Lab Quiz 1 Material (02/06/2025) + Ch. 4 & 5 (E2) Flashcards
At the light microscope level, the {…} and {…} components of the various organs of the body exhibit a recognizable and often distinctive pattern of organization.
1) Cells
2) Extracellular
An organized aggregation of cells that functions in a collective manner.
What is a tissue?
List the 4 basic types of tissues that make up all organs.
1) Epithelium
2) Connective
3) Muscle
4) Nerve
This tissue type covers body surfaces, lines body cavities, and forms glands.
What is epithelium?
This tissue type underlies or supports the other 3 basic tissues, both structurally and functionally.
What is connective?
This tissue type is made up of contractile cells and is responsible for movement?
What is muscle?
This tissue type receives, transmits, and integrates information from outside and inside the body to control the activities of the body.
What is nerve?
In classifiying the basic tissues, two different definitional parameters are used. The basis for the definition of epithelial and connective tissue is primarily {…} (morphological OR functional?), while for muscle and nerve tissue, it is primarily {…} (morphological OR functional?).
1) Morphological
2) Functional
In what two manners is epithelium characterized?
1) Close cell apposition
2) Presence of a free surface
Epithelial cells are usually joined by specialized cell-to-cell junctions, which create a selective barrier between these two environments (i.e., epithelium separates these spaces).
What are the external environment & underlying connective tissue?
Describe the intercellular space between epithelial cells in 2 key points.
1) Minimal
2) Devoid of any structure, except where junctional attachments are present
Free surfaces of epithelium are characteristic of 3 main anatomical surfaces. Please list these surfaces.
1) Exterior of the body
2) Outer surface of many internal organs
3) Lining of body cavities and tubes that ultimately communicate with the exterior of the body
The epithelium also forms {…} and their ducts that help secrete their products onto a free surface or into the lumen of a tube.
Glands
Classifications of epithelium are usually based on 2 parameters. What are these parameters?
1) Shape of cells
2) Number of cell layers
List the 3 epithelial cell shapes.
1) Squamous (flat)
2) Cuboidal
3) Columnar
List the 2 epithelial layer types.
1) Simple (single layer)
2) Stratified (multiple layers)
What is the purpose of special structural surface modifications on epithelium?
To perform special functions
What are the 3 special structural surface modifications that simple epithelia may possess?
1) Microvilli
2) Stereocilia
3) Cilia
What are the 2 special structural surface modifications that stratified epithelia may possess?
1) Keratinized exterior of body
2) Non-keratinized lumen of internal organs
All epithelia rest on this structural attachment site for overlying epithelial cells and underlying connective tissue.
What is the basal lamina?
Why is epithelium an avascular tissue?
The blood vessels from connective tissue are restricted from passing through the basal lamina
What are the 2 methods in which epithelial cells receive nutrients?
1) Absorption from the free surface
2) Diffusion from underlying tissues
The intervening spaces occupied by material produced by connective tissue cells make up this cellular network.
What is the extracellular matrix?
What 2 factors does the classification of connective tissue take into account?
1) Nature of the connective tissue cells
2) Composition/organization of extracellular matrix
Where does embryonic connective tissue derive from?
The mesoderm
What is the mesoderm?
The middle embryonic germ layer
This type of connective tissue is found to be closely associated with most epithelia.
What is loose connective tissue?
What 2 main components does the extracellular matrix for loose connective tissue consist of?
1) Loosely arranged collagen fibers
2) Numerous cells, including fibroblasts
What is the purpose of fibroblasts in the extracellular matrix?
NOTE: Think about why collagen is essential to the matrix
To form and maintain the extracellular matrix
This type of connective tissue contains numerous, densely-packed collagen fibers and is ideal for where strength is required.
What is dense connective tissue?
List the 3 examples of specialized connective tissue mentioned in the text.
1) Bone
2) Cartilage
3) Blood
This specialized connective tissue has a matrix mineralized by calcium and phosphate molecules associated with collagen fibers.
What is bone?
This specialized connective tissue possesses a matrix that contains a large amount of water bound to hyaluronan aggregates.
What is cartilage?
This specialized connective tissue consists of cells and an extracellular matrix in the form of a protein-rich fluid called plasma that circulates throughout the body, transporting oxygen and removing carbon dioxide and metabolites from the tissues.
What is blood?
How does adipose differ from other types of specialized connective tissue?
Its predominant distinguishing features are related to the cells (adipocytes) and NOT to the extracellular matrix
For what purpose do adipocytes serve?
Energy storage
Epithelium also forms the secretory, or {…}, portion of glands and their ducts.
