of these clustered transmembrane proteins bind plakoglobins, catenin-like proteins which link to larger proteins called ______ in an electron-dense plaque.
desmogleins, desmocollins, desmoplakins
______ in turn bind intermediate filament proteins rather than actins. Epithelial desmosomes attach to cable-like filaments of cytokeratin, sometimes referred to ______. Such intermediate filaments are very strong and desmosomes provide firm cellular adhesion and strength throughout the epithelium.
Desmoplakins, tonofilaments
Various ______ (______) diseases, such as ______, involving the epidermis or stratified squamous epithelia of the oral mucosa, are due to abnormal desmosome function caused by autoimmune reactions against specific desmogleins that reduce cell-to-cell adhesion. Similar disorders arise with genetic mutations for various junctional proteins.
blistering, bullous, pemphigus vulgaris
______ junctions mediate intercellular communication in many epithelia and most mammalian tissues.
Gap
Gap junctions consist of transmembrane protein complexes, called ______, which form circular patches in the plasma membrane.
connexons
Each connexon has a central pore about ______ nm wide.
1.5
When cells connect, ______ align between adjacent membranes, forming numerous aligned pairs. These junctions allow the exchange of small molecules (<1.5 nm) between cells.
connexons
______ are specialized structures that anchor epithelial cells to the basal lamina, ensuring tissue stability.
Hemidesmosomes
These resemble half-desmosomes but use integrins instead of cadherins to connect cytokeratin filaments to laminin in the basal lamina.
Hemidesmosomes
In ______, integrins link indirectly to cytokeratin intermediate filaments inside the cell and bind primarily to laminin molecules in the basal lamina outside the cell.
hemidesmosomes
______ are crucial for maintaining the strong adhesion of epithelial cells to the underlying basal lamina, ensuring the stability and structural integrity of epithelial tissues.
Hemidesmosomes
Smaller and more numerous than hemidesmosomes, these junctions connect integrins to actin filaments.
Focal Adhesions
These play a key role in cell movement, signaling, and adhesion by initiating intracellular phosphorylation cascades.
Focal Adhesions
______ anchor cells to the extracellular matrix (ECM), particularly during cell movement, repair, and reorganization of epithelial tissues.
Focal adhesions
Unlike hemidesmosomes, ______ are smaller, more numerous, and link integrins to actin filaments rather than intermediate filaments.
focal adhesions
Focal adhesions connect integrins to actin filaments via paxillin and are associated with ______.
focal adhesion kinase (FAK)
Upon integrin binding to ECM proteins like laminin, ______ initiates a signaling cascade that affects cell adhesion, mobility, and gene expression. These structures are crucial for cell migration, particularly in nonepithelial cells such as fibroblasts, and play a significant role in tissue repair and cellular responses to the environment.
FAK
SPECIALIZATIONS OF THE APICAL CELL SURFACE
Microvilli
Stereocilia
Cilia
The ______ ends of many columnar and cuboidal epithelial cells have specialized structures projecting from the cells. These function either to increase the apical surface area for better absorption or to move substances along the epithelial surface.
apical
Many cells have ______ projections best seen with the electron microscope. Such extensions usually reflect the movements and activity of actin filaments and are both temporary and variable in their length, shape, and number.
cytoplasmic
These are usually of uniform length and are bristle-like protrusions found on cell surfaces.
Microvilli
These can be found in epithelia specialized for absorption the apical cell surfaces and are often filled with an array of projecting microvilli.
Microvilli
In cells such as those lining the small intestine, densely packed ______ are visible as a brush or striated border projecting into the lumen.
microvilli
Each ______ contains bundled actin filaments that are capped and bound to the surrounding plasma membrane by actin-binding proteins.
microvillus
Although ______ are relatively stable structures, the microfilament arrays within them are dynamic and undergo various myosin-based movements. These movements help maintain optimal conditions for absorption through the numerous channels, receptors, and other proteins in the plasma membrane.
microvilli
The ______ filaments extend into the terminal web of cortical microfilaments located at the base of the microvilli.
actin
______ disease, also called ______ or ______, is a disorder of the small intestine in which one of the first pathologic changes is loss of the microvilli brush border of the absorptive cells.
Celiac, gluten-sensitive enteropathy, sprue
______ disease is caused by an immune reaction against the wheat protein gluten during its digestion, which produces ______ (intestinal inflammation), changes to the epithelial cells leading to malabsorption, and eventually to pathologic changes in the intestinal wall. The malabsorption problems and structural changes are reversible when gluten is removed from the diet.
