CELL JUNCTION PowerPoint Presentation

CELL JUNCTION PowerPoint Presentation

2016-05-18 107K 107 0 0

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CELL JUNCTIONS. In certain tissues the membranes of adjacent cells may join and form a junction called a cell junction.. These are specialized areas of the cell membrane that provide contact between the cells.. ID: 325431

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Slide1

CELL JUNCTION

Slide2

CELL JUNCTIONS

In certain tissues the membranes of adjacent cells may join and form a junction called a cell junction.

These are specialized areas of the cell membrane that provide contact between the cells.

Slide3

TYPES OF CELL JUNCTIONS

Two factors are important

1: shape and extent of the contact

This may be in the form of a spot or

puctate

area of limited extent called

macula.

Or this can be like a belt or girdle around the cell called

zonula

.

2: The relative closeness and nature of cell contact:

Here the following terms are used

Occludens

Adherens

Gap

Slide4

CELL JUNCTIONS

1:OCCLUDENS :

In this type of junctions the intercellular space is virtually obliterated and outer surface of the two cell membranes appear in contact or even fused.

2: ADHERENS:

In this type the intercellular space is apparent being about 20-25nm wide and dense granular material is present in the intercellular space.

3: GAP:

The third types is gap junction which show a narrow intercellular space of about 3nm.

Slide5

TYPES OF CELL JUNCTIONS

On the basis of two factors discussed above Cell junctions are classified as

Maccula

adherens

(

desmosomes

or spot

desmosomes

)

Zonula

adherens

(belt

desmosomes

)

Zonula

occludens

(tight junctions)

Gap junctions(nexus)

Slide6

TYPES OF CELL JUNCTIONS

1.MCULA ADHERENS:

Usually found between epithelial cells

Discoid structures called

desmosomes

are present at various levels with their long axes perpendicular to the basement membrane of epithelium.

In the region of a

desmosome

the intercellular gap is about 25nm wide and contain an adhesive glycoprotein called

desmocollin

.

Intracytoplasmic

densities called attachment plaques are present beneath the plasma membrane of both the cells forming the junction.

Groups of intermediate filaments are inserted into the attachment plaques or they make hairpin loops and turn back into the cytoplasm

Hemidesmosomes

are sometimes seen which are structures, half of a

desmosome

Slide7

Slide8

TYPES OF CELL JUNCTIONS

2. ZONULA ADHERENS

(BELT DESMOSOME)

As the name indicates

zonula

adherens

is present like a girdle around each cell making the junction.

The intercellular gap is of normal width(20nm)

The gap is not bridged by filaments

This type of gap junction is found among epithelial cells, fibroblasts, smooth muscle cells etc.

Slide9

TYPES OF CELL JUNCTIONS

3.ZONULA OCCLUDENS (tight junctions):

It is like

zonula

adherens

in the form of girdle around both the cells forming the junction.

But here the membranes of the cells are very close and are apparently fused leaving no intercellular

gap.

Slide10

TYPES OF CELL JUNCTIONS

4.GAP JUNCTIONS (NEXUS):

The membranes of the adjoining cells are closely apposed but there is a gap of 2-3nm which permit colloidal substances.

Like

desmosomes

the nexuses usually form limited attachment plaques.

Gap junctions are widely distribute in the body and found in cardiac muscles, smooth muscles, liver,kidny,thyroid,skin etc.

In smooth and cardiac muscles they help in spreading impulses from cell to cell

Gap junctions provide communication channels between adjacent cells.

Their intercellular gap is traversed by hollow tube like structure.

Slide11

JUNCTIONAL COMPLEX

In may areas like small intestinal mucosa the adjacent epithelial cells are joined by a series of different cell junctions which are collectively called

junctional

complex.

Junctional

complex comprises of

zonula

occludens

,

zonula

adherens

and macula

adherens

Slide12

TYPES OF JUNCTIONS

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