Epithelium and Glands
Simple Cuboidal Epithelium
Simple cuboidal epithelium, thyroid
Simple cuboidal epithelial cells that line the thyroid
follicles of the thyroid gland are called
Adjacent follicles are separated by a thin layer of con-
nective tissue, containing occasional F
cular cells are normally
in shape but become
columnar when stimulated or in a state of hyperfunc-
—excessively high levels of
thyroid hormone secretion). At the other extreme,
these cells may become ﬂ
attened and squamous—like
when they are inactive or in a state of hypofunction
—excessively low levels of thyroid
±ollicular cells synthesize and release a precursor
of thyroid hormones
(T3 and T4)
the lumen of the follicle where it forms the colloid.
Thyroid hormones are essential for normal brain and
body development in infants and for the regulation of
the metabolic rate in adults, and they affect the func-
tion of every organ system.
A representation of simple cuboidal epithelium
lining the thyroid follicle.
A layer of
rests on a thin
nuclei are round and located in the center of the cell. These cells
have a large amount of
rough endoplasmic reticulum (RER)
in the cytoplasm, which reﬂ ects their
high metabolic activity and production of secretory granules con-
taining thyroglobulin. The thyroglobulin is secreted via
into the follicular lumen, where it is stored as a
. The api-
cal (luminal) surface of these cuboidal cells is characterized by
numerous short microvilli.
is a condition characterized by the
overproduction of thyroid hormone. In this condition,
the follicular cells have changed from cuboidal cells to
as a result of their high activity.
Symptoms include nervousness, irritability, increased heart
, increased perspiration, difF
ing, muscle weakness, warm moist skin, trembling hands,
and hair loss. This disorder is seen most often in women
20 to 40 years age.
, the most common form
of hyperthyroidism, results from antibodies in the blood
that mimic thyroid-stimulating hormone, stimulating the
thyroid to grow and secrete excessive thyroid hormone.
Symptoms of thyroid hyperfunction also can be induced
by excessive thyroid hormone medication.
At the other extreme, in
, there are
very low levels of thyroid hormone secretion and follicular
cells become ﬂ
at, squamous cells; the patient may experi-
ence weight gain, somnolence, fatigue, and depression.
Active columnar cell