lecture 3 Flashcards
what is a gland
it is an epithilial cell, or collection of cells specialised for secretion
what is exocrine
a gland with a duct that secretes to an epithilial surface
what is endocrine
a ductless gland, where hormones secrete into the bloodstream
mucous gland secrete
mucus. stain poorly in H&E (light)
serous gland secrete
enzyme, watery, no mucus. stain pink in H&E
merocrine secretion. an example and what is it
exocytosis product in a vesicle approaches cell surface continuity between vesicle and membrane- transiently larger salivary glands/ sweat gland
apocrine secretion
endocytosis non membrane structure e.g lipid approaches cell surface makes contact and pushes through apical membrane the apical (lumenal) cytoplasm pinches off membrane transiently smaller e.g. mammary glands
what are myoepithilial cells
contraction pushes lumenal content towards duct e.g. secretion of milk from acini
holocrine secretion
disintegration of cell to release contents e.g. sebaceous gland to fill hair follicle with sebum
what is endocytosis
engulf material initially on the outside of the cell It is the opposite of exocytosis (merocrine secretion). Endo/Exocytosis are coupled in transepithelial transport.
describe how endocytosis and secretion combine to give transepithelial transport
When a molecule is too large to penetrate membranes it can be shunted across from one component of the body to another. - Material is endocytosed at one surface of the cell - The transport vesicle shuttles it across the cytoplasm - The material/vesicle is then exocytosed at the opposite surface.
Golgi Apparatus – Structure:
- Stack of disc-shaped cisternae - One side of the discs are flattened, other side is concave - Discs have swelling at their edges (Vesicles that bud off) - Distal swellings pinch off as migratory Golgi Vacuoles
Golgi Apparatus – Function:
compartmentalise
Packaging through condensation of contents
Glycosylation
Transport
Golgi Apparatus – Product Destinations:
- Majority extruded in secretory vesicles - Some retained for use in the cells (eg lysosomes) - Some enter the plasma membrane (Glycocalyx)
Golgi Apparatus – Glycosylation & Specificity
- Branching sugars offer:
complex shapes for specific interactions in the glycocalyx
Enzymatic destruction of this layer alters specificity
Adhesion to substrates & neighbouring cells - Communication with neighbouring cells -
Mobility of cells .
Describe simple mechanisms of control secretion
Nervous Control - e.g. sympathetic nervous stimulation of adrenal medullary cells leads to the release of adrenaline. Endocrine control – e.g. adrenocorticotrophic hormone (ACTH) stimulates the cortex of the adrenal gland to secrete hormones (e.g. Cortisol) Neuro-endocrine control – e.g. nervous cells of the hypothalamus control ACTH secretion from the anterior pituitary gland Negative feedback chemical mechanism – e.g. the inhibitory effect of high thyroxine (T3 & T4) levels on TSH synthesis by the anterior pituitary gland.
classify gland by structure
secretory part: uni/multicellular
acinar(bulbous)/ tubular
coiled/branched
duct: simple/ coumpound
what is the faulty gene in CF and where is it located
cystic fibrosis transmembrane regulator on apical membranes of epithilial cells
what is the cause of cystic fibrosis
the CFTR is absent on apical membranes. cl transport is comprimised. na transport is comprimised (more in cell) water doesnt leave epithilium. mucus is viscous. cant be moved to oropharynx for swallowing. pulmonary infection
what is meconium ileus
when babies cant pass first stool.
CF causes viscous mucus in GI tract. less easy to pass stool.
constipation and invagination of GI tract in older patients
why is sweat testing indicative of CF
no CFTR on apical membrane of epithilial cells lining the sweat gland duct. poor reabsorption of cl ions sweat is rich with cl and na. very salty
describe thyroid follicle and production of hormones
a follicle contains the colloid and the simple cuboidal epithilium surrounding it
SC synthesis and secrete thyroglobulin
simple cuboidal cells take up iodide from blood –> oxidise to iodine–> colloid
iodination of thyroglobulin occurs in colloid
forms thyroxine and tri-iodothyronine in colloid
t3 and t4 receptor mediated endocytosis into SC then exocytosis into capillary lumen bloodstream
which cells do parathyroid glands have
chief cells with secrete parathyroid hormone, controls calcium
