Stomach (Gastric) : Definition, Structure and Functions

A. UNDERSTANDING THE DEFINITION OF STOMACH (GASTRIC)

Stomach is a digestive organ that is shaped like a pouch and is located in the left abdominal cavity above the diaphragm. Another name is the gastric. Gastric main function is to store and process food. Gastric pH less than 2 degrees, which are highly acidic. At both ends of the stomach (before and after passage of the stomach) there are two narrowing tube so that the food is being processed in the stomach do not go down or up to another organ when the gestation takes place. On the inside of the gastric there are glands that produce gastric juice. The size of the stomach at each individual is different, but usually able to accommodate 1.5 liters of food.

STOMACH

B. THE FUNCTIONS OF STOMACH (GASTRIC)

To store and process food.
To destroy harmful bacteria and micro-organisms contained in food. pH of stomach is highly acidic so they are capable to killing bacteria.
Begins the digestion of fat.
Transform proteins into peptone.
Changing caseinogen into casein.
It can also control the production of hormones.

C. THE STRUCTURE OF STOMACH (GASTRIC)

The Stomach has a wall structure that similar to most of the small intestine and other digestive organs. Hull structure composed by four walls below (From outside to inside):

1. Layer Serous

Is the outer layer that serves as a protection of the stomach. Cells contained in this layer can produce liquid that reduces friction between the stomach with other digestive organs.

2. Muscle Layer

Muscle layer of the stomach is a layer of smooth muscle that works involuntary. There are three types of muscle fibers, elongated, circular and diagonal. The combination of these three types of muscle contraction will produce gastric peristalsis which serves to break down the food and took it to the next digestive organ.

3. Submucosa Layer

Layer that composed by connective tissue containing blood vessels, lymphatics, nerves and mucous glands. The blood vessels in the submucosal layer of the stomach plays an important role in passing the food and nutrition.

STOMACH LAYERS AND STRUCTURE

4. Mucous Layer

This layer served in the secretion process. Mucous layer serves to issue various types of fluids such as enzymes, stomach acid, and hormones. There are 3 types of cells in the mucosa layer, namely:

Goblet cells, function to produce mucus or slime that keeps the inner layer not damaged.
Parietal cells, used to produce stomach acid and serves to activate the pepisn enzyme.
Chief cell serves to produce pepsinogen (pepsin enzyme in an inactive form). This enzyme is produced in an inactive form so they do not digest their own protein.

D. PARTS OF STOMACH (GASTRIC)

1. Cardiac

The first part of the hull which serves as the entrance of food from the esophagus (gullet).

2. Fundus

The central part of the stomach that have rounded shape. This section is often called the corpus (body of the stomach).

3. Pylori

The lower part of the stomach is associated with the small intestine.

In the stomach there are two valve (sphincter), is a narrowing at both ends. At the end of the hull bordering with esophagus,there is cardia sphincter, whereas at the end of the hull bordering with small intestine, there is pylori sphincter. Both sphincter function to keep food stays in the stomach during the digestion process takes place, but it also prevents stomach acid to get into other organs.

E. GASTRIC JUICE COMPOSITION AND FUNCTION

HCL (Stomach Acid), a is highly acid liquid produced by parietal cells. Function to kill bacteria in food, stimulate the intestines liver and pancreas, change pepsinogen into pepsin.
Pepsin, serves to convert protein into albumosa + peptone.
Lipase, serves to transform fat into fatty acids + glycerol.
Renin, serves to convert protein from milk to lactose.
Gastrin, serves as a hormone that increases production of gastric glands to their secretion.
Mucin, serves to protect the stomach wall.

F. DIGESTION PROCESS IN THE STOMACH (GASTRIC)

1. Mechanical Process

Esophagus move food to enter the stomach, the food is then digest in the stomach for approximately 2-5 hours. Stomach has a layer of muscle that will combine to perform mechanical digestion to break down food. The combination of the contraction of their muscles is going to create a movement that will encourage the food slowly. The movement is called peristalsis. Peristaltic movements will occur every 15-25 seconds.

2. Chemical Process

Chemical digestion process that occurs in the stomach conducted by the gastric juice. In this case the food is broken down into simpler form to be easily absorbed in the intestine. Gastric juice will keep food free from bacteria and acidic. Furthermore, the food will move towards the small intestine and the condition of the pH is neutralized by other organs such as the pancreas and intestine.

G. EMPTYING PROCESS

Gastric emptying occurs because nerve stimulation as a result of the presence of food in the stomach. And the presence of the gastrin hormone which is a component of gastric juice will stimulate the cardiac sphincter to contract, increasing gastric movement, and relaxation of the pyloric sphincter so that a process of making food go to the next digestive organ. Gastric emptying all its contents into the small intestine approximately 2-6 hours after the food starts to digest. Gastric emptying speed is highly dependent on the concentration of the food there.

Some of the factors that affect the rate of gastric emptying are :