Chapter 5: Epithelial Tissues Flashcards
This tissue is composed of flattened, irregularly shaped cells that form a continuous surface and supported by an underlying basement membrane
It’s found in lining surfaces in passive transport (diffusion) of either gases (as in the lungs) or fluids (as in the walls of blood capillaries); forms lining of the pleural, pericardial, and peritoneal cavities
Simple squamous epithelium
This tissue type consists of cells perpendicular to the basement membrane that appear square with a round nucleus usually located within the center of the cell
These tissue cells usually line small ducts and tubules that may have excretory, secretory, or absorptive functions (e.g., collecting tubules in kidney, small excretory ducts in salivary glands)
Simple cuboidal epithelium
This tissue consists of cells perpendicular to the basement membrane that appear columnar and tall with elongated nuclei that may be located towards the base, center, or occasionally apex of cytoplasm (nucleus polarity)
They are generally found on absorptive surfaces (i.e., stomach)
Simple columnar epithelium
This tissue type is found largely in the female reproductive tract and assists in the movement of fluid or minute particles
Simple columnar ciliated epithelium
The appearance of cells in this tissue conveys the wrong impression of more than one cell layer because each cell remains connected to the basement membrane
It is found almost exclusively in the airways of the respiratory system (often called respiratory epithelium)
Pseudostratified columnar ciliated epithelium
How can pseudostratified columnar ciliated epithelium be distinguished from stratified epithelium?
- Individual cells of pseudostratified epithelium demonstrate nucleus polarity
- Cilia are never present on true stratified epithelium
_____________________________ is defined as epithelium consisting of two or more layers with mainly protective function with the degree and nature of stratification related to physical stress exposure (generally ill-suited for absorption – thickness)
Stratified epithelium
This tissue consists of variable number of cell layers that exhibit maturation from a cuboidal basal layer to a flattened surface area
It’s adapted to withstand abrasion with plentiful cell junctions and intermediate filament (keratin) cytoskeleton (e.g., oral cavity, pharynx, esophagus, anal canal, uterine cervix, vagina)
Stratified squamous epithelium
This tissue constitutes epithelial surface of skin (epidermis) and is adapted to withstand constant abrasion and dessication
It’s marked by intermediate (keratin) filaments cross-linked with proteins in keratinization, resulting in a tough, non-living surface layer
Keratinizing stratified squamous epithelium
This tissue consists usually of only two to three layers of cuboidal cells
It’s often confined to lining of larger excretory ducts of exocrine glands
Stratified cuboidal epithelium
__________________ is found only in the urinary tracts of mammals, where specialized to withstand stretch and toxicity
Transitional epithelium
Intercellular junction type that controls paracellular diffusion and prevents exchange of intrinsic proteins and lipids between apical and basolateral plasma membrane
Tight junctions
What are the main protein components of tight junctions?
Claudins, occludins
What cytoskeleton connections do tight junctions make?
Actin microfilaments
Where are tight junctions found in epithelial cells?
At the luminal end of the lateral cell membrane
What are six characteristics of epithelial tissues?
- Function as an interface tissue
- Exhibit polarity
- Avascular but innervated
- Supported by connective tissue
- Regenerative
- “Cellular” (little extracellular space)
When you skin your knee, what tissue bleeds?
Connective tissue - remember epithelial tissue is avascular and cannot bleed
What’s the name of the uppermost portion of the basal membrane?
Basal lamina
The basement membrane is composed of two layers. What are they?
- Basal lamina
- Reticular lamina
What are the four structural/functional domains of an epithelial cell?
- Apical
- Lateral
- Basal
- Basolateral
The _______________ surface is also called the “free surface” and borders the lumen or exterior surface
Apical
__________________ refers to the side surface that faces neighboring cells
Lateral
The __________________ surface is the bottom surface near the basal lamina
Basal
The _________________ surface is a subset of lateral surface that resides within the basal and lateral domains and covers “corners”
Basolateral
What type of epithelium allows passage of materials by diffusion and filtration in sites where protection is not important and secretes lubricating substances in serosae
Simple squamous epithelium
What type of epithelium aids in secretion and aborption?
