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A trophozoite (G. trope, nourishment + zoon, animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing Plasmodium falciparum and those of the Giardia group. [1] The complementary form of the trophozoite state is the thick-walled cyst form. They are often different from the cyst stage, which is a ...
[1] [2] [3] The parasite attaches to the intestinal epithelium by a ventral disc (syn. adhesive disc or sucker), and reproduces via binary fission. [4] [5] G. duodenalis is a non-invasive parasite, that does not spread to other parts of the gastrointestinal tract, but remains confined to the lumen of the small intestine.
A trophozoite (G. trophē, nourishment + zōon, animal) is the activated, intracellular feeding stage in the apicomplexan life cycle. After gorging itself on its host, the trophozoite undergoes schizogony and develops into a schizont, later releasing merozoites.
About 40 species have been described, but most of them are probably synonyms. [11] Currently, five to six morphologically distinct species are recognised. [12] Giardia duodenalis (=G. intestinalis, =G. lamblia) infect humans and other mammals, G. microti infects voles, G. muris is found in other mammals, G. ardeae and G. psittaci in birds, and G. agilis in amphibians. [4]
Duodenal glands are situated within the mucosa and submucosa of the duodenum. They are most abundant near the pylorus, growing shorter and more sparse distally towards the terminal portion of the duodenum. [1] The duodenum can be distinguished from the jejunum and ileum by the presence of Brunner's glands in the submucosa. [citation needed]
The stomach is a distensible organ and can normally expand to hold about one litre of food. [22] This expansion is enabled by a series of gastric folds in the inner walls of the stomach. The stomach of a newborn baby will only be able to expand to retain about 30 ml.
[1] [4] The trophozoites then colonize the large intestine, where they live in the lumen and feed on the intestinal flora. [1] [4] Some trophozoites invade the wall of the colon using proteolytic enzymes and multiply, and some of them return to the lumen. [1] [4] [6] In the lumen, trophozoites may disintegrate or undergo encystation.
The acid and semi-digested fats in the duodenum trigger the enterogastric reflex – the duodenum sends inhibitory signals to the stomach by way of the enteric nervous system, and sends signals to the medulla that (1) inhibit the vagal nuclei, thus reducing vagal stimulation of the stomach, and (2) stimulate sympathetic neurons, which send ...