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The Digestive System
Maria Rose, Elliot Kavanagh, Zhuojing Zhang and Andrew Banks
The digestive system responsible for the ingestion, digestion, and absorption of food. It
consists of parts of the body, working together, that help turn food and liquids into the building
blocks and fuel the body needs. Digestion involves the mixing of food, its movement through
the digestive tract, and the chemical breakdown of the large molecules of food into smaller
molecules.
Digestion begins in the mouth, when we chew and swallow, and is completed in
the large intestine and, the anus. The chemical process varies for different kinds of food.
Mouth:
•
The mouth is the entrance to the human digestive system.
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Teeth grind the food, breaking it down mechanically, while the three salivary glands release saliva
containing enzymes, breaking down starch and fat chemically.
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Saliva makes food easier to swallow by moistening it, as well as preventing the erosion of tooth
enamel by changing the pH (acidity level).
Esophagus:
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The esophagus is a soft muscular tube that moves food from the mouth to the stomach.
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After entering the body through the mouth, food travels down the esophagus, being transported by
muscular contractions. The inside of the esophagus is very moist, which helps in breaking down food
and preventing damage to the rest of the digestive system.
Stomach:
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The stomach has a lining that’s tough enough to hold in the highly acidic environment needed to
break down food.
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Food and drink then reaches the stomach where it is further broken down into smaller pieces. Two
components that are essential to digestion in the stomach are its gastric juices, which are produced in
large amounts and can be very acidic and its muscular contractions.
Small Intestine:
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The small intestine is called small because of its width not its length. It’s actually much longer than the
large intestine. The small and large intestines form one continuous tube.
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The small intestine consists of three parts – the duodenum, jejunum and ileum.
Duodenum – first part of the small intestine, as long as the width of twelve
fingers.
Jejunum – middle section of the small intestine and is about 5 to 8
feet(1.5 to 2.5 meters) long.
Ileum - final 16-20 feet (5 to 6 meters).
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The broken down food then moves into the small intestine (the portion of the digestive system where
most of the nutrient extraction takes place). As food moves through the small intestine, it is mixed with
bile, which is produced by the liver, as well as pancreatic juices, which come from the pancreas.
These two liquids help further the digestive process, breaking down the nutrients in food to the point
where it can be absorbed by the blood.
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Villi, tiny living extrusions which gather nutrients on a fine scale are found inside the small intestine.
Large Intestine:
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The large intestine is 3 or 4 inches around (about 7 to 10 centimeters) and would measure 5 feet
(approx. 1.5 meters) long if you spread it out.
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The large intestine consists of three parts – the cecum, colon and rectum.
Cecum - pouch-like beginning of the large intestine.
Colon - largest part of the large intestine (consists of three parts: the
ascending,
transverse and descending colon).
Rectum -final 6- 8 inches and stores feces
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The large intestine has a tiny tube with a closed end coming off it called the appendix. It's part of the
digestive tract, but doesn't seem to serve a purpose.
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The food passes through a part of the large intestine called the colon which is where the body gets its
last chance to absorb the water and some minerals into the blood. As the water leaves the waste
product, what's left gets harder and harder as it keeps moving along, until it becomes a solid.
Anus:
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The final components of the digestive system are the large intestine, the anus, and the urinary tract,
which separate the liquid matter from the solid matter and send them to their respective exit ports.
The anus marks the exit point of the digestive tract where feces leave the body.