ALIMENTARY CANAL OF COCKROACH

Cockroach is an omnivorous animal eating anything ranging from starchy and sweet things to papers, clothes etc. Its alimentary canal is therefore adapted to suit its type of diet. The alimentary canal consists of foregut, midgut and hindgut.

1) Foregut

Foregut consists of mouth, oesophagus, crop and gizzard.

 

a) Mouth

The mouth is modified for cutting and chewing. It consists of the following: Labrum, hypopharynx, mandibles, first maxillae, labium and second maxillae.

• Labrum: Labrum is a flap-like structure regarded as the upper lip of the mouth. It is sensitive to various chemical substances and thus acts as taste buds.
• Hypopharynx: This is a membranous tongue-like structure located on the back of the mouth. It helps in swallowing of food.
• Mandibles: Two mandibles, one on each side, are the jaws of the mouth. They are heavily built and toothed for biting, cutting and chewing.
• First maxillae: Under each mandible lies a first maxilla. Each maxilla is toothed and assists the mandible in cutting food. It also helps in directing food into the mouth. The maxillary palp is sensitive to chemicals and touch and therefore helps in locating food substances.
• Labium and second maxillae: Two maxillae are fused at the base to form the labium or lower lip. They also, assist in food cutting and direct the cut food into the mouth.

 

Salivary glands

Salivary glands open into the mouth via salivary ducts. The salivary glands secrete digestive enzyme (amylase) which starts the digestion of starchy food.

 

b) Oesophagus

The oesophagus is short, narrow and tubular and connects the mouth with the thin-walled crop. The oesophagus functions as a passage through which food passes from the mouth to the stomach.

 

c) Crop

The crop is thin-walled and large. It acts as a temporary storage chamber and most digestion occurs here. (Note: Cockroach has no stomach).

 

d) Gizzard (proventriculus)

The gizzard is a highly muscular bag where hard food substances are ground into smaller particles before digestion.

 

2) Midgut

The midgut consists of six mesenteric (hepatic or digestive) caeca. The caeca open into the midgut and secrete digestive juice which contains the three kinds of enzymes that complete the digestion of carbohydrates, proteins and fats. Digestion and absorption take place in the midgut.

 

3) Hindgut

The hindgut consists of small intestine, rectum and anus. Between the midgut and hindgut are many fine structures called Malpighian tubules. They excrete nitrogenous wastes. The rectum absorbs water from the faeces and let the dry faeces pass out through the anus.

 

In summary, the cockroach feeds on household materials like books, sugar and food. The alimentary canal of a cockroach includes the mouth (mandibles), salivary gland, oesophagus, crop, gizzard, mid-gut, caecum, ileum, rectum, hind gut, malpighian tubules and anus. The mouth is surrounded by mouth parts such as maxillae, mandibles and labium with sharp cutting edges for the cutting and grinding of food. A pair of salivary glands opens into the mouth which secrets enzymes for digestion of food.

The food is then swallowed through the muscular oesophagus into the crop. The crop is where the food is stored. The food is later taken to a muscular gizzard for grinding. The short mid-gut has six fleshy vascularised diverticulum or midgut caecum which increases the surface area for digestion and absorption. The hind gut consisting of ileum, colon, and rectum shapes the faeces into pellets and absorbs water and mineral salts. The faeces are later passed out through the anus.