Epithelium Flashcards
What are the functions of the epithelia?
The functions of epithelia include protection, absorption, secretion and sensory reception
What are microvilli? What do they help with?
These are projection of the cell surface with an actin core that increase surface area for absorption. Actin filaments are anchored in the terminal web. They are not motile in themselves, although if the terminal web is moved, the microvilli spread apart.
What cell surface structure is motile?
The vast majority of ciilia are motile (microvilli and stereocillia are not). These have a (9+2 microtubules organization; axoneme). Dynein is critical for moving the arms. There are some “primary cilia” that are not motile (and are lacking the central microtubules). Some cells (such as sperm cells) have a single flagella that has a similar structure to a large, long cillium).
What is a stereocillia?
These are not motile and are essentially long microvilli. They are found in the inner ear and the epididymus.
What are zone occludins?
Tight junctions. Seal neighboring cells together to prevent leakage of molecule between them. Their transmembrane proteins are claudins and occludins
What are Zona Adherens?
Joins an actin bundle in one cell to a similar bundle in a neighboring cell. Anchoring proteins are cadherins.
What are Macula Adherens?
Desmosomes. Joins intermediate filaments in one cell to those in another cell with cadherins and integrins (strong attachment?
What are gap junctions?
Allow passage of water and soluble ion and molecules. Uses connexins to form channels
What is the basement membrane?
All epithelia rest on a basement membrane. It is a layer between epithelium and connective tissue that stains well with PAS because it has lots of glycoproteins. It has type IV collagen fibers, laminin, proteoglycans and many other components. It is important for support and migration of epithelial cells.
What are hemidesmosomes?
These are structures that bind intermediate filaments to the basement membrane with integrins.
What is the definition of a simple epithelia and what are the types?
A simple epithelium has every cell resting on the basement membrane. The types include: simple squamous, with cells of flattened shape; simple cuboidal, with box-shaped cells; simple columnar, with tall cells, usually having microvilli or cilia; pseudostratified, where every cell touches the basement membrane even though there appear to be several rows of nuclei.
What are the types of stratified epithelia?
Stratified squamous epithelia are found in places wehre there is exposure to abrasion or other physical trauma. In moist places it is non-keratinized, while in dry places it is keratinized. Stratified cuboidal is quite rare, though it is found in certain large ducts. Stratified columnar is very rare, only appearing in epithelial to mucous membrane transitions (anus).
Which type of epithelium is most likely to be ciliated.
Pseudostratified columnar is usually ciliated, being most common in the respiratory system.
Which type of epithelium is found in the urinary bladder?
Transitional epithelium (urothelium) can change shape depending on stresses placed upon it. Stretching of the organ flattens cells, while a relaxed organ results in pillow-shaped cells.
What are the two main types of glands?
Exocrine (secrete onto a surface or into a duct) and endocrine (secrete into the circulation) glands.
