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Glands
143
Glands
Glands are composed from epithelial cells - single or
groups - producing substance with biological function
–secretion
Cla ssific at ion
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Exocrine glands: secretion is produced on surface
Endocrine glands: secretion (hormone) is produced into the
blood
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Exocrine and endocrine glands
Exoc rine gla nd
Endoc rine gla nd
Connection to the surface Connection with surface
remains direct or throught is lost during development
duct
Secretion (hormone) is
Secretion/product of the
produced to the
gland is drained by the
intercellular space
duct
(connective tissue) and it
is drained to the blood
Exocrine glands
Classification
1. according to the mechanism how secret is
produced
2. according to the localization of glandular cells in
the relationship to surface
3. according to the structure of the secretory portion
4. according to the composition of the secretion
Classification according to the
mechanism how secret is produced
Merocrine secretion – secretory granules are released using
exocytosis
Ecrine secretion – transport of molecules and ions via carriers.
Water follows them – they produce water and ions, or/and other
molecules
Apocrine secretion (apocytosis) – a piece of cytoplasm is separated
and forms secretion (lipids of milk during lactation)
Holocrine secretion – cell differentiates gradually (stores lipid
droplets), then undergoes apoptosis and is desintegrated
Merocrine gland
Secretion by
exocytosis : RER and
GA – secretory granules
Examples : majority of
exocrine glands
Apocrine secretion
Secretion of lipids in
mammary gland – lipid
droplets are without
membrane –
accumulation lipids in
apical region of the cell –
detachment of apical
cytoplasm
Holocrine secretion
Accumulation of lipid
droplets (without
membrane) in cytoplasm
of the cell – apoptosis –
whole cell is changed into
the secretion –
sebaceous gland in the
skin
Eccrine secretion
Secretion of water and
ions – as hypotonic
solution
Secretory portion –
Isotonic product, wich is
changed in duct
Absorption of ions, but
not water
Cystic fibrosis
Mutation in the gene for chloride ion transporter–
secretion is isotonic – water cannot solve the mucus
(it stays too sticky)
Types of the secretion
Localization of glands
I nt ra e pit he lia l gla nds:
goblet cells (produce mucus)
All cells within epithelial linig of
some organs produce mucus
(they are not called goblet cells)
– stomach, uterus
12
10
8
Sloupec 1
Sloupec 2
Sloupec 3
6
Ex t ra e pit he lia l gla nds
Localized beneath epithelium
which develop from
They are composed from
secretory portion and ducts
4
2
0
Řádek 1
Řádek 2
Řádek 3
Řádek 4
Stomach
Secretory portion
Consists of one layer of cells
sitting on the basement membrane
and surrounding the lumen,
Tubular (mucous glands, ecrine
sweat glands, stomach)
Acinar (pancreas,parotis)
Alveolar (sebaceous glands)
Tuboacinar (submandibular gland,
sublingual gland)
Tuboalveolar (mammary gland
during lactation, apocrine sweat
glands, prostate)
Gland architecture
Simple tubular glands – they can be without any duct, they empty on the
surface directly – stomach, uterus
Or they have duct
Composed glands have a tree of ducts
Epithelial cells in ducts can change composition of the secretion (content
of ions, water)
Primary secretion is changed in secondary one
Ducts:
• Intralobular (intercalated, striated)
• Interlobular
• Main
Ducts
Intralobular ducts
A) only transport the product of secretion
B) transport and modification of the product
A) simple cuboidal epithelium
B) simple cuboidal epithelium with basal labyrinth –
striated ducts
Interlobular ducts (in connective tissue septa)
Glands
Nature of the secretion
Secretion of exocrine glands (except for sebaceous) are
watery
Transport of ions and water (sweat, tears)
Serous
Mucous
Mixed – sero-mucous – combination of both types –
separately or within one secretory portion – serous
demilune – a cap of serous cells in the bottom of the
mucous tubule
Serous cell
Round nucleus

RER, GA

Secretory granules

Produces proteins -
enzymes
Mucous cell
It produces mucus

RER and GA
Mucous cells secretory granules –
glycoprotein:

PAS +, water-soluble
Salivary glands
Mucous tubules
Serous – acini
Ducts:
Intercalated
Striated
Interlobular
Main
Striated duct
Baso-lateral labyrinth –
Invaginaion of
plasmalemma and
mitochondria

Na,K ATP ase
 Absorption of ions
Myoepithelial cells
Contractile epithelial cells, which help to displace
secretion from secretory portions and small ducts (in
sweat, mammary, salivary and tear glands, in glands
of esophagus and respiratory pathways). They are
not present in pancreas.
Starlike (basket) cells located beneath epithelial cell
in secretory portion and in small ducts
Myoepithelial cells
Content of cytokeratins as
in epithelial cells and
actin and myosin as in
smooth muscle cells
It has common basal
lamina with epithelial cells
Regulation of the secretion
Secretory activity is under control of autonomous
nerve system, and hormones
During pathological conditions: mediators of
inflamatory respose change quantity and quality of
the product
Endocrine glands
Reverse polarity – cell
produces secretion
toward the basal lamina
Structure of endocrine
glands – cords of cells or
follicles (thyroid gland
have to store iodine)
Thyroid gland
Cuboidal epithelium –
follicles
Colloid inside – content
of thyroglobulin
Storage of hormones
Liver – structure – cords of
hepatocytes – combination of
exocrine and „endocrine“ gland