Cell junctions

Tight junctions

Found in barrier tissues where it is important to prevent leakage - stomach, bladder, intestines

Individual sealing strands (transmembrane)

Hold together adjacent cells - to make them electrically tight - no ions or molecules can pass

P=occludins and Claudine

Adherens junction

Like a belt

Are for flexible support so are found in places such as the skin, heart muscle and intestinal lining

P=cadherin - spans gap + links to Catenin-binds to actin

Protein plaque like structure, creates a bridge between two cell membranes

Prevents cell seperation from tension such as contraction

Desmosomes

Heavy duty anchors - (spot welds/button structure) found in skin, cervix, heart

P:cadherin (spans gap) links to desmoplakin - links to keratin

Protein plaque - Gap is mainted but more subtle due to isolated points of contact between cells

Gap junction

Made up of 2 hemichannels

A hemichannel/connexon is made up of 6 connexion proteins

These migrate and dock together at a chemical level. The opening is the cell has special molecules that control what goes in and out

Found: cardiac muscle, smooth muscle

Allows rapid communication through electrical impulse, ions etc

Hemidesmosomes

Connect epithelium to basement membrane

P=integrin proteins (span gap) Link to laminin in BM and keratin in cytoplasm

*prevents sliding and migration

What forms a junctional complex?

TAD

Tight, adherens, desmosome

Which junction is not lateral but instead basal?

Hemidesmosome

Label A,B,C,D and E

A=tight junction

B=adherens

C=gap

D=desmosome

E=hemidesmosome

What is 1 and 2?

1=tight 2=adherens