Epithelium Week 2 Flashcards
What are the 4 basic tissues in the body?
Epithelium, Muscle, Nerve, Connective Tissue
What are epithelia ?
Sheets of cells that cover or line internal and external body surfaces
Form secretory glands and ducts
What are the functions of epithelia?
- Protection
- Absorption (intestinal lining)
3.Secretion (salivary gland)
Cells are ________ packed together in epithelia with one free surface that faces the __________.
Tight, lumen of the organ (internal cavity)
_____________ attaches the epidermis to the ___________ .
Connective tissue , basement membrane
What is the basement membrane and what is its function?
An acellular meshwork of carbohydrates and proteins that serve as a filter and membrane.
What is the name of the connective tissue that attaches the epithelium to the basement membrane? What additional function does it have?
Lamina propria; Since the epithelium is avascular, the lamina propria provides nutrition and O2 via vessels
Is the epithelia vascular or avascular ?
Avascular
What cells are in a single layer and are flat?
Simple Squamous
Describe the cytoplasm and nucleus of simple squamous epithelial cells
Scanty (thin) cytoplasm and flat nuclei
Simple squamous cells are specialized for ___________
Simple diffusion across cytoplasm
Where are simple squamous cells located?
Air sacs of lungs, lining of blood vessels, structures in kidney
Describe the structure of simple cuboidal cells. How do they appear in a histological section?
Equal physical dimensions. They appear as squares in histological sections in one layer.
Nuclei appear ________ in simple cuboidal cells
Round
What are the functions of simple cuboidal cells?
Protection
Absorption
Secretion of substances needed for the organs they line
Where are simple cuboidal cells found?
Collecting tubules of kidney participate in reabsorption of water and filter
What cells are taller than they are wide and in one layer?
Simple Columnar Epithelium
Nuclei appear __________ in simple columnar epithelium.
Round; nuclei are pushed to the area AWAY from the lumen to create space for cell activities such as secretion.
What are the functions of simple columnar epithelium?
- Protection
- Absorption and secretion
- Transport of materials
Where can simple columnar epithelial cell be found?
Bronchial tubes of lungs, uterine tubes, lining of stomach and intestinal tract
How are stratified epithelia classified?
By the TOP layer of cells.
Which layer of stratified epithelia can touch the basement membrane?
Only the last layer
How are nuclei arranged in stratified epithelia?
They are aligned with each other
The rarer kinds of stratified epithelia are _____________. They are found in _________.
Stratified columnar and cuboidal , large glands and the male urethra
Where are stratified cuboidal epithelium found ?
Sweat glands, cells recycle sodium and chloride ions in sweat
Where are stratified columnar epithelia found?
Male urethra to protect tissue from urine by secreting mucus
What is the most common stratified cell?
Stratified squamous
Describe what stratified squamous cells look like. What do the nuclei look like?
Piles of flat cells with many layers, lines of nuclei are hard to see.
Where are stratified squamous cells located?
Anywhere there is friction; vocal cords, esophagus, epidermis, vagina
What adaptation allows for stratified squamous cells to sustain friction. Describe it.
Keratinization, Cells synthesize keratin filaments that enhance cell toughness.
How do keratinized cells appear compared to non keratinized cells?
Keratinized cells may eject organelles including nuclei so cells close to the lumen will lack nuclei
In keratinized cells, cells _______ from the lumen will lack nuclei.
close
Epithelium has a ________ turnover rate.
high
What are pseudo stratified epithelium? Which cells touch the basement membrane?
Epithelia of different shapes and sizes that ALL touch the basement membrane?
What is urothelium?
Urothelium is transitional epithelium that is found in the bladder and the ureter.
What is the function of the urothelium?
To maintain the urinary barrier even when the bladder is full.
Describe the two distinct appearances of transitional epithelium ?
There is a compact version and a taller version when the bladder is empty. Both versions have unique rounded cells.
What are umbrella cells?
Umbrella cells are a key feature of transitional epithelium that are rounded whose dense plaques help maintain barrier function
Can umbrella cells be multinucleated?
Yes
Epithelial cells are _____. This means that there is an ________ distribution of proteins and organelles in the cytoplasm.
polar, uneven
Describe the polarity of epithelial cells.
There are 3 domains.
