Download glandular epithelium

GLANDULAR EPITHELIUM
• Membrane epithelium
becomes glandular
epithelium when it
invaginates / involutes
into the tissue layer /
layers below, forming a
gland
• There are two main
types of gland. They
are exocrine and
endocrine.
FORMATION of Exocrine/Endocrine glands
• Form the same way.
• During prenatal development, some epithelial
cells form a downward fold (invagination) into
the connective tissue
• These invaginations may be composed of one
or more cells and they are called glands.
• Glands usually in cuboidal and columnar
epithelium.
EXOCRINE GLANDS
• In exocrine glands, the
original invagination
develops into a duct.
• The duct is a
passageway that
remains open to the
free surface.
• Products are secreted
to surface via the duct
• Exocrine glands may be unicellular or they
may be multicellular. (see board (
• example : unicellular exocrine gland is the
goblet cell. Produce mucus. Located
throughout the body.
• Typical exocrine glands include sweat glands,
salivary glands, mammary glands, stomach,
liver.
Multicellular exocrine glands are
divided into two general categories
according to structure :
simple and compound
simple
(exocrine)
gland =
connects to
the free
surface via an
unbranched
duct
compound
(exocrine)
gland =
connects to
the free
surface via
branched
ducts
Both may be further classified
according to the
shape of the part of the gland
that produces the secretions.
(see next slide)
These areas
may be:
1. tubular =
secretion area
is shaped like
a tube
2. alveolar / acinar
= secretion area is
shaped like a sac
ENDOCRINE GLANDS
In endocrine glands,
the connection to the
free surface is lost.
Endocrine glands secrete products directly into the
blood or lymph fluids because ducts are absent.
Thyroid gland
neurons
Glands located
atop kidneys
GLANDULAR SECRETIONS
(see Handout – no need to copy)
• 1). merocrine = The secretory cells (cells that
produce the secretions) discharge only the
secretions they produce.
• 2). apocrine = The secretion is produced in the
secretory cell. It accumulates in the end of the
cell (apical portion). The end of the cell pinches
off and the secretion is released along with the
tip of the cell.
• 3). holocrine = The secretion is produced and
accumulates in the secretory cell. Then the cell
dies, disintegrates and is discharged from the
gland along with the secretion.
Complete “Name that Tissue” and
hand in!