Parenchyma
Specialized epithelial cells can also function as receptors for…
The special senses (smell, taste, hearing, and vision)
What are the 3 principal characteristics of epithelial cells?
1) Forming cell junctions
2) Functional and morphological polarity
3) Basal surface attached to underlying basement membrane
What are the 3 distinct morphological surface domains of epithelial cells?
1) Free surface (apical domain)
2) Lateral domain
3) Basal domain
Epithelial cells that lack a free surface (apical domain) aggregate to form this tissue type.
What is epithelioid tissue?
List 6 organs in which you will find epithelioid tissues.
NOTE: To be more specific, there are 4 organs and 2 glands mentioned in the text
1) Testes
2) Ovaries
3) Pancreas
4) Adrenal gland
5) Pituitary gland
6) Thymus
List 2 conditions under which epithelioid patterns may form.
1) Connective tissue macrophages responding to injury/infection
2) Tumors derived from epithelium
Epithelium creates a {…} barrier between the external environment and underlying connective tissue.
Selective
Which layer of cells determines the classification of stratified epithelium’s shape?
The surface layer
Aside from the number of cell layers and shape of surface cells, what is another factor for classifying epithelium’s structure?
Specialization of the apical cell surface domain (i.e., the presence of special structural surface modifications)
What are 2 special categories/classifications of epithelium?
1) Pseudostratified epithelium
2) Transitional epithelium (urothelium)
What is so special about the appearance of pseudostratified epithelium?
It appears stratified since some cells don’t reach the free surface, but all cells rest on the basement membrane, unlike truly stratified epithelium (i.e., it is SIMPLE EPITHELIUM)
What is so special about transitional epithelium?
NOTE: Be sure to mention the number of layers
It is a stratified epithelium with specific morphological characteristics that allow it to distend
The epithelial lining of blood and lymphatic vessels is called this.
What is endothelium?
The epithelial lining of the ventricles and atria of the heart is called this.
What is endocardium?
The epithelium that lines the walls and covers the contents of the closed cavities of the body (i.e., the abdominal, pericardial, and pleural cavities).
What is mesothelium?
Epithelial cells are polygonal in shape, generally oriented along the axis of the vessel, with the exception of these vessels, which are found in lymphatic tissues.
What are postcapillary venules?
How is the endothelium of postcapillary venules shaped? Columnar, cuboidal, or squamous?
It is cuboidal
What is another name for these postcapillary venules?
High endothelial venules (HEV)
The columnar epithelium of the stomach and gastric glands serves this function.
What is secretion?
The columnar epithelium of the intestines and proximal convoluted tubules in the kidneys serves this function.
What is absorption?
The epithelium involved in transporting materials via motile cilia or transport to and from connective tissue serves this function.
What is transportation?
The stratified squamous epithelium of the skin (epidermis) and the urothelium (transitional epithelium) of the urinary bladder serves this function.
What is mechanical protection?
The epithelium that receives and transduces external stimuli serves this function.
What is receptor function?
In some pseudostratified epithelia, basal cells are the {…} cells that give rise to the mature functional cells of the epithelium, thus balancing cell turnover.
Stem
The asymmetric organization of different cellular components to enable specialized functions.
What is cell polarity?
What 2 factors determine the functional polarity of all 3 cell domains?
1) Biochemical characteristics of each surface
2) Geometric arrangements of cells
These cells are characterized by large amounts of the contractile proteins actin and myosin in their cytoplasm and by their particular cellular arrangement in the tissue.
What are muscle cells?
What is the common shared characteristic between smooth, skeletal, and cardiac muscle?
NOTE: Think about the cytoplasm of muscle cells/fibers
The bulk of the cytoplasm consists of the contractile proteins actin and myosin, which form thin and thick myofilaments, respectively
Which 2 muscle tissue types are striated? Which 1 is NOT striated?
Skeletal & cardiac - striated
Smooth - NOT striated
What causes muscle striations?
The specific arrangement/order of myofilaments
Which 2 proteins are responsible for muscle cells being able to contract?
Actin & myosin
How are actin & myosin capable of producing muscle movement?
NOTE: Think about how actin & myosin are organized
Actin & myosin are so highly ordered that the contractile activity of muscle cells can successfully produce movement
Although all cells exhibit electrical properties, nerve cells, or {…}, are highly specialized to transmit electrical impulses from one site in the body to another; they are also specialized to integrate those impulses.
Neurons
A single, long {…} (sometimes longer than a meter) carries impulses {…} from the cell {…}, which contains the neuron’s nucleus.