- Apical
- Basal
- Lateral
Describe the Apical domain of the cell
Cell surface that faces the lumen
Describe the Basal domain of the cell
Cell surface that attaches to the basement membrane in simple epithelium
Describe the lateral domain of the cell
Cell surface attached to other surfaces in the epithelial sheet
Describe the 2 main functions of the apical domain
Proteins to allow for interaction with the lumen
Specialization to increase surface area or help move substances
What are the three apical specializations ?
Microvilli , Cilia and Stereocilia
Microvilli are ______, finger-like projections of _____ length on the _______ domain. They are responsible for ________.
short, uniform, apical , absorption
How do Microvilli appear on TEM vs the light microscope ?
Individual structures on the TEM
On the light microscope, microvilli can’t be resolved individually. They look like a brush border.
How do microvilli appear on a light microscope?
Brush border
Microvilli are supported by ____________ which insert into a network of cytoskeletal proteins called the ____________.
actin filaments, terminal web
What can be seen as a fuzzy border on a TEM?
Glycocalyx
Cilia are _________, hair like specializations that are in the _________ domain.
longer, apical
Cilia are microtubules or microfilaments?
Microtubules
Describe the structure of cilia
Cilia are arranged in a 9+2 pattern of doublets
Cilia are specialized for _________.
Motility
Attached to __________ are ______ motor proteins which allow cilia to move.
outer microtubule pairs , dyenin
Primary ciliary dyskinesia is a recessive/dominant genetic disorder. Which cilia in the body are affected?
recessive, all cilia are affected
Stereocilia are related to ________ which means they are made of _______.
Microvilli, actin filaments that attach to the terminal web.
Are stereocilia motile?
No
Where are stereocilia found?
Epididymis and inner ear
What is the basal domain?
The area OPPOSITE to the apical domain it is furthest away from the lumen of the organ. It produces a layer of extracellular matrix called the basement membrane.
What are two important structures of the basal domain?
Hemidesmosomes and basal infoldings as well as the basement membrane
Hemidesmosomes are located in the _________ domain. They are responsible for ________.
Basal , serving as junctions to attach the basal domain to the basement membrane and increasing structural integrity
Hemidesmosomes consist of ____________ that anchor to structures inside the cell by _________________ and out side the cell by _____________.
Plaques
Connecting to the intermediate filaments (keratin) of the cytoskeleton via intracellular plaque
using the extracellular domains of integrins and lamins within the hemidesmosome to bind to molecules in the basal lamina (of the basement membrane).
What are basal infoldings? What is another name for them?
Basal infoldings allow the plasma membrane of the cell to fold to create more surface area.
What is the basement membrane?
It is an extracellular matrix produced by the basal domain of epithelial cells. It it is attached to the epithelial cell via hemidesmosomes.
What provides nutrition and O2 to the epithelial cell+ basement membrane complex ?
Lamina propria
Is the basement membrane cellular or acellular?
Acellular
What is the function of the basement membrane?
Structural support for epithelium and attachment site to lamina propria
Semipermeable filter
Mutations in which part of the epithelial cell can lead to kidney disease? Why?
Basement membrane because one of it’s prime functions is to act as a semipermeable filter
Mutations in the basement membrane can cause ________ disease.
kidney
What are the 3 important macromolecules of the basement membrane?
Collagen fibers
lamins
Integrin proteins
Basement Membrane Appearance on H&E
Is the Basement Membrane basophilic or acidophilic? Is it basic or acidic?
Appears as the acellular pink area in basal domain of epithelium.
Acidophilic , Basic
Basement Membrane Appearance on TEM
There will be two distinct layers of the Basement Membrane present.
- Basal Lamina which will appear as a dense line
- Reticular Lamina which will appear below the basal lamina
What is basal lamina?
Basal lamina is a layer of the basement membrane that contains molecules with a permeability barrier.
What is reticular lamina?
Reticular lamina is a layer of the basement membrane underneath the basal lamina that connects the basal lamina to the lamina propria and provides structure.
What is reticular lamina made of?
Collagen fiber mesh
What is a transmembrane protein? Give two examples
Proteins that span the plasma membrane that can interact with substances in and out of the cell
Claudin and Occludin which make up tight junctions of the occluding junction class.
What is the lateral domain?
The lateral domain is the site of attachment to other cells
What is the function of the lateral domain?
Form junctions to attach cells to each other and regulate transport.
What is the difference between a transcellular pathway and a paracellular pathway?
Transcellular is through the cell and paracellular is between cells.
What are the three junctions associated with the lateral domain?
