Tissues:
The living fabric
Ch 4 a
Epithelial Tissue
Tissues
• Histology = Study of tissues
• Tissue = Groups of cells similar in
structure and function
• The four types of tissues
– Epithelial - covering
– Connective - support
– Muscle - movement
– Nerve - control
Epithelial Tissue
• 2 types
– Covering and lining epithelium
– Glandular epithelium
Epithelial Tissue
Covering and lining
epithelium
Epithelial Tissue
• A sheet of cells that covers a
body surface or lines a body
cavity
• Forms boundaries between
different environments
Epithelial Tissue Functions
• Protection
• Absorption
• Filtration
• Excretion
• Secretion (from glands)
• Sensory reception
Characteristics of
Epithelial Tissue
• Cellularity – composed almost
entirely of cells
– Very little extracellular
material
• Special contacts – form
continuous sheets held together
by tight junctions and
desmosomes
Characteristics of
Epithelial Tissue
• Polarity – apical and basal
surfaces
– Apical = free upper surface
exposed to exterior of body
or cavity (some are slick, some
have cilia, most have
microvilli)
– Basal = lower surface
attached
Characteristics of
Epithelial Tissue
• Basal surface attached to
basement membrane
– basal laminae – thin, adhesive,
non-cellular
– reticular laminae – fine
network of collagen fibers
belonging to the connective
tissue underneath, non-cellular
Characteristics of
Epithelial Tissue
• All epithelial tissue are
supported by and rest upon
connective tissue
Characteristics of
Epithelial Tissue
• Avascular but innervated –
contains no blood vessels but
supplied by nerve fibers –
nourished by diffusion
• Regenerative – rapidly replaces
lost cells by cell division
Classification of Epithelia
Simple
stratified
Figure 4.1a
Classification of
Epithelia
• Squamous
• Cuboidal
• Columnar
Figure 4.1b
Epithelia: Simple Squamous
• Single layer of flattened cells
with disc-shaped nuclei and
sparse cytoplasm
Epithelia: Simple Squamous
• Functions
– Diffusion and filtration
– Provide a slick, friction-reducing
lining in lymphatic and
cardiovascular systems
• Present in the kidneys, lungs,
lining of heart, blood vessels,
lymphatic vessels
Epithelia: Simple Squamous
Figure 4.2a
Epithelia: Simple Cuboidal
• Single layer of cubelike cells
with large, spherical central
nuclei
• Function in secretion and
absorption
• Present in kidney tubules, ducts
and secretory portions of small
glands, and ovary surface
Epithelia: Simple Cuboidal
• Single layer of cubelike cells with large,
spherical central nuclei
• Function in secretion and absorption
• Present in kidney tubules, ducts and
secretory portions of small glands, and
ovary surface
Figure 4.2b
Epithelia: Simple Columnar
• Single layer of tall cells with
oval nuclei; many contain cilia
• Goblet cells are often found in
this layer
– Cells that secrete a
protective lubricating mucus
• Function in absorption and
secretion
Epithelia: Simple Columnar
• Nonciliated type line digestive
tract and gallbladder
• Ciliated type line small bronchi,
uterine tubes, and some regions
of the uterus
• Cilia help move substances
through internal passageways
Epithelia: Simple Columnar
Figure 4.2c
Epithelia: Pseudostratified
Columnar
• Single layer of cells with
different heights; some do not
reach the free surface
• Nuclei are seen at different
layers
Epithelia: Pseudostratified
Columnar
• Function in secretion and
propulsion of mucus
• Present in the male spermcarrying ducts (nonciliated) and
trachea (ciliated)
Epithelia: Pseudostratified
Columnar
• Single layer of cells with different
heights; some do not reach the free
surface
• Nuclei are seen at different layers
• Function in secretion and propulsion of
mucus
• Present in the male sperm-carrying
ducts (nonciliated) and trachea
(ciliated)
Figure 4.2d
Epithelia: Stratified Squamous
• Thick membrane composed of
several layers of cells
• Function in protection of
underlying areas subjected to
abrasion
Epithelia: Stratified Squamous
• Forms the external part of the
skin’s epidermis (keratinized
cells), and linings of the
esophagus, mouth, and vagina
(nonkeratinized cells)
Epithelia: Stratified Squamous
• Thick membrane composed of several
layers of cells
• Function in protection of underlying
areas subjected to abrasion
• Forms the external part of the skin’s
epidermis (keratinized cells), and linings
of the esophagus, mouth, and vagina
(nonkeratinized cells)
Figure 4.2e
Epithelia: Stratified Cuboidal
• Stratified cuboidal
– Quite rare in the body
– Found in some sweat and
mammary glands
– Typically two cell layers thick
Epithelia: Stratified Columnar
• Stratified columnar
– Limited distribution in the
body
– Found in the pharynx, male
urethra, and lining some
glandular ducts
– Also occurs at transition areas
between two other types of
epithelia
Epithelia: Transitional
• Several cell layers, basal cells
are cuboidal, surface cells are
dome shaped
• Stretches to permit the
distension of the urinary
bladder
• Lines the urinary bladder,
ureters, and part of the urethra
Epithelia: Transitional
• Several cell layers, basal cells are
cuboidal, surface cells are dome shaped
• Stretches to permit the distension of
the urinary bladder
• Lines the urinary bladder, ureters, and
part of the urethra
Figure 4.2f
Epithelial Tissue
Glandular Epithelia
Epithelia: Glandular
• A gland is one or more cells that
makes and secretes an aqueous
fluid
Epithelia: Glandular
• Glands Classified by:
– Site of product release –
• Endocrine (internally secreting)
or Exocrine (externally
secreting)
– Relative number of cells forming
the gland –
• Unicellular (one cell) &
Multicellular (many cells)
Endocrine Glands
• Ductless glands that produce
hormones
• Secretions include amino acids,
proteins, glycoproteins, and
steroids
Exocrine Glands
• More numerous than endocrine
glands
• Secrete their products onto
body surfaces (skin) or into
body cavities
Exocrine Glands
• Examples include mucous, sweat,
oil, and salivary glands, the liver
(which secrets bile), the
pancreas (which secrets
enzymes) and others
Unicellular Exocrine Glands
• The only important unicellular
exocrine gland is the goblet cell
– Found in linings of intestinal
and respiratory tracts
– Secrets mucus
Multicellular Exocrine Glands
• Multicellular exocrine glands
are composed of a duct and
secretory unit
• Classified according to:
– Simple or compound duct type
– Structure of their secretory
units
Structural Classification of
Multicellular Exocrine Glands
Figure 4.3a-d
Structural Classification of
Multicellular Exocrine Glands
Figure 4.3e-g
Modes of Secretion
• Merocrine – products are
secreted by exocytosis (e.g.,
pancreas, sweat, and salivary
glands)
• Holocrine – products are secreted
by the rupture of gland cells (e.g.,
sebaceous glands)
Modes of Secretion
Merocrine
Holocrine
Figure 4.4
• http://www.youtube.com/watch?v=7z2v
Yr5YjD8
Simple cuboidal epithelium
Simple cuboidal epithelium
Transitional epithelium
Transitional epithelium
Pseudostratified epithelium
Stratified squamous epithelium
What
tissue is
this?
Simple columnar epithelial tissue
Quiz – Next time!
I will be checking study
guides up to 1-8
•
•
•
•
•
•
•
•
•
Ap = tip
Areola = space
Basal = foundation
Blast = forming
Chyme = juice
Crine = separate
Endo = within
Epi = upon, over
Glia = glue
•
•
•
•
•
•
•
•
•
•
Holo = whole
Hormon = excite
Hyal = glass
Lamina = thin plate
Mero = part
Meso = middle
Retic = network
Sero = watery fluid
Squam = a scale
Strat = layer