Each day, about 9 liters of fluid enters the duodenum. Most chemical digestion takes place in the duodenum by chemicals secreted by the liver, pancreas and small intestine. The other two sections of the small intestine, the jejunum and the ileum, absorb food molecules by way of the villi directly into the blood stream.
Histamine is synthesised in the brain in the hypothalamus, in a specific area known as the tuberomamillary nucleus (TMN), where it acts as a signalling messenger (or neurotransmitter). The hypothalamus is the area of the brain that overseas the metabolic processes of the body found in the central nervous system.
1 Much of the histamine in the body is produced by the granules in mast cells and basophils as part of a local immune response to the presence of invading bodies. Histamine is also made in the brain where it acts as a neurotransmitter or chemical messenger that carries signals between nerves. 2  Another important site where histamine is stored and released is in the enterochromaffin-like (ECL) cells of the stomach.