the spines have between 10 and 15 points, whereas at the posterior end, they have up to 30 points. The tegument is a syncytial epithelium. This means it is made from the fusion of many cells, each containing one nucleus, to produce a multinucleated cell membrane. In the case of F. hepatica, no nuclei are in the outer cytoplasm between the basal and apical membranes. Thus, this region is referred to as anucleate. Instead, the nuclei are found in the cell bodies, also known as tegumental cells, these connect to the outer cytoplasm via thin cytoplasmic strands. The tegumental cells contain the usual cytoplasmic organelles (mitochondria, Golgi bodies, and endoplasmic reticulum). The tegument plays a key role in the fluke's infection of the host. Studies have shown that certain parts of the tegument (in this case, the antigen named Teg) can actually suppress the immune response of the mammalian host. This means that the fluke is able to weaken the immune response, and increase its chances of a successful infection. A successful infection is needed for the fluke to have enough time to develop into an adult and continue its lifecycle. Digestive system The alimentary canal of F. hepatica has a single mouth which leads into the blind gut; it has no anus. The mouth is located within the anterior sucker on the ventral side of the fluke. This mouth leads to the pharynx, which is then followed by a narrow oesophagus. The oesophagus, which is lined with a thin layer of epithelial cells, then opens up into the large intestine. As no anus is present, the intestine branches, with each branch ending blindly near the posterior end of the body. Flukes migrate into smaller capillaries and bile ducts when feeding within the host. They use their mouth suckers to pull off and suck up food, bile, lymph, and tissue pieces from the walls of the bile ducts. F. hepatica relies on extracellular digestion which occurs within the intestine of the host. The waste materials are egested through the mouth. The nonwaste matter is adsorbed back in through the tegument and the general surface of the fluke. The tegument facilitates this adsorption by containing many small folds to increase the surface area. Respiratory system F. hepatica has no respiratory organs: the adult flukes respire anaerobically (without oxygen). Glycogen taken from within the host is broken down by glycolysis to produce