1) Axon
2) Away
3) Body
Multiple {…} receive impulses and carry them toward the cell body.
Dendrites
The axon terminates at a neuronal junction called a {…} at which electrical impulses are transferred from one cell to the next by secretion of {…}, chemical substances released at synapses to generate electrical impulses in the adjacent communicating neuron.
1) Synapse
2) Neuromediators
In the {…} (CNS), which comprises the brain and spinal cord, the supporting cells are called {…} cells.
1) Central nervous system
2) Neuroglial
These are the 2 types of supporting cells of the peripheral nervous system (PNS).
What are Schwann (neurilemmal) & satellite cells?
The sheath that insulates and speeds conduction in certain types of neurons.
What is the myelin sheath?
Nerve cell bodies in the PNS, including the autonomic nervous system (ANS), are seen in aggregations called {…}, where they are surrounded by satellite cells.
Ganglia
These are nervous system cells, similar to the cells of the choroid plexus in the CNS, that retain the absorptive and secretory functions characteristic of epithelial cells.
What are ependymal cells?
The germ disc formed during the gastrulation phase of early embryo development.
What is the trilaminar embryo (germ disc)?
The three germ layers include the {…}, {…}, and {…}, which give rise to all the tissues and organs.
1) Ectoderm
2) Mesoderm
3) Endoderm
The {…} is the outermost of the three germ layers.
Ectoderm
The epidermis, cornea, lens epithelia (of the eye), enamel organ, enamel, internal ear, adenohypophysis (anterior lobe of the pituitary gland), oral cavity mucosa, and lower part of the anal canal all comprise this ectoderm class.
What is the surface ectoderm?
The neural tube and neural crest comprise this ectoderm class.
What is the neuroectoderm?
Components of the CNS are included in this portion of the neuroectoderm.
What is the neural tube?
Components of the PNS are included in this portion of the neuroectoderm.
What is the neural crest?
The middle of the 3 primary germ layers of an embryo.
What is the mesoderm?
Connective tissue, striated & smooth muscles, heart, blood & lymphatic vessels, the spleen, kidneys, gonads, mesothelium, and the adrenal cortex comprise this germ layer.
What is the mesoderm?
The innermost layer of the 3 germ layers.
What is the endoderm?
The alimentary canal epithelium, extramural digestive gland endothelium, epithelium of the urinary bladder, most of the urothelium, respiratory system epithelium, thyroid, parathyroid, thymus gland, tonsils (parenchyma), tympanic cavity epithelium, and auditory (Eustachian ) tubes comprise this type germ layer.
What is the endoderm?
Human embryonic stem cells derived from early embryos are considered {…} stem cells, capable of differentiating into various somatic cells and tissues.
Pluripotent
Tumor cells arising from pluripotential stem cells can form this type of tumor, which contains a variety of mature tissues arranged in an unorganized manner.
What is a teratoma?
A benign tumor (mature teratoma) of the ovary with a normal female karyotype of 46XX.
What is a dermoid cyst?
How do pluripotent stem cells found in tumors contribute to the development of teratomas?
The pluripotent stem cells in the tumor can differentiate and resemble cells originating from all three germ layers
The cranium (skull), connective tissue of the head, and dentin comprise this type of mesoderm.
What is the head mesoderm?
The skeletal muscle of the trunk and limbs (excluding cranium), muscles of head, dermis of skin, and connective tissue comprise this type of mesoderm.
What is paraxial mesoderm?
The urogenital system, including gonads, ducts, & accessory glands, comprises this type of mesoderm.
What is the intermediate mesoderm?
The connective tissue & muscle of viscera, serous membranes of pleura, pericardium & peritoneum, blood & lymph cells, cardiovascular & lymphatic systems, spleen, and adrenal cortex comprise this type of mesoderm.
What is the lateral mesoderm?
Name the type of epithelium based on the given locations:
-vascular system (endothelium)
-body cavities (mesothelium)
-Bowman capsule (kidney)
-respiratory spaces in lung
What is simple squamous?
Name the type of epithelium based on the given locations:
-small ducts of exocrine glands
-surface of ovaries (germinal epithelium)
-kidney tubules
-thyroid follicles
What is simple cuboidal?
Name the type of epithelium based on the given locations:
-small intestine & colon
-stomach lining & gastric glands
-gallbladder
What is simple columnar?
Name the type of epithelium based on the given locations:
-trachea & bronchial tree
-ductus deferens
-efferent ductules of epididymis
What is pseudostratified?
Name the type of epithelium based on the given locations:
-epidermis
-oral cavity & esophagus
-vagina
What is stratified squamous?
