Answer:
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Explanation:
A hollow muscular organ about the size of 2 closed fists, the stomach is located inferior to the diaphragm and lateral to the liver on the left side of the abdominal cavity. The stomach forms part of the gastrointestinal tract between the esophagus and the duodenum (the first section of the small intestine).
The wall of the stomach contains several layers of epithelium, smooth muscle, nerves, and blood vessels. The innermost layer of the stomach is made of epithelium containing many invaginations known as gastric pits. The cells of the gastric pits produce gastric juice - an acidic mixture of mucus, enzymes and hydrochloric acid.
The hollow portion of the stomach serves as the storage vessel for food before it moves on to the intestines to be further digested and absorbed. At the inferior end of the stomach is a band of smooth muscle called the pyloric sphincter. The pyloric sphincter opens and closes to regulate the flow of food into the duodenum.
The gallbladder is a 3-inch long pear-shaped sac located on the posterior border of the liver. Connected to the bile ducts of the liver through the cystic duct, the gallbladder receives bile transported from the liver for storage on a regular basis to prepare for the digestion of future meals. During digestion of a meal, smooth muscles in the walls of the gallbladder contract to push bile into the bile ducts that lead to the duodenum. Once in the duodenum, bile helps with the digestion of fats.
The pancreas is a 6-inch long heterocrine gland located inferior to the stomach and surrounded by the duodenum on its medial end. This organ extends laterally from the duodenum toward the left side of the abdominal cavity, where it tapers to a point.
The pancreas is considered a heterocrine gland because it has both endocrine and exocrine gland functions. Small masses of endocrine cells known as pancreatic islets make up around 1% of the pancreas and produce the hormones insulin and glucagon to regulate glucose homeostasis in the blood stream. The other 99% of the pancreas contains exocrine cells that produce powerful enzymes that are excreted into the duodenum during digestion. These enzymes together with water and sodium bicarbonate secreted from the pancreas are known as pancreatic juice.
The stomach, gallbladder, and pancreas work together as a team to perform the majority of the digestion of food.
Food entering the stomach from the esophagus has been minimally processed — it has been physically digested by chewing and moistened by saliva, but is chemically almost identical to unchewed food.
Upon entering the stomach, each mass of swallowed food comes into contact with the acidic gastric juice, which contains hydrochloric acid and the protein-digesting enzyme pepsin. These chemicals begin working on the chemical digestion of the molecules that make up the food.
At the same time, the food is mixed by the smooth muscles of the stomach wall to increase the amount of contact between the food and the gastric juice. The secretions of the stomach also continue the process of moistening and physically softening the food until the food becomes an acidic semi-liquid material known as chyme.
At this point, the stomach begins to push the chyme through the pyloric sphincter and into the duodenum.
In the duodenum, the bulk of digestion is completed thanks to the preparation of chyme by the stomach and the addition of secretions from the gallbladder and pancreas. Bile from the gallbladder acts as an emulsifier to break large masses of fats into smaller masses. Pancreatic juice contains bicarbonate ions to neutralize the hydrochloric acid of chyme. Enzymes present in the pancreatic juice complete the chemical digestion of large molecules that began in the mouth and stomach.
The completely digested food is then ready for absorption by the intestines.