watch video for mouth parts and dissection of digestive system in periplaneta http://www.youtube.com/watch?v=b04hc_kOY10
The digestive glands associated with the alimentary canal of cockroach are
hepatic caecae and
glandular cells of the mesenteron.
A pair of salivary glands are present . They ae attached to the ventrolateral sides of the crop, one on each side.
Each salivary gland has two lobes.Each lobe of salivary gland has many lobues called acini.Each acinus is a group of secretory cells called zymogen cells with a small ductile.The ducts of both the lobes of a salivary glandunite to form a common salivary duct on each side.The two common salivary ducts are joined to form the median salivary duct.
A sac like structure called salivary receptacle is present between the two lobes of salivary gland.It stores saliva.It leads into a receptacular duct or reservoir duct.The reservoir ducts of both sides are united to form a common receptacular duct.
The median salivary duct opens into the common receptacular duct. Later these two form an efferent salivary ductThe efferent salivary duct opens at the base of the hypopharynx.Acinar cells secrete saliva, which contains starch digesting enzymes such as amylase.
2) HEPATIC CAECAE :-
Six to eight fingerlike hepatic caeca are present at the junction of gizzard and midgut.They are secretory and absorptive in function.
3) GLANDULAR CELLS OF MIDGUT :-
The glandular cells of midgut secrete enzymes such as maltase, invertase, ptoteases and lipases.
PHYSIOLOGY OF DIGESTION
The physiology of digestion in periplaneta includes
1) FOOD COLLECTION :–
- Cockroach is an omnivorous insect.It feeds on all types of organic matter.
- It locates the food by the olfactory sensilla of antenna, labial palps and maxillary palps.
- The food is seized with the help of forelegs , labrum and labium.
- The food is passed to the mandibles for biting and chewing.
- The laciniae , galeae , glossae and paraglossae hold the food during chewing.
- The labrum and labium prevent the food from falling down.
- The food is mixed with saliva during mastication.
- After swallowing the food pass through the pharynx and oesophagus , and reaches the crop.
- In the crop the food is mixed with digestive juices that are regurgigated into it through the grooves of gizzard.
- Hence, most of the food is digested in the crop.
An enzyme salivary amylase converts starches into disaccharides.
Invertase or sucrose digests sucrose into glucose and fructose.
Maltase converts maltose into glucose.
The enzyme lipase digests lipids into fatty acids and glycerol.
Proteases digest proteins into aminoacids.
The enzyme cellulose secreted by the microorganisms present in the hindgut converts cellulose into glucose.
5.The partly digested food is filtered by the bristles of the gizzard and later it passes through the stomodeal valve into the ventriculus.
6.In the posterior absorptive part of the ventriculus, the digested food is absorbed in to the haemolymph through the peritrophic membrane.
7.The undigested food is passed into the ileum, colon, and then reaches the rectum.
8.In the rectum the water is reabsorbed by rectal papillae.
9.Finally the remaining material is defaecated as dry pellets.