Name the type of epithelium based on the given locations:
-sweat gland ducts
-large duct of exocrine
-anorectal junction
What is stratified cuboidal?
Name the type of epithelium based on the given locations:
-largest ducts of exocrine glands
-anorectal junction
What is stratified columnar?
Name the type of epithelium based on the given locations:
-renal calyces
-ureters
-bladder
-urethra
What is transitional (urothelium)?
List the 3 functions of simple squamous epithelium.
1) Exchange
2) Barrier
3) Lubrication
List the 4 functions of simple cuboidal epithelium.
1) Absorption
2) Conduit
3) Barrier
4) Secretion
List the 3 functions of pseudostratified epithelium.
1) Secretion
2) Conduit
3) Absorption
List the 2 functions of stratified squamous.
1) Barrier
2) Protection
List the 2 shared functions of stratified columnar and stratified cuboidal epithelium.
1) Barrier
2) Conduit
List the 2 functions of transitional epithelium (urothelium)?
1) Barrier
2) Distensible property
In many epithelial cells, the {…} domain exhibits special structural surface modifications to carry out specific functions.
Apical
These structural surface mods are cytoplasmic processes that contain a core of actin filaments.
What are microvilli?
These structural surface mods are microvilli of unusual lengths.
What are stereocilia (stereovilli)?
These structural surface mods are cytoplasmic processes containing a bundle of microtubules.
What are cilia?
A reversible conversion of one mature epithelial cell type to another mature epithelial cell type.
What is epithelial metaplasia?
The most common epithelial metaplasia that occurs in glandular epithelium, where the columnar cells become replaced by the stratified squamous epithelium.
What is columnar to squamous?
In intestinal absorptive cells, this surface structure was originally called the {…} border; in the kidney tubule cells, it is called the {…} border.
1) Striated
2) Brush
Microvilli contain a conspicuous core of about 20–30 {…} filaments. Their barbed (plus) ends are anchored to {…}, a 95-kDa actin-bundling protein located at the tip of the microvillus.
1) Actin
2) Villin
The actin bundle of microvilli extends down into the apical cytoplasm. Here, it interacts with this horizontal network of actin filaments lying just below the base of the microvilli.
What is the terminal web?
The actin filaments inside the microvillus are cross-linked at 10-nm intervals by other {…} proteins, such as {…} (57 kDa), {…} (30 kDa), and {…} (68 kDa).
1) Actin-binding
2) Fascin
3) Espin
4) Fimbrin
In addition, the core of actin filaments is associated with {…}, a molecule that binds the actin filaments to the plasma membrane of the microvillus.
Myosin I
The terminal web is composed of {…} filaments stabilized by {…} (468 kDa), which also anchors the terminal web to the apical cell membrane.
1) Actin
2) Spectrin
The presence of {…} and {…} in the terminal web explains its contractile ability.
1) Myosin II
2) Tropomyosin
Stereocilia are not widely distributed among epithelia. They are, in fact, limited to the {…}, the proximal part of the {…} deferens of the male reproductive system, and the {…} (hair) cells of the {…} ear.
1) Epididymis
2) Ductus
3) Sensory
4) Inner
Unusually long, immotile microvilli.
What are stereocilia?
Like microvilli, stereocilia are supported by internal bundles of {…} filaments that are cross-linked by {…}.
1) Actin
2) Fimbrin
Unlike microvilli, an 80-kDa actin-binding protein, {…}, closely associated with the plasma membrane of stereocilia, anchors the actin filaments to the plasma membrane.
Ezrin
The stem portion of the stereocilium and the apical cell protrusion contain this cross-bridge–forming molecule.
What is α-actinin?
The stereocilia of the sensory epithelium are exquisitely sensitive to mechanical vibration and serve as sensory {…} rather than absorptive structures.
Mechanoreceptors
The internal structure of stereocilia is characterized by the high density of {…} filaments extensively cross-linked by {…}, which is critical to the normal stereocilia structure and function.
1) Actin
2) Espin
Unlike other stereocilia, the stereocilia of sensory epithelia lack both {…} and {…}.
1) Ezrin
2) α-actinin
Because stereocilia can be easily damaged by overstimulation, they have a molecular mechanism to continuously renew their structure, which needs to be maintained in proper working condition for a lifetime. Using fluorescent-labeled actin molecules, researchers have found that actin monomers are constantly added at the tips and removed from the base of the stereocilia, whereas the entire bundle of actin filaments moves toward the base of the stereocilium, in a highly regulated process/effect of the actin core structure referred to as this.
What is the treadmilling effect?
