The digestive system of cockroach consists of
an alimentary canal and
the associated glands.
The preoral cavity , surrounded by the mouth parts, is present in front of the mouth.The hypopharynx divides the mouth in into two chambers called
anterior – cibarum and
posterior – salivarium.
ALIMENTARY CANAL :-
The alimentary cnal of cockroach is a long tube and coiled at some places. It extends between the mouth and the anus . It is divided in to three regions, namely ,
Foregut or stomodaeum ,
Midgut or mesenteron , and
Hindgut or proctodaeum.
The foregut and the hindgut are internally lined by ectoderm. The mesenteron is lined by the endodermal cells.
FOREGUT OR STOMODAEUM :-
- The foregut includes
- The foregut is internally lined by a chitinous cuticle.
- Mouth opens in the pharynx, which in turn leads into a narrow tubular oesophagus.
- The oesophagus opens behind into a thin walled distensible sac called crop.
- The crop serves as a reservoir for storing food.Its outer surface is covered by a network of tracheae.
- A thick walled muscular gizzard or proventriculus is present behind the crop.
The chitinous inner lining of the gizzard has six powerful chitinous plates or teeth. A hairy pad with backwardly directed bristles is present behind each teeth.
Among these teeth , food is thoroughly ground into fine particles. These fine food particles are filtered with the bristles. Thus the gizzard acts both as a grinding mill and also as a sieve.
A funnel ike membranous projection of the gizzard called stomodaeal valve is present at the junction of gizzard and the midgut. This valve prevents the backward passage of food from the mesenteron into the gizzard.
MIDGUT (MesenteronOr Ventriculus) :-
- The midgut is a short and narrow tube behind the gizzard. It is also called mesenteron or ventriculus.
- Six to eight finger like projections called hepatic caecae are present between the ventriculus and the gizzard, arising from ventriculus.
They are helpful in digestion and absorption of the digested food materials.
- Ventriculus is divided into
an anterior –secretory part and
a posterior – absorptive part.
- The secretory part of the midgut has many gland cells and it secrete several enzymes. In the mesenteron the food bolus is enveloped by a chitinous and porus membrane called peritrophic membrane. It is secreted by the stomodeal valve of the gizzard.
The peritrosphic membrane protects the wall of the the ventriculus from hard food particles in the food.
- Digested food is absorbed inro the blood through the peritrophic membrane in the posterior absorptive region of the ventriculus.
- The opening of the ventriculus into the hindgut is controlled by a sphincter muscle. It prevents entry of undigested food and uric acid from the hindgut into the midgut.
HINDGUT ( PROCTODAEUM ):-
- The hindgut isa long coiledtube.
- It consists of three regions namely ileum,colon and rectum.
- The midgutis internally lined by chitinous cuticle.
- The ilium is a short tube, that lies behind the mesenteron.
- Six bundles of fine yellowtubules called Malpighian tubules open in to the ilium near the junction of mesenteron and ilium.
- Ilium collects uric acid from Malpighian tubules and undigested food from mesenteron.
- The ilium opens behind into a long coiled tube called colon.
- Colon leads behind into a shortand wide rectum.
- Rectum bears six longitudinal chitinous folds called rectal papillae on its inner surface.They are concern with the reabsorption of water from the undigested food.
- The rectum opens out through the anus.