Celiac, diffuse enteritis
These are finger-like projections that are sometimes branched.
Stereocilia
These are longer than microvilli and less motile than microvilli.
Stereocilia
These are cylindrical, long structures that have the same characteristics as a cell membrane.
Stereocilia
______ are a much less common type of apical process, primarily found on the absorptive epithelial cells lining the male reproductive system.
Stereocilia
Like microvilli, ______ increase the cell’s surface area, aiding in absorption. In addition to this, more specialized ______ with a motion-detecting function play a crucial role in the sensory cells of the inner ear.
stereocilia, stereocilia
Structurally, ______ resemble microvilli as they contain arrays of microfilaments and actin-binding proteins, sharing similar diameters and connections to the cell’s terminal web.
stereocilia
These are short, hair-like structures present on cell
surfaces and can be motile or non-motile.
Cilia
______ cilia help in movement and locomotion, such as in Protozoans.
Motile
Primary cilia are ______, they are used to sense external cues such as light and odour.
nonmotile
Cilia’s core structure consisting of nine peripheral microtubule doublets (in which a few tubulin protofilaments are shared) arrayed around two central microtubules. This 9 + 2 assembly of microtubules is called an ______.
axoneme
Cilia
As with other microtubules, ______ and ______ dynein motors move along the peripheral microtubules for the transport of molecular components into and out of these structures.
kinesin, cytoplasmic
Cilia
Microtubules of ______ are continuous with those in basal bodies, which are apical cytoplasmic structures located just below the cell membrane. Basal bodies have a structure similar to centrioles, consisting of triplets of microtubules and dynamic tubulin protofilaments that form rootlets anchoring the entire structure to the cytoskeleton.
axonemes
______ exhibit rapid beating patterns that move fluid and suspended matter in one direction along the epithelium.
Cilia
______ motion occurs through successive changes in the conformation of the axoneme, where various accessory proteins make each cilium relatively stiff yet elastic.
Ciliary
Complexes with axonemal dynein bound to one microtubule in each doublet extend as “______” toward a microtubule in the adjacent doublet. Powered by ______, dynein induces the sliding of adjacent doublets relative to each other, bending the axoneme. A rapid series of these sliding movements produces the beating motion of the ______.
arms, ATP, cilium
The long ______ that extends from each fully differentiated sperm cell has an axonemal structure similar to that of a cilium and moves through a comparable mechanism.
flagellum
Mutations in the proteins of cilia and flagella are associated with immotile cilia syndrome, also known as ______ syndrome.
Kartagener
This condition results in chronic respiratory infections due to the impaired cleansing action of cilia in the respiratory tract and male infertility caused by immotile spermatozoa.
Kartagener syndrome
______ syndrome is an autosomal recessive genetic condition and a form of primary ciliary dyskinesia (PCD), a disorder in which the cilia do not function properly. These hair-like structures are found on the surface of cells in the lungs, airways, and other areas. They move in a wave-like motion, helping to position organs during fetal development and clearing mucus, bacteria, and debris from the lungs and airways.
Kartagener
Types of Epithelia
Covering (lining) epithelia
Secretory (glandular) epithelia
There are also lining epithelia that also secrete (ex. ______ lining). There are also glandular cells that are distributed among thw lining cells (ex. ______ cells in small intestine and trachea)
stomach, mucous
Cells of covering epithelia are organized into one or more layers that cover the surface or line the cavities of an organ:
One Layer - ______
cell forms: ______, ______, ______
Simple, squamous, cuboidal, columnar
Cells of covering epithelia are organized into one or more layers that cover the surface or line the cavities of an organ:
Two or more layers - ______
cell forms: ______ (dry), ______ (moist), ______,
______, ______
Stratified, squamous keratinized, sqamous nonkeratinized, cuboidal, transitional, columnar
Cells of covering epithelia are organized into one or more layers that cover the surface or line the cavities of an organ:
Layers of cells with nuclei at different levels - ______
Pseudostratified
These are flat and wide cells that facilitate the movement of the viscera (mesothelium), active transport by pinocytosis (mesothelium and endothelium), secretion of biologically active molecules (mesothelium)
Found at: lining of vessels; serous lining of cavities: pericardium, pleura, peritoneum
Squamous
Cube-shaped cells that covers and secretes.
