Meghan Barboza, PhD
Online course
Wikipedia Commons
 Glycocalyx
 Basal Lamina
 Cell Junctions
 Microvilli/Stereocilia
 Cilia
Glycocalyx
 Protective mechanical
barrier associated with
the cell membrane in all
cells
 Enhances selectivity or
permeability
 Receptor sites for target
molecules
Glycocalyx
 Best developed in columnar
epithelial cells with microvilli
(small intestine especially)
Image from Wikipedia commons
Basal Lamina
(not to be confused with the basement membrane)
 Extracellular matrix secreted by epithelial cells
 Visible only with TEM
 Makes up a portion of the basement membrane
www.columbia.edu proximal convoluted tubule
Cell Junctions
 Within Epithelium there are
four types of cell junctions
which in certain conditions
can be observed
Cell junctions
 Macula adherens
(desmosome)
www.histology.leeds.ac.uk
www.histology.leeds.ac.uk
Hemidesmosomes
 Hemidesmosomes
 “half desmosomes”
 attach the basal cell membrane to
the basal lamina.
Types of Cell Junctions
 Macula adherens
(desmosomes)
 hemidesmosomes
 Zonula adherens
 Linked to actin
cytoskeleton
Zonula adherens
www.studyblue.com
Types of Cell Junctions
 Macula adherens
(desmosomes)
 Zonula adherens
 Zonula occludens
(tight junction)
Types of Cell Junctions
 Macula adherens
(desmosomes)
 Zonula adherens
 Zonula occludens
(tight junction)
 Gap Junction
(Nexus)
Gap Junction
Junctional Complex
 Zonula occludens
 Zonula adherens
 Macula adherens
 Gap Junctions
Junctional Complex
 Zonula occludens
 Zonula adherens
 Macula adherens
 Gap junctions
Combined Create
the:
 Terminal Bar
Only one cell junction is unique to epithelia
Zonula adherens
http://medlib.bu.edu/histology/p/20604loa.htm
Apical Projections
Microvilli
Stereocilia
Cilia
Microvilli
 Actin core
http://www.cytochemistry.net/cellbiology/actin_filaments_intro.htm
Microvilli
 Enhances
absorption
 Expand surface
area of cells
apex up to
10,000 times
Microvilli: Principal
Location
 Mucosal lining of most of the
GI tract
Stereocilia
(long microvilli)
Actin core
Stereocilia: Principal Locations
 Lining of portion of the male
reproductive tract
(epididymis)
Stereocilia: Principal Locations
 Lining of portion of the male
reproductive tract
(epididymis)
 Lining of the inner ear
scienceblogs.com
Cilia
Cilia: Principal Locations
 Mucosal lining of most of
the respiratory tract
Cilia: Principal Locations
 Mucosal lining of most of
the respiratory tract
 Lining of uterine portion of
the female reproductive
tract
Cilia: Kinetic Activity
 Propels material along
(airways) on the
mucociliary escalator.
 Create current for
movement of egg down
uterine tube.
 Provided by axoneme
(organized set of nine
pairs of microtubules
surrounding two singlets)
Copyright © The McGraw-Hill Companies, Inc.
Check your understanding
 Why is the zonula adherans only found in
epithelia and not other tissues? Or looking at
another way, why are the other cell junctions
found in other tissues in addition to epithelia?
 Why would glycocalyx be associated with
microvilli?
 What is the terminal bar and why can we see it
using a light microscope?
 To which organelle do cell junctions attach?