Complete the following statement :
$(a)$ In cockroach,grinding of food particles is performed by ........ .
$(b)$ Malpighian tubules help in the removal of ........ .
$(c)$ The hindgut of the cockroach is differentiated into ........ .
$(d)$ In the cockroach,blood vessels open into spaces called ........ .

(A) Gizzard: It is a muscular structure with many folds,located after the foregut,and possesses $6$ highly chitinous plates called teeth which grind the food.
$(b)$ Excretory products: Malpighian tubules help in removing nitrogenous excretory materials from the haemolymph. Thus,they function as excretory organs.
$(c)$ Ileum,colon,and rectum: The hindgut is broader than the midgut and is differentiated into these three parts,where the rectum opens outside through the anus.
$(d)$ Haemocoel: The blood vessels are poorly developed and open into spaces called the haemocoel,where the internal organs are bathed in haemolymph.