Lecture 3: Epithelium Flashcards
Define epithelium
a sheet of cells that line all body surfaces, cavities, and tubular organs
True or False
Epithelium arise only from ectoderm
FALSE
epithelium arises from all three germ layers
Main characteristics of epithelium
- polar
- avascular
- comprised of tightly packed cells with little to no intercellular substances
Describe the polar sheets of epithelium
- it contains an apical surface on the outside
2. it has a basal surface lying on supportive CT with contains a basement membrane and basal lamina
True or False: The basal surface of the epithelial sheet is exposed to the external environment
FALSE: the apical surface is exposed to the external environment
What is the basement membrane of an epithelial cell?
found between the connective tissue and the cell itself. It is made up of basal lamina, laminin, and type IV collgens
What is the role of the basal lamina?
it is made up of collagenous fibers and work to anchor the epithelial sheet to the underlying tissue.
What is laminin?
Laminin is an adhesive molecule that is found in the basement membrane of an epithelial cell and works to anchor the epithelial sheets to its underlying tissue.
True or False: The basement membrane is visible under light microscopy
TRUE –> the basal lamina is only visible under electron microscopy
What are the two broad classifications of epithelial cells?
- simple
2. Stratified
What are the types of simple epithelium?
- squamous
- columnar
- cuboidal
Describe a simple squamous cell?
- they are flat
- gases and liquids diffuse across easily
- line moist internal surfaces
Describe the three main locations where you find simple squamous?
- endothelium-line blood vessels, lymphatics and heart
- mesothelium-line serous body cavities and outer tubular organs in the abdomen
- epithelium(not special name)-line small tubules of the kidneys
Describe a simple cuboidal cell.
width and heigh of cells are equal; line small ducts
Where might you find simple cuboidal cells?
secretory ducts in the pancreas, collecting and other tubules of the kidney
Describe a simple columnar cell.
Height of the cells are greater than the width; have secretory and absorptive capability
Where might you find simple columnar cells?
lining most of the GI tract and in the uterus
Describe pseudostratified columnar cells
stacks of columnar cells. All cells touch basal lamina, but not all cells reach the lumen; usually have cilia
Where would you most likely find pseudo stratified epithelium?
where particulate matter is moved in the reproductive and respiratory tracts
What is it meant by stratified?
comprised of two or more layers, the top layer defines the epithelium
Describe stratified squamous
surface cells are squamous but cells below are often polyhedral; usually serves as a protective role
What are the types of stratified squamous?
- keratinized (dry, cornfield)
2. non-keratinized (wet)
Where would you find a non-keratizined layer of stratified squamous epithelium?
esophagus
What type(s) of epithelium typically line large ducts?
stratified columnar or cuboidal
Define a transitional epithelium
layered epithelium that changes its appearance between cuboidal and columnar
Where is transitional epithelium most likely found?
bladder
What are the functions of the epithelium?
- protection (skin)
- secretion (exocrine glands)
- absorption (intestine)
- excretion (kidney tubules)
- sensation (tastebuds, retina)
- transportation (trachea)
- reproduction (testes)
What are the components of the apical surface of the polar epithelial cell?
hydrolases, glycolipids, Na ion dependent transporters, Cl ion channel