What key factor of the stereocilium does the treadmilling effect depend on?
The length of the stereocilium
Common surface mods that are present on nearly every cell in the body.
What are cilia?
Cilia are hair-like extensions of the apical plasma membrane containing an {…}, the microtubule-based internal structure. The axoneme extends from the {…} body, a centriole-derived, {…} (MTOC) located in the apical region of a ciliated cell.
1) Axoneme
2) Basal
3) Microtubule-organizing center
The cilia, basal bodies, and basal body-associated structures form this component of a cell.
What is the ciliary apparatus?
This class of cilia is historically the most studied and is found in large numbers on the apical domain of many epithelial cells.
What is motile cilia?
Motile cilia and their counterparts, {…}, possess a typical {…} axonemal organization with microtubule-associated motor proteins that are necessary for the generation of forces needed to induce motility.
1) Flagella
2) 9 + 2
This class of cilia refers to solitary projections found on almost all eukaryotic cells.
What is primary cilia (monocilia)?
What does the term “monocilia” refer to when describing primary cilia?
It refers to the fact that only a single cilium per cell is usually present
For what two reasons are primary cilia immotile?
1) Different arrangements of microtubules in the axoneme
2) Lack of microtubule-associated motor proteins
What are 3 key functions of primary cilia?
NOTE: Just list the sensors that they act as
1) Chemosensors
2) Osmosensors
3) Mechanosensors
It is now widely accepted that the primary cilia of cells in developing tissues are essential for…
Normal tissue morphogenesis
This class of cilia is found in the embryo on the bilaminar embryonic disc at the time of gastrulation.
What are nodal cilia?
Nodal cilia are concentrated in the area surrounding this node, hence their name.
What is the primitive node?
Nodal cilia have an axonemal internal architecture similar to that of primary cilia; however, they are distinct in their ability to perform clockwise {…} movement.
Rotational
Nodal cilia play an important role in early…
Embryonic development
Motile cilia are capable of moving {…} and {…} along epithelial surfaces.
1) Fluid
2) Particles
How do motile cilia appear under the light microscope?
Short, fine, hair-like structures
In a ciliated epithelial tissue slide, a thin, dark-staining band is usually seen extending across the cell at the base of the cilia. This dark-staining band represents these structures.
What are the basal bodies?
Electron microscopy of a cilium in a longitudinal profile reveals an internal core of microtubules called this.
What is an axoneme?
What does the 9 + 2 pattern of the axoneme refer to?
NOTE: Think about how the axoneme looks like in a longitudinal section
The characteristic 9 pairs/doublets of circularly arranged microtubules surrounding 2 central microtubules
The microtubules composing each doublet are constructed so that the wall of one microtubule, designated the {…} microtubule, is actually {…}; it shares a portion of the wall of the other microtubule of the doublet, the {…} microtubule.
1) B
2) Incomplete
3) A
How do the A & B microtubules differ in terms of the number of tubulin protofilaments comprising them?
A - 13
B - 10
When seen in cross-section at high resolution, each doublet exhibits a pair of “arms” that contain this microtubule-associated motor protein.
What is ciliary dynein?
A passive elastic component formed by {…} (165 kDa) permanently links the A microtubule with the B microtubule of adjacent doublets at 86-nm intervals.
Nexin
The two central microtubules of the axoneme are separate but partially enclosed by these projections at 14-nm intervals along the length of the cilium.
What are central sheath projections?
These structures extend from each of the nine doublets toward the two central microtubules at 29-nm intervals.
What are radial spokes?
How do the basal bodies and their associated structures help the cilia?
They firmly anchor the cilia in the apical cell cytoplasm
The {…} microtubule array courses from the tip of the cilium to its base, whereas the outer paired microtubules join the {…} body.
1) 9 + 2
2) Basal
The basal body is a modified centriole. It functions as an MTOC consisting of nine short microtubule {…} arranged in a ring.
Triplets
Each of the paired microtubules of the ciliary axoneme (A and B microtubules) is continuous with two of the triplet microtubules of the basal body. The third incomplete {…} microtubule in the triplet extends from the bottom to the {…} zone at the top of the basal body near the transition between the basal body and the axoneme.
1) C
2) Transitional
The two {…} microtubules of the cilium originate at the transitional zone and extend to the top of the axoneme.
Central
This basal body-associated structure is a collar-like extension between the transitional zone of a basal body and the plasma membrane originating near the top end of the basal body C microtubule and inserting into the cytoplasmic domain of the plasma membrane. IT TETHERS THE BASAL BODY TO THE APICAL PLASMA MEMBRANE.
