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INTERCELLULAR JUNCTION
1. Tight junction
2. Desmosomes
3. Gap junction
Tight junctions
Ridge like structures between adjacent
cells.
Made up of proteins
Cells are bound together .
Found in epithelial cells
intestinal
mucosa
renal tubles
Form selective barrier
Eg.Blood brain barrier .
•Functions
•Helps in maintaining the functional polarity.
•Localizing the membrane proteins in one place.
They are important in preventing
molecules leaking between the cells
and providing control of passage for
materials through the epithelial sheet.
It is made up of proteins called claudins
and occludins.
 Desmosome or maculae adherens
• fasten cells together strengthening the tissue.
 Desmo (‘bound’), soma (‘body’).
 Adjacent membranes become thickened and the
space in between is filled with filament like material.
 Fibrils arise from this portion to the interior of the
membrane.
 Hemi desmosome – half desomoses on the basal
sides of the cell .
Plasma membranes
of adjacent cells
Microvilli
Intercellular
space
Basement membrane
Intercellular space
Plaque
Intermediate
filament (keratin)
Linker glycoproteins
(cadherins)
(b) Desmosomes: Anchoring junctions bind adjacent cells together
and help form an internal tension-reducing network of fibers.
Figure 3.5b
•Gap junctions or communicating
junctions .
•Gap junctions form channels between
cells.
• Allow ions and small molecules to pass
directly from one cell to another. These
channels are formed by membrane
proteins called connexin.
•Six connexins in the cell membrane form
a channel called a connexon
 Functions
 . Gap junctions permit electrical signals to pass
directly from one cell to another.
 Gap junctions are found in heart and smooth
muscle cells and between some neurons.
 To regulate the membrane potential between
cells and allow electrical impulses to pass
between cells.
 Electrical impulses passing between cardiac
muscle cells it lead conduction of the beat.
 Also gap junctions provide the contractions of the
smooth muscle cells of the uterus during birth
Plasma membranes
of adjacent cells
Microvilli
Intercellular
space
Basement membrane
Intercellular
space
Channel
between cells
(connexon)
(c) Gap junctions: Communicating junctions allow ions and small molecules to pass from one cell to the next for intercellular communication.
Figure 3.5c