Group: Adam Pashley, Matthew Serrant, Gyasi Vialva-
Husbands, Christopher Voss, Dion Williams.
Class: 3-4 Teacher: Mr. Cooper
The oesophagus is a muscular tube that connects the throat to the stomach.
Its role in digestion is simple: to move boluses of food from the pharynx to the stomach.
In its role as the first conduit in the digestive tube, the oesophagus is routinely exposed to rough and abrasive foodstuffs, like fragments of bone, fibrous plant leaves and
Doritos. Its surface should therefore be resistant to trauma, and indeed, the oesophagus is lined with mucous membrane and it is also lined with muscle.
Absorption in the oesophagus is virtually nothing but the saliva from your mouth secretes mucus to aid in lubrication.
The oesophagus has an epiglottis which is a flap of cartilage at the root of the tongue which prevents food from entering the windpipe during swallowing. At the bottom of the oesophagus there is a muscle which prevents the reflux of stomach acids

into the oesophagus which can damage and wear the epiglottis and oesophagus.
Epiglottis
During swallowing, boluses of food are propelled through the oesophagus by strong peristaltic movements. This peristaltic movement allows humans to eat and drink upside down. In dogs and humans, it takes 4-5 seconds for the bolus to travel down the oesophagus. If the bolus is not delivered in "one pass", secondary waves of peristalsis are initiated at the point where the bolus of food stopped, which will then ensure that the bolus is delivered to the stomach.
Peristalsis

The stomach is a saclike enlargement of the alimentary canal, as in humans and certain animals, forming an organ for storing, diluting and digesting food.
The stomach is a hollow organ composed of several strong muscular layers. It is located under the rib cage and connected at each opening to the oesophagus and the small intestine, respectively. The stomach stores, mixes and digests the food that we eat.
The stomach has several distinct features. They are:
 CURVATURES- The left hand-side of the stomach is known as the greater curvature, since it is much larger and the right-hand side is known as the lesser curvature.
 CARDIA- The cardia is the uppermost section of the stomach. Once masticated food is swallowed, it travels through the oesophageal sphincter and empties into the cardia.

 FUNDUS- The fundus is the upper left portion of the stomach, as the rounded part of the upper stomach, it allows for an accumulation of stomach gases produced by chemical digestion.
 CORPUS- The corpus also known as the body of the stomach is the main region, or central portion, of the stomach.
 PYLORUS- The pylorus is the lower section if the stomach.
Food that has been thoroughly processed is moved to the pylorus. It then passes through the sphincter and into the small intestine.
 RUGAE- The rugae are the folds that line the wall of the stomach. They allow the stomach to expand which enables the organ to hold up to 1 ½ liters of food. This biological form of temporary storage allows you to eat faster than you digest.
The Stomach Wall
The stomach wall has many layers. The innermost layer of the stomach wall is called mucosa and the stomach acids are produced and secreted in this layer. The next layer is submucosa, which is made of connective tissues. This layer is covered by muscularis externa and then serosa.
Muscularis externa consists of three layers of muscles, which are responsible for mixing the food with enzymes and

the movement of the food. So this layer has an important role in the function of the stomach. The outermost layer is serosa which is also made with connective tissues.
The Stomach wall
The Gastric Pits
The Gastric Pits are the numerous depressions in the mucous membrane lining the stomach, into which gastric glands discharge their secretions. Cells in the gastric pits secrete mucus and a base, bicarbonate. This mucus coat containing the base is able to neutralize the acid secreted by another group of cells. The stomach contents are acidic, but the acid is neutralized by the mucus if the acid tries to come in contact with the cells of the stomach.

Stomach Secretions
The inner surface of the stomach has different types of epithelial cells that produce various secretions which aid the process of digestion. This includes mucus cells that produce mucus, which is alkaline in nature. This mucus prevents harm to the inner layer of the stomach from acids.
There are chief cells that produce an enzyme called pepsin
(aids in the stomach function of breaking down proteins) and parietal cells that produce hydrochloric acid (fights microorganisms and digests food). Another type of epithelial cell in the stomach, are the G cells that produce a hormone called gastrin. The inner surface of the stomach

has several folding that are termed as rugae, which flatten as the stomach expands.
Diagram showing the Parts of the Stomach

After food is chewed and moistened in the mouth, it passes through the oesophagus into the stomach. This is the second step in the digestion of everything you consume. Food is mixed with stomach acid and enzymes to break the food down into smaller pieces. This combination of food and stomach "juices" is called chyme. The stomach also stores food temporarily, releasing chyme in small amounts into the small intestine, where it is further broken down into nutrients to be absorbed into the body.
The stomach can be compared to an engine of a car which consumes the fuel and provides the energy to move the car.
Facts about the Digestive System
1. An adult oesophagus ranges from 10 to 14 inches in length, and 1 inch in diameter.
2. We make 1 to 3 pints of saliva a day.
3. Muscles contract in waves to move the food down the oesophagus. This means that food would get to a person's stomach, even if they were upside down on their head

4. It takes your mouth, oesophagus, stomach, small intestine, large intestine, gallbladder, pancreas and liver just to digest a glass of milk.
5. An adult’s stomach can hold approximately 1.5 litres of material.
6. The average male will eat about 50 tons of food during his lifetime in order to sustain a weight of 150 pounds.
7. Within the colon, a typical person harbours more than 400 distinct species of bacteria
8. The liver is the largest organ in the body and performs more than 500 functions.
9. The small intestine (pronounced in-test-in) is a long tube about 1 and a half to 2 inches around, and about 22 feet long.
10. A full grown horse?? Their coiled up intestines are 89 feet long.
11. People can, and have lived without a stomach if it has been removed because of disease.
12. When you blush, the lining of the stomach also turns red.
13. The stomach produces a new layer of mucus every two weeks so it doesn’t digest itself.
14. Food stays in your stomach for 2 to 3 hours.