Your Stomach and digestion
Published: February 28, 2014
The stomach is often described as though it is the major digestive organ of your gastrointestinal (GI) tract. Although your stomach plays a very important role in the digestive process of the food that you consume as an initiator of protein and lipid digestion, and facilitates the release of some micronutrients, very few nutrients are absorbed from your stomach into your body.
Your stomach, which is part of your GI tract, is a muscular pouch-like organ located in your abdominal cavity just below your diaphragm, and slightly to the left side of the centre of your body. In addition to the circular and longitudinal smooth muscles characteristic of the GI tract, your stomach wall has a third layer of diagonal smooth muscle.
Smooth muscle, also found in other internal organs, differs from skeletal muscle in that its cells are shaped like spindles and muscle contractions are slower and last longer. The action of the muscles of the GI tract is to push undigested and partially digested food through the GI tract to facilitate digestion and absorption of nutrients.
Your stomach is closed off from the esophagus, the muscular tube which connects your mouth to your stomach, by the lower esophageal sphincter and from your small intestine by the pyloric sphincter. A sphincter is circular muscle which surrounds an opening within the body and which opens and closes that opening.
Within your GI tract several sphincter muscles regulate the passage of food particles through the tract. As the bolus, a small ball of chewed food mixed with saliva in the mouth, passes from your esophagus into your stomach the lower esophageal sphincter muscle closes to ensure that the bolus remains in your stomach. The bolus is gradually squeezed...
Whitney, E. & Rady Rolfes, S. (2005). Understanding Nutrition. Belmont, CA: Thomson Wadsworth
Gropper, S.S., Smith, J.L. & Groff, J.L. (2005). Advanced Nutrition and Human Metabolism (4thEd.). Belmont, CA: Thomson Wadsworth.