Epithelial Tissue: Structure and Function
How many layers are pseudostratified epithelium?
1, but looks like 2
What are the two primary characteristics of Epithelium?
1. Avascular 2. Has a free surface.
What are the two portions of the basement membrane and from where are they derived?
1. Basal lamina---derived from epithelial tissue 2. Lamina reticularis---derived from connective tissue
What are the four apical modifications?
1. Cilia 2. Stereocilia 3. Microvilli 4. Keratinization
What are the two types of epithelial glands/down growths?
1. Exocrine Glands 2. Endocrine Glands
What is the function of anchoring junctions?
1. Machanical stability by linking cytoskeleton of neighboring cells. 2. Also participate in intra and intercellular signaling
What are the three different modes of secretion in epithelial glands?
1. Merocrine 2. Apocrine 3. Holocrine
What are the main functions of epithelial tissue?
1. Protection 2. Absorption 3. Excretion 4. Sensory Reception 5. Movement of Materials 6. Form Gland
What are the main 3 epithelial cell shapes?
1. Squamous 2. Cuboidal 3. Columnar
What are the roles of zonula occludens?
1. They prevent migration between apical and lateral membrane domains. 2. They are involved in intracellular signaling
What are the function of ZO-1 proteins?
1. They suppress tumors 2. Mediate actin binding
What are the PDZ domain proteins?
1. ZO-1 2. ZO-2 3. ZO-3
What are the anchoring junctions?
1. Zonula Adherens 2. Macula Adherens
What cell-cell junctions are typically found in electron microscopy?
1. Zonula occludens 2. Zonula adherens 3. Macula adherens
What is the core of microvilli?
Actin
What is the core of stereocilia?
Actin
What are macula adherens also known as?
Desmosomes
What is the function of stereocilia?
Detection. They are long and thin like fingers!
What are downgrowths of epithelial tissue?
Epithelial glands
Are multicellular glands considered exocrine or endocrine glands?
Exocrine glands (Sweat Glands)
What are the differences between exocrine and endocrine glands?
Exocrine--do contain ducts and empty their product to the surface Endocrine--do not contain ducts and empty their products into the surrounding connective tissue to eventually lead to the blood.
What does basal mean?
Faces the basal lamina or basement membrane.
What does apical mean?
Faces the free surface.
T/F The terminal bar is most often found using a compound light microscope.
False! It is most often seen in electron microscopy.
What is the function of microvilli?
Increase surface area.
Where is transitional epithelium found? What does it do and what cells are found in it?
It is found in the urinary bladder. This is because it has the unique ability to stretch. It is also found in the ureters and the urethra. Umbrella cells are found in this epithelium.
What is the terminal Bar?
It is the space between an apical modification and epithelium.
What is holocrine secretion?
It is when the cell dies and releases it's contents.
What is apocrine secretion?
It is when the product is released from the apical surface is surrounded by cytoplasm and plasma membrane. (Mammary glands)
What is merocrine secretion?
It is when the vesicles fuse with the apical surface to excrete contents. (Exocytosis)
What is the purpose of the basement membrane?
It separates underlying connective tissue from the epithelium.
What does it mean when skin is said to be keritanized?
Keritanized epithelium causes a water barrier. Epidermis is keritanized.
Where are cell-cell junctions found?
Lateral/Basal surface
Where are gap junctions found?
Laterally
Where are desmosomes found?
Laterally and basally
Where are macula adherens found?
Laterally and basally
Where are zonula adherens found?
Laterally and basally
What color is the basement membrane when stained?
Magenta due to vast amounts of carbohydrates.
What is the function of ZO-3
Mediate actin binding
What is the core of cilia?
Microtubules (axoneme)
Contraction of the terminal web causes what apical modification to contract?
Microvilli
Are sweat glands multicellular or unicellular?
Multicellular
What is a unique feature in holocrine secretion?
Pyknotic: When cells start to fragment and condense
What is the function of ZO-2 proteins?
Responds epidermal GF signaling
What are the functions of epithelial glands?
Secretions: Lubrication, Modify pH, Enzymes (digestion)
What is the difference between simple vs. stratified epithelium.
Simple: Only one layer Stratified: Two or more layers
What are the functional differences between Squamous and Cuboidal/Columnar Epithelium?
Squamous is for fast diffusion and Cuboidal/Columnar is for more regulated, specific absorption and secretion.
What does it mean when something is on the lateral surface?
Surface between cells inbetween the apical and basal surface.
What are connexons?
They are found on gap junctions and they are poors between cells for communication. They maintain continuity between cells: electrical & metabolic.
What are cell-cell junctions?
They attach and anchor cells. They seal adjacent cell membranes.
What are the functions of cilia?
They move material along the apical surface.
What is the function of PDZ domain proteins?
To recognize internal elements of junctions to initiate cell signaling pathways.
Are goblet cells unicellular or multicellular?
Unicellular
Are unicellular glands considered exocrine or endocrine? Why
Unicellular glands are considered exocrine glands because they release their product into the surface EVEN THOUGH they DO NOT have ducts!
Where are the PDZ domain proteins found?
Zonula Occludens
What are also known as tight junctions?
Zonula occludens
What tight junctions are the most apical?
Zonula occludens
