Epithelial Tissues IV Flashcards
Epithelial cell polarity is crucial to allow _______, _______ and _______
(1) unidirectional secretion and/or absorption of molecules to or from one side of the epithelium, (2) for “trans-epithelial” transport of ions, macromolecules from the apical to basal surfaces (or visa versa) and (3) for localizing and orienting intercellular signaling either among epithelial cells, or between epithelial cells and other cell types
transcytosis
The endocytosis of substances from one membrane region, followed by trans-cellular transport of the vesicles and their exocytosis from another membrane region
Apical surface modifications
microvilli and cilia
basolateral surface modificators
Infolds and outfolds of the BL membrane
microvilli: what are they? where are they found? what is their function?
Cell surface extensions (protrusions) that contain actin bundles connected to cytoskeletal elements in the cell interior. The primary function of microvilli is to increase surface area, which greatly increases the rate/efficiency of membrane transport and secretion. The size and abundance of microvilli varies with cell type.
stereocilia
An unusual type of microvillus found in the epididymis and in sensory cells in the ear. These are extremely long, actin-filled microvilli, and are not related to cilia. In the ear, stereocilia function in the reception of sound.
Cilia:
Microtubule-containing extensions (protrusions). There are at least three kinds of cilia
primary cilium is? function?
a single (one/cell) non-motile microtubule-based extension found on many different epithelial cell types. Primary cilia organize and promote signal transduction systems (receptors and effectors) that control epithelial cell division, fate (differentiated state), and function.
Motile cilia are? found where? function?
related microtubule extensions that move, and are found only on specific epithelial cell types; these cilia wave like a boat oar to move mucous and other materials along passageways. Thus they tend to be found in epithelia of the respiratory tract (to move junk and mucous out of the airways), and in the oviduct (to assist in moving ova towards the uterus).
sensory cilia are? function? they are connected to the _____ system.
not motile and appear to function in sensory reception (e.g. in vestibular hair cells of the ear). These sensory cilia are likely specific variations of primary cilia, specialized to house sensory (touch, taste) systems that are connected to the central nervous system.
Mutations in proteins common to cilia or their support structures result in
a large set of diseases called ciliopathies.
basal lamina
thin sheet of extracellular material that underlies that basal surface of each epithelial tissue
basal laminae are formed by
collagen, a fibrous protein, forming sheets of thin fibers that are interwoven with a variety of other extracellular glycoproteins
_______ and some other glycoproteins including ______ and _______ are common to most basal laminae
- network-forming collagen
- lamins
- entactin
Basil laminae important functions (7)
(1) mediate attachment of epithelia to underlying CT
(2) contribute to selective filtration
(3) establishment and maintenance of epithelial cell polarity
(4) “highways” for the migration of cells through CT
(5) barrier
(6) control gene expression to affect their proliferation of development
(7) control the development, morphogenesis and organization of epithelial cells (“tissue scaffolding function, therefore critical for repair of epithelial tissue)
