This presentation has a short introduction about the different types of tissues (epithelium, connective, muscular, nervous), but focuses mainly on epithelial tissues - its characteristics, functions, and types. This also contains the different surface modifications of epithelial tissues - apical, lateral and basal. Lastly, glands are also discussed here. Endocrine and exocrine glands are differentiated based on characteristics and functions.

1. EPITHELIAL TISSUE Clarence Witty H. Mendoza,
RMT

2. TISSUES
 Are larger structural and
functional units of cells
having closely related
functions joined together
by intercellular
substances and/or cell-
to-cell junctions

3. BASIC TYPES OF TISSUES
Epithelial tissues
Connective tissues
Muscular tissues
Nervous tissues
These tissues
function in
close
association
with each
other.

4. CHARACTERISTICS OF EP. TISSUES
 high cellularity
 avascular
 exhibit polarity

5. PRINCIPAL FUNCTIONS OF EP.
TISSUES
 Covering, lining, and protecting surfaces (e.g. skin)
 Absorption (e.g. intestines)
 Secretion (e.g. epithelial cells of glands)
 Contractility (e.g. myoepithelial cells)

6. EMBRYONIC ORIGIN OF EPITHELIAL
TISSUES
EPITHELIUM
Ectoder
m
Endoderm
Mesoderm

7. BASAL LAMINA
 amorphous extracellular material
where the deepest layers of the
epithelium rests
 a mixture of glycoproteins, collagen
and proteoglycans
 secreted by the ep.
Functions:
 provides structural support to the
overlying ep.
 serves as an impermeable barrier that
allows only water & small molecules to
pass through

8. BASAL LAMINA
Layers:
 lamina rara externa (lamina
lucida)
 lamina densa
 lamina interna

9. BASEMENT MEMBRANE

11. GENERAL CLASSIFICATION OF EP.
TISSUES
• Covering ep. (skin)
• Lining ep. (luminal surfaces
of visceral organs)
Surface
epithelium
• Elaborate (synthesize;
produce)
• Release (secretions)
Glandular
epithelium NOTE:
Some surface
epithelium are also
secretory epithelium

12. SURFACE EPITHELIUM
- depends on its location
e.g.
 skin – protective
 GI tract – absorptive
 neuroepithelial cells of the taste buds – sensory cells
 olfactory cells in the nose – sensory cells
 kidney – excretion and maintenance of fluid balance
 testes – germ cells

13. CLASSIFICATION OF SURFACE EP.
TISSUES ACCDG TO NUMBER OF
LAYERS
Simple Ep.
Stratified Ep.
These tissues are further
classified according to
their:
shape
surface modifications

14. SIMPLE EPITHELIAL TISSUES
Simple Squamous
Epithelium
Simple Cuboidal
Epithelium
Simple Columnar
Epithelium
Pseudostratified Columnar
Epithelium

15. 1. SIMPLE SQUAMOUS EPITHELIUM
- single layer, thin, flattened cells
Functions
Lining Lung alveoli, parietal layer of the Bowman’s
capsule (kidneys)
MESOTHELIUM - Serous cavities (pericardium,
peritoneum, pleura)
ENDOTHELIUM – lining of vessels/luminal
surface (heart, blood, lymphatic vessels)
Movement Facilitates the movement of the viscera
(mesothelium)
Active transport by pinocytosis (mesothelium
and endothelium)
Secretion Secretion of biologically active molecules
(mesothelium)

16. Nuclei of the simple sq.
ep.
(KIDNEYS)

17. 2. SIMPLE CUBOIDAL EPITHELIUM
- single layer, square, round
nucleus at center, roughly as tall
as they are wide
Functions:
 absorption
 barrier
 secretion
Ex: small ducts of exocrine glands,
surface of ovary, kidney tubules,
thyroid follicles, pancreas

18. pancreatic duct
mesothelium covering
an ovary
renal collecting tubule

19. 3. SIMPLE COLUMNAR EPITHELIUM
- Single layer, tall cells, nuclei form a
single row at the basal part of the cell
Functions:
 absorption
 secretion
 lubrication
 protection
Ex. lining of fallopian tube, gallbladder,
stomach, intestine, ducts of exocrine
glands

20. 3. SIMPLE COLUMNAR EPITHELIUM
CILIATED SIMPLE COLUMNAR
EP. – fallopian tube, uterus,
ovary