Simple cuboidal epithelium
What type of epithelium functions in absorption; secretion of mucus, enzymes, and other substances; and when ciliated movement of mucus or reproductive cells by ciliary action
Simple columnar epithelium
__________________ cells secrete mucus
Goblet
What type of epithelium functions in secretion, particularly of mucus, and propulsion of mucus by ciliary but is present only in a few places in the body?
Pseudostratified columnar epithelium
What type of epithelium protects underlying tissues subjected to abrasion?
Stratified squamous epithelium
Where would non-keratinized stratified squamous epithelium be found?
Moist linings of esophagus, mouth, vagina
Where would keratinzed stratified squamous epithelium be found in the body?
Epidermis of the skin, a dry membrane
______________________ is the process of cells filling with keratin
Cornification or keratinization
In ________________________ stratified squamous epithelium, apical cells have squamous shape that retain nuclei and are often found in areas exposed to abrasion.
Non-cornified or non-keratinized
In _______________________ stratified squamous epithelium, apical cells retain shape but lack nuclei; cells are “dead,” composed only of protein and lipid
Cornified or keratinized
_________________ __________________ epithelium functions in protection and lines the larger ducts of mammary glands, sweat glands, salivary glands, and the pancreas
Stratified cuboidal epithelium
What type of epithelium is found in the vas deferens and the pharynx?
Stratified columnar epithelium
What type of epithelium is a “true” stratified epithelium that can “stretch,” thereby found in the lining of the urinary bladder, ureters, and urethra?
Transitional epithelium
What is distensibility?
Stretching
_________________ epithelium resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome-shaped or squamous-like, depending on the degree of organ stretch
Transitional
In transitional epithelium, the top layer of squamous cells are also known as what?
Umbrella cells
____________________ cells have ciliar on their free surface that beat in synchrony to move substances over the epithelial sheet
Ciliated cells
__________________ cells are found in most epithelial layers; these specialized cells secrete substances onto the surface of the cell sheet
Secretory cells
On what surface of an epithelial cell would you find microvilli and stereocillia?
Apical surface
____________________ are an actin-based extension of the plasma membrane that function to increase surface area and found throughout the body but most commonly in the small intestine and colon and the tubules of the kidney
Microvilli
Cells with microvilli are also called ______________ _____________
Brush borders
______________________ are actin-based microvilli that are very long and are located in the sensory cells of the inner ear and the male reproductive tract
Stereocillia
Where are two places in the male reproductive tract that stereocillia may be found?
Vas deferens
Epididymis
Identify:
Function: move secretions and foreign bodies away with a certain direction of rapid, wave-like motions from the hair-like structures that cover their free surfaces
Location: Respiratory tract, Uterine tubes
Cilia
Cell ______________ function to adhere cells together and to prevent unwanted things from entering epithelial or connective tissues
Junctions
What are the five types of cell junctions discussed in class?
- Tight junctions
- Adherens junctions
- Desmosomes
- Gap junctions
- Hemidesmosomes
________________ _______________ seal neighboring cells together in an epithelial sheet to prevent leakage of molecules between them
Tight junctions
_________________ _______________ join an actin bundle in one cell to a similar bundle in a neighboring cell
Adherens junctions
____________________ join the intermediate filaments in one cell to those in a neighbor via plaques produced at the plasma membrane
Desmosomes
____________ ______________ allow the passage of small water-soluble ions and molecules, thereby functioning as a type of communication junction
Gap junctions
In tight junctions, members of the transmembrane protein families, the _________________ and ________________, form tight links between adjacent cells
Claudins
Occludins
What junctions hold cells together to withstand mechanical stress?
Anchoring junctions
How do anchoring junctions work to resist mechanical stress?
By transmitting the stress across the phospholipid bilayer; they’re intergrated through the entire cell through cytoskeletal filaments
What are cilia?
CILIA are hair-like organelles that move secretions and foreign bodies away via a direction of rapid, wave-like motions
______________ are hair-like organelles that move secretions and foreign bodies away via a direction of rapid, wave-like motions and are most commonly located in the respiratory tract and uterine (fallopian) tubes
Cilia
Where are ciliated epithelial tissues often found?
