Flashcards in Unit 6 - Exocrine Glands Deck (55):
how to exocrine glands develop?
as invaginations of surface epithelium
-induction by connective tissue
-retain connection with surface via ducts
what are the different options for structure of:secretory portion?
acinar or tubular
-acinus = berry-like cluster of cells with a central lumen
what are the components of a gland? what do they do?
1. secretory portion
-may be branched or unbranched
-produce secretory product
2. conducting portion (duct)
-may be branched or unbranched
-modifies secretory product by absorption
-in some glands, ducts also have secretory functions
what are simple glands VS compound glands?
simple: single, unbranched duct/conducting portion
-secretory portion can be branched or unbranched
compound: multiple branched ducts/conducting portions
-secretory portion is acinar, tubular, or tubuloacinar
-have connective tissue capsule
are the following glands simple or compound?
1. sweat gland
2. sebaceous gland
3. salivary gland
4. exocrine pancreas
what is holocrine secretion? what is an example of this?
lysis of cells filled with secretory cells
-sebaceous glands of skin
what is apocrine secretion? what is an example of this?
shedding of apical cell segment filled with secretory product (cell "decapitation" as it pinches off)
what is merocrine secretion? what is this called in sweat glands? what are examples of this?
exocytosis of PRO or glycoPRO
-called "eccrine" in sweat glands
-sweat glands, salivary glands, exocrine pancreas
what types of cells are in merocrine/eccrine glands?
what do serous cells in merocrine glands stain with, do, and have in cytoplasm?
-stain well with H&E
-abundant RER and perinuclear Golgi in basal portion of cell
--secretory granules in apical cytoplasm (exocytosis)
what do mucous cells in merocrine glands stain with, do, and have in cytoplasm?
-have mucins (heavily glycosylated glycoPRO) that stain poorly with H&E, but well with PAS (periodic acid-Schiff) stain
-abundant RER and perinuclear Golgi in basal part of cell
--mucin-filled secretory granules in apical cytoplasm (exocytosis)
what happens to mucin upon secretion?
becomes mucus (viscous, jelly-like protective lubricant)
where are and what do myoepithelial cells in merocrine glands do?
located w/in same basal lamina as secretory or duct cells
-triangular and elongated nucleus
-have long, actomyosin-rich processes that surround epithelial cells
-contraction helps expel secretory product
-found in sweat, salivary, and mammary glands
how does ion and fluid transport across epithelium work?
ion channels and pumps
-tight junctions seal off apical surface from basal surface
-differential distribution of ion channels and pumps
-mitochondria provide source of E
-membrane specializations increase surface area
what is the structure of sebaceous glands, what are their secretions, and what do they do?
simple branched acinar glands for holocrine secretion of sebum (via pykonotic apoptosis)
-associated with hair follicles (short duct)
-have basal layer of stem cells that proliferate and differentiate into sebocytes
what do sebaceous glands secrete and what does this contain?
sebum made of:
what are sebaceous glands associated with clinically?
origin of acne
-increased sebaceous gland activity at puberty
-hair follicle may become plugged
-skin bacteria (Propionibacterium acnes) break sebum into free fatty acids
-FA cause irritation and inflammation
-inflammation attracts neutrophils, further escalating inflammation
what is the structure of eccrine sweat glands, where are they, and what do they do? what kinds of cells are in them?
simple (coiled) tubular glands for merocrine secretion
-located in dermis (everywhere but lips)
-function for thermoregulation and excretion
-stratified cuboidal epithelium of secretory coil has pale (clear) cells, dark cells, and myoepithelial cells
what is sweat composed of? what can this indicate?
water, ammonia, NaCl, urea, uric acid, organic compounds, bacterial peptides, proteolytic enzymes
-if altered composition, can be a disease indicator
how is secretion of eccrine sweat glands controlled?
by cholinergic fibers of sympathetic nervous system
what are pale (clear) cells of eccrine sweat glands? what do they do and contain?
secrete fluid to make water of sweat
-pyramidal to columnar in shape
-located at periphery, resting on basal lamina
-have abundant mitochondria and tight junctions
-possess microvilli and intracellular canaliculli
what are dark cells of eccrine sweat glands? what do they do, secrete, and where are they?
pyramidal in shape, loccated near lumen
-secrete glycoPRO and PRO, including bactericidal peptides
what are sweat ducts? where are they and what do they do?
epithelium stains darker than in secretory coil
-reabsorbs NaCl and water
-abundant Na+/K+ ATPase in basal membrane
what are apocrine sweat glands? where are they, what do they do?
located in axillary, areolar, and perineal regions and associated with hair shafts
-despite name, has merocrine secretion
-simple coiled glands
--secretory part is lined by simple cuboidal epithelium and has large lumen
-secretions may include pheromones
what are apocrine sweat gland secretions stimulated by?
adrenergic fibers of sympathetic nervous system
what does septa do for compound glands?
divide parenchyma into lobules
-contains interlobular ducts
what does connective tissue stroma of compound glands contain?
