Junctions, Glads and Membranes Flashcards
Define cell juntions.
contact points between the plasma membranes of tissue cells.
define tight junctions.
work like “zippers” to connect cells in epithelium that lines the body cavities.
what is the purpose of tight junctions.
prevent digestive juices from seeping between the epithelial cells that line the stomach and intestines.
What are desmosomes.
work-like “snaps” to attach adjacent cells to one another in tissues that need to resist mechanical stresses.
where are desmosomes common.
among cells in the superficial layer of the skin and between myocytes. heart mucles.
Define gap junctions.
use protein channels called connections to form tiny, fluid-filled channels between adjacent cells.
location of gap junctions.
in intercalated dics where the nerve signals travel very quickly through the heart. and are allowed electrical signals to pass from one myocyte to another.
Composition of glands.
epithelial cells that produce and release aqueous secretions.
define exorine glands.
secrete their products into ducts to be released at the surface of the body or into the lumen of another organ.
define endocrine glands.
have no ducts and secretes hormones into the extracellular fluid.
what can exorine glands be calssified as?
unicellular which can be mucous cells or goblet cells.
multicellular glands which are usually enclosed within a capsule that divided into lobes, which are subdivided into lobules. example are salivary glands, pancreas, mammary glands.
serous glands.
produce thin wateray fluids, such as perspiration or tears.
mucous glands.
produce the glycoprotein mucin that absorbs water to become sticky mucus.
merocrine (eccrine) glands.
release their secretions by exocytosis. examples salivary, sweat, pancreatic glands.
apocrine glands.
similary to merocrine but are sweat glands in the armpit or mammary gland.
