Digestion

digestivedigestdigesteddigestibilitydigestive systemabsorptiondigestibledigestingdigestive processdigestive secretions
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma.wikipedia
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Small intestine

small bowelsmall intestinessmall
In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. When the pyloric sphincter valve opens, chyme enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine, in which digestion continues.
It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion.

Human digestive system

digestive systemdigestivedigestive tract
In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva.
The process of digestion has three stages.

Digestive enzyme

digestive enzymespancreatic enzymepancreatic enzymes
The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. In mammals, preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach.
Digestive enzymes are found in the digestive tracts of animals (including humans) and in the tracts of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular survival.

Chewing

masticationchewmasticate
In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva.
It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes.

Stomach

gastriccardiafundus
It will then travel down the esophagus and into the stomach by the action of peristalsis. In mammals, preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach.
The stomach has a dilated structure and functions as a vital digestive organ.

Bolus (digestion)

bolusbolusesgobbet
After undergoing mastication and starch digestion, the food will be in the form of a small, round slurry mass called a bolus.
In digestion, a bolus (from Latin bolus, "ball") is a ball-like mixture of food and saliva that forms in the mouth during the process of chewing (which is largely an adaptation for plant-eating mammals).

Saliva

salivationspittlespit
In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva. In mammals, preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach.
The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats.

Liver

hepaticliver protein synthesislivers
When the pyloric sphincter valve opens, chyme enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine, in which digestion continues.
The liver is an organ only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces biochemicals necessary for digestion.

Peristalsis

peristalticgut motilityperistaltic contractions
It will then travel down the esophagus and into the stomach by the action of peristalsis.
In much of a digestive tract such as the human gastrointestinal tract, smooth muscle tissue contracts in sequence to produce a peristaltic wave, which propels a ball of food (called a bolus while in the esophagus and upper gastrointestinal tract and chyme in the stomach) along the tract.

Mucus

mucousmucinousslime
Saliva, a liquid secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food; the saliva also contains mucus, which lubricates the food, and hydrogen carbonate, which provides the ideal conditions of pH (alkaline) for amylase to work.
Mucus serves to protect epithelial cells in the linings of the respiratory, digestive, and urogenital systems, and structures in the visual, and auditory systems from pathogenic fungi, bacteria and viruses.

Defecation

defecatedefecatingbowel movement
Waste material is eliminated from the rectum during defecation.
Defecation is the final act of digestion, by which organisms eliminate solid, semisolid, or liquid waste material from the digestive tract via the anus.

Pylorus

pyloric sphincterpyloricpyloric antrum
When the pyloric sphincter valve opens, chyme enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine, in which digestion continues.
It may temporarily become partially or completely shut off from the remainder of the stomach during digestion by peristaltic contraction of the prepyloric sphincter; it is demarcated, sometimes, from the pyloric canal by a slight groove.

Food

foodsfoodstufffood products
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma.
A negative-calorie food is food that supposedly requires more food energy to be digested than the food provides.

Gastrovascular cavity

coelenterongastrovascularblind gut
The gastrovascular cavity functions as a stomach in both digestion and the distribution of nutrients to all parts of the body.
The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Cnidaria (including jellyfish and corals) and Platyhelminthes (flatworms).

Animal

Animaliaanimalsmetazoa
Animals have a tube (gastrointestinal tract) in which internal digestion occurs, which is more efficient because more of the broken down products can be captured, and the internal chemical environment can be more efficiently controlled.
Typically, there is also an internal digestive chamber with either one opening (in Ctenophora, Cnidaria, and flatworms) or two openings (in most bilaterians).

Proteolysis

proteolyticprotein degradationpolyprotein
Gastric juice in the stomach starts protein digestion.
In human digestion, proteins in food are broken down into smaller peptide chains by digestive enzymes such as pepsin, trypsin, chymotrypsin, and elastase, and into amino acids by various enzymes such as carboxypeptidase, aminopeptidase, and dipeptidase.

Crop (anatomy)

cropcropscraw
A crop, or croup, is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion.
A crop (sometimes also called a croup or a craw, or ingluvies) is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion.

Starch

starcheswheat starchrice starch
Saliva, a liquid secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food; the saliva also contains mucus, which lubricates the food, and hydrogen carbonate, which provides the ideal conditions of pH (alkaline) for amylase to work.
Digestive enzymes have problems digesting crystalline structures.

Nutrition

nutrition sciencenutritionalnutritional science
Instead they extract more nutrition from grass by giving their food a second pass through the gut.
It includes food intake, absorption, assimilation, biosynthesis, catabolism and excretion.

Cellulose

cellulolyticcellulosiccellulose ester
Fibre, especially cellulose and hemi-cellulose, is primarily broken down into the volatile fatty acids, acetic acid, propionic acid and butyric acid in these chambers (the reticulo-rumen) by microbes: (bacteria, protozoa, and fungi).
Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha.

Large intestine

coloncolorectallarge bowel
Water and minerals are reabsorbed back into the blood in the colon (large intestine) where the pH is slightly acidic about 5.6 ~ 6.9.
The large intestine produces no digestive enzymes — chemical digestion is completed in the small intestine before the chyme reaches the large intestine.

Cephalic phase

In mammals, preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach.
The cephalic phase of digestion is the gastric secretion that occurs even before food enters the oral cavity.

Venus flytrap

Dionaea muscipulaVenus fly trapDionaea
In a plant such as the Venus Flytrap that can make its own food through photosynthesis, it does not eat and digest its prey for the traditional objectives of harvesting energy and carbon, but mines prey primarily for essential nutrients (nitrogen and phosphorus in particular) that are in short supply in its boggy, acidic habitat.
If the prey is unable to escape, it will continue to stimulate the inner surface of the lobes, and this causes a further growth response that forces the edges of the lobes together, eventually sealing the trap hermetically and forming a "stomach" in which digestion occurs.

Gastrointestinal tract

intestinegastrointestinaldigestive tract
Animals have a tube (gastrointestinal tract) in which internal digestion occurs, which is more efficient because more of the broken down products can be captured, and the internal chemical environment can be more efficiently controlled. A crop, or croup, is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion. Instead they extract more nutrition from grass by giving their food a second pass through the gut.
The gastrointestinal tract (digestive tract, alimentary canal, digestion tract, GI tract, GIT) is an organ system within humans and other animals which takes in food, digests it to extract and absorb energy and nutrients, and expels the remaining waste as feces.

Bile

biliarybiliousgall
In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile, pancreatic juice and intestinal juice.
Bile or gall is a dark green to yellowish brown fluid, produced by the liver of most vertebrates, that aids the digestion of lipids in the small intestine.