Found at: covering of ovary and thyroid
Cuboidal
Tall cells that protect, lubricate, absorb, and
secrete
Found at: intestine and gallbladder lining
Columnar
These cells are packed with keratin filaments which makes them dry. These cells protects and prevents water loss or dehydration of the tissue. Contains many desmosomes and become more irregular in shape. They then flatten as the keratin accumulates (keratinization). It moves progressively toward the skin surface and becomes thin, metabolically inactive packets (squames) of keratin lacking nuclei.
Squamous Keratinized
Only a sparse amount of keratin is found in these cells which makes them moist. They protect structures where dehydration is not a problem, it secretes, and prevents water loss. The flattened cells on the surface layer retain their nuclei and most metabolic functions.
Found at: mouth, esophagus, larynx, vagina, anal canal
Squamous Nonkeratinized
These large, dome - like cells (umbrella cells) lines much of the urinary tract, extending from the kidneys to the proximal part of the urethra. These cells protect underlying tissues from the hypertonic and potentially cytotoxic effects of urine. Unique morphological features of the cells allow distension of stransitional epithelium as the urinary bladder fills which allow the cells to adjust their relationship with one another.
Transitional / Urothelium
These rare cells occur in the excretory ducts of salivary and sweat glands where the double layer of cells allows additional functions.
Cuboidal
These rare cells is seen in the conjunctiva lining the
eyelids, where it is both protective and mucus secreting.
Columnar
These are Several layers with nuclei at different levels and Their basal ends all rest on the basement
membrane.
Pseudostratified Covering/ Lining
These are Tall, irregular cells are attached to basement mambrane.
Columnar
Epithelial cells that function mainly to produce and secrete various macromolecules may occur in epithelia with other major functions or comprise
specialized organs called ______.
GLANDS
Secretory cells may synthesize, store, and release ______ (eg, in the pancreas), ______ (eg, adrenal, sebaceous glands), or complexes of ______ and ______ (eg, salivary glands). Epithelia of ______ glands secrete all three substances.
proteins, lipids, carbohydrates, proteins, mammary
______ secretory cells, sometimes called unicellular glands, are common in simple cuboidal, simple columnar, and pseudostratified epithelia.
Scattered
This is An important, easily seen example that is abundant in the lining of the small intestine and respiratory tract, which secretes lubricating mucus that aids the function of these organs.
Goblet Cell
Glands develop from covering epithelia in the fetus by cell proliferation and growth into the underlying connective tissue, followed by further differentiation:
______ glands and ______ Glands
Exocrine, Endocrine
______ glands remain connected with the surface epithelium, the connection forming the tubular ducts lined with epithelium that deliver the secreted material where it is used.
Exocrine
The epithelia of ______ glands are organized as a continuous system of many small secretory portions and ducts that transport the secretion out of the gland.
exocrine
In both exocrine and endocrine glands, the secretory units are supported by a stroma of ______ tissue. In larger glands, layers of ______ tissue also surround the larger ducts, form partitions or ______ separating the gland into lobules, each containing secretory units connected to a small part of the duct system, and enclose the entire gland as its ______.
connective, connective, septa, capsule
Glands can be ______ (ducts not branched) or ______ (ducts with two or more branches).
simple, compound
Glands
Secretory portions can be ______ (either short or long and coiled) or ______ (rounded and saclike); either type of secretory unit may be branched, even if the duct is not branched.
tubular, acinar
Compound glands can have branching ducts and can have multiple ______, ______, or ______ secretory portions.
tubular, acinar, tubuloacinar
______ glands lack ducts; secreted substances are hormones carried throughout the body by the interstitial fluid and blood, with specificity produced by the hormone receptors of target cells.
Endocrine
Three Basic Mechanisms for releasing the product are commonly used by cells specialized for secretion
and cells engaged in each type of secretion can be
distinguished histologically:
Merocrine Secretion
Holocrine Secretion
Apocrine Secretion
This is the most common method of protein or glycoprotein secretion and involves typical exocytosis from membrane-bound vesicles or secretory granules.
Merocrine Secretion
Here cells accumulate product continuously as they enlarge and undergo terminal differentiation, culminating in complete cell disruption that releases the product and cell debris into the gland’s lumen. This is best seen in the sebaceous glands producing lipid rich material in skin.
