The Digestive System - by Jon Phillips


The system of organs used to breakdown and absorb nutrients from the foods the human body ingests. The system includes the esophagus, stomach, small intestine, large intestine, lover, gallbladder, pancreas, and rectum.

1. Structure/ Function
Esophagus- This organ is a long tube of tissues that connects the mouth to the stomach. Food passes through this muscle at a about 2 to 8 seconds from start to finish depending on the type of food ingested, the food is then emptied into the stomach for digestions. It runs the length of the chest cavity passing between the lungs and heart cavity.
Stomach- A "J- shaped" pouch of muscle tissues that utilize powerful enzymes and acids to breakdown the food into what is known as "Chyme". The stomach is the main site of protein digestion and breakdown in the Digestive System. The "chyme" that is produced is then emptied into the small intestine for further digestion.
Small Intestine- The small intestine is an organ spanning 24 feet in length and is composed of 3 sections: Duodenum, Jejunum, and Ileum. These 3 sections play the vital role of nutrient absorption and distribution to the blood, eventually traveling to the cells. The remaining substance is passed along to the Large Intestine, after this period.
Large Intestine- The large intestine is essentially the conclusion for the digestion of foods, any remaining nutrients are absorbed and the waste is excreted as feces. The large intestine is composed of the rectum, cecum, and colon. The large intestine spans a length of 5 feet producing essential vitamins like vitamin B and K.
Liver- In the process of digestion the liver produces "bile" that is used to breakdown and absorb the fats in foods. The liver has many other vital roles of filtering blood, metabolizing protein and carbohydrates, and aides in regulating blood sugar levels.

Accessory Organs
Pancreas- Considered to be a part of the endocrine system, the pancreas is vital for digestion due to its production of a cocktail substance composed of enzymes and sodium bicarbonate that stop the breakdown process of the pepsin within the small intestine.
Gallbladder- store the bile before it is used in small intestine for digestion



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2. Enzymes/ Hormones and 3. Regulation
Salivary Amylase- is produced by salivary glands and is the first step in digestion, it begins once food enters the mouth and chewing begins. The product of this enzyme is Maltose.
Pancreatic Amylase- is produced by the Pancreas. The product of this enzyme is Maltose.
Maltase- is produced in the small intestine. The product of this enzyme is Glucose.
Pepsin- is produced by stomach muscosa. The product of this enzyme is Peptides.
Trypsin- is produced by the pancreas. The product is Peptides.
Peptidases- is produced by intestinal mucosa. The product is Amino Acids.
Lipase- is produced by the pancreas. The product is Fatty Acids and Glycerol.

Hormones
Gastrin- is produced by the stomach and released in the presence of food in the stomach, and stimulates the stomach to produce gastric juices used in digestion.
Secretin- is produced by the duodenum in the small intestine, and is produced in the presence of chyme. Secretin stimulates the pancreas to produce sodium bicarbonate and the liver to produce bile.
CCK- is produced by the duodenum in the small intestine, and is secreted by the presence of food in small intestine. CCK causes the gallbladder to secrete bile and the pancreas to produce pancreatic enzymes.
GIP- is produced by the duodenum in the small intestine, and inhibits gastric glands and stomach mobility.



4. Communication
The digestive system is put bluntly, as straight shot. Food enters the system through the mouth and exits out the rectum at the end of digestion. Each organ of the system is kept closed off or open by sphincters, sphincters are basically control valves for the movement of food as it goes through the process of digestion. Each of the organs plays a critical role but each in good time. None of the organs acts without the organ above it in order first doing it part in digestion example: the small intestine digesting food before the large intestine. Each absorbs and produces individual vitamins/ nutrients for the body.


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Sources:
About.com
faculty.clintoncc.suny.edu
Textbook
Notes