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In most vertebrates, digestion is a multistage process in the digestive system, starting from ingestion of raw materials, most often other organisms. Ingestion usually involves some type of mechanical and chemical processing. Digestion is separated into four steps: Ingestion: placing food into the mouth (entry of food in the digestive system),
Most molluscs have a complete digestive system with a separate mouth and anus. The mouth leads into a short esophagus which leads to a stomach. Associated with the stomach are one or more digestive glands or digestive caeca. Digestive enzymes are secreted into the lumen of these glands. Additional extracellular digestion takes place in the stomach.
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body.
Some pathogens are transmitted via ingestion, including viruses, bacteria, and parasites.Most commonly, this takes place via the faecal-oral route.An intermediate step is often involved, such as drinking water contaminated by faeces or food prepared by workers who fail to practice adequate hand-washing, and is more common in regions where untreated sewage is common.
Intracellular digestion can also refer to the process in which animals that lack a digestive tract bring food items into the cell for the purposes of digestion for nutritional needs. This kind of intracellular digestion occurs in many unicellular protozoans, in Pycnogonida , in some molluscs , Cnidaria and Porifera .
Gastrointestinal physiology is the branch of human physiology that addresses the physical function of the gastrointestinal (GI) tract.The function of the GI tract is to process ingested food by mechanical and chemical means, extract nutrients and excrete waste products.
Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized. Some protozoa use phagocytosis as means to obtain nutrients. Where phagocytosis is used as a means of feeding and provides the organism part or all of its nourishment, it is called phagotrophy and is distinguished from osmotrophy ...
The gastrointestinal tract contains the gut microbiota, with some 1,000 different strains of bacteria having diverse roles in the maintenance of immune health and metabolism, and many other microorganisms. [8] [9] [10] Cells of the GI tract release hormones to help regulate the digestive process.