Lecture 4: Characteristics Of Epithelial Tissues I Flashcards Preview

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Flashcards in Lecture 4: Characteristics Of Epithelial Tissues I Deck (18):

What is the difference between epithelial cells and epithelioid cells?

- Epithelial tissues have relatively little intercellular matrix.
- Epithelial tissues typically display free surfaces.
- Epithelioid tissues resemble epithelial tissues but lack a free surface.


What is the difference between apical domains and basolateral domains?

Apical domains: These are the surfaces of the cells that are in contact with a lumen (i.e., kidney tubule cells and glandular duct cells) or external environment(i.e., surface cells of the epidermis).
- Basolateral domains: These include the surfaces of cells that are locked together by special junctional complexes with neighboring cells as well as the surface opposite the apical domain that is in contact with the basal lamina.


Epithelial Cells are found in all 3 germ layers. Give an example of types of epithelial tissue in each germ layer

- Ectoderm: I.e., the skin epidermis and glands
- Endoderm: I.e., the lining of the gastrointestinal tract (including glands)
- Mesoderm: I.e., the lining of blood vessels, mesothelium, Bowman’s capsule


What are the two components of the basment membrane and what are it's 3 functions?

- Basal lamina - next to the epithelial layer and is 50nm thick. It is composed of type IV collagen plus glycoproteins and is (PAS+). It is absent in lymph vessels and hepatic sinusoids.
- The reticular lamina is in contact with underlying connective tissue and consists of argyrophilic fibers, reticular fibers and glycoproteins.

- Functions include: 1. Selective filtration barrier, 2. Scaffold for embryogenesis and regeneration, and 3. Stabilization of tissue shapes


What are the three major functions of all epithelial tissues?

- Epithelial tissues line body cavities and cover body surfaces.
- Epithelial tissues form secretory and excretory parts of glands. - Epithelial tissues may be innervated.


List the most basic way to classify types of epithelium

- By # of Layers: (Simple = One Layer), (Stratified = Multiple Layers)

- By Shape: Squamous (flattened), Cuboidal (height approximately equal to width), Columnar (height greater than width)


What are the 3 apical surface modifications present on epithelial cells?

What does keratinized mean and how does it separate types of tissue

Surface Modifications (Cilia, Stereocilia, and Microvilli(brush border)

Keratinized: Nucleus starts to disappear in the outer layers - Epidermis
Non-Keratinized or Lightly Keratinized: Nucleus remains intact across all layers - Esophagus or Vagina


At this point, figure out how to get all those goddamn photomicrographs on here. You'll need 'em.


Or at least review the fuck out of those photomicrograph slides in the Lecture


Describe pseudostratified cells

- Technically it's a type of simple epithelium
- It first looks stratified, but all cells are in contact with the basal lamina. Best way to identify is to notice is that nuclei are kind of randomly positioned.
- This may have to do with stem cells, but I'm not clear on that.


Describe Transitional Epithelium

Kind of like pseudostratified...at first it looks stratified, (though it's simple) but when the nuceli are at varying positions, and the Heads are DOME-shaped, and all the cells are in contact with the basal lamina, it would seem that it's transitional.
- Found in the ureter
- Personally, I think they look like cuboidal cells, but with a "haze" over the dome-shaped top.


Describe the polarity of the apical domains and the basolateral domains

- Apical domain usually faces the lumen and can have cilia, stereocilia, or microvilli on it
- Basolateral domains usually have intercellular junctions (not to mention the lateral sides), which are meant to communicate/connect with neighbor cells and the basement membrane.


Describe the difference between cilia, microvilli, and stereocilia.

- Cilia: A core of microtubule doublets in a 9+2 concentric arrangement surrounded by plasma membrane.
- Microvilli: A core of actin-containing microfilaments.
- Stereocilia: Contains a core actin microfilaments. But tend to be longer than microvili and branched.


Where is simple squamous epithelium found?

Where is simple cuboidal epithelium found?

Simple columnar epithelium cells?

- Lines ducts, vessels, and tubular structures, forms the walls of bowman's capsules, inner surfaces of membranous labyrinth, and the tympanic membrane.
- Kidney Tubules (Usually has a microvilli brush border), also found on ovaries, glands, bronchioles, and lens of the eye anterior.
- More often striated, but they often have an apical surface composed of microvilli, upper respiratory tract, uterus, nasal passages, and the central canal of the spinal cord. Non-ciliated columnar epithelium is found on the lining of the stomach, gall bladder, and the excretory ducts of the glands.


Where is stratified squamous epithelium found?

Stratified Cuboidal?

Stratified Columnar?

- Epidermis, cornea. Non-keratinized squamous is found in the vagina, esophagus, lining of the mouth, tongue and part of the epiglottis.
- Stratified cuboidal is rare, but found in the anus, excretory ducts of some glands, and part of the male urethra.
- Stratified columnar is also rare, but found in sweat glands, conjunctiva of the eye, male urinary tract, epiglottis, and pharynx.


Where are pseudostratified epithelial cells found?


- Ciliated pseudostratified is found in the trachea. Stereocilliated pseudostratified are found in the epididymis.

- Transitional is found strictly in the urinary system. That's why it's also called urothelium.


What are the two types of epithelium?
What type of epithelial tissue is most commonly associated with protection?
Describe the type of epithelia that modify concentration
Describe the type of cells associated with secretion and absorption

- Covering/Lining, and Glandular
- All of them do to an extent, but especially stratified squamous
- They come in tight barriers, or leaky barriers (mostly in the gall bladder and renal tubes)
- These are usually pseudostratified. The height usually signifies the level of secretory and absorptive activity. But they can also be simple columnar such as in the gall bladder and renal tubes, which help with glandular function


Describe microvilli brush borders

- These are non-motile, fingerlike projections that run uniformly across the apical membrane supported by cross-linked actin bundles. These are usually found on the intestinal and renal portions and function in absorption.
- Within these, is an actin filament core that extends into the terminal web into the cytoskeleton. The distal end of the actin filament core is capped with formin, which interacts with the barbed end of the actin.
- The actin filaments that make up the core are cross-linked by villin and fimbrin, which connect to the intermediate filaments of the web.


Describe the structure of cilia?

- Contains 9 peripheral doublets and central pair of microtubules. Each doublet consists of an alpha tubule and a beta tubule.
- Alpha tubules contain 13 protofilaments, and radial spokes extending to the sheath around the central pair. There is a pair of dynein arms projecting to the neighboring beta tubule of the next doublet.
- Beta Tubules: Made up of 10-11 protofilaments.