Exocrine Glands- Sum 6 Flashcards
exocrine glands function
- secrete non-hormonal products
- secrete enzymes, mucus, lipids
- secretions released onto epithelial surface directly OR via ducts
most but not all will have ducts
endocrine glands
function
- secrete hormones
- no ducts - secretions releaed into bloodstream OR intracellular space
general structure of glands
- parenchyma = functional portion
- stroma = CT cover, dividers, scaffolding
parenchyma
secretory units to secrete a product
ducts to transport product out of gland or modify the secretion
stroma
collagenous CT- covers gland (external capsule) and divides it into lobes and lobules AND forms pathways (inward)
reticular CT forms internal 3D scaffold to surround and support indiv units
general drainage
smallest ducts drain 1 secretory unit > merge into larger ducts
1-2 large ducts drain entire gland
will run in septae/trabeculae b/t lobules
duct wall appearance
simple cuboidal or columnar
(largest are stratified cuboidal or columnar)
large circular or oval nuclei
ways to classify exocrine glands
- what it secretes/product
- how it secretes/mode
- morphology (# cells, shape and branching pattern)
types of secretion products
- mucous glands - secrete mucus
- serous glands - enzymes in watery fluid
- mixed/seromucous glands- cells of mucous and serous , intermed viscosity
- sebaceous glands- sebum (oily, waxy)
mucus components
mucous glands
mucinogen (glycoprotein) = mucin
rich in glycosylated proteins + some carbs
mucous acini = cell clusters each w/ central lumen
so PAS +
mucous glands
function
protection (vs pathogens, particles, stomach acids)
lubrication
palatine glands of hard and soft palate
serous glands
secretions
-rich in nonglycosylated + poorly glycosylated proteins
-primarily enzymes
-often antibodies
serous glands
histology
round nuclei @ basal end or central
perinuclear cytoplasm is basophilic
apical cytoplasm is acidophilic (sec vesicles)
mixed/seromucous glands
histology
both serous and mucous cells
serous demilunes are an artefact of formalin fixation
serous demilunes
artefacts of formalin fixation
-mucinogens swell during prep > mucous cells in tissue swell and push nuclei to basal end = serous cell b/t 2 swollen mucous cells get squished outwards to periphery
only occur in mixed/seromucous acini
cell junctions still maintain lateral connections
sebum
sebaceous glands
rich in lipids + FA’s + wax esters + squalene
sebaceous gland
histology
sebum not pick up stain well
nuclei central and round
@hair follicles
steroids on sebum
androgens stimulate
estrogens inhibit
sebaceous gland histology
not pick up well so faint or non staining
nuclei central, round, euchromatic
look similar to mucous acini but nuclei are different
types of secretion modes
- merocrine (most common)
- holocrine
- apocrine
merocrine secretion
via exocytosis so least destructive
almost every exocrine gland in the body
apocrine secretion
apical end pinches off - moderate destruction
large amounts of complex protein/lipid mixture secreted at once
@mammary glands
apocrine SWEAT glands use merocrine secretion, not the same thing
holocrine secretion
via cell disintegration so most destructive
@sebaceous glands only
unicellular exocrine glands
classify morphology
goblet cells only
@epithelia lining respiratory and intestinal tracts
multicellular exocrine glands
classifying morphology
secretory sheets
-no lumen or ducts
@smaller intraepithelial glands (small patches form indents ‘quasi lumen’ no ducts)
and complex multicellular glands (exocrine so true lumen and ducts)
complex multicellular glands
detailed
-organized infolding off main epithelium
-both ducts (nonsecretory, conduit) and secretory units (syn product and secrete into lumen)
nearly every named exocrine gland in body
tubular glands
secretory portion is a tube but can be straight, branched, or coiled
acinar glands
acinus = any spherical exocrine secretory unit (acini plural) mucous/serous/seromucous/or sebaceous
small central lumen normal BUT if very large then = alveolar glands
solo or branched or adj to others
tubuloacinar glands
both tubular and acinar portions
i.e Brunner’s glands @ duodenum
myoepithelial cells function
contract entire secretory unit (acinus) to push secretions out and into duct toward luminal epithelium
rapid expression
@mammary glands, sweat glands, salivary glands, iris of eye
myoepithelial cells histology
smooth muscle features
-keratin IFs + actin + myosin
connect to secretory cells w/ desmosomes and gap junctions
sit b/t secretory cell and BM
exocrine glands
clinical relevance
many cancers originate in exocrine glands (adenomas, adenocarcinomas)
subject to infection, inflammation, injury from
-over/undersecretion and blockage of ducts