21. renal collecting duct
oviduct lining, with both
secretory and ciliated cells
lining of the gall
bladder

22. 4. PSEUDOSTRATIFIED COLUMNAR
EPITHELIUM
“False stratified epithelium”
- Cells are attached to basal lamina even
though their nuclei lie at different levels.
- The height of some cells does not extend
to the surface
Functions:
 protection
 transport of particles trapped in mucus out of
air passages
 secretion

23. 4. PSEUDOSTRATIFIED COLUMNAR
EPITHELIUM
Ex: lining of the membranous and spongy part of the male
urethra
Ciliated
pseudostratified ep.
(respiratory ep.)
- lining of trachea, bronchi,
nasal cavity

25. STRATIFIED EPITHELIAL TISSUES
Stratified Squamous
Epithelium
Stratified Cuboidal
Epithelium
Stratified Columnar
Epithelium
Transitional Epithelium

26. 1. STRATIFIED SQUAMOUS
EPITHELIUM• “dry”; superficial layers are dead cells; no
nucleus & organelles
•Cells closer to the underlying connective
tissue are usually cuboidal or low columnar
•Impervious to water
•Ex. epidermis
Keratinized
•“wet”; kept moist by glandular secretions
•Flattened cells retain their nuclei
•Lines wet cavities
•Ex. Mouth, vagina, esophagus, urethra,
cornea
Non-
keratinized

28. 2. STRATIFIED CUBOIDAL
EPITHELIUM
Functions:
 Protection
 Secretion
Ex. Sweat glands, salivary
glands, developing ovarian
follicles

29. 3. STRATIFIED COLUMNAR
EPITHELIUM
- Lines large ducts of some
glands

30. 4. TRANSITIONAL EPITHELIUM/
UROTHELIUM
- Unique to mammals
- manifest features that are between
stratified squamous and stratified
cuboidal
- designed to withstand stretching
Cuboidal
(basal cells)
Umbrella cells – domelike cells
that are protective against
hypertonic and potentially
cytotoxic effects of
urine(superficial cells)

31. 4. TRANSITIONAL EPITHELIUM/
UROTHELIUM
Location: lining of the renal calyces, renal pelvis, urinary bladder,
ureter, and upper part of the urethra
- the form of the surface cells changes according to the degree of
distention of the bladder wall

32. SURFACE MODIFICATION OF
EPITHELIAL CELLS
Apical surface
microvilli
cilia
flagella
stereocila
Lateral surface
Zonula occludens
Zonula adherens
Desmosome
Gap junction
Basal surface
hemidesmosome
Basal infoldings of
the plasmalemma

33. 1. APICAL MODIFICATION
MICROVILLI
- minute fingerlike projections that extend from the apical
surface of the cell
Striated border/ brush border
(stomach)

34. • Within each microvillus
are bundles of actin
filaments cross-linked to
each other and to the
surrounding plasma
membrane by other
proteins

35. 1. APICAL MODIFICATION
CILIA (KINOCILIA)
- Elongated, highly motile,
longer and two times wider
that microvillus
- Exhibit rapid back and forth
movements coordinated to
propel a current of fluid and
suspended matter in one
direction

36. 1. APICAL MODIFICATION
FLAGELLA
- Long cilia
- Functions to propel
the cell
- Spermatozoon (called
tail)

37. 1. APICAL MODIFICATION
stereocila
- microvilli that are as long as cilia
- non-motile and core consists of
actin filaments
Location: vas deferens, testes, hair
cells of the inner ear

38. 2.LATERAL SURFACE
MODIFICATION
INTERCELLULAR JUNCTIONS
Zonula occludens
Zonula adherens
Desmosomes
Gap junctions
Juxtaluminal junction
complex/
terminal bar

39. 2. LATERAL MODIFICATIONS
INTERCELLULAR JUNCTIONS
Zonula Occludens (Tight junction/ Closing Belt)
- Most apically situated
 Zonula – indicates that junctions form bands
completely encircling each cells
 Occludens – refers to membrane fusions that
close off the space between the cells
Principal function:
Seals to prevent the
flow of materials
between the cells
(paracellular pathway)

