Epithelial Tissue
Almaas Raziuddin, Rija Khan, Robina Sandhu
Introduction
Epithelial tissue comprises one of the four basic tissue
types. The epithelial tissues are all made of “closely
aggregated polyhedral cells with strong adhesion to one
another and attached to a thick layer of ECM”
(Mescher). There are three main functions of epithelial
tissue including: 1) lining, covering and protection, 2)
absorption, and 3) secretion. Epithelial tissue is
divided into two sections that consist of the
covering/lining epithelia and secretory epithelia. The
varying types of covering epithelial tissue include
simple squamous, stratified squamous, simple
columnar, simple columnar with goblet and striated
border, pseudostratified columnar, cuboidal and
transitional.
Stratified Squamous Epithelium
Stratified epithelium is composed of two or more layers
of cells. It functions to protect, secrete, and prevent
water loss. Stratified squamous epithelia protect
against possible invasion of underlying tissue by foreign
microorganisms. When looking at the epidermis,
differentiating cells become keratinized, helping
prevent dehydration.
a.
b.
Simple Columnar Epithelium with Goblet
and Striated Border
Simple columnar epithelium with goblet cells and a
striated border is abundant within the lining of the
small intestine. A major function of the small intestine
is absorption and the microvilli of the brush border
allow for this by increasing surface area. More goblet
cells appear moving down the small intestine, and are
especially abundant in the colon, while the brush
border disappears here. Additional examples of areas
with this epithelia are linings of the oviduct, efferent
testis ducts, ependymal cells and small bronchi.
Cuboidal Epithelium
Cuboidal epithelium contains cells that are roughly
equal in length and width. Due to their increased
thickness, their cytoplasm contains more organelles
and mitochondria allowing for more active transport
across the epithelium as well as other functions
requiring energy. Examples of areas with cuboidal
epithelium are: glandular excretory ducts, the Henle
ascending loop, ovarian follicle cells, and hepatocytes.
a.
b.
Simple Squamous Epithelium
Simple epithelial tissue is comprised of one layer of
cells. Simple squamous epithelium is distributed along
the lining of vessels, where it regulates passage of
substances into the underlying tissue. This type of
covering epithelia mainly functions to facilitate the
movement of the viscera (mesothelium). It also takes
part in active transport by pinocytosis and secretes
biologically active molecules. Some examples of this
tissue type include the endothelium, mesothelium, and
blood vessels.
a.
b.
Figure 6. a. The epithelia of the thyroid gland consists of many
cuboidal cells critical for providing energy. X10. H&E. b. Cuboidal
epithelium making up the duct (D) of a salivary gland. 400x. H&E.
http://histologycourse.com/Epithelium-Lecture%205.pdf [3]
Figure 2. a. Stratified squamous epithelium of the human scalp seen
through dense layers of darkly stained nuclei. 10x H&E. b. A closer
view of stratified squamous cells in the epithelium of the esophagus.
The esophageal lining is not made up of keratinized epithelia but
protection is still a main function 40x. H&E.
Simple Columnar Epithelium
Simple columnar epithelium is composed of polarized
cells that are taller than they are wide. Arranged in a
single layer, each cell makes contact with the
basement membrane. The nuclei of simple columnar
cells are evenly arranged at the base of each cell,
which are connected by tight and adherent junctions.
Often lined with cilia, simple columnar epithelial cells
are specialized for absorption and protection by
secreting mucus and acting as a selectively permeable
barrier, as well as providing sensory input and
transporting nutrients. They are found in the lining of
many digestive and reproductive organs.
Figure 4. Simple columnar epithelia in the large intestine with a striated
border and goblet cells shown as the light circular structures on the
periphery of the cells. X10. H&E.
Pseudostratified Columnar Epithelium
Pseudostratified columnar epithelium is characterized
by tall, irregular cells that are all arranged in a single
layer and attached to the basement membrane. These
cells appear to to be stratified due to the placement of
their nuclei at different levels and differing cell
heights. Primary functions include absorption and
mucus secretion, the latter of which is made possible
by goblet cells in the free surface. Ciliated
pseudostratified columnar epithelium is found in the
upper respiratory tract. Nonciliated versions are found
in the ductus deferens of the human male. A
stereociliated form is found in the epididymis.
Transitional Epithelium
Also called urothelium, transitional epithelium lines
the urinary tract, from the kidneys to the proximal
region of the urethra. It is made up of multiple layers
of large, dome-like, superficial umbrella cells that
have a specialized membrane in order to withstand and
protect underlying tissues from the hypertonic and
cytotoxic effects of urine. These cells can be
binucleate and have unique properties that allow
transitional epithelium to distend as the bladder fills.
Also found in glandular ducts of the prostate,
transitional epithelium can provide a large amount of
sperm.
Figure 7. Large, round, unstretched transitional epithelial cells (c) are
characteristic of an empty bladder. This picture of the human bladder
lining also depicts connective tissue (ct), red blood cells (rbc) that are
stained pink, lumen (lu), and the epithelial base (unlabeled arrows).
x400. http://www.eugraph.com/histology/epith/trans.html [6]
References
Figure 1. a. Simple squamous epithelia of the kidney. X40. H&E. b. Simple
squamous epithelia of renal corpuscle of the kidney. The upward arrow
represents the glomerulus and the downward arrow is directed toward the
Bowman’s capsule. x400. H&E. http://histologycourse.com/EpitheliumLecture%205.pdf [3]
RESEARCH POSTER PRESENTATION DESIGN © 2011
www.PosterPresentations.com
Figure 3. Darkly stained nuclei can be seen lined up at the basal surface of
the cells above the basement membrane in simple columnar epithelium of
the stomach. Gastric pits, which are characteristic of the stomach are
difficult to see in this photomicrograph. x10. H&E.
Figure 5. Pseudostratified columnar epithelium in the epididymal duct
of a Rhesus monkey, shown in Helly’s fluid. Stereocilia resorb fluid and
allow sperm to become motile here.x612. H&E.
http://www.anatomyatlases.org/MicroscopicAnatomy/Section02/Plat
e0219.shtml [4]
1. Mescher, A.L. (2010) Junqueira’s basic histology text & atlas. 12th ed. Singapore. The
McGraw Hill Companies.
2.. Leboffe, Michael J. A Photographic Atlas of Histology. Englewood: Morton Publishing
Company, 2003.
3. http://histologycourse.com/Epithelium-Lecture%205.pdf
4. http://www.anatomyatlases.org/MicroscopicAnatomy/Section02/Plate0219.shtml
5. https://bcrc.bio.umass.edu/courses/fall2012/biol/biol523/content/transitionalepithelium-box-1357-100x-magnification
6. http://www.eugraph.com/histology/epith/trans.html