Respiratory tract and uterine (fallopian) tubes
_________________ are minute finger-like, actin-based projections of the plasma membrane that increase the surface area of a cell and are commonly found in the small intestine or colon and kidney tubules, areas where absorption occurs
Microvilli
What are stereocilia? Where are they found?
STEREOCILIA are extremely long microvilli usually found singly or in small numbers as sensory cells of the inner ear and in the vas deferens and epididymis of the male reproductive tract
What links adjacent or lateral surfaces of epithelial cells together to form a continuous, cohesive sheet?
Cell junctions
What type of junction seals neighboring cells together in an epithelial sheet to prevent leakage of molecules?
Occluding or tight junctions
What proteins are involved in tight junctions?
Claudins, occludins
____________________ hold cells together to resist mechanical stress by transmitting stress across the phospholipid bilayer’s cytoskeletal filaments via attachment of INTRACELLULAR ANCHOR PROTEINS to TRANSMEMBRANE ADHESION PROTEINS
Anchoring junctions
What type of junctions joins actin bundles in one cell to a similar bundle in a neighboring cell and present as a continuous belt below tight junctions?
Adherens junctions
What transmembrane protein is involved with adherens junctions?
Cadherins
______________________ link intermediate filaments of adjacent cells together as point contacts via protein plaques.
Desmosomes
What type of junction faciliates communication?
GAP junctions
GAP junctions are broad patches where adjacent plasma membranes are closely opposed, leaving a narrow intervening gap of __ to __ nm through which small molecules (_______ molecular weight) and ions can pass
2 to 3 nm
<1000 MW
What junctions are regulated by calcium?
GAP junctions
Adherens junctions
What proteins make up gap junctions?
Connexins
Connexins form cylindrical aqueous channels called _______________ at the gap junction site and may be homomeric or heteromeric
Connexons
What junctions bind the base of the cell to the underlying basement membrane?
Hemidesmosomes
How do hemidesmosomes bind to the basement membrane?
via binding of the epithelial cell’s transmembrane protein INTEGRIN to its binding partner LAMININ in the basal lamina, thereby linking the cell’s intermediate filament to the basement membrane
______________ are composed of one or more cuboidal or columnar cells specialized to produce and secrete products into ducts or body fluids
Glands
_________________ glands are “ductless” as they secrete hormones into the bloodstream and include many components of the endocrine system
Endocrine
What are exocrine glands?
They have “true ducts” as they secrete products “outside” or onto a surface
Sweat glands are also known as…?
Sudoriferous glands
Oil glands are also known as….
Sebaceous glands
How can exocrine glands be classified? (Hint - there are three ways)
- Secretion type
- Secretion pathway
- Morphology
What are the two types of exocrine glands on the basis of secretion type?
Serous glands
Mucous glands
_________________ glands secrete watery products with enzymes that function in lubrication (e.g., salivary glands)
Serous glands
_____________ glands secrete mucus products that function in protection in the digestive and respiratory systems
Mucous glands
What three types of exocrine glands are there on the basis of secretion pathway?
Merocrine
Apocrine
Holocrine
What type of gland releases watery, protein-rich fluids by exocytosis?
Merocrine glands
_________________ glands lose small portions of their apical cell bodies and cytoplasms during secretion
Apocrine glands
What types of glands are apocrine?
Some sweat glands
Mammary glands
Ear wax
What type of glands lyse in order to secrete?
Holocrine glands
What types of glands are holocrine?
Sebaceous
On the basis of morphology, exocrine glands can be separated according to duct arrangement. Duct system may be unbranched (_____________) or branched (______________), tubular or _____________(roughly spherical)
Simple
Compound
Acinar
_________________ glands are individual secretory cells (e.g., goblet cells) that produce mucin and mucus while ______________ glands are invaginated cellular sheets of an organ and can be merocrine or holocrine (e.g., salivary glands, sebaceous glands)
Unicellular
Multicelluar