40. 2. LATERAL MODIFICATIONS
INTERCELLULAR JUNCTIONS
Zonula Adherens (Adhering belt/ Belt
desmosome/ Band desmosome)
- Also encircles the cell usually immediately
below the zonula occludens
- cell membrane of adjoining cells neither
adhere nor fuse; they are separated by
intercellular space filled with cadherins
(extracellular material) that provides firm
adhesion of one cell to its neighbors

41. 2. LATERAL MODIFICATIONS
INTERCELLULAR JUNCTIONS
Desmosomes(Macula adherens/ Spot
Desmosome)
- form button-like adhesions arranged in a line
around the cell
- appear as thickening of the cell
- with intermediate filaments converging and
inserting into each half disc
Location: epidermis
Principal function:
Provides firm adhesion
among cells

42. 2. LATERAL MODIFICATIONS
INTERCELLULAR JUNCTIONS
Gap Junctions (Nexus/ Communicating Junction)
- broad area where the plasma membranes of
adjoining ep. cells are closely apposed w/ each
other
- perforated by tiny tubes called connexons
Principal function:
permit the rapid
exchange between cells
of molecules with small

45. 3. BASAL SURFACE MODIFICATIONS
- For better attachment or for more efficient functioning
Hemidesmosomes
- Identical to half a desmosome
- Exists in the stratum basale of the skin
Basal infoldings of the plasmalemma
- Present in cells lining segments of the renal tubule
- increase the absorptive capacity of the cell

46. GLANDULAR EPITHELIUM

47. GLANDULAR EPITHELIUM
Glandular
epithelium
Glands Secretions

48. ENDOCRINE GLANDS
- Ductless glands
- Arise in the embryo as
invagination of the covering
epithelium
Secretions: HORMONES
(chemical messengers)
Ex: adrenal gland, thyroid
gland, islets of Langerhans
(pancreas)

49. EXOCRINE GLANDS
Unicellular glands
- Exemplified by the goblet
cells
- Lines respiratory and
digestive tract

50. EXOCRINE GLANDS
Multicellular glands
- All other glands
 Secretory ep. sheet (e.g. ependymal – lines the choroid
plexus w/c produces CSF)
 Intraepithelial gland (e.g. penile urethra – secretory cells that
gather around a small orifice and form shallow invaginations)
 Glands with ducts – (e.g. major salivary glands, pancreas,
liver - possess “true” ducts)

51. CLASSIFICATION OF EXOCRINE GLANDS
BASED ON MORPHOLOGY OF DUCT
• single,
unbranched
duct
Simple
• duct with
branches
Compound

52. SECRETORY UNITS OF
EXOCRINE GLANDS
TUBULAR GLANDS
 Secretory tubules – blind ending tubes
ACINOUS OR ALVEOLAR GLANDS
 Acini; alveoli – globular or basket-like structures
TUBULOALVEOLAR (TUBULOACINOUS) GLAND
Further
classified
into
BRANCHED
or COILED

53. SIMPLE TUBULAR
Crypts of Lieberkuhn
(intestinal glands)

54. SIMPLE COILED TUBULAR
Sweat glands

55. SIMPLE BRANCHED TUBULAR
Cardiac glands
(stomach)

56. SIMPLE ACINAR

57. SIMPLE BRANCHED ACINAR
Sebaceous glands

58. COMPOUND BRANCHED
TUBULAR

59. COMPOUND ACINAR

60. COMPOUND TUBULO-ACINAR
Major salivary glands
(parotid,
submandibular,
sublingual)

61. BASED ON TYPE OF SECRETION
MUCOUS CELLS (mucus secreting)
 Mucin containing – forms mucus that lubricates the covering
epithelia
 Ex. Sublingual gland
SEROUS CELLS (serous secreting)
 enzymes
 Ex. Parotid gland, pancreas
Mixed gland – both are present; mucinous cell capped by
serous demilunes (“mucoserous”)
 Ex. submandibular gland

62. BASED ON MECHANISM OF
PRODUCT RELEASE
(MODE OF SECRETION)
 Merocrine (eccrine) -
exocytosis, cell remains intact
Ex. Pancreatic acinar cells, major salivary
glands
 Apocrine - secretes product
with apical portion of cell;
Ex. Sweat glands, lactating mammary
glands, ceruminous glands in the skin
 Holocrine - whole cell
disintegrates when it secretes

63. END.