Alimentary Canal
The oral sucker encloses a ventral mouth which leads into a funnel- shaped mouth cavity, followed by a round muscular pharynx with thick walls, and a small lumen. The pharynx has pharyngeal glands. F. indica has a short muscular pharynx from which arises an oral pouch which is about half the size of the pharynx.
There is a short narrow oesophagus leading into an intestine which divides into two branches or intestinal caeca or crura each running on one side to the posterior end, and ending blindly.
The intestinal caeca give out a number of branching diverticula in order to carry food to all parts of the body since there is no circulatory system. The median diverticula are short and lateral ones are long and branching. There is no anus.
The interior part of the alimentary canal up to the oesophagus is lined with cuticle and serves as a suctorial fore gut; the intestine is lined with endodermal columnar epithelial cells. The caceal epithelium has secretory gland cells.
Food, Feeding and Digestion
It feeds on bile, blood, lymph and cell debris. The oral sucker and pharynx together constitute an effective suctorial apparatus. Digestion is extracellular, occurs in intestine. The digested food material is distributed by branching diverticula of intestine to all parts of the body as the circulatory system is not found in this animal. Thus, the digestive system functions as a gastro vascular system.
In fact, the digested nutrients are passed into the parenchyma through intestinal diverticula; from parenchyma they are diffused into the various organs of the body. Reserve food, mostly in the form of glycogen and fats is stored in the parenchyma.
However, monosaccharide sugars like glucose, fructose, etc., are directly diffused into the body of the fluke through general body surface from the surrounding fluid of the host. The indigestible remains of the food, if any, are probably said to be ejected through the mouth.
Respiration of Fasciola Hepatica
Mode of respiration is anaerobic or anoxybiotic. In fact, glycogen is metabolised to carbon dioxide and fatty acids releasing energy in the form of heat.
The process is completed in following steps
- The glycogen undergoes anaerobic glycolysis to form pyruvic acid,
- The pyruvic acid is decarboxylated to form carbon dioxide and an acetyl group,
- The acetyl group then combines with coenzyme A to form acetyl coenzyme A, and
- The acetyl coenzyme A is then finally condensed and reduces to form fatty acids.
The carbon dioxide, thus, produced is diffused out through general body surface and the fatty acids are excreted through the excretory system.