What is the alar sheet (transitional fiber)?
This basal body-associated structure is an accessory structure that is usually found in the mid-region of the basal body and is hypothesized to function in coordinating ciliary movement.
What is the basal foot?
This basal body-associated structure is composed of longitudinally aligned protofilaments containing rootletin (a 220-kDa protein). Additionally, this structure projects deep into the cytoplasm and firmly anchors the basal body within the apical cell cytoplasm.
What is the striated rootlet?
This action is based on the movement of the doublet microtubules in relation to one another.
What is ciliary action?
The ciliary {…} (protein) located in the arms of the A microtubule forms temporary cross-bridges with the B microtubule of the adjacent doublet. Hydrolysis of ATP produces a {…} movement of the bridge along the B microtubule.
1) Dynein
2) Sliding
The dynein molecules produce a continuous shear force during this sliding directed toward the ciliary tip. Because of this ATP-dependent phase, a cilium that remains rigid exhibits a rapid forward movement called the…
Effective stroke
At the same time, the passive elastic connections provided by the protein nexin and the radial spokes accumulate the energy necessary to bring the cilium back to the straight position. Cilia then become flexible and bend toward the lateral side on the slower return movement, the…
Recovery stroke
In contrast to motile cilia with the 9 + 2 pattern of microtubules, primary cilia, or monocilia, display a {…} microtubule arrangement.
9 + 0
Where will you find primary cilia?
In most cells of epithelial, connective, muscle, & nervous tissues
Primary cilia are also present in {…} cells and in almost all cells during {…} and fetal development.
1) Stem
2) Embryogenesis
Examples of cells possessing primary cilia in epithelium include the epithelial cells of the rete testis and efferent ductules in the {…} reproductive tract, epithelial cells lining the uterine tube (uterus [endometrium]) and vagina in the {…} reproductive tract, epithelial cells lining the {…} tract, epithelial cells of {…} tubules (Fig. 5.10b), epithelial-like ependymal cells lining the fluid-filled cavities of the {…} (CNS), photoreceptor cells in the {…}, and the vestibular hair cells of the {…}.
1) Male
2) Female
3) Biliary
4) Kidney
5) Central nervous system
6) Retina
7) Ear
Primary cilia were formerly classified as nonfunctional vestigial developmental abnormalities of 9 + 2 motile cilia. Experimental studies have elevated the status of primary cilia to the level of important cellular {…} devices, acting similarly to an antenna on a global positioning system (GPS) device, which receives signals from a satellite to pinpoint the user’s location, primary cilia receive chemical, osmotic, light, and mechanical stimuli from the extracellular environment.
Signaling
Primary cilia function in secretory organs such as the kidneys, liver, or pancreas as sensors of fluid flow. For instance, primary cilia found in the glomerulus and tubular cells of the kidney function as {…}; fluid flow through the renal corpuscle and tubules causes them to bend, which initiates an influx of calcium into the cell.
Mechanoreceptors
In humans, mutations in {…}, {…}, and {…} genes appear to affect the development of these primary cilia, leading to {…} (PKD).
1) PKD1
2) PKD2
3) PKHD1
4) Polycystic kidney disease
The proteins {…} and {…} encoded by PKD1 and PKD2 genes, respectively, are essential in the formation of the {…} channels associated with primary cilia.
1) Polycystin-1
2) Polycystin-2
3) Calcium
The PKHD1 gene encodes the large protein {…} that targets the polycystin-2–binding domain.
Fibrocystin/polyductin
Internal organs in the body show a {…} asymmetry in position and morphology.
Left-right
Cilia are essential in breaking the left-right symmetry seen in the early stages of embryo development. This process begins on the ventral surface of the bilaminar embryonic disc in the area near the {…} (ventral) node, a transient midline structure formed during gastrulation.
Primitive
A specialized type of motile cilium (one per cell) has been observed in cells of this area that are similar in appearance to the primary cilia. However, despite their 9 + 0 architectural pattern, they are motile and capable of producing a {…} clockwise rotation. Owing to their presence near the primitive node, these cilia are called {…} cilia.
1) Unidirectional
2) Nodal
During gastrulation, the clockwise rotation of nodal cilia generates a leftward unidirectional flow (nodal flow) of the {…} fluid.
Extraembryonic
For instance, nonmotile primary cilia surrounding the primitive node react to the stronger fluid flow on the left side by opening mechanoreceptor calcium channels and initiating specific signaling mechanisms that differ from those on the right side of the embryo. This leads to asymmetric {…} gene expression later in development.
