Glands Flashcards
give two different natures of secretion
mucous glands- secrete mucus rich in mucine (highly glycosylated polypeptides). swell in water. lightly stained in H and E
serous glands - secretion is watery and free of mucus - look pink in HandE
describe merocrine
like exocytosis
membrane bound component approaches CSM, fuses with plasma membrnae, contents are in continuity with extracellular space, plasma membrane becomes larger, membrane retrieved.
describe apocrine
non membrane bound strucutrea approaches cell surface, makes contact and pushes up apical membrane, thin layer of apical cytoplasm wraps around droplet, pinches off from cell, plasma membrane is smaller, membraned added to regain original area.
e.g. mammary gland lipid droplet secretion
describe holocrine
disintergration of cell that releases contents and discharges whole cell.
e.g. sebaceous gland cells fill hair follicle with sebum.
describe mechanism of endocytosis
active bulk transport of substances into a cell.
material is engulfed from outside by invagination, forming a vacuole
pinocytosis - same but smaller infoldings. mainly of liquids or large macromoleucles
coupled with trans-epithelial transport
describe how endocytosis and secretion combine to give trans-epithelial transport
material endocytosed at one surface
transport vesicle shuttles across cytoplasm
material exocytosed at opposite surface
used for molecules that are too large to penetrate membrane
define golgi apparatus and give 4 functions
Golgi - cluster of vesicles, tubules and cisternae. cisternae have one side flat, and the other concave, with swellings at ends that pinch off as migratory Golgi vacuoles.
packages through condensation of contents
modifies macromolecules e.g. adds sugars to protiens and lipids
sorts proteins into compartments
transports by producing resultatn vesicles.
mechanism and importance of glycosylation of proteins in Golgi
proteins are recieved from RER, glycosylation occurs in cisternae, proteins move in from flat side of cisternae to curved side.
importance as gives proteins molecular specificity. allows specific interaction with other proteins. allows for adhesion, mobility of cell,s communication and contact inhibition of movement and division.
give four methods of secretion
nervous - sympathatic nervous stimulation of adrenal medullary cells to realease adrenaline
endocrine control - ACTH stimulates adrenal gland cortex to secrete corisol
neuro-endocrine control - nervous cells in hypothalamus control sectreion of homrones from anterior pituitary gland
negative feedback - high thryoxine levels inhibits thryoiid stimulation hormone.
steps in thryoid hormone synthesis
synthesis and secretion of thyrodglobulin into coloid
uptake of iodide from blood and oxidation to iodine with release into colloid
iodiation of thyroglobulin in colloid
formation of T3 and T4 by oxidative coupling reactions
reabsorption of colloid by receptor medicated endoxytosis
release of T3 and T4 by exocytosis.
define gland, endocrine and exocrine.
an epithelial cell or collection of cells specialised for secretion.
endocrine - ductland gland that secretes substances direclty into the bloodstream
exocrine - a gland with ducts that secretes on to an epithelial surface.
describe three ways to describe a multicellular gland
simple / compound (branched or not)
acinar or tubular
coiled or branched
give four methods of control of secretion
nervous secretion - sympathetic nervous stimulation to release adrenaline
endocrine control - ACTH stimulates release of cortisol
neuro-endocrine control - nervous cell sin hypothalamus control secretion of hormone from anterior pituitary
negative feed back
give four methods of control of secretion
nervous secretion - sympathetic nervous stimulation to release adrenaline
endocrine control - ACTH stimulates release of cortisol
neuro-endocrine control - nervous cell sin hypothalamus control secretion of hormone from anterior pituitary
negative feed back
