glands introduction Flashcards
definition of a gland
an aggregate of epithelial cells that are specialised for the secretion of a substance. thy regulate human physiology but receiving stimulus from CNS and circulating chemicals from neighbouring cells.
features of an endocrine gland
they are ductless. secrete directly into the blood and substances travel to a distant part of the body
features of an exocrine gland
they are ducted and secrete into a location through a duct. usually secrete enzymes or lubricants.
examples of endocrine glands
pituitary gland, thyroid gland and parathyroid gland
examples of exocrine glands
salivary, pancreas, mammary, sweat, sebaceous and lachrymal gland
pituitary gland
inferior to hypothalamus. Anterior produces ACTH, LH ,FSH and TSH. regulates most glands of the body. Posterior produces ADH to prevent water loss from kidneys and oxytocin
thyroid gland
produces T3 and T4 controlling metabolism and involved in calcium homeostasis
parathyroid gland
controls calcium homeostasis
salivary gland
secrete salvia which has role in digestion and lubrication
pancreas
secretes enzymes amylase, trypsin and lipase.
mammary
produces colostrum in milk in response to oxytocin and prolactin
sweat glands
secrete sweat which help to regulate body temp
sebaceous
secrete sebum onto skin/ in ear to protect skin from pathogens
lachrymal glands
secrete water into eye to lubricate it also produce lysozymes
how are exocrine glands generated in uetero development
growth signal received, proliferation of cells and epithelial cells invade the space created by digestion by enzymes. central cells die off producing a duct
how endocrine glands are generated in utero development
growth signal received, proliferation of cells and epithelial cells invade the space created by digestion by enzymes. angelic factors are produced and this stimulates blood vessel growth and then the link to starting cells is broken by apoptosis
how does branching of ducts occur
a growth hormone is realised and the epithelial cells will grow towards it
name the shapes of ducts and draw them
simple, simple branched ad compound tubular. simple, simple branched and compound alveolar
what are myoepithelial cells
act as both epithelial cells and smooth muscle cells. have the ability to squeeze duct to help release product
different types of secretion
merocrine, apocrine and holocrine
merocrine
fusion of vesicles with apical membrane e.g exo and end crime glands of pancreas. vesicles move along microtubules and when ca2+ present fuse with membrane. pretty much the same as normal exocytosis
apocrine
partial loss of cytoplasm e.g lactating mammary glands or sweat glands
holocrine
complete loss of cytoplasm e.g sebaceous gland
difference between regulated and constitutive secretion
regulated- only related upon stimulation
constitutive- continuously released
role of Golgi in secretion
vesicles emerge from trans Golgi face and become glycolated in the Golgi
why do cells become glycolated
to aid protein folding, prevent protein digestion and lipid digestion and cell recognition
exo,endo,pino and phagocytosis
exo-secretion via vesicle fusing with membrane
end-englufing molecules form outside into vesicle
Pino-liquid droplets ingested by cells
phago-envleoping cells and other particles
what is transepithelial transport
movement through cells;
1) move through aqueous channels at both end
2) move through lipid membrane at both ends
3) transported by carrier proteins at both end s
4) be englulfed by membrane, travel through and exit by exocytosis
how are glands controlled
hormonal- most prevelant in endocrine glands
humeral- by feedback loops
neural- by stimulus e.g saliva
what is neurocrine communication
example= hypothalamus to pituitary. electrical signal causes release of substance into blood which acts on target cell