Holocrine Secretion
Here product accumulates at the cells’ apical ends, portions of which are then extruded to release the product together with small amounts of cytoplasm and cell membrane. Lipid droplets are secreted in the mammary gland in this manner
Apocrine Secretion
Exocrine glands with merocrine secretion can be further categorized as either ______ or ______ according to the nature of their secretory products, which give distinct staining properties to the cells.
serous, mucous
______ cells synthesize proteins that are mostly not glycosylated, such as digestive enzymes.
Serous
The cells have well-developed RER and Golgi complexes and are filled apically with secretory granules in different stages of maturation. ______ cells therefore stain intensely with basophilic or acidophilic stains. Acini of the pancreas and parotid salivary glands are composed of ______ cells.
Serous, serous
______ CELLS such as goblet cells, also have RER and Golgi complexes and are filled apically with secretory granules, but these contain heavily glycosylated proteins called ______.
MUCOUS, mucins
When _______ are released from the cell, they become hydrated and form a layer of mucus. The ______ mucins are usually washed from cells during routine histological preparations, causing the secretory granules to stain poorly with eosin. Sufficient oligosaccharides remain in developing mucinogen granules, however, to allow mucous cells to be stained by the PAS method.
mucins, hydrophilic
Some salivary glands are mixed ______ glands, having both serous acini and mucous tubules with clustered serous cells. The product of such glands is a mixture of digestive enzymes and watery mucus.
seromucous
In addition to secretory cells, epithelia of many exocrine glands contain contractile ______ CELLS at the basal ends of the secretory cells.
MYOEPITHELIAL
______ cells are rich in actin filaments and myosins. Strong contractions in these cells serve to
help propel secretory products from acini into the duct system.
Myoepithelial
______ glands lack myoepithelial cells and are specialized either for protein or steroid hormone synthesis, with cytoplasmic staining characteristic of RER or SER, respectively.
Endocrine
______ signaling involves hormone transport in the blood to target cells throughout the body, often within other endocrine glands. The receptors may also be on cells very close to the hormone-secreting cell or on the secreting cell itself, signaling which is termed paracrine or autocrine, respectively.
Endocrine
Important but inconspicuous ______ or ______ cells also occur singly or in small groups in epithelia of the digestive, respiratory, and other organ systems. Hormones are also secreted from some cells specialized for other functions, such as certain cardiac muscle cells or fat cells.
endocrine, paracrine
The pancreas contains both ______ and ______ cells. Liver cells exert both functions in the same cells, secreting bile components into a duct system and releasing other products to the bloodstream.
endocrine, exocrine
______ have the ability to actively transport certain ions against concentration and electrical potential gradients.
Cells
This is The transfer of ions and water via aquaporins in either direction across the epithelium.
Transcellular Transport
______ tight junctions prevent paracellular diffusion or backflow between the cells.
The basal membrane of these cells is elaborately folded, with ______ located between the folds to supply ATP for a Na+/K+ pumps.
Lateral membrane folds interdigitating between the cells increase surface area for transport.
Apical, mitochondria
Transcytosis
All cells can internalize extracellular molecules and fluid using ______ and formation of cytoplasmic, membrane-bound vesicles.
endocytosis
Transcytosis
Examples are simple squamous epithelial cells lining blood and lymphatic capillaries (______) or body cavities (______).
endothelia, mesothelia
Transcytosis
Abundant in pinocytotic vesicles, which cross the thin cells in both directions and release their contents on the opposite side by ______.
exocytosis
Transcytosis
Occurs between the ______ and ______ membranes domains in cells of simples cuboidal and columnar epithelia.
apical, basolateral
______ tissues are labile structures whose cells are renewed continuously by mitotic activity and stem cell populations.
Renewal varies widely.
Epithelial
In stratified epithelial tissues, stem cells and mitosis occur only within the ______ layer in contact with the basal lamina.
basal
______ cells are located only in restricted niches some distance from the transit amplifying cells and differentiating cells.
Stem
Benign and malignant tumors can arise from most types of ______ cells.
epithelial
______ - Malignant tumors of epithelial origin.
Carcinomas
______ - Malignant tumors from glandular epithelial tissue.
Adenocarcinomas
Adenocarcinomas are the most common tumors after age ______.
