Answer
The mouth, oropharynx, esophagus, stomach, small intestine, large intestine, and anal canal are the parts of the GI tract that come in contact with food. The following are some of the major functions carried out in these structures or organs:
The mouth: In the mouth, the teeth mechanically break down food into smaller pieces, a process called mastication. Mixing is carried out by tongue and muscles of the oral cavity. The ingested and masticated food is softened by mixing with saliva that is poured into the oral cavity from the salivary glands. Salivary amylase begins carbohydrate digestion in the mouth. However, amylase is not the only enzyme secreted in the mouth. Lingual lipase begins the process of lipid digestion which develops further in the stomach.
The oropharynx; This structure helps with mixing and swallowing.
The esophagus. This is the tube through the food is transported from oral cavity to the stomach
The esophagus participates in swallowing. Its muscles move boluses of food stomach by waves of involuntary muscular contractions called peristalsis. On its way to the stoach the process of carbohydrate break-down by
salivary amylase continues.
Stomach. The stomach is the largest of the primary digestive organs. It stores food mixes and digests food and moves digested food into the small intestine for further digestion and absorption..
The stomach secretes a proteolytic enzyme , pepsin that digests protein food substances. It also secrete hydrochloric acid that facilitates pepsin action but shuts down the action of salivary amylase which requires a pH of about 6.7 for optimal activity.
The Small Intestine. This organ includes the duodenum (12 ins) the jejunum and the ileum (the most distal segment). The small intestine receives partially digested food from the stomach. At the dudenum it is the site of reception of bile and pancreatic juice. . Pancreatic enzymes fuction at a higher pH tan does pepsin so in the duodenum th acidic chyme is buffered to a pH of about 6 to facilitate the activity of pancreatic enzymes. The function of bile is to emulsify lipid to help in their digestion. The small intestine is very long 10 feet to 25 feet dependent on heght oof an individual human . Tis provides much surface area for absorption. . In addition the small intestine has circular folds and the mucosa is thrown into villi the structure of which is particularly designed to aid absorption of nutrients.
The colon or large intestine is the last part of the Gi tract. It is usually considered as comprising the ascending colon, the transverse colon, the descending colon, the sigmoid colon and the anal canal. The function of the colon is mainly to absorb fluids and compact and store undigested, unabsorbed food, wastes, cell debris and bacteria for elimination. This compacted material is calledfeces and the process of expelling it through the anus is called defecation.
Work Step by Step
The mouth is for mechanical breakdown of food, beginning of enzymatic digestion and swallowing.
The esophagus is mainly for transporting food to the stomach.
The stomach mixes food and its enzymes participate in digestion of proteins.
All kind of food are digested in the small intestine. It is the main site of absorption of nutrients.
The Large intestine, absorbs fluids, compacts and eliminates wastes.
