Hi, today we are going to discuss the alimentary canal of cockroach which will give an idea about the digestive system in most of the insects. Some parts of the alimentary canal in cockroach are similar to that of the alimentary canal in humans but there are some organs which are unique.
Study of the alimentary canal is very useful to understand various parts of the alimentary canal because it covers almost all features of the alimentary canal and it has some extra structure which is not observed in all animals. To understand the whole alimentary canal of cockroach easily we will discuss them in three parts – foregut, midgut and hindgut.
Table of Contents
Foregut:
The foregut is the very first part of the alimentary canal which starts from the mouth. Mouth open into a chamber pharynx and the pharynx extend further into a long tube like structure oesophagus.
The wall of oesophagus is very thin and narrow which opens into a structure crops and it is a special structure in some animals like cockroach. The crop part have muscular part at the beginning called gizzard or proventriculus.
Chitinous structure present in foregut is very useful for grinding the food into small pieces the periventricular teeth present in foregut also made of chitin. Salivary gland secretion open into mouth cavity near labium through common salivary passage.
Midgut:
After the foregut the next part of the alimentary canal in cockroach is midgut which is the real gut because it has the stomach part. Oesophagus opens into the stomach but at the joining point of the stomach and oesophagus six pairs of gastric caeca open.
The gastric juice reaches the stomach from gastric caeca secretion. One major difference between the foregut and midgut is that, the foregut lined by chitin but the midgut is lined by peritrophic membrane.
The peritrophic membrane line the stomach which is permeable for digestive enzymes and absorption of digested food can be possible through the peritrophic membrane.
Hindgut:
The stomach part of midgut extends further and opens into the very first part of the alimentary canal hindgut. At the junction of stomach and hindgut a large number of tubular structures open into an alimentary canal which are known as Malpighian tubules.
Hindgut of cockroach is a coiled structure consisting of three parts anterior part ileum, middle part colon and posterior part rectum. The posterior part of hindgut open into external anus which is lined by cuticle.
How Digestion Occurs in Elementary Canal:
Digestion processes start from the mouth in cockroaches, the mandibles and maxillae help to break the food particles into small pieces. Then the food reaches in the mouth cavity where the salivary glands secretion mix with food to digest the food partially.
Specially carbohydrates start to digest partially in the mouth cavity in the cockroach. The salivary secretion also helps to lubricate the food which is very helpful to swallow the food without any difficulty.
Then the food reaches the oesophagus from the mouth cavity where no digestion occurs then the food reaches the crop part. In crop food mastication occurs and stored for some time and the food then transfers from crop to gizzard. In gizzard food where food breaks down into very small pieces due to grinding.
Then food enters into the stomach but the entry of food into stomach is controlled by a stomodeal valve present at the junction of gizzard and stomach. Due to the presence of stomodeal valve food do not backflow into oesophagus and smoothly enter into the stomach.
The main digestion occurs in the stomach with the help of digestive enzymes coming from gastric caeca. Major enzymes present in gastric caeca secretion are tryptase, maltase, amylase, lipase and invertase.
Reference: Alimentary Canal of Cockroach
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