45
An ______ is a tissue in which cells are bound tightly together structurally and functionally to form a sheetlike or tubular structure with little extracellular material between the cells.
epithelium
Cells in epithelia each have an ______ side facing the sheet’s free surface and a ______ side facing a basement membrane and underlying connective tissue.
apical, basal
Epithelia are often specialized for absorption or transcytosis, pinocytosis of material at the ______ side and exocytosis at the ______ side (or vice versa).
apical, basolateral
Cells of most ______ exhibit continuous renewal, with the locations of stem cells and rates of cell turnover variable in various specialized epithelia.
epithelia
The ______ of all epithelia is a thin extracellular layer of specialized proteins, usually having two parts: a ______ and a more fibrous ______
basement membrane, basal lamina, reticular lamina
The ______ is a thin meshwork of type IV collagen and laminin produced by the epithelial cells.
basal lamina
The ______ contains type III collagen and anchoring fibrils of type VII collagen, all secreted by cells of the immediately adjacent connective tissue.
reticular lamina
Together, these components attach epithelia to connective tissue, regulate/filter substances passing from connective tissue into epithelia, provide a guide or scaffold during tissue regeneration after injury, and compartmentalize epithelial cells from other tissues.
basal lamina and reticular lamina
______ junctions are well developed in epithelia and consist of three major types and functions.
Intercellular
______ or ______ junctions are formed by interacting transmembrane proteins such as claudin and occludin; linear arrangements of these linked proteins surround the apical ends of the cells and prevent paracellular passage of substances (between the cells.)
Tight, occluding
______ or ______ junctions, formed by interacting proteins of the cadherin family, are points of strong attachment holding together cells of the epithelium.
Adherent, anchoring
______ composed of transmembrane integrins attach cells to proteins of the basal lamina.
Hemidesmosomes
______ or ______ junctions are points of cell contact where both plasma membranes have numerous hexameric complexes of transmembrane connexons, each forming a channel allowing passage of small molecules from one cell to the other.
Gap, communicating
Apical Structures of Epithelial Cells
Microvilli
Stereocilia
Cilia
These are small membrane projections with cores of actin filaments that generally function to increase epithelial cells’ apical surface area for absorption.
Microvilli
These are long microvilli with specialized mechanosensory function in cells of the inner ear and for absorption in tissues of the male reproductive tract.
Stereocilia
These are larger projecting structures with a well-organized core of microtubules (in a 9 + 2 arrangement called the axoneme) in which restricted, dynein-based sliding of microtubules causes ciliary movement that propel material along an epithelial surface.
Cilia
This is an epithelium in which the basement membrane has one cell layer.
Simple
The cells of different ______ epithelia range widely in height, from very thin or squamous, to roughly cuboidal, to very tall or columnar.
simple
These are Epithelia with two or more layers of cells.
Stratified
______ glands have epithelial ducts carrying secretions to specific sites; the ducts of simple glands are ______ and those of compound glands are ______.
Exocrine, unbranched, branched
The secretory portions of exocrine glands may form round, saclike ______ (also called ______) or elongated tubules; both types of secretory units may themselves branch.
acini, alveoli
______ glands lack ducts; secreted substances are hormones carried throughout the body by the interstitial fluid and blood, with specificity produced by the hormone receptors of target cells.
Endocrine
Glands have three basic secretory mechanisms: ______, which uses exocytosis; ______, in which terminally differentiated cells filled with lipid product are released; and ______, in which apical, product-filled areas of cells are extruded.
merocrine, holocrine, apocrine
Exocrine glands producing mucus, or similar individual cells called goblet cells, are called ______ glands; oligosaccharide components of mucus stain poorly with routine dyes but stain well with PAS stain.
mucous
Exocrine glands producing largely enzymes (proteins) are called ______ glands and stain darkly with H&E due to the cells’ content of RER and secretory granules.
serous
Which specialization of the apical cell surface has more bristle-like structure and are usually uniform in length?
Microvilli
An important, easily seen example that is abundant in the lining of the small intestine and respiratory tract, which secretes lubricating mucus that aids the function of these organs?
Goblet Cells
The region of the cell contacting the ECM and connective tissue
basal pole
three components of the basal lamina
type IV collagen
Laminin
Nidogen and perlecan
Which is an example of transcytosis?
a. simple squamous epithelial cells lining blood
b. Na+/K+ pump
c. stratified epithelial tissues
a. simple squamous epithelial cells lining blood
This allows cells to maintain the required low intracellular sodium concentration
Na+/K+ pump
synthesize proteins that are mostly not glycosylated, such as digestive enzymes
Serous Cells
