$(A)$ Plasmodesmata :

$\Rightarrow$ Structure : It is a narrow pathway connecting cell wall between two cells.

Function : It makes transport and communication possible between two nearly cells.

$\Rightarrow$ Plasmodesmata allow molecules to travel between plant cells through the symplastic pathway.

$(B)$ Middle lamella :

$\Rightarrow$ Structure : It is a layer located in cell wall. It is mainly made up of calcium pectate.

Function : It connects two near by cells.

$(C)$ Secondary Wall :

$\Rightarrow$ Structure : It is such a wall that cannot expand. It is made up of hemicellulose fibre in cell wall of plant cell.

$\Rightarrow$ Function: It provides firmness to cells.