-capillary plexus that surrounds secretory and ductal components
-nerves that control secretion: parasympathetic stimulation and sympathetic inhibition
-lymphocytes and plasma cells
what does compound gland parenchyma contain?
-secretory acini or tubules
what are functions and composition of saliva?
-moisture and lubrication
-initiation of digestion of CHO: alpha amylase
-immune defense: lysozyme, lactoferrin, and sIgA
-secretion of Ca and P to make acquired pellicle (film over tongue and teeth)
what are clinical correlations with salivary glands?
1. reduced function of salivary glands due to radiotherapy or disease
-oral mucosa atrophy
2. salivary gland tumors
--65% of benign tumors
--accumulation of cartilage-like material made by myoepithelial cells
what kind of cells do acini of compound glands contain?
serous, mucous, mixed, or myoepithelial cells
what do serous cells of salivary glands have?
pyramidal in shape
-secrete PRO including sIgA
-secrete bicarbonate and absorb Cl-
what do mucous cells of salivary glands have?
cuboidal to columnar in shape
what do myoepithelial (basket) cells of salivary glands have?
reside w/in basal lamina
-triangular or elongated nuclei
-long contractile processes
-also in intralobular ducts
what are intercalated ducts of salivary glands like? what do they do?
small, 4-6 cells in circumference
-cuboidal cells that lack secretory granules
-connects secretory portion to intralobular duct
what are intralobular ducts of salivary glands like? what do they do?
more than 6 cells in circumference, and lined by simple columnar epithelium (but striated in serous glands)
-have basal striations and active transport of ions
-mucous glands lack striated ducts
-apical surface has tight junctions
-also secrete sIgA
what are basal striations?
in intralobular ducts
-basal membrane infoldings that house mitochondria
what are interlobular ducts of salivary glands like? what do they do?
large ducts in septa, lined with stratified cuboidal-to-columnar epithelium
what is the saliva composition compared to blood plasma?
what is the mechanism of sIgA secretion?
(salivary) IgA transcytosis
1. plasma cells secrete IgA dimer
2. IgA binds receptor on an acinar cell
3. endocytosis at base of acinar cell
4. proteolytic processing
5. exocytosis of sIgA at apical surface
composition of submandibular gland and what they secrete
compound tubuloacinar cell
-mostly serous, with mucous acini
--mixed acini have serous demilunes (artifacts)
--serous secrete PRO (including lysozyme)
-shorter intercalated ducts
-mostly striated intralobular ducts
composition of parotid gland and what they secrete
compound acinar gland
-all serous, with abundant adipose tissue
-secretes alpha-amylase and other PRO
-intercalated ducts are long
-intralobular ducts are striated
composition of sublingual gland
compound tubuloacinar gland
-mostly mucous acini
-some mixed acini with serous demilunes
-intralobular ducts are NOT striated
what is structure of exocrine pancreas?
compound acinar gland (similar to parotid)
-lobules separated by connective tissue septa
-septa have blood vessels, lymphatics, nerves, and ducts
what do pancreatic secretions contain? what do they do and how are they activated?
-digestive proenzymes (lipases, nucleases, amylases)
--inactive proennzymes are activated by enterokinase cleavage in duodenum
-bicarbonate neucralizes stomach acid, creating optimum pH for pancreatic enzymes
how are pancreatic secretions regulated?
-acidic chyme stimulates enteroendocrine cells in duodenum
-enteroendocrine cells release CCK and secretin
--CCK stimulates proenzyme secretion
--secretin stimulates HCO3- secretion
what is a diagnostic feature of endocrine pancreas?
islet of Langerhans
what are special features of serous acini exocrine pancreas?
polarized serous cells surround small lumen
-abundant RER and Golgi
-zymogenic granules in apical half of cell
-lack myoepithelial cells
what is secretion of serous acini of exocrine pancreas stimulated by?
CCK from enteroendocrine cells in duodenum
what are special features of intercalated ducts of exocrine pancreas?
protrude into acini as centroacinar cells
-lack secretory granules
what is secretion of intercalated ducts of exocrine pancreas stimulated by?
secretin from enteroendocrine cells in duodenum stimulates bicarbonate release
what are special features of intralobular ducts of exocrine pancreas?
secrete bicarbonate-rich fluid
what are special features of interlobular ducts of exocrine pancreas?
low columnar epithelium
secrete bicarbonate-rich fluid
what is the Gomori stain?
stains the secretory product bright pink