Occluding
Adhering
Communicating
Occluding junctions _____________ and ________________ via a ___________ pathway. An example of an occluding junction is __________.
Seal cells together and control transport of substances via a paracellular path way.
Tight junctions
Adhering junctions ___________ attach cells ____________ or ____________. Examples of adhering junctions are _________.
mechanically attach cells together or to the ECM.
Zonula Adherens , Macula Adherens (desmosomes)
Communicating junctions mediate passage of __________ from ___________. An example is ___________.
chemical or electrical signals from one cell to another.
Gap Junctions
Tight junctions are a type of ____________ that is important to _________________. The other name for tight junctions are ______________.
They are a type of occluding junction that is important to cellular polarity and selective permeability. The other name is Zona Occludens.
Tight junctions form ______ that _______________ prevent _______________. If apical channel proteins bring in nutritents that travel to the basal domain they ________.
seals that prevent proteins from migrating to the wrong domain. Apical channel proteins that bring in nutrients from the lumen cannot function properly if they travel to the basal domain. Tight junctions prevent this.
Tight junctions limit ______________.
Limit transcellular transport. For example, a molecule from Cell A can’t just diffuse back into the lumen via the lateral domain
Tight junctions are found in the ____________.
Lateral domain adjacent to the apical domain.
Tight junctions are made of ______________ called ________ and __________.
Where do they attach?
Transmembrane proteins, claudin and occludin
Inside they cell, the proteins are locked into the actin filaments of the terminal web. Outside the cell, they attach to neighboring transmembrane proteins.
Occludin - Occluding junction - Tight Junction
What is a Zonula Adherens?
Zonula Adherens is a adhering junction that attaches cells together to stabilize the sheet.
Describe the structure of Zonula Adherens
They form a continuous belt (zona) on the lateral surface of each cell.
Zonula Adherens are made of ___________ called _________. These hold the ________ of cells together. Inside the cell, the protein attaches to the _______________. Outside the cell the protein attaches to ____________.
Transmembrane proteins called cadherins (adheren - cadherin). These hold the plasma membrane of neighbording cells together. Inside the cell, the protein attaches to the actin filaments of the terminal web of the cytoskeleton.
Where are Zonula Adherens located?
Directly opposed in adjacent cells found below tight junctions.
What are Macula Adherens? What is another name for them?
Macula Adherens are a type of adhering junction that is also known as a desmosome
What is the function of the desmosome? What type of junction is it?
Form a series of spot welds to stabilize epithelium. Adhering junction
Where are desmosomes/macula adherens located?
Adbundant on lateral surface below tight junction and zona adherens
Desmosomes hold __________ by _____________ and ___________. Outside the cell _____________ , inside the cell ___________________.
the plasma membranes of cells, Desmocollins and desmogleins
Outside the cell, desmocollins and desmogliens attach to each other. Inside the cell, think protein plaques serve as insertion points for the intermediate fibers of the cytoskeleton.
In the disease ______________ , individual make _______________ that bind to and disrupt ___________ causing severe blistering of skin.
Pemphigus , antibodies, desmosomes/macula adherens
What is a gap junction?
Gap junctions are a type of communicating junctions that permit the flow of ions and small molecules. (Electrochemical communication)
What are examples of things that can travel to gap junctions?
Potassium, Sodium and Calcium can travel via gap junctions in heart muscle cells to allow the heart to contract in a coordinated fashion.
Where are gap junctions located?
In the lateral domain below tight junctions and the Zonula Adherens
Gap junctions are made of ___________ that form ________________ called _________.
transmembrane proteins called connexin that form channels between cells called connexon.
______ connexin makes _____ connexon. ________ connexon makes ___________.
6 connexin makes 1 connexon. 2 connexon make a gap junction.
Order the junctions of the lateral domain from the apical to the basal lamina.
Microvilli are present on the apical surface of an epithelial cell.
Tight junctions
Zonula Adherens
Gap Junctions
Macula Adherens (desmosomes)
Hemidesmosomes
Hemidesmosomes attach the basal layer of the cell to the basal lamina of the basement membrane.
Which junctions are associated with actin filaments of the cytoskelton?
Tight (Occluding) and Zonula Adherens (adhering)
Which junctions are associated with intermediate filaments of the cytoskeleton?
Macula Adherense/ desmosomes and Hemidesmosomes
Which junctions are NOT associated with the cytoskeleton?
Gap junctions