Left-sided
What happens when nodal cilia are immotile or absent?
Nodal flow doesn’t occur, leading to random placement of internal body organs
Primary ciliary dyskinesia (immotile cilia syndrome) often results in this condition in which the position of the heart and abdominal organs is reversed.
What is situs inversus?
How common is primary ciliary dyskinesia (PCD)?
1 in 20,000 births
Motile cilia covering the epithelium of the respiratory tract are responsible for the clearance of the airway. Failure of the mucociliary transport system occurs in this syndrome (PCD disorder) characterized by a structural abnormality resulting in the absence of dynein arms.
What is Kartagener syndrome?
What does electron microscopy reveal about the basal feet of those afflicted with Kartagener syndrome?
The basal feet are misoriented and point in different directions
This PCD disorder is characterized by malformation of the radial spokes and dynein arms, affecting ciliary function in the respiratory tract.
What is Young syndrome?
Some individuals with PCD may also develop symptoms of this condition, characterized by the accumulation of fluid in the brain.
What is hydrocephalus internus?
What percentage of patients with PCD have situs inversus?
50%
The first stage of ciliogenesis includes the generation of…
Centrioles
During the {…} stage of motile cilia formation, the assembly of two single, central microtubules begins in the transitional zone from γ-tubulin rings. The subsequent polymerization of tubulin molecules occurs within the ring of doublet microtubules, thus yielding the characteristic axonemal 9 + 2 arrangement. Subsequently, the axoneme grows upward from the basal body, pushing the cell membrane outward to form the {…} cilium.
1) Elongation
2) Mature
During the growth and elongation of the cilium, precursor molecules are delivered from the cell body to the most distal end of the elongating axoneme by {…} (IFT).
Intraflagellar transport
Cargo molecules (including inactive cytoplasmic dynein molecules) are loaded onto the IFT platform while it is docked near the base of the cilium. Utilizing {…} as a motor protein, the fully loaded platform is moved upward toward the tip of the cilium (anterograde transport).
Kinesin II
The IFT utilizes {…} platforms assembled from approximately 17 different intraflagellar {…} proteins that move up and down the growing axoneme between the outer doublets of microtubules and the plasma membrane of the elongating cilium
1) Raft-like
2) Transport
The platform turns around and heads back to the base of the cilium (retrograde transport) after picking up turnover products (including inactivated kinesin II). During this process, cytoplasmic {…} is activated and utilized as a motor protein to return the platform to the base of the cilium.
Dynein
Mutations in genes encoding IFT raft proteins result in the loss of cilia or ciliary dysfunctions. For instance, the IFT20 raft protein transports cargo proteins for sperm flagella formation. What 2 things does a mutation in IFT20 gene affect in males?
1) Fertility
2) Spermiogenesis
The lateral domain of epithelial cells is in close contact with the opposed lateral domains of neighboring cells. Like the other domains, the lateral domain is characterized by the presence of unique proteins, in this case, the {…} (CAMs) that are part of junctional specializations.
Cell adhesion molecules
Viewed with the light microscope (LM), terminal bars represent epithelial {…} attachment sites.
Cell-to-cell
In addition to aiding cell-to-cell attachment sites, the terminal bar of the lateral domain also acts as a…
Barrier
The specific structural components that make up the barrier and the attachment device are readily identified with electron microscopy (EM) and are collectively referred to as this complex.
What is the junctional complex?
These junctional complexes, also called tight junctions, are essential for establishing a barrier between different compartments of the body and allow epithelial cells to function as a barrier.
What are occluding junctions?
Occluding junctions form this primary barrier between adjacent cells.
What is the paracellular diffusion barrier?
Because they are located at the most apical point between adjoining epithelial cells, occluding junctions act as fences to prevent the migration of lipids and specialized membrane proteins between the apical and lateral surfaces, thus maintaining cell {…} and integrity of these two domains. In addition, occluding junctions recruit various signaling molecules to the cell surface and link them to the {…} filaments of the cell cytoskeleton.
1) Polarity
2) Actin
These junctional complexes provide mechanical stability to epithelial cells by linking the cytoskeleton of one cell to the cytoskeleton of an adjacent cell. These junctions are important in creating and maintaining the structural unity of the epithelium.
What are anchoring junctions?
Anchoring junctions interact with both {…} and {…} filaments and can be found not only on the lateral cell surface but also on the basal domain of the epithelial cell.
1) Actin
2) Intermediate
These junctional complexes allow direct communication between adjacent cells by diffusion of small (<1.2 kDa) molecules (e.g., ions, amino acids, sugars, nucleotides, second messengers, metabolites). This type of intercellular communication permits the coordinated cellular activity that is important for maintaining organ homeostasis.
