Digestive system of nematode

Digestive System:

Ø  Complete digestive system

Ø  It is a long, straight tube extends from the Mouth to Anus and floats in the fluid filled body cavity.

Ø  On cross section, the digestive tract resembles a tube within a tube.

A. Mouth:

o   Located at anteriorly – terminal or sub-terminal

o   Usually surrounded by the cuticular structure, the 3 lips; one dorsal and two ventral. Each lip bears 2 papillae (Sensory organs). e.g. Ascaridoidea

o   But in some cases, there are two lateral lips each carrying 3 papillae. e.g. Spiruroidea

o   In some, no lips but only papillae are present

o   Secondary structures; leaf crown may developed (e.g. Filaroidea)

o   The mouth opening may lead to a buccal cavity of variable sizes. The buccal capsule may bear various teeth like structure.

o   Leaf crown: Collectively the papillae on lips/Mouth opening known as leaf crown ( may number as many as 40)

B. Pharynx:

o   A muscular pharynx is needed to pump food into the intestine .The shape of the phranyx is characteristics in some groups.

C. Esophagus:

o   It is a cuticular tube & is composed of thick muscular layer containing 3 glands which helps to digestion & generation of anticoagulants & haemolysin. The oesophagus pumps food into the intestine. Oesophagus is important for classification of nematodes:

o   posteriorly it may have a swelling called oesophageal bulb which contain a vulvular apparatus .e.g:Heterakis

o   In others, posterior portion is non muscular-glandular called ventriculus     e.g:Toxocara sp.

D. Oesophagus-intestinal valve:

·   It is a dorso-ventrally or laterally elongated short structure which connect oesophagus with intestine.

E. Intestine:

·   It is usually straight tube but sometimes caeca or loops may occur. It is composed of a single layer of epithelial cells. The luminal surfaces possess microvilli which increases the absorptive capacity of the cell.

F.Anus/cloaca:

·   It is posterior end of the alimentary canal. In female it called anus & in male it is called cloaca because ejaculatory duct opens there. Behind the anus the remaining posterior part is called tail. There may be papillae in front of the anus/cloaca or behind it, in the tail butter known as caudal papillae which aid in copulation.