Epithelial Tissue

1. Epithelial Tissue
Rizka Vidya Lestari, S.Si., M.Biomed
Bagian Histologi
Fakultas Kedokteran, Universitas Mataram

2. Introduction
• Epithelium is one of the four basic tissues of the body
• It is composed of very closely packed, contiguous cells, with no
extracellular material in the extracellular spaces.
• Form membranes as sheets covering the body surface and lining its
internal surface or occur as secretory elements known as glands.

3. The principal functions of epithelial tissues
• Covering, lining, and protecting surfaces (eg, epidermis)
• Absorption (eg, the intestinal lining)
• Secretion (eg, parenchymal cells of glands)
• Membranes that line serous body cavities are referred to as
mesothelia
• Membranes that lining blood and lymph vessels and the chambers of
the heart are known as endothelia

5. Simple Squamous Epithelium
• Composed of one layer of uniform flat cells
• Rest on the basement membrane
• Apical surfaces are smooth
• The width of the cells is greater than their height
• The nuclei appear flattened and can easily be recognized following HE
staining
• Lining the posterior surface of the cornea; blood vessels and
lymphatic vessels; surface of the body cavities (pericardial, pleural,
and peritoneal cavities) and alveoli of the lungs

7. Simple Cuboidal Epithelium
• Composed of one layer of uniform cuboidal cells
• Rest on the basement membrane
• The cell’s height, width, and depth are roughly equal
• Nuclei are centrally placed and spherical in shape
• Some cuboidal cells have long and abundant microvilli, which form a
brush border on their apical surfaces
• Lining most of the tubules in the kidney and in some excretory ducts
of glands

9. Simple Columnar Epithelium
• Composed of one layer of columnar
• cells resting on the basement membrane
• The cell’s height is greater than the width
• The elongated ovoid nucleus is most often located in the basal region of
the cell.
• The apical surface of this epithelium may reveal microvilli (to increase the
apical surface area of the cell to aid in absorption of fluid and other
material from a lumen)
• Can be found in the digestive tract, oviducts (fallopian tubes) in the female
reproductive system, and ductuli efferentes testis of the male reproductive
system.

11. Pseudostratified Columnar Epithelium
• Composed of one layer of nonuniform cells that vary in shape and
height
• Cells appear similar to stratified cells, but all cells are in contact with
the basement membrane
• Most cells are tall columnar cells, also some short basal cells, and
stem cells
• Found in the respiratory tract and has long fingerlike, motile
structures called cilia on the apical surface of the cells
• Found in the linings of the respiratory tract, including the nasal cavity,
trachea, and primary bronchi (respiratory epithelium )

13. Stratified Squamous Epithelium
• Contains several layers of cells
• Cells in the superficial layer being flattened
• protects the body against injury, abrasion, dehydration, and infection.
• This epithelium may be keratinized or nonkeratinized, depending on
functional demands
• Keratinized top layers consist of either thick or thin keratinized cells (fl
attened, nonnucleated dead cells), found in skin
• Nonkeratinized surface cells are nucleated, covers wet surfaces and is found
lining the oral cavity (soft palate, cheeks, and fl oor of the mouth),
esophagus, vagina, and true vocal cords

15. Stratified Cuboidal Epithelium
• Composed of two or three layers of cuboidal cells with the basal layer
of cells often appearing nonuniform in distribution
• Mainly found lining large ducts of exocrine glands
• The cells often have smooth apical surfaces and form barriers and
ducts

17. Stratified Columnar Epithelium
• Composed of two or three layers of cells
• The top layer is columnar and the basal layer is usually cuboidal
• This is not a common type of epithelium and has a very limited
distribution
• Found in the conjunctiva of the eye and in some large ducts of the
exocrine glands

19. Transitional Epithelium
• Stratified epithelium (urothelium)
• Lines the excretory channels leading from the kidney (renal calyces,
ureters, bladder, and proximal segment of the urethra)
• Contain four to six cell layers in the relaxed state
• In the empty bladder, the basal cells are mostly cuboidal and the
middle layer is polygonal, although surface cells bulge into the lumen
“dome shaped” or umbrella cells

21. Various Surfaces Of Epithelial Cells
1. Free Surface Modifications
• Microvili
• Stereocilia
• Cilia
2. Lateral Surface Modifications
• Zonula occludens (tight/ occluding junction)
• Zonula adherens (adhering junction)
• Macula adherens (demosomes)
• Gap junction
3. Basal Surface Modifications
• Hemidesmosomes
• Three components of basement membrane (lamina lucida, lamina densa, lamina
reticularis)

24. Galnds
• Endocrine
Release their products into interstitial fluid or directly into the
bloodstream
• Exocrine
Secrete their products either through ducts into the lumen of an organ
or directly onto the body surfaces

25. Classification of Exocrine Glands
1. Classified by Product
• serous glands (watery proteinaceous fluid, ex: parotid, von Ebner of the
tongue, pancreas, and sweat glands)
• mucous glands (viscous mixture of glycoprotein and water, ex: goblet cells in
the small and large intestines, respiratory epithelium, hard and soft palates,
and stomach.
• mixed glands/seromucous (submandibular gland, sublingual gland, and glands
in the trachea and esophagus)
• sebaceous glands (produce lipids, ex: skin)

28. 2. Classified by Mechanisms of Secretion
• Merocrine secretion
the secretory product is released from the cell by exocytosis without the loss
of cell material (cytoplasm), ex: zymogen granules by pancreatic acinar cells
• Apocrine secretion
the secretory product is released together with part of the apical cytoplasm
of the secretory cell, ex: lipid secretion by epithelial cells of the mammary
gland
• Holocrine secretion
the secretory product is released by disintegration of the entire cell, ex: fatty
lubricant secretory product, sebum, is released by the cells of sebaceous
glands

30. 3. Classified by Morphology
• Unicellular
Composed of only single cells. The secretory products are released
directly onto the surface of an epithelium, ex: Goblet cells
• Multicellular
Consist of numbers of secretory cells arranged in different
organizations (acini or tubules)

33. TERIMA KASIH…
Semoga Bermanfaat