What are communicating junctions?
These represent the most apical component in the occluding junction complex between epithelial cells.
What are zonula occludens?
This zonula occludens protein forms the backbone of ZO strands; it also forms and regulates aqueous channels used for paracellular diffusion.
What is claudin?
This zonula occludens protein is present in most occluding junctions and maintains a barrier between apical and lateral cell surface.
What is occludin?
This zonula occludens protein is present in occluding junctions in endothelial cells and mediates interactions between endothelial cells and monocyte adhesions.
What is JAM?
This zonula occludens protein is present in specific areas of ZO at tricellular contacts.
What is tricellulin?
This zonula occludens protein is an important link in transduction of signals from all transmembrane proteins; it interacts with actin filaments & has tumor suppressor action.
What is ZO-1?
This zonula occludens protein is required in the epidermal growth factor–receptor signaling mechanism.
What is ZO-2?
This zonula occludens protein interacts with ZO-1, occludin, and actin filaments of the cell cytoskeleton.
What is ZO-3?
What are the 2 types of adherens junctions associated with anchoring junctions?
1) Zonula adherens
2) Macula adherens
The {…} adherens encircles the cell just below its tight junction and is composed of {…} complexes that interact with actin filaments.
1) Zonula
2) E-cadherin-catenin
The {…} adherens (desmosome) provides a scattered, localized, spot-like junction and is composed of {…} and {…} that attach to the desmosomal plaques anchoring the intermediate filaments.
1) Macula
2) Desmogleins
3) Desmocollins
These junction complexes consist of an accumulation of transmembrane channels in a tightly-packed array, allowing for the exchange of ions, regulatory molecules, and small metabolites between cells.
What are communicating (gap) junctions?
These are the two half-channels that form the transmembrane channels of the communicating junction.
What are connexons?
The {…} domain is characterized by the presence of a {…} membrane, {…} matrix junctions (focal adhesions and hemidesmosomes), and basal cell membrane {…}.
1) Basal
2) Basement
3) Cell-to-extracellular
4) Infoldings
The {…} membrane (periodic acid–Schiff [PAS] positive in LM) is a dense layer of specialized extracellular matrix proteins that consists of a {…} lamina (visible in EM) and a {…} lamina.
1) Basement
2) Basal
3) Reticular
The {…} lamina is attached to the underlying {…} lamina (type III collagen) via anchoring fibrils (type VII collagen) and to elastic fibers via fibrillin microfibrils.
1) Basal
2) Reticular
The {…} membrane serves as an attachment site of epithelia to connective tissue, compartmentalizes connective tissue, filters substances that pass to and from the epithelium, provides a scaffold during tissue regeneration, and is involved in cell signaling.
Basement
These are the integrin-based, dynamic anchoring junctions that anchor actin filaments to the basement membrane. Their fast formation and dismantling provide the molecular bases for cell migration.
What are focal adhesions?
These are the integrin-based, stable anchoring junctions that anchor the intermediate filaments to the basement membrane via intercellular plaques.
What are hemidesmosomes?
Glands are classified into two groups according to how their secretory products are released: {…} and {…} glands.
1) Exocrine
2) Endocrine
These glands secrete their products directly onto a surface or through epithelial ducts that may modify their secretion (concentrating, removing, or adding substances).
What are exocrine glands?
Exocrine glands are classified as either {…} glands, which produce mucous secretions, or {…} glands, which produce protein-rich watery secretions.
1) Mucous
2) Serous
Cells of exocrine glands have three mechanisms of secretion: {…} (in which secretory product is released by exocytosis), {…} (in which secretory product is released in vesicles containing a thin layer of cytoplasm), and {…} (in which secretory product is accompanied by cell debris from the dying secretory cell).
1) Merocrine
2) Apocrine
3) Holocrine
These glands lack a duct system and secrete their products (hormones) into the bloodstream to reach a specific receptor on distant target cells.
What are endocrine glands?
Epithelial cells can undergo {…} (EMT) in which they lose their epithelial characteristics and acquire mesenchymal cell features. The reverse process is called {…} (MET). Both processes occur in the embryonic development, wound healing, fibrosis, and malignant transformation of cancer cells.
1) Epithelial-mesenchymal transition
2) Mesenchymal-epithelial transition
Epithelial cells belong to the category of continuously {…} cell populations. The replacement cells are produced by the mitotic division of adult {…} cells residing in different sites, called {…}, in various epithelia.
1) Renewing
2) Stem
3) Niches
