Stomach And Intestines

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Stomach And Intestines
Stomach And Intestines
Video: Stomach And Intestines
Video: How your digestive system works - Emma Bryce 2023, February

Stomach and intestines

The chyme enters the stomach from the esophagus. The front wall of this J-shaped hollow muscular organ lies directly behind the left costal arch in the left upper abdomen. Size and shape can vary from person to person. The next stop in digestion is the intestine, a muscular tube of considerable size. Overall, the intestine comes to a length of approx. Up to seven meters. The internal structure of the small intestine is particularly noteworthy. With its numerous protuberances on the inner wall of the intestine, the inner surface increases many times over and ensures the optimal absorption of important substances.


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  • ">What are the tasks of the stomach?


  • Layer structure of the stomach
  • The intestine
  • What are the tasks of the intestine?
  • The small intestine
  • The colon

">The capacity of the stomach depends, among other things, on the physique of the person. But gender and eating habits also have an influence. The stomach is divided into several sections, the stomach entrance (cardia, cardia), the dome of the stomach (fundus, fundus ventriculi, fundus gastricus), the stomach body (corpus gastricus), the antrum and the stomach exit (pylorus).

What are the tasks of the stomach?

The stomach acts as a reservoir and passes the chyme on to the duodenum in portions. The length of time the food remains in the stomach varies from person to person and depends on its composition. It can be a few hours in healthy people. Fat stays in the stomach the longest, protein has a medium length and carbohydrates have the shortest stay in the stomach. The higher the calorie density of a food, the longer the chyme stays in the stomach. Liquids (e.g. water) pass through the stomach relatively quickly.

Scheme stomach © stockshoppe

Other tasks of the stomach are to mix the food thoroughly and to chop it up (mechanically) and to digest the chyme by adding digestive juices (hydrochloric acid, enzymes such as pepsin) and to prepare it for further digestion (chemical).

The most important tasks at a glance:

  • Reservoir function
  • Killing of microorganisms
  • Chopping up the contents of the stomach / food
  • digestion
  • targeted gastric emptying
  • Co-Vitamin Intrinsic Factor (for vitamin B12 absorption)

Note The stomach does not function in isolation, but in cooperation with the upper small intestine, especially the duodenum, but also with the pancreas and the biliary tract. For example, the pancreas influences the motility of the stomach.

Layer structure of the stomach

The stomach wall consists of several layers, which are made up of muscle fibers, mucous membrane and connective tissue, as well as blood vessels, nerves, etc. In the gastric mucosa there are many small glands with different cell types (main, attendant, minor and ECL cells). The glands produce hydrochloric acid and digestive enzymes such as lipases and pepsin. This gastric juice also serves to protect the organism from invading bacteria. The gastric juice is a very acidic liquid (pH 1 to 2). The stomach produces up to four liters of gastric juice every day.

Since the gastric juice is relatively aggressive due to its low pH value and the protein-degrading substances it contains and could damage the stomach wall, the glands in the gastric mucosa produce substances that protect the stomach from "self-digestion". Viscous mucin and buffering hydrogen carbonate are protective.

Note The parietal cells of the gastric mucosa produce a substance that is essential for the absorption of vitamin B12 (intrinsic factor). For more information about vitamin B12 in nutrition, see Vitamin B12 (Cobalamin).

The intestine

The next stop in digestion is the intestine, a muscular tube of considerable size. Overall, the intestine has a length of about seven meters. The internal structure of the small intestine is particularly noteworthy. With its numerous villi and crypts (protuberances on the inner wall of the intestine), the inner surface increases many times over and ensures the optimal absorption of important substances. The inside of the intestine can be imagined like an accordion. If you were to unfold the inner surface of the small intestine, this would correspond to an area of ​​about 200 square meters.

What are the tasks of the intestine?

The intestine is divided into different functional units. Each one has its own special tasks. A broad distinction is made between the small intestine and the large intestine. The intestine fulfills many important tasks. On the one hand, it makes the ingredients of food available to the organism, breaks them down and absorbs them (resorption), which is a function of the small intestine. It also regulates and controls the body's supply of fluids, which is primarily a function of the large intestine. Last but not least, it plays a role in the functioning of the immune system.

The most important tasks at a glance:

  • Digestion of the porridge (fermentation to amino acids, monosaccharides and fatty acids / digestion, absorption / absorption through the intestinal wall into the portal blood and to the organs, etc.)
  • Production of hormones (= messenger substances)
  • Defense against pathogens
  • Participation in the regulation of the water balance

The small intestine

The first station after the stomach is the duodenum. This is followed by the empty intestine and the ileum, together they form the small intestine. This is where the entire breakdown and absorption of nutrients, salts (electrolytes, minerals), vitamins, trace elements and water takes place.

In the duodenum, digestive secretions from the pancreas and bile are added to the chyme. Special glands (Brunner's glands) secrete mucus and buffering substances to protect against the acidic gastric juice. The duodenum is C-shaped and encloses the head of the pancreas.

The small intestine is divided into the following sections:

  • Duodenum (duodenum)
  • Jejunum
  • Ileum

Numerous enzymes break down the food components carbohydrates, fats and proteins into their building blocks such as monosaccharides, fatty acids and amino acids. Via the intestinal cells (enterocytes) with their microvilli (surface-enlarging threads), the substances are absorbed into the bloodstream and / or lymphatic system and transported to different locations using various mechanisms.

The small intestine also produces hormonally active substances that regulate or influence the gastric function and the movements of the intestine as well as the activity of the gall bladder and pancreas (gastrin, secretin, motilin, cholecystokinin). In the small intestine, an average of several liters of fluid are secreted each day and are partially filtered back together with the fluid that has been drunk (remainder reabsorbed in the large intestine). There are numerous defense cells in the small intestine, such as lymphocytes, etc., which are indirectly involved in the immune system.

The colon

The small intestine is followed by the caecum, colon and rectum, together they form the large intestine. This is where the remaining intestinal contents are transported to the anus (anus) and to excretion. Most of the absorption of important substances from the intestine has already taken place in the small intestine. Nevertheless, water, short-chain fatty acids and electrolytes (salts) are reabsorbed here.

The colon is divided into the following sections:

  • Appendix (cecum)
  • Colon (colon)
  • Rectum (rectum)

Compared to the other sections of the intestine, the large intestine is particularly densely populated with billions of bacteria. They determine the very individual intestinal flora of a person. The intestinal bacteria (enterobacteria) perform valuable tasks, including breaking down soluble fiber into short-chain fatty acids, which in turn have a positive effect on the passage. Intestinal bacteria produce e.g. vitamin K.

Urge to defecate

Special cells regulate the motor skills so that the intestinal contents are gradually moved forward (pacemaker cells). The bowel movements (peristalsis) are subject to the daily rhythm (circadian rhythm), ie the bowel is less active at night, for example.

In this part of the intestine, the stool contains very little water. If the stool reaches the rectum, the urge to defecate is triggered by a stretching stimulus.

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