gland secretions Flashcards
Secretion involves 3 distinct cellular activities:
- uptake of simple materials from the extracellular fluid
- processing of these within the cell: produce a more complex product
- release, or transport, of these products
what is excretion
which is the removal of waste products
can all cells secrete
yes
two functional types of glands
- Exocrine: release secretory products onto surface epithelium via
a duct - eg sweat glands, salivary glands
- Endocrine: no duct connecting secretory portion to surface epithelium, secrete products directly into blood or lymph (hormones)
- eg pancreas, thyroid gland
what forms multicellular exocrine and endocrine galnds
epithelial sheets
3 modes of secretion in exocrine glands
- Merocrine (eccrine)
- Apocrine
- Holocrine
merocrine (eccrine) secretion
(exocrine)
- vesicles are released via exocytosis when the vesicle
membranes fuse with the cell membrane - most common form of secretion
- e.g. some sweat glands, salivary glands
what is the most common form of secretion
Merocrine (eccrine)
Apocrine secretion
(exocrine)
- secretory vesicles accumulate at the apical portion of cell
- mass of cytoplasm and vesicles is then pinched off
- e.g. mammary gland, some sweat glands
holocrine secretion
(exocrine)
- secretory products accumulate and the cell ruptures
- death of cell
- e.g. sebaceous glands
A further classification of glands is based on structure:
unicellular and multicellular
unicellular glandular structure
- goblet cells of digestive & respiratory tracts
- the only type of unicellular gland
- secrete mucin –> mucous
most glands are multi or uni cellular
multicellular
goblet cells are found where
amongst columnar cells of epithelium
* digestive tract
* respiratory tract
in goblet cells there is Expanded apical portion (theca) contains
mucigen droplets
in goblet cells mucigen released by ____ secretion
merocrine
what makes up mucous
mucigen + H2O
describe nucleus in goblet cells
basal nucleus
describe cytoplasm in goblet cells
- Basophilic cytoplasm
- rER & free ribosomes
Multicellular Exocrine Glands: Secretions discharged onto epithelial surface via
ducts
Multicellular Exocrine Glands: * The deeper cells within the connective tissue are
secretory
*However, cells lining the duct may also produce secretion
Multicellular Exocrine Glands: how is secretion discharged
Secretion is discharged from the cell surface into the duct, and then to the epithelial surface
what are the 2 classifications of Multicellular Exocrine Glands based on their morphology
- duct system
- secretory end-pieces
the 3 types of duct system
(multicellular exocrine glands)
- Simple; single, unbranched duct (may be coiled)
- Simple branched; two or more secretory areas empty into a common duct
- Compound; branched duct system
3 types of secretory end pieces
(multicellular exocrine glands)
- Tubular
- Alveolar (acinar): rounded cluster of cells
- Tubuloalveolar: tubular region ending in a rounded alveolus
what kind of glands are intestinal glands
simple tubular
what kind of glands are stomach (gastric) glands
simple branched tubular
what kind of glands are sebaceous glands
simple branched alveolar
what kind of glands are duodenal glands
compound tubular
what kind of glands are mammary glands
compound alveolar
what kind of glands are salivary glands
compound tubuloalveolar
in compound glands: secretory portions form ____ which may cluster into _____ separated by collagenous connective tissue
lobules
lobes
for compound glands: Nerves, blood and lymph vessels enter via
connective tissue septae
Duct system begins within the lobules as ______ –> ______ –> ______ –> ______
intercalated ducts →
intralobular (striated) duct →
intralobar duct →
excretory duct
compound glands:
intercalated ducts →
intralobular (striated) duct→
intralobar duct →
excretory duct
out of these which may modify the secretion
intralobular ducts
what kind of ducts are exocrine pancreas glands
compound alveolar
Mucous glands
- mucin
- thick, sticky, glycoprotein
serous glands
- watery
- enzymes
mixed glands
- contain more than one cell type
- produce both mucous & serous secretions
most glands secrete how often
at a low level continuously
rate of secretion can be modulated by what
hormones, autonomic innervation or a combination of both
In glands with alveoli _____ contract to squeeze secretion into the ducts
contractile myoepithelial cells
in endocrine glands Connection with surface epithelium
is lost
where do endocrine glands secrete their products
Secrete products directly into blood or lymph
transported throughout the body to target organ or tissue
are endocrine glands vascularized
yes, Well vascularised
endocrine secretions are
hormones such as
* proteins
* steroids
endocrine glands are adapted for
storing and releasing products as required
storage in endocrine glands is usually
intracellular
*however, in thyroid stored in extracellular follicles
what kind of secretion do endocrines usually have
merocrine secretion
endocrine glands often form
cords or clumps
pancreas glands
exocrine and endocrine glands
islets of langerhands
endocrine glands in pancreas
in thyroid endocrine cells are arranged
into follicles surrounding a
mass of secretory product (colloid; thyroglobulin)
