Digestive Process Essay, Research Paper

It is in the mouth, that the Thanksgiving feast begins its journey through the

fabulous digestive system. It is here that the lips, cheeks and tongue,

carefully position the food that the teeth will chew. This chewing process

breaks up the food, this being a part of mechanical digestion. While the teeth

grind up the turkey and tasty stuffings, the salivary glands begin emitting

enzymes, these enzymes being contained in saliva. This saliva helps to dissolve

some foods, and adds mucus to make the food’s passage through the digestive

system a little more "speedy". The saliva also attacks dangerous

microorganisms which enter the mouth. Saliva also contains an enzyme which helps

to break down carbohydrates into sugars. As the food is being ground and coated

with saliva, it’s passed over the taste buds, which in turn send messages to the

brain. The brain uses this information to decide whether or not the food should

be swallowed. The food is then gathered into a ball, called a bolus, and it is

pushed down into the pharynx by way of the tongue. This bolus of

"Thanksgiving meal" is then passed down the esophagus, the esophagus

being a 24cm long tube which connects the pharynx and stomach. Lining the walls

of the esophagus are rings of muscle which contract in waves, pushing the bolus

down the length of the esophagus. At the base of the esophagus, where the

esophagus and stomach join, a thick ring of muscle called a sphincter, is found.

This sphincter acts like a valve, as it allows food to pass into the stomach but

does not permit it to pass back up through the esophagus. The stomach, which is

in the essence a large muscle sack, contains three sets of glands which produce

gastric fluids. One set produces mucus which coats the food, making it slippery,

and it protects the stomach walls from being digested by its own secretions. The

second set of manufactures hydrochloric acid, which aids in the

"break-down" of foods. In conjuction with hydrochloric acid, pepsin,

which aids in the "break-down" of protein into smaller polypeptides,

begins the process of protein digestion. The stomach’s muscular walls move

around the "food" and mucus, mixing them with the gastric fluids

produced. The "food" becomes a pasty substances referred to as chyme,

after about 2 or 3 hours of grinding within the stomach. The pyloric valve, or

gateway between the stomach and small intestine, opens. The chyme contained in

the stomach is then forced down into the small intestine by a process called

persitalsis. The chyme is then forced along the entire 20ft of small intestine,

where the process of breaking down the "food", and taking out its

vitamins, minerals, etc., is continued. These vitamins and minerals will be used

throughout the rest of the body, once they have been placed into the

bloodstream. After making its way through the small intestine, the chyme is

passed on through the colon, or large intestine. The colon proceeds to remove

water from the chyme passing through it, reducing it into solid waste, or feces.

Again, through the process of persitalsis, the fecal matter is passed through

the colon, where it will then gather at the end of the colon, in rectum. Muscles

located in the colon prevent the feces from being released until it becomes

convenient for us to expel them from the body, by way of the anus.