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Trophozoites adhere to host epithelial cells via a specialized disk-shaped organelle called the ventral disk. [14] Cysts are oval-shaped cells slightly smaller than trophozoites. [15] They lack flagella, and are covered by a smooth, clear cyst wall. [15] Each cyst contains four nuclei and fragments of the ventral disc. [15]
Less common symptoms include vomiting and blood in the stool. [1] Symptoms usually begin one to three weeks after exposure and, without treatment, may last two to six weeks or longer. [4] Giardiasis usually spreads when Giardia duodenalis cysts within faeces contaminate food or water that is later consumed orally. [1]
Giardia (/ dʒ iː ˈ ɑːr d i ə / or / ˈ dʒ ɑːr d i ə /) is a genus of anaerobic flagellated protozoan parasites of the phylum Metamonada that colonise and reproduce in the small intestines of several vertebrates, causing the disease giardiasis. Their life cycle alternates between a swimming trophozoite and an infective, resistant cyst.
Giardiasis is a disease of the small intestine caused by a protist parasite Giardia lamblia. This does not spread but remains confined to the lumen of the small intestine. [47] It can often be asymptomatic, but as often can be indicated by a variety of symptoms. Giardiasis is the most common pathogenic parasitic infection in humans. [48]
Most diplomonads are double cells: they have two nuclei, each with four associated flagella, arranged symmetrically about the body's main axis. Like the retortamonads, they lack both mitochondria and Golgi apparatuses.
The gut-associated lymphoid tissue lies throughout the intestine, covering an area of approximately 260–300 m 2. [5] In order to increase the surface area for absorption, the intestinal mucosa is made up of finger-like projections (), covered by a monolayer of epithelial cells, which separates the GALT from the lumen intestine and its contents.
Goblet cells secrete mucus, which lubricates the passage of food along and protects the intestinal wall from digestive enzymes. In the small intestine, villi are folds of the mucosa that increase the surface area of the intestine. The villi contain a lacteal, a vessel connected to the lymph system that aids in the removal of lipids and tissue ...
The glycocalyx is located on the apical surface of vascular endothelial cells which line the lumen.When vessels are stained with cationic dyes such as Alcian blue stain, transmission electron microscopy shows a small, irregularly shaped layer extending approximately 50–100 nm into the lumen of a blood vessel.