Transcript Epithelial Tissues

Tissues and a Introduction
to the Epithelium
Levels of Organization
atoms→molecules→organelles→cells
→tissues
In the body, tissues can be classified into the following functions:
Epithelial – cover 1
Connective – support 2
Movement – muscle 3
Control – nervous 4
Epithelial Tissues
• Epithelial cells can be classified into 2
types, those that cover surfaces and
cavities and those that form a glandular
function.
Epithelial tissues have the following
functions:
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Protection
Absorption
Filtration
Excretion
Secretion
Sensory Reception
Characteristics of epithelial tissues:
• Epithelial cells have an upper or free
surface.
Characteristics of epithelial tissues:
• Epithelial cells have an upper or free
surface.
• This is known as the Apical Surface
Polarity
• The apical surface
can be modified by
microvilli or cilia.
• Microvilli are seen
with cells associated
with absorption.
Polarity
• The microvilli can be
so thick that it can be
described as a brush
boarder.
Polarity
• The bottom side of
the epithelial cell is
called the basal
surface.
• It is supported by a
non cellular, adhesive
sheet called the basal
lamina.
Specialized Contacts
• Epithelial cells have
contact with each
other.
• These lateral contacts
are the desmosomes
and tight junctions.
Specialized Contacts
• The tight junction
forms an
impermeable junction
between each cell
and thus prevents
diffusion between the
cells.
Specialized Contacts
• The desmosomes
help hold the cell’s
shape with anchoring
junctions scattered
between each cell.
Connective Tissue Support
• The basilar surface attached to a
connective tissue net work.
• There are two parts. The first is the basal
lamina secreted from the epithelial cell.
• The second is the reticular lamina that is
made of collagen which is produced by
fibroblasts.
Connective Tissue Support
• Together the basal
lamina and reticular
lamina form the
basement
membrane.
• This forms the
foundations which
anchor the epithelial
cells.
Avascular but Innervated
• Epithelial cells do not have a blood supply
• They depend on diffusion for the delivery
of nutrients and removal of wastes.
• They do have a nerve supply, innervated,
for sensory function.
Regeneration
• Do to their protective
function; epithelial
cells need to be
continually replaced.
• Mitotic figures are not
uncommon.
Cancer
• Many cancers are of epithelial origin.
• The greater the mitotic index, the greater
the chance of cancer.
Cancer Types
Cancer Types
• Lung cancer caused
by smoking typically
starts in the bronchial
epithelium
